Programs & Examples On #Escript

eScript is designed to describe the various steps in adding support for a new programming language to Eclipse.

Crop image to specified size and picture location

You would need to do something like this. I am typing this off the top of my head, so this may not be 100% correct.

CGColorSpaceRef colorSpace = CGColorSpaceCreateDeviceRGB(); CGContextRef context = CGBitmapContextCreate(NULL, 640, 360, 8, 4 * width, colorSpace, kCGImageAlphaPremultipliedFirst); CGColorSpaceRelease(colorSpace);  CGContextDrawImage(context, CGRectMake(0,-160,640,360), cgImgFromAVCaptureSession);  CGImageRef image = CGBitmapContextCreateImage(context); UIImage* myCroppedImg = [UIImage imageWithCGImage:image]; CGContextRelease(context);       

Pass PDO prepared statement to variables

You could do $stmt->queryString to obtain the SQL query used in the statement. If you want to save the entire $stmt variable (I can't see why), you could just copy it. It is an instance of PDOStatement so there is apparently no advantage in storing it.

Instantiating a generic type

You basically have two choices:

1.Require an instance:

public Navigation(T t) {     this("", "", t); } 

2.Require a class instance:

public Navigation(Class<T> c) {     this("", "", c.newInstance()); } 

You could use a factory pattern, but ultimately you'll face this same issue, but just push it elsewhere in the code.

java doesn't run if structure inside of onclick listener

both your conditions are the same:

if(s < f) {     calc = f - s;     n = s; }else if(f > s){     calc =  s - f;     n = f;  } 


if(s < f)   


}else if(f > s){ 

are the same

change to

}else if(f < s){ 

Autoresize View When SubViews are Added

Yes, it is because you are using auto layout. Setting the view frame and resizing mask will not work.

You should read Working with Auto Layout Programmatically and Visual Format Language.

You will need to get the current constraints, add the text field, adjust the contraints for the text field, then add the correct constraints on the text field.

Generating a list of pages (not posts) without the index file

I have never used jekyll, but it's main page says that it uses Liquid, and according to their docs, I think the following should work:

<ul> {% for page in site.pages %}     {% if page.title != 'index' %}     <li><div class="drvce"><a href="{{ page.url }}">{{ page.title }}</a></div></li>     {% endif %} {% endfor %} </ul> 

Warp \ bend effect on a UIView?

What you show looks like a mesh warp. That would be straightforward using OpenGL, but "straightforward OpenGL" is like straightforward rocket science.

I wrote an iOS app for my company called Face Dancerthat's able to do 60 fps mesh warp animations of video from the built-in camera using OpenGL, but it was a lot of work. (It does funhouse mirror type changes to faces - think "fat booth" live, plus lots of other effects.)

Read input from a JOptionPane.showInputDialog box

Your problem is that, if the user clicks cancel, operationType is null and thus throws a NullPointerException. I would suggest that you move

if (operationType.equalsIgnoreCase("Q")) 

to the beginning of the group of if statements, and then change it to


This will make the program exit just as if the user had selected the quit option when the cancel button is pushed.

Then, change all the rest of the ifs to else ifs. This way, once the program sees whether or not the input is null, it doesn't try to call anything else on operationType. This has the added benefit of making it more efficient - once the program sees that the input is one of the options, it won't bother checking it against the rest of them.

Uploading into folder in FTP?

The folder is part of the URL you set when you create request: "". If you use "" then the file will be uploaded to a folder named wibble.

You may need to first use a request with Method = WebRequestMethods.Ftp.MakeDirectory to make the wibble folder if it doesn't already exist.

Call japplet from jframe

First of all, Applets are designed to be run from within the context of a browser (or applet viewer), they're not really designed to be added into other containers.

Technically, you can add a applet to a frame like any other component, but personally, I wouldn't. The applet is expecting a lot more information to be available to it in order to allow it to work fully.

Instead, I would move all of the "application" content to a separate component, like a JPanel for example and simply move this between the applet or frame as required...

ps- You can use f.setLocationRelativeTo(null) to center the window on the screen ;)


You need to go back to basics. Unless you absolutely must have one, avoid applets until you understand the basics of Swing, case in point...

Within the constructor of GalzyTable2 you are doing...

JApplet app = new JApplet(); add(app); app.init(); app.start(); 

...Why are you adding another applet to an applet??

Case in point...

Within the main method, you are trying to add the instance of JFrame to itself...

f.getContentPane().add(f, button2); 

Instead, create yourself a class that extends from something like JPanel, add your UI logical to this, using compound components if required.

Then, add this panel to whatever top level container you need.

Take the time to read through Creating a GUI with Swing

Updated with example

import java.awt.BorderLayout; import java.awt.Dimension; import java.awt.EventQueue; import java.awt.event.ActionEvent; import javax.swing.ImageIcon; import javax.swing.JButton; import javax.swing.JFrame; import javax.swing.JPanel; import javax.swing.JScrollPane; import javax.swing.JTable; import javax.swing.UIManager; import javax.swing.UnsupportedLookAndFeelException;  public class GalaxyTable2 extends JPanel {      private static final int PREF_W = 700;     private static final int PREF_H = 600;      String[] columnNames                     = {"Phone Name", "Brief Description", "Picture", "price",                         "Buy"};  // Create image icons     ImageIcon Image1 = new ImageIcon(                     getClass().getResource("s1.png"));     ImageIcon Image2 = new ImageIcon(                     getClass().getResource("s2.png"));     ImageIcon Image3 = new ImageIcon(                     getClass().getResource("s3.png"));     ImageIcon Image4 = new ImageIcon(                     getClass().getResource("s4.png"));     ImageIcon Image5 = new ImageIcon(                     getClass().getResource("note.png"));     ImageIcon Image6 = new ImageIcon(                     getClass().getResource("note2.png"));     ImageIcon Image7 = new ImageIcon(                     getClass().getResource("note3.png"));      Object[][] rowData = {         {"Galaxy S", "3G Support,CPU 1GHz",             Image1, 120, false},         {"Galaxy S II", "3G Support,CPU 1.2GHz",             Image2, 170, false},         {"Galaxy S III", "3G Support,CPU 1.4GHz",             Image3, 205, false},         {"Galaxy S4", "4G Support,CPU 1.6GHz",             Image4, 230, false},         {"Galaxy Note", "4G Support,CPU 1.4GHz",             Image5, 190, false},         {"Galaxy Note2 II", "4G Support,CPU 1.6GHz",             Image6, 190, false},         {"Galaxy Note 3", "4G Support,CPU 2.3GHz",             Image7, 260, false},};      MyTable ss = new MyTable(                     rowData, columnNames);      // Create a table     JTable jTable1 = new JTable(ss);      public GalaxyTable2() {         jTable1.setRowHeight(70);          add(new JScrollPane(jTable1),                         BorderLayout.CENTER);          JPanel buttons = new JPanel();          JButton button = new JButton("Home");         buttons.add(button);         JButton button2 = new JButton("Confirm");         buttons.add(button2);          add(buttons, BorderLayout.SOUTH);     }      @Override      public Dimension getPreferredSize() {         return new Dimension(PREF_W, PREF_H);     }      public void actionPerformed(ActionEvent e) {         new AMainFrame7().setVisible(true);     }      public static void main(String[] args) {          EventQueue.invokeLater(new Runnable() {             @Override             public void run() {                 try {                     UIManager.setLookAndFeel(UIManager.getSystemLookAndFeelClassName());                 } catch (ClassNotFoundException | InstantiationException | IllegalAccessException | UnsupportedLookAndFeelException ex) {                     ex.printStackTrace();                 }                  JFrame frame = new JFrame("Testing");                 frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);                 frame.add(new GalaxyTable2());                 frame.pack();                 frame.setLocationRelativeTo(null);                 frame.setVisible(true);             }         });     } } 

You also seem to have a lack of understanding about how to use layout managers.

Take the time to read through Creating a GUI with Swing and Laying components out in a container

xlrd.biffh.XLRDError: Excel xlsx file; not supported

As noted in the release email, linked to from the release tweet and noted in large orange warning that appears on the front page of the documentation, and less orange, but still present, in the readme on the repository and the release on pypi:

xlrd has explicitly removed support for anything other than xls files.

In your case, the solution is to:

  • make sure you are on a recent version of Pandas, at least 1.0.1, and preferably the latest release. 1.2 will make his even clearer.
  • install openpyxl:
  • change your Pandas code to be:
    df1 = pd.read_excel(
         os.path.join(APP_PATH, "Data", "aug_latest.xlsm"),

Target class controller does not exist - Laravel 8

The way to define your routes in laravel 8 is either

// Using PHP callable syntax...
use App\Http\Controllers\HomeController;
Route::get('/', [HomeController::class, 'index']);


// Using string syntax...
Route::get('/', 'App\Http\Controllers\HomeController@index');

A resource route becomes

// Using PHP callable syntax...
use App\Http\Controllers\HomeController;
Route::resource('/', HomeController::class);

This means that in laravel 8, there is no automatic controller declaration prefixing by default.

If you want to stick to the old way, then you need to add a namespace property in the app\Providers\RouteServiceProvider.php and activate in the routes method.

Follow this image instructions below:

enter image description here

iPhone is not available. Please reconnect the device

If you are connecting it with a cable, clean the build folder, run it on the simulator, and then run it again immediately on your phone.

If you are using it without a cable, make sure the Wi-Fi connection is exactly the same on both your PC and your phone or turn the personal hotspot on your phone and connect your PC to the hotspot to make sure they're using the exact same connection.

DevTools failed to load SourceMap: Could not load content for chrome-extension

For me, the problem was caused not by the app in development itself but by the Chrome extension: React Developer Tool. I solved partially that by right-clicking the extension icon in the toolbar, clicking "manage extension" (I'm freely translating menu text here since my browser language is in Brazilian Portuguese), then enabling "Allow access to files URLs." But this measure fixed just some of the alerts.

I found issues in the react repo that suggests the cause is a bug in their extension and is planned to be corrected soon - see issues 20091 and 20075.

You can confirm is extension-related by accessing your app in an anonymous tab without any extension enabled.

error TS1086: An accessor cannot be declared in an ambient context in Angular 9

Adding skipLibCheck: true in compilerOptions inside tsconfig.json file fixed my issue.

"compilerOptions": {
   "skipLibCheck": true,

TS1086: An accessor cannot be declared in ambient context

In my case, mismatch of version of two libraries.

I am using angular 7.0.0 and installed

"@swimlane/ngx-dnd": "^8.0.0"

and this caused the problem. Reverting this library to

"@swimlane/ngx-dnd": "6.0.0"

worked for me.

Maven dependencies are failing with a 501 error

Try to hit the below URL in any browser. It will return 501

Please try with https. It will download a pom.xml file:

Please add it ( in the setting.xml file:

      <id>Central Maven repository</id>
      <name>Central Maven repository https</name>

Visual Studio Code PHP Intelephense Keep Showing Not Necessary Error

If you see this immediately after adding a new Vendor class, be sure to run the VScode command (control-shift-P) Index Workspace

Element implicitly has an 'any' type because expression of type 'string' can't be used to index

With out typescript error

    const formData = new FormData();
        var d =Object.values(newCategory)[i];

Invalid hook call. Hooks can only be called inside of the body of a function component

I have just started using hooks and I got the above warning when i was calling useEffect inside a function:

Then I have to move the useEffect outside of the function as belows:

 const onChangeRetypePassword = async value => {
  await setRePassword(value);
//previously useEffect was here

//useEffect outside of func 

 useEffect(() => {
  if (password !== rePassword) {

}, [rePassword]);

Hope it will be helpful to someone !

Typescript: No index signature with a parameter of type 'string' was found on type '{ "A": string; }

Don't Use Any, Use Generics

// bad
const _getKeyValue = (key: string) => (obj: object) => obj[key];
// better
const _getKeyValue_ = (key: string) => (obj: Record<string, any>) => obj[key];
// best
const getKeyValue = <T extends object, U extends keyof T>(key: U) => (obj: T) =>

Bad - the reason for the error is the object type is just an empty object by default. Therefore it isn't possible to use a string type to index {}.

Better - the reason the error disappears is because now we are telling the compiler the obj argument will be a collection of string/value (string/any) pairs. However, we are using the any type, so we can do better.

Best - T extends empty object. U extends the keys of T. Therefore U will always exist on T, therefore it can be used as a look up value.

Here is a full example:

I have switched the order of the generics (U extends keyof T now comes before T extends object) to highlight that order of generics is not important and you should select an order that makes the most sense for your function.

const getKeyValue = <U extends keyof T, T extends object>(key: U) => (obj: T) =>

interface User {
  name: string;
  age: number;

const user: User = {
  name: "John Smith",
  age: 20

const getUserName = getKeyValue<keyof User, User>("name")(user);

// => 'John Smith'

Alternative syntax

const getKeyValue = <T, K extends keyof T>(obj: T, key: K): T[K] => obj[key];

Access blocked by CORS policy: Response to preflight request doesn't pass access control check

You may need to config the CORS at Spring Boot side. Please add below class in your Project.

import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;

import org.springframework.context.annotation.Configuration;
import org.springframework.web.servlet.config.annotation.CorsRegistry;
import org.springframework.web.servlet.config.annotation.EnableWebMvc;
import org.springframework.web.servlet.config.annotation.ResourceHandlerRegistry;
import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;

public class WebConfig implements Filter,WebMvcConfigurer {

    public void addCorsMappings(CorsRegistry registry) {

    public void doFilter(ServletRequest req, ServletResponse res, FilterChain chain) {
      HttpServletResponse response = (HttpServletResponse) res;
      HttpServletRequest request = (HttpServletRequest) req;
      System.out.println("WebConfig; "+request.getRequestURI());
      response.setHeader("Access-Control-Allow-Origin", "*");
      response.setHeader("Access-Control-Allow-Methods", "POST, PUT, GET, OPTIONS, DELETE");
      response.setHeader("Access-Control-Allow-Headers", "Content-Type, Access-Control-Allow-Headers, Authorization, X-Requested-With,observe");
      response.setHeader("Access-Control-Max-Age", "3600");
      response.setHeader("Access-Control-Allow-Credentials", "true");
      response.setHeader("Access-Control-Expose-Headers", "Authorization");
      response.addHeader("Access-Control-Expose-Headers", "responseType");
      response.addHeader("Access-Control-Expose-Headers", "observe");
      System.out.println("Request Method: "+request.getMethod());
      if (!(request.getMethod().equalsIgnoreCase("OPTIONS"))) {
          try {
              chain.doFilter(req, res);
          } catch(Exception e) {
      } else {
          response.setHeader("Access-Control-Allow-Origin", "*");
          response.setHeader("Access-Control-Allow-Methods", "POST,GET,DELETE,PUT");
          response.setHeader("Access-Control-Max-Age", "3600");
          response.setHeader("Access-Control-Allow-Headers", "Access-Control-Expose-Headers"+"Authorization, content-type," +




To append Token to each request you can create one Interceptor as below.

import { Injectable } from '@angular/core';
import { HttpEvent, HttpHandler, HttpInterceptor, HttpRequest } from '@angular/common/http';
import { Observable } from 'rxjs';

export class AuthInterceptor implements HttpInterceptor {

  intercept(req: HttpRequest<any>, next: HttpHandler): Observable<HttpEvent<any>> {
    const token = window.localStorage.getItem('tokenKey'); // you probably want to store it in localStorage or something

    if (!token) {
      return next.handle(req);

    const req1 = req.clone({
      headers: req.headers.set('Authorization', `${token}`),

    return next.handle(req1);



Errors: Data path ".builders['app-shell']" should have required property 'class'

NONE of the above-given answers works for me.

My original goal was to fix the sometimes CONSTANT COMPILING of my project with VSCode.

I tried many, many ways, but NOTHING was working -- the project just WON'T COMPILIE!

Finally I found out what the problem here is:

I cloned the project from my company's repository, and all the code from there HAS TO go exactly with the versions of dependencies when the existing part of the project was coded.

In the end, I deleted the previously cloned project AGAIN (quite a few times), and cloned AGAIN (also a few times), and DID NOTHING BUT RAN "npm install", and everything started to work.

The lesson I learned here is that:

Sometimes you'll make the situation worse when you try to fix some problems (the one I had was the CONSTANT COMPILING of my project).

But it doesn't mean we cannot try to fix the problems. We can. But when everything becomes a mess, we'd better go with the original code.

Fortunately the CONSTANT COMPILING of my project happens only once a while, not all the time. It's not fixed, but I have to bear with it, otherwise my project won't even compile.

Why am I getting Unknown error in line 1 of pom.xml?

You must to upgrade the m2e connector. It's a known bug, but there is a solution:

  1. Into Eclipse click "Help" > "Install new Software..."

  2. Appears a window. In the "Install" window:

    2a. Into the input box "Work with", enter next site location and press Enter

    2b. Appears a lot of information into "Name" input Box. Select all the items

    2c. Click "Next" Button.

Finish the installation and restart Eclipse.

The POST method is not supported for this route. Supported methods: GET, HEAD. Laravel

There are multiple ways you can handle this:

  1. If you insist on using PUT you can change the form action to POST and add a hidden method_field that has a value PUTand a hidden csrf field (if you are using blade then you just need to add @csrf_field and {{ method_field('PUT') }}). This way the form would accept the request.

  2. You can simply change the route and form method to POST. It will work just fine since you are the one defining the route and not using the resource group.

The iOS Simulator deployment targets is set to 7.0, but the range of supported deployment target version for this platform is 8.0 to 12.1

Instead of specifying a deployment target in pod post install, you can delete the pod deployment target, which causes the deployment target to be inherited from the podfile platform.

You may need to run pod install for the effect to take place.

platform :ios, '12.0'

  post_install do |installer|
    installer.pods_project.targets.each do |target|
      target.build_configurations.each do |config|
        config.build_settings.delete 'IPHONEOS_DEPLOYMENT_TARGET'

Typescript: Type 'string | undefined' is not assignable to type 'string'

try to find out what the actual value is beforehand. If person has a valid name, assign it to name1, else assign undefined.

let name1: string = ( ? : undefined;

Typescript: Type X is missing the following properties from type Y length, pop, push, concat, and 26 more. [2740]

You have forgotten to mark the getProducts return type as an array. In your getProducts it says that it will return a single product. So change it to this:

public getProducts(): Observable<Product[]> {
    return this.http.get<Product[]>(`api/products/v1/`);

useState set method not reflecting change immediately

Much like setState in Class components created by extending React.Component or React.PureComponent, the state update using the updater provided by useState hook is also asynchronous, and will not be reflected immediately.

Also, the main issue here is not just the asynchronous nature but the fact that state values are used by functions based on their current closures, and state updates will reflect in the next re-render by which the existing closures are not affected, but new ones are created. Now in the current state, the values within hooks are obtained by existing closures, and when a re-render happens, the closures are updated based on whether the function is recreated again or not.

Even if you add a setTimeout the function, though the timeout will run after some time by which the re-render would have happened, the setTimeout will still use the value from its previous closure and not the updated one.

console.log(movies) // movies here will not be updated

If you want to perform an action on state update, you need to use the useEffect hook, much like using componentDidUpdate in class components since the setter returned by useState doesn't have a callback pattern

useEffect(() => {
    // action on update of movies
}, [movies]);

As far as the syntax to update state is concerned, setMovies(result) will replace the previous movies value in the state with those available from the async request.

However, if you want to merge the response with the previously existing values, you must use the callback syntax of state updation along with the correct use of spread syntax like

setMovies(prevMovies => ([...prevMovies, ...result]));

Can't perform a React state update on an unmounted component

try changing setDivSizeThrottleable to

this.setDivSizeThrottleable = throttle(
  () => {
    if (this.isComponentMounted) {
        pdfWidth: this.pdfWrapper!.getBoundingClientRect().width - 5,
  { leading: false, trailing: true }

Android Gradle 5.0 Update:Cause: org.jetbrains.plugins.gradle.tooling.util

For anybody facing a similar issue at this point in time, all you need to do is update your Android Studio to the latest version

TypeScript and React - children type?

This has always worked for me:

type Props = {
  children: JSX.Element;

ERROR in The Angular Compiler requires TypeScript >=3.1.1 and <3.2.0 but 3.2.1 was found instead

In my case below command worked for windows. It will install latest required version between 3.1.1 and 3.2.0. Depending on OS use either double or single quotes

npm install typescript@">=3.1.1 <3.2.0" 

React Hook Warnings for async function in useEffect: useEffect function must return a cleanup function or nothing

I read through this question, and feel the best way to implement useEffect is not mentioned in the answers. Let's say you have a network call, and would like to do something once you have the response. For the sake of simplicity, let's store the network response in a state variable. One might want to use action/reducer to update the store with the network response.

const [data, setData] = useState(null);

/* This would be called on initial page load */
    .then(data => {
    .catch(err => {
        /* perform error handling if desired */
}, [])

/* This would be called when store/state data is updated */
    if (data) {
        setPosts( => {
            /* do what you want */
}, [data]);

Reference =>

Xcode 10.2.1 Command PhaseScriptExecution failed with a nonzero exit code

I tried most of above. I was developing in Flutter so what worked for me was pub cache repair.

FATAL ERROR: Ineffective mark-compacts near heap limit Allocation failed - JavaScript heap out of memory in ionic 3

same issue on centos server 7, but this solved my problem:

node --max-old-space-size=X node_modules/@angular/cli/bin/ng build --prod

Where X = (2048 or 4096 or 8192 o..) is the value of memory

A fatal error occurred while creating a TLS client credential. The internal error state is 10013

Basically we had to enable TLS 1.2 for .NET 4.x. Making this registry changed worked for me, and stopped the event log filling up with the Schannel error.

More information on the answer can be found here

Linked Info Summary

Enable TLS 1.2 at the system (SCHANNEL) level:

Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.2]
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.2\Client]
[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\SecurityProviders\SCHANNEL\Protocols\TLS 1.2\Server]

(equivalent keys are probably also available for other TLS versions)

Tell .NET Framework to use the system TLS versions:

Windows Registry Editor Version 5.00

This may not be desirable for edge cases where .NET Framework 4.x applications need to have different protocols enabled and disabled than the OS does.

How to set width of mat-table column in angular?

using css we can adjust specific column width which i put in below code.


 width: 100%;

.mat-column-username {
  word-wrap: break-word !important;
  white-space: unset !important;
  flex: 0 0 28% !important;
  width: 28% !important;
  overflow-wrap: break-word;
  word-wrap: break-word;

  word-break: break-word;

  -ms-hyphens: auto;
  -moz-hyphens: auto;
  -webkit-hyphens: auto;
  hyphens: auto;

.mat-column-emailid {
  word-wrap: break-word !important;
  white-space: unset !important;
  flex: 0 0 25% !important;
  width: 25% !important;
  overflow-wrap: break-word;
  word-wrap: break-word;

  word-break: break-word;

  -ms-hyphens: auto;
  -moz-hyphens: auto;
  -webkit-hyphens: auto;
  hyphens: auto;

.mat-column-contactno {
  word-wrap: break-word !important;
  white-space: unset !important;
  flex: 0 0 17% !important;
  width: 17% !important;
  overflow-wrap: break-word;
  word-wrap: break-word;

  word-break: break-word;

  -ms-hyphens: auto;
  -moz-hyphens: auto;
  -webkit-hyphens: auto;
  hyphens: auto;

.mat-column-userimage {
  word-wrap: break-word !important;
  white-space: unset !important;
  flex: 0 0 8% !important;
  width: 8% !important;
  overflow-wrap: break-word;
  word-wrap: break-word;

  word-break: break-word;

  -ms-hyphens: auto;
  -moz-hyphens: auto;
  -webkit-hyphens: auto;
  hyphens: auto;

.mat-column-userActivity {
  word-wrap: break-word !important;
  white-space: unset !important;
  flex: 0 0 10% !important;
  width: 10% !important;
  overflow-wrap: break-word;
  word-wrap: break-word;

  word-break: break-word;

  -ms-hyphens: auto;
  -moz-hyphens: auto;
  -webkit-hyphens: auto;
  hyphens: auto;

IntelliJ can't recognize JavaFX 11 with OpenJDK 11

The issue that JavaFX is no longer part of JDK 11. The following solution works using IntelliJ (haven't tried it with NetBeans):

  1. Add JavaFX Global Library as a dependency:

    Settings -> Project Structure -> Module. In module go to the Dependencies tab, and click the add "+" sign -> Library -> Java-> choose JavaFX from the list and click Add Selected, then Apply settings.

  2. Right click source file (src) in your JavaFX project, and create a new file. Inside the file write the following code :

    module YourProjectName { 
        requires javafx.fxml;
        requires javafx.controls;
        opens sample;

    These 2 steps will solve all your issues with JavaFX, I assure you.

Reference : There's a You Tube tutorial made by The Learn Programming channel, will explain all the details above in just 5 minutes. I also recommend watching it to solve your problem:

What is "not assignable to parameter of type never" error in typescript?

You need to type result to an array of string const result: string[] = [];.

Support for the experimental syntax 'classProperties' isn't currently enabled

I created a symlink for src/components -> ../../components that caused npm start to go nuts and stop interpreting src/components/*.js as jsx, thus giving that same error. All instructions to fix it from official babel were useless. When I copied back the components directory everything was BACK TO NORMAL!

How to convert string to boolean in typescript Angular 4

In your scenario, converting a string to a boolean can be done via something like someString === 'true' (as was already answered).

However, let me try to address your main issue: dealing with the local storage.

The local storage only supports strings as values; a good way of using it would thus be to always serialise your data as a string before storing it in the storage, and reversing the process when fetching it.

A possibly decent format for serialising your data in is JSON, since it is very easy to deal with in JavaScript.

The following functions could thus be used to interact with local storage, provided that your data can be serialised into JSON.

function setItemInStorage(key, item) {
  localStorage.setItem(key, JSON.stringify(item));

function getItemFromStorage(key) {
  return JSON.parse(localStorage.getItem(key));

Your example could then be rewritten as:

setItemInStorage('CheckOutPageReload', [this.btnLoginNumOne, this.btnLoginEdit]);


if (getItemFromStorage('CheckOutPageReload')) {
  const pageLoadParams = getItemFromStorage('CheckOutPageReload');
  this.btnLoginNumOne = pageLoadParams[0];
  this.btnLoginEdit = pageLoadParams[1];

What is the Record type in typescript?

A Record lets you create a new type from a Union. The values in the Union are used as attributes of the new type.

For example, say I have a Union like this:

type CatNames = "miffy" | "boris" | "mordred";

Now I want to create an object that contains information about all the cats, I can create a new type using the values in the CatName Union as keys.

type CatList = Record<CatNames, {age: number}>

If I want to satisfy this CatList, I must create an object like this:

const cats:CatList = {
  miffy: { age:99 },
  boris: { age:16 },
  mordred: { age:600 }

You get very strong type safety:

  • If I forget a cat, I get an error.
  • If I add a cat that's not allowed, I get an error.
  • If I later change CatNames, I get an error. This is especially useful because CatNames is likely imported from another file, and likely used in many places.

Real-world React example.

I used this recently to create a Status component. The component would receive a status prop, and then render an icon. I've simplified the code quite a lot here for illustrative purposes

I had a union like this:

type Statuses = "failed" | "complete";

I used this to create an object like this:

const icons: Record<
  { iconType: IconTypes; iconColor: IconColors }
> = {
  failed: {
    iconType: "warning",
    iconColor: "red"
  complete: {
    iconType: "check",
    iconColor: "green"

I could then render by destructuring an element from the object into props, like so:

const Status = ({status}) => <Icon {...icons[status]} />

If the Statuses union is later extended or changed, I know my Status component will fail to compile and I'll get an error that I can fix immediately. This allows me to add additional error states to the app.

Note that the actual app had dozens of error states that were referenced in multiple places, so this type safety was extremely useful.

Find the smallest positive integer that does not occur in a given sequence

I've not seen a C# solution that uses Linq yet... the following is the simplest way (I think) to get 100% pass on this test:

using System;
using System.Linq;

class Solution {
    public int solution(int[] A) => Enumerable.Range(1, 100001).Except(A).Min();

However, I should note that whilst the above is simple, and will get 100% pass on the test, it's not the most efficient. For a more efficient Linq solution, something like the following will work better:

using System;
using System.Collections.Generic;

public static int solution(int[] A)
    var set = new HashSet<int>(A);

    return Enumerable.Range(1, A.Length + 1).First(i => !set.Contains(i));

Under which circumstances textAlign property works in Flutter?

textAlign property only works when there is a more space left for the Text's content. Below are 2 examples which shows when textAlign has impact and when not.

No impact

For instance, in this example, it won't have any impact because there is no extra space for the content of the Text.

  textAlign: TextAlign.end, // no impact

enter image description here

Has impact

If you wrap it in a Container and provide extra width such that it has more extra space.

  width: 200,
  child: Text(
    textAlign: TextAlign.end, // has impact

enter image description here

Deprecated Gradle features were used in this build, making it incompatible with Gradle 5.0

Solution for the issue: deprecated gradle features were used in this build making it incompatible with gradle 6.0. android studio This provided solution worked for me.

First change the classpath in dependencies of build.gradle of your project From: classpath '' To: classpath ''

Then make changes in the file this file exists in the Project's gradle>wrapper folder From: distributionUrl=https\:// To: distributionUrl=https\://

Then Sync your gradle.

Confirm password validation in Angular 6

This question could be solved with a combination of these two answers: and

So first of all, you would need a custom validator for checking the passwords, that could look like this:

checkPasswords(group: FormGroup) { // here we have the 'passwords' group
  const password = group.get('password').value;
  const confirmPassword = group.get('confirmPassword').value;

  return password === confirmPassword ? null : { notSame: true }     

and you would create a formgroup for your fields, instead of just two form controls, then mark that custom validator for your form group:

this.myForm ={
  password: ['', [Validators.required]],
  confirmPassword: ['']
}, { validators: this.checkPasswords })

and then as mentioned in other answer, the mat-error only shows if a FormControl is invalid, so you need an error state matcher:

export class MyErrorStateMatcher implements ErrorStateMatcher {
  isErrorState(control: FormControl | null, form: FormGroupDirective | NgForm | null): boolean {
    const invalidCtrl = !!(control?.invalid && control?.parent?.dirty);
    const invalidParent = !!(control?.parent?.invalid && control?.parent?.dirty);

    return invalidCtrl || invalidParent;

in the above you can tweak when to show error message. I would only show message when the password field is touched. Also I would like above, remove the required validator from the confirmPassword field, since the form is not valid anyway if passwords do not match.

Then in component, create a new ErrorStateMatcher:

matcher = new MyErrorStateMatcher();

Finally, the template would look like this:

<form [formGroup]="myForm">
    <input matInput placeholder="New password" formControlName="password" required>
    <mat-error *ngIf="myForm.hasError('required', 'password')">
      Please enter your new password

    <input matInput placeholder="Confirm password" formControlName="confirmPassword" [errorStateMatcher]="matcher">
    <mat-error *ngIf="myForm.hasError('notSame')">
      Passwords do not match

Here's a demo for you with the above code: StackBlitz

Rounded Corners Image in Flutter

Using ClipRRect you need to hardcode BorderRadius, so if you need complete circular stuff, use ClipOval instead.

    height: 100,
    width: 100,
    fit: BoxFit.cover,

Couldn't process file resx due to its being in the Internet or Restricted zone or having the mark of the web on the file

None of these answers worked for me, I had to do the following:

  1. Start Menu > type 'Internet Options'.
  2. Select Local intranet zone on the Security tab then click the Sites button
  3. Click Advanced button
  4. Enter file://[computer name]
  5. Make sure 'Require server verification...' is unticked


Failed to configure a DataSource: 'url' attribute is not specified and no embedded datasource could be configured

Just add : @SpringBootApplication(exclude = {DataSourceAutoConfiguration.class }) works for me.

I was getting same error I tried with @EnableAutoConfiguration(exclude=...) didn't work.

How to use `@ts-ignore` for a block

If you don't need typesafe, just bring block to a new separated file and change the extension to .js,.jsx

Everytime I run gulp anything, I get a assertion error. - Task function must be specified

I get the same error when using Gulp. The solution is to switch to Gulp version 3.9.1, both for the local version and the CLI version.

sudo npm install -g [email protected]

Run in the project's folder

npm install [email protected]

Handling back button in Android Navigation Component

If you are using BaseFragment for your app then you can add onBackPressedDispatcher to your base fragment.

//Make a BaseFragment for all your fragments
abstract class BaseFragment : Fragment() {

private lateinit var callback: OnBackPressedCallback

 * SetBackButtonDispatcher in OnCreate

override fun onCreate(savedInstanceState: Bundle?) {

 * Adding BackButtonDispatcher callback to activity
private fun setBackButtonDispatcher() {
    callback = object : OnBackPressedCallback(true) {
        override fun handleOnBackPressed() {
    requireActivity().onBackPressedDispatcher.addCallback(this, callback)

 * Override this method into your fragment to handleBackButton
  open fun onBackPressed() {


Override onBackPressed() in your fragment by extending basefragment

//How to use this into your fragment
class MyFragment() : BaseFragment(){

private lateinit var mView: View

override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?, savedInstanceState: Bundle?): View? {
    mView = inflater.inflate(R.layout.fragment_my, container, false)
    return mView.rootView

override fun onBackPressed() {
    //Write your code here on back pressed.


Select default option value from typescript angular 6

<select class="form-control" [value]="defaultSelectedCurrency" formControlName="currency">
<option *ngFor="let item of currency" [value]="item.value" [selected]="item.isSelected">{{item.key}}</option>

currency = [
    { key: 'USD', value: 'USD', isSelected: true },
    { key: 'AUD', value: 'AUD', isSelected: false }
  defaultSelectedCurrency: string;

 ngOnInit() {
    this.defaultSelectedCurrency = this.currency[0].value;

Vue.js get selected option on @change

Use v-model to bind the value of selected option's value. Here is an example.

<select name="LeaveType" @change="onChange($event)" class="form-control" v-model="key">
   <option value="1">Annual Leave/ Off-Day</option>
   <option value="2">On Demand Leave</option>
var vm = new Vue({
    data: {
        key: ""
    methods: {
        onChange(event) {

More reference can been seen from here.

Google Maps shows "For development purposes only"

Now google maps is free for development only.

If you want to use map free like earlier, then create an account with valid details (billing, payment, etc.) google gives $200 MONTHLY CREDIT Which is EQUIVALENT To FREE USAGE

For more details please see Googles new price details: google map new pricing

Also see the old price details: Old one

How to add image in Flutter

The problem is in your pubspec.yaml, here you need to delete the last comma.

uses-material-design: true,

Authentication plugin 'caching_sha2_password' is not supported

I had this same issue but my resolution was different because this didn't completely work.

I found this on a GitHub forum - copy and paste this into your terminal. You don't have to change your password; it can be the exact same.

ALTER USER 'root'@'localhost' IDENTIFIED WITH mysql_native_password BY '{NewPassword}';

Flutter Circle Design

Try This!


I have added 5 circles you can add more. And instead of RaisedButton use InkResponse.

import 'package:flutter/material.dart';

void main() {
  runApp(new MaterialApp(home: new ExampleWidget()));

class ExampleWidget extends StatelessWidget {
  Widget build(BuildContext context) {
    Widget bigCircle = new Container(
      width: 300.0,
      height: 300.0,
      decoration: new BoxDecoration(

    return new Material(
      child: new Center(
        child: new Stack(
          children: <Widget>[
            new Positioned(
              child: new CircleButton(onTap: () => print("Cool"), iconData: Icons.favorite_border),
              top: 10.0,
              left: 130.0,
            new Positioned(
              child: new CircleButton(onTap: () => print("Cool"), iconData: Icons.timer),
              top: 120.0,
              left: 10.0,
            new Positioned(
              child: new CircleButton(onTap: () => print("Cool"), iconData:,
              top: 120.0,
              right: 10.0,
            new Positioned(
              child: new CircleButton(onTap: () => print("Cool"), iconData: Icons.local_pizza),
              top: 240.0,
              left: 130.0,
            new Positioned(
              child: new CircleButton(onTap: () => print("Cool"), iconData: Icons.satellite),
              top: 120.0,
              left: 130.0,

class CircleButton extends StatelessWidget {
  final GestureTapCallback onTap;
  final IconData iconData;

  const CircleButton({Key key, this.onTap, this.iconData}) : super(key: key);

  Widget build(BuildContext context) {
    double size = 50.0;

    return new InkResponse(
      onTap: onTap,
      child: new Container(
        width: size,
        height: size,
        decoration: new BoxDecoration(
          color: Colors.white,
        child: new Icon(

java.lang.NoClassDefFoundError:failed resolution of :Lorg/apache/http/ProtocolVersion

This link android-9.0-changes-28-->Apache HTTP client deprecation explains reason for adding the following to your AndroidManifest.xml:

<uses-library android:name="org.apache.http.legacy" android:required="false"/>

With Android 6.0, we removed support for the Apache HTTP client. Beginning with Android 9, that library is removed from the bootclasspath and is not available to apps by default.

Can not find module “@angular-devkit/build-angular”

If you are updating from angular 7 to angular 8 then do this

ng update @angular/cli @angular/core

for more information read here

Could not find module "@angular-devkit/build-angular"

I am facing the same issue since 2 days.

ng -v :6.0.8
node -v :8.11.2
npm -v :6.1.0

Make sure you are in the folder where angular.json is installed. Get into that and type ng serve. If the issue still arises, then you are having only dependencies installed in node_modules. Type the following, and it will work:

npm i --only=dev

Can't bind to 'dataSource' since it isn't a known property of 'table'

Remember to add MatTableModule in your app.module's imports i.e.

In Angular 9+

import { MatTableModule } from '@angular/material/table'  

  imports: [
    // ...
    // ...

Less than Angular 9

import { MatTableModule } from '@angular/material'  

  imports: [
    // ...
    // ...

ERROR Error: StaticInjectorError(AppModule)[UserformService -> HttpClient]:

Simply i have import in appmodule.ts

import { HttpClientModule } from '@angular/common/http';
  imports: [
     HttpClientModule  <<<this 

My problem resolved

Importing json file in TypeScript

Often in Node.js applications a .json is needed. With TypeScript 2.9, --resolveJsonModule allows for importing, extracting types from and generating .json files.

Example #

// tsconfig.json_x000D_
    "compilerOptions": {_x000D_
        "module": "commonjs",_x000D_
        "resolveJsonModule": true,_x000D_
        "esModuleInterop": true_x000D_
// .ts_x000D_
import settings from "./settings.json";_x000D_
settings.debug === true;  // OK_x000D_
settings.dry === 2;  // Error: Operator '===' cannot be applied boolean and number_x000D_
// settings.json_x000D_
    "repo": "TypeScript",_x000D_
    "dry": false,_x000D_
    "debug": false_x000D_
_x000D_ by:

Angular - "has no exported member 'Observable'"

I had a similar issue. Back-revving RXJS from 6.x to the latest 5.x release fixed it for Angular 5.2.x.

Open package.json.

Change "rxjs": "^6.0.0", to "rxjs": "^5.5.10",

run npm update

AttributeError: Module Pip has no attribute 'main'

This helps me,

curl -o

If you are using python3 and not set it default. do this,


It works for me.

How to open Android Device Monitor in latest Android Studio 3.1

To get it to work I had to switch to Java 8 from Java 10 (In my system PATH variable) then go to C:\Users\Alex\AppData\Local\Android\Sdk\tools\lib\monitor-x86_64 and run monitor.exe.

Failed to auto-configure a DataSource: 'spring.datasource.url' is not specified

your dependency based on data is trying to find their respective entities which one has not been created, comments the dependencies based on data and runs the app again.

<!-- <dependency> -->
        <!-- <groupId>org.springframework.boot</groupId> -->
        <!-- <artifactId>spring-boot-starter-data-jpa</artifactId> -->
        <!-- </dependency> -->

Round button with text and icon in flutter

If you need a button like this:

You can use RaisedButton and use the child property to do this. You need to add a Row and inside row you can add a Text widget and an Icon Widget to achieve this. If you want to use png image, you can use similar widget to achieve this.

    onPressed: () {},
    color: Theme.of(context).accentColor,
    child: Padding(
      padding: EdgeInsets.fromLTRB(
          SizeConfig.safeBlockHorizontal * 5,
          SizeConfig.safeBlockHorizontal * 5,
      child: Row(
        mainAxisAlignment: MainAxisAlignment.spaceBetween,
        children: <Widget>[
            style: TextStyle(
              fontSize: 20,
              fontWeight: FontWeight.w700,
              color: Colors.white,
            color: Colors.white,

Converting a POSTMAN request to Curl

enter image description here

You can see the button "Code" in the attached screenshot, press it and you can get your code in many different languages including PHP cURL

enter image description here

What could cause an error related to npm not being able to find a file? No contents in my node_modules subfolder. Why is that?

In my case, this error happened with a new project.

none of the proposed solutions here worked, so I simply reinstalled all the packages and started working correctly.

Unable to compile simple Java 10 / Java 11 project with Maven

Boosting your maven-compiler-plugin to 3.8.0 seems to be necessary but not sufficient. If you're still having problems, you should also make sure your JAVA_HOME environment variable is set to Java 10 (or 11) if you're running from the command line. (The error message you get won't tell you this.) Or if you're running from an IDE, you need to make sure it is set to run maven with your current JDK.

Getting "TypeError: failed to fetch" when the request hasn't actually failed

Note that there is an unrelated issue in your code but that could bite you later: you should return res.json() or you will not catch any error occurring in JSON parsing or your own function processing data.

Back to your error: You cannot have a TypeError: failed to fetch with a successful request. You probably have another request (check your "network" panel to see all of them) that breaks and causes this error to be logged. Also, maybe check "Preserve log" to be sure the panel is not cleared by any indelicate redirection. Sometimes I happen to have a persistent "console" panel, and a cleared "network" panel that leads me to have error in console which is actually unrelated to the visible requests. You should check that.

Or you (but that would be vicious) actually have a hardcoded console.log('TypeError: failed to fetch') in your final .catch ;) and the error is in reality in your .then() but it's hard to believe.

Error:(9, 5) error: resource android:attr/dialogCornerRadius not found

Had the same issue while working on an application with several modules, check to make sure as you increase the compileSdkVersion and targetSdkVersion to 28+ values in a module you also do for the others.

A module was running on compileSdkVersion 29 and targetSdkVersion 29 while a second module of the application was running on compileSdkVersion 27 and targetSdkVersion 27.

Changing the second module to also compile for and target SDK version 29 resolved my issue. Hope this helps someone.

How to remove whitespace from a string in typescript?

The trim() method removes whitespace from both sides of a string.

To remove all the spaces from the string use .replace(/\s/g, "")

 this.maintabinfo = this.inner_view_data.replace(/\s/g, "").toLowerCase();

After Spring Boot 2.0 migration: jdbcUrl is required with driverClassName

As this post gets a bit of popularity I edited it a bit. Spring Boot 2.x.x changed default JDBC connection pool from Tomcat to faster and better HikariCP. Here comes incompatibility, because HikariCP uses different property of jdbc url. There are two ways how to handle it:


There is very good explanation and workaround in spring docs:

Also, if you happen to have Hikari on the classpath, this basic setup does not work, because Hikari has no url property (but does have a jdbcUrl property). In that case, you must rewrite your configuration as follows:



There is also how-to in the docs how to get it working from "both worlds". It would look like below. ConfigurationProperties bean would do "conversion" for jdbcUrl from app.datasource.url

public class DatabaseConfig {
    public DataSourceProperties dataSourceProperties() {
        return new DataSourceProperties();

    public HikariDataSource dataSource(DataSourceProperties properties) {
        return properties.initializeDataSourceBuilder().type(HikariDataSource.class)

Flutter: how to make a TextField with HintText but no Underline?

new flutter sdk since after integration of web and desktop support you need to specify individually like this

    keyboardType: inputType,
    decoration: new InputDecoration(
        border: InputBorder.none,
        focusedBorder: InputBorder.none,
        enabledBorder: InputBorder.none,
        errorBorder: InputBorder.none,
        disabledBorder: InputBorder.none,
            EdgeInsets.only(left: 15, bottom: 11, top: 11, right: 15),
        hintText: "Hint here"),

'ls' is not recognized as an internal or external command, operable program or batch file

If you want to use Unix shell commands on Windows, you can use Windows Powershell, which includes both Windows and Unix commands as aliases. You can find more info on it in the documentation.

PowerShell supports aliases to refer to commands by alternate names. Aliasing allows users with experience in other shells to use common command names that they already know for similar operations in PowerShell.

The PowerShell equivalents may not produce identical results. However, the results are close enough that users can do work without knowing the PowerShell command name.

Angular 5, HTML, boolean on checkbox is checked

Here is my answer,

In row.model.ts

export interface Row {
   otherProperty : type;
   checked : bool;
   otherProperty : type;

In .html

<tr class="even" *ngFor="let item of rows">
   <input [checked]="item.checked" type="checkbox">

In .ts

rows : Row[] = [];

update the rows in component.ts

ERROR Source option 1.5 is no longer supported. Use 1.6 or later

This error might be also for plugin versions. You can fix it in the .POM file like the followings:


How to avoid the "Windows Defender SmartScreen prevented an unrecognized app from starting warning"

If you have a standard code signing certificate, some time will be needed for your application to build trust. Microsoft affirms that an Extended Validation (EV) Code Signing Certificate allows us to skip this period of trust-building. According to Microsoft, extended validation certificates allow the developer to immediately establish a reputation with SmartScreen. Otherwise, the users will see a warning like "Windows Defender SmartScreen prevented an unrecognized app from starting. Running this app might put your PC at risk.", with the two buttons: "Run anyway" and "Don't run".

Another Microsoft resource states the following (quote): "Although not required, programs signed by an EV code signing certificate can immediately establish a reputation with SmartScreen reputation services even if no prior reputation exists for that file or publisher. EV code signing certificates also have a unique identifier which makes it easier to maintain reputation across certificate renewals."

My experience is as follows. Since 2005, we have been using regular (non-EV) code signing certificates to sign .MSI, .EXE and .DLL files with time stamps, and there has never been a problem with SmartScreen until 2018, when there was just one case when it took 3 days for a beta version of our application to build trust since we have released it to beta testers, and it was in the middle of certificate validity period. I don't know what SmartScreen might not like in that specific version of our application, but there have been no SmartScreen complaints since then. Therefore, if your certificate is a non-EV, it is a signed application (such as an .MSI file) that will build trust over time, not a certificate. For example, a certificate can be issued a few months ago and used to sign many files, but for each signed file you publish, it may take a few days for SmartScreen to stop complaining about the file after publishing, as was in our case in 2018.

As a conclusion, to avoid the warning completely, i.e. prevent it from happening even suddenly, you need an Extended Validation (EV) code signing certificate.

js 'types' can only be used in a .ts file - Visual Studio Code using @ts-check

Just default the variable to the expected type:

(number=1) => ...
(number=1.0) => ...
(string='str') ...

Still getting warning : Configuration 'compile' is obsolete and has been replaced with 'implementation' indicates that plugins sometimes can introduce "compile" dependencies and that's what triggers the warning. Probably just easiest to star that issue and wait until they fix it to point out which plugins are causing the issue.

Python Pandas - Find difference between two data frames

Using the lambda function you can filter the rows with _merge value “left_only” to get all the rows in df1 which are missing from df2

df3 = df1.merge(df2, how = 'outer' ,indicator=True).loc[lambda x :x['_merge']=='left_only']

How do I deal with installing peer dependencies in Angular CLI?

Peer dependency warnings, more often than not, can be ignored. The only time you will want to take action is if the peer dependency is missing entirely, or if the version of a peer dependency is higher than the version you have installed.

Let's take this warning as an example:

npm WARN @angular/[email protected] requires a peer of @angular/[email protected] but none is installed. You must install peer dependencies yourself.

With Angular, you would like the versions you are using to be consistent across all packages. If there are any incompatible versions, change the versions in your package.json, and run npm install so they are all synced up. I tend to keep my versions for Angular at the latest version, but you will need to make sure your versions are consistent for whatever version of Angular you require (which may not be the most recent).

In a situation like this:

npm WARN [email protected] requires a peer of @angular/core@^2.4.0 || ^4.0.0 but none is installed. You must install peer dependencies yourself.

If you are working with a version of Angular that is higher than 4.0.0, then you will likely have no issues. Nothing to do about this one then. If you are using an Angular version under 2.4.0, then you need to bring your version up. Update the package.json, and run npm install, or run npm install for the specific version you need. Like this:

npm install @angular/[email protected] --save

You can leave out the --save if you are running npm 5.0.0 or higher, that version saves the package in the dependencies section of the package.json automatically.

In this situation:

npm WARN optional SKIPPING OPTIONAL DEPENDENCY: [email protected] (node_modules\fsevents): npm WARN notsup SKIPPING OPTIONAL DEPENDENCY: Unsupported platform for [email protected]: wanted {"os":"darwin","arch":"any"} (current: {"os":"win32","arch":"x64"})

You are running Windows, and fsevent requires OSX. This warning can be ignored.

Hope this helps, and have fun learning Angular!

Failed linking file resources

This similar error may also show if you have deleted an Activity java file previously and have not deleted the corresponding xml layout file.

Delete the xml file for the deleted Activity java file and Clean or Rebuild the project.

The reason behind it may be because of the mismatch of context in the xml. (This might occur if you are copy-pasting an xml layout code) Match the tools:context to the java file of the activity.


How to Set/Update State of StatefulWidget from other StatefulWidget in Flutter?

Although most of these previous answers will work, I suggest you explore the provider or BloC architectures, both of which have been recommended by Google.

In short, the latter will create a stream that reports to widgets in the widget tree whenever a change in the state happens and it updates all relevant views regardless of where it is updated from.

Here is a good overview you can read to learn more about the subject:

ASP.NET Core - Swashbuckle not creating swagger.json file

You might forgetting to include.. StartUp.cs/Configure()


Check if you forgot to include, you error must be remove.

ReferenceError: fetch is not defined

It seems fetch support URL scheme with "http" or "https" for CORS request.

Install node fetch library npm install node-fetch, read the file and parse to json.

const fs = require('fs')
const readJson = filename => {
  return new Promise((resolve, reject) => {
    if (filename.toLowerCase().endsWith(".json")) {
      fs.readFile(filename, (err, data) => {
        if (err) {
    else {
      reject(new Error("Invalid filetype, <*.json> required."))

// usage
const filename = "../data.json"
readJson(filename).then(data => console.log(data)).catch(err => console.log(err.message))

Anaconda / Python: Change Anaconda Prompt User Path

In both: Anaconda prompt and the old cmd.exe, you change your directory by first changing to the drive you want, by simply writing its name followed by a ':', exe: F: , which will take you to the drive named 'F' on your machine. Then using the command cd to navigate your way inside that drive as you normally would.

document.getElementById replacement in angular4 / typescript?

You can tag your DOM element using #someTag, then get it with @ViewChild('someTag').

See complete example:

import {AfterViewInit, Component, ElementRef, ViewChild} from '@angular/core';

    selector: 'app',
    template: `
        <div #myDiv>Some text</div>
export class AppComponent implements AfterViewInit {
    @ViewChild('myDiv') myDiv: ElementRef;

    ngAfterViewInit() {

console.log will print Some text.

How to iterate using ngFor loop Map containing key as string and values as map iteration

This is because map.keys() returns an iterator. *ngFor can work with iterators, but the map.keys() will be called on every change detection cycle, thus producing a new reference to the array, resulting in the error you see. By the way, this is not always an error as you would traditionally think of it; it may even not break any of your functionality, but suggests that you have a data model which seems to behave in an insane way - changing faster than the change detector checks its value.

If you do no want to convert the map to an array in your component, you may use the pipe suggested in the comments. There is no other workaround, as it seems.

P.S. This error will not be shown in the production mode, as it is more like a very strict warning, rather than an actual error, but still, this is not a good idea to leave it be.

Read response headers from API response - Angular 5 + TypeScript

In my case in the POST response I want to have the authorization header because I was having the JWT Token in it. So what I read from this post is the header I we want should be added as an Expose Header from the back-end. So what I did was added the Authorization header to my Exposed Header like this in my filter class.

response.addHeader("Access-Control-Expose-Headers", "Authorization");
response.addHeader("Access-Control-Allow-Headers", "Authorization, X-PINGOTHER, Origin, X-Requested-With, Content-Type, Accept, X-Custom-header");
response.addHeader(HEADER_STRING, TOKEN_PREFIX + token); // HEADER_STRING == Authorization

And at my Angular Side

In the Component.

this.authenticationService.login(, this.f.password.value)
    (data: HttpResponse<any>) => {
    error => {
      this.loading = false;

At my Service Side.

return<any>(Constants.BASE_URL + 'login', {username: username, password: password},
  {observe: 'response' as 'body'})
  .pipe(map(user => {
       return user;

How to add icon to mat-icon-button

My preference is to utilize the inline attribute. This will cause the icon to correctly scale with the size of the button.

    <button mat-button>
      <mat-icon inline=true>local_movies</mat-icon>

    <!-- Link button -->
    <a mat-flat-button color="accent" routerLink="/create"><mat-icon inline=true>add</mat-icon> Create</a>

I add this to my styles.css to:

  • solve the vertical alignment problem of the icon inside the button
  • material icon fonts are always a little too small compared to button text
button.mat-button .mat-icon,
a.mat-button .mat-icon,
a.mat-raised-button .mat-icon,
a.mat-flat-button .mat-icon,
a.mat-stroked-button .mat-icon {
  vertical-align: top;
  font-size: 1.25em;

'mat-form-field' is not a known element - Angular 5 & Material2

the problem is in the MatInputModule:

exports: [

ng serve not detecting file changes automatically

I had the same issue and figured out, that some files in my Angular Project were only permitted to the user root and to the corresponding group root. You can check that with ls -hal. I fixed it by setting both to the user I used the system with.

You can do that with: chown -R username:groupname *

If you want to know what exactly this command does, checkout:

Docker: Got permission denied while trying to connect to the Docker daemon socket at unix:///var/run/docker.sock

I`m using the official jenkins docker image ( but I think this solution is applicable to most use cases where we want to run Docker inside a Docker container.

The recommended way for using Docker inside a Docker container, is to use the Docker deamon of the host system. Good article regarding that:

The secret to handle the permission issue, which this question is about, is to add permissions for the user of the container inside the container, not the host system. Only root user has permissions to do that by default, so

docker exec -it -u root <container-name> bash
usermod -a -G docker <username>

will do it. Remember to restart the container.

I guess the simpliest way to achive this is to create a customised Dockerfile:

# Official jenkins image
FROM jenkins/jenkins:lts
# Swith to root to be able to install Docker and modify permissions
USER root
RUN apt-get update
# Install docker
RUN curl -sSL | sh
# Add jenkins user to docker group
RUN usermod -a -G docker jenkins
# Switch back to default user
USER jenkins

# Bild the image:
# sudo docker build -t yourusername/imagename .
# Run the image and mount with the followin bind mount option:
# sudo docker run --name imagename -d -p8080:8080 -v /var/run/docker.sock:/var/run/docker.sock yourusername/imagename

axios post request to send form data

In my case I had to add the boundary to the header like the following:

const form = new FormData();
form.append(, fs.createReadStream(pathToFile));

const response = await axios({
    method: 'post',
    url: '',
    data: form,
    headers: {
        'Content-Type': `multipart/form-data; boundary=${form._boundary}`,

This solution is also useful if you're working with React Native.

Angular Material: mat-select not selecting default

A very simple way to achieve this is using a formControl with a default value, inside a FormGroup (optional) for example. This is an example using an unit selector to an area input:



exampleForm: FormGroup;

this.exampleForm ={
  areaUnit: [this.H_AREA_UNIT],


<form [formGroup]="exampleForm">
   <mat-select formControlName="areaUnit">
     <mat-option [value]="H_AREA_UNIT">h</mat-option>
     <mat-option [value]="M_AREA_UNIT">m</mat-option>

How can I fix "Design editor is unavailable until a successful build" error?

In my case, it was because it didn't like that I left the minSDK and targeSdk in the manifest. Go figure.

INSTALL_FAILED_USER_RESTRICTED : android studio using redmi 4 device

It's common problem and solution is pretty simple. Just follow the below steps:

Open Mobile Settings

Scroll Down & Go to Additional Settings

Open Developer options

(Note: if Developer Option is not visible, click 7 times on Build Number)


Turn off "MIUI optimization" & Restart it.

Make sure USB Debugging is ON & Install via USB is enabled.

Set USB Configuration to Charging (Optional)

No provider for HttpClient

To resolve this problem HttpClient is Angular's mechanism for communicating with a remote server over HTTP.

To make HttpClient available everywhere in the app,

  1. open the root AppModule,

  2. import the HttpClientModule from @angular/common/http,

    import { HttpClientModule } from '@angular/common/http';

  3. add it to the @NgModule.imports array.

    imports:[HttpClientModule, ]

ReactJS and images in public folder

You should use webpack here to make your life easier. Add below rule in your config:

const srcPath = path.join(__dirname, '..', 'publicfolder')

const rules = []

const includePaths = [
    // handle images
      test: /\.(png|gif|jpe?g|svg|ico)$/,
      include: includePaths,
      use: [{
        loader: 'file-loader',
        options: {
          name: 'images/[name]-[hash].[ext]'

After this, you can simply import the images into your react components:

import myImage from 'publicfolder/images/Image1.png'

Use myImage like below:

<div><img src={myImage}/></div>

or if the image is imported into local state of component

<div><img src={this.state.myImage}/></div> 

I get "Http failure response for (unknown url): 0 Unknown Error" instead of actual error message in Angular

For me it was caused by a server side JsonSerializerException.

An unhandled exception has occurred while executing the request Newtonsoft.Json.JsonSerializationException: Self referencing loop detected with type ...

The client said:

POST http://localhost:61495/api/Action net::ERR_INCOMPLETE_CHUNKED_ENCODING
ERROR HttpErrorResponse {headers: HttpHeaders, status: 0, statusText: "Unknown Error", url: null, ok: false, …}

Making the response type simpler by eliminating the loops solved the problem.

Why AVD Manager options are not showing in Android Studio

It Seems your AVD Manager is missing from root SDK directory please follow the Steps

  1. Go to sdk\tools\lib\ and copy AVDManager.exe
  2. Paste it to root of your sdk Directory. Now you have sdk\AVD Manager.exe

Now try to run it.

How to remove an unpushed outgoing commit in Visual Studio?

Open the history tab in Team Explorer from the Branches tile (right-click your branch). Then in the history right-click the commit before the one you don't want to push, choose Reset. That will move the branch back to that commit and should get rid of the extra commit you made. In order to reset before a given commit you thus have to select its parent.

Depending on what you want to do with the changes choose hard, which will get rid of them locally. Or choose soft which will undo the commit but will leave your working directory with the changes in your discarded commit.

How to work with progress indicator in flutter?

I took the following approach, which uses a simple modal progress indicator widget that wraps whatever you want to make modal during an async call.

The example in the package also addresses how to handle form validation while making async calls to validate the form (see flutter/issues/9688 for details of this problem). For example, without leaving the form, this async form validation method can be used to validate a new user name against existing names in a database while signing up.

Here is the demo of the example provided with the package (with source code):

async form validation with modal progress indicator

Example could be adapted to other modal progress indicator behaviour (like different animations, additional text in modal, etc..).

How to import JSON File into a TypeScript file?

let fs = require('fs');
let markers;
fs.readFile('./markers.json', handleJSONFile);

var handleJSONFile = function (err, data) {
   if (err) {
      throw err;
   markers= JSON.parse(data);

How to convert column with string type to int form in pyspark data frame?

You could use cast(as int) after replacing NaN with 0,

data_df = df.withColumn("Plays", df.call_time.cast('float'))

How to solve npm install throwing fsevents warning on non-MAC OS?

I got the same error. In my case, I was using a mapped drive to edit code off of a second computer, that computer was running linux. Not sure exactly why gulp-watch relies on operating system compatibility prior to install (I would assume it has to do with security purposes). Essentially the error is checking against your operating system and the operating system calling the node module, in my case the two operating systems were not the same so it threw it error. Which from the looks of your error is the same as mine.

The Error

Unsupported platform for [email protected]: wanted {"os":"darwin","arch":"any"} (current: {"os":"win32","arch":"x64"})

How I fixed it?

I logged into the linux computer directly and ran

npm install --save-dev <module-name>

Then went back into my coding environment and everything was fine after that.

Hope that helps!

How to add a new project to Github using VS Code

Well, It's quite easy.

Open your local project.

enter image description here

Add a file (If you don't have anything to add yet)

enter image description here

Click on Publish on Github

enter image description here

Choose as you wish

enter image description here

Choose the files you want to include in firt commit.
Note: If you don't select a file or folder it will added to .gitignore file

enter image description here

You are good to go. it is published.

P.S. If this was you first time. A prompt will ask for for your Github Credentials fill those and you are good to go. It is published.

Get safe area inset top and bottom heights

Try this :

In Objective C

if (@available(iOS 11.0, *)) {
    UIWindow *window =;
    CGFloat topPadding =;
    CGFloat bottomPadding = window.safeAreaInsets.bottom;

In Swift

if #available(iOS 11.0, *) {
    let window = UIApplication.shared.keyWindow
    let topPadding = window?
    let bottomPadding = window?.safeAreaInsets.bottom

In Swift - iOS 13.0 and above

// Use the first element from windows array as KeyWindow deprecated

if #available(iOS 13.0, *) {
    let window =[0]
    let topPadding =
    let bottomPadding = window.safeAreaInsets.bottom

.net Core 2.0 - Package was restored using .NetFramework 4.6.1 instead of target framework .netCore 2.0. The package may not be fully compatible

That particular package does not include assemblies for dotnet core, at least not at present. You may be able to build it for core yourself with a few tweaks to the project file, but I can't say for sure without diving into the source myself.

Codesign wants to access key "access" in your keychain, I put in my login password but keeps asking me

I had the same problem: while building iOS release for Flutter project, was asked for keychain password, entered Apple ID password for developer account, no luck. Finally succeeded by entering password for computer I was using (which was an on-line mac server). Hope that helps.

Angular: Cannot Get /

First, delete existing files package.lock.json and node_modules from your project. Then, the first step is to write npm cache clean --force. Second, also write this command npm i on the terminal. This process resolve my error. :D

phpMyAdmin ERROR: mysqli_real_connect(): (HY000/1045): Access denied for user 'pma'@'localhost' (using password: NO)

I just finished setting up my XAMPP on the MAC and had the same trouble. I just fixed it. It is not quite clear what OS you're using but you need to run the XAMPP security. You indicate you've done that, but here it is anyway for the MAC

sudo /Applications/XAMPP/xamppfiles/xampp security 

Set your password on the questions you get.

In you're phpmyadmin import the "create_tables.sql" .. Which can be found in the ./phpmyadmin/sql folder.

Next open the file inside the ./phpmyadmin folder.

$cfg['Servers'][$i]['controluser'] = 'pma';
$cfg['Servers'][$i]['controlpass'] = 'you_password';

Make sure to log out and log in to reflect the changes within phpmyadmin

Eclipse No tests found using JUnit 5 caused by NoClassDefFoundError for LauncherFactory

Answers so far did not adress the problem of sharing code with other people who don't necessarily use Eclipse. Here is one proposition. The key is to use a maven profile to solve the Eclipse Case.

It assumes you have defined a property junit5.version in your pom like:


then in the profiles section add the following:


All you have to do after this is to select the profile in your local Eclipse: Right click on your project and select Maven > Select Maven Profiles... (or hit Ctrl + Alt + P), and then check the "eclipse" profile we just created.

Selection Of Maven Profile

With that you are done. Your Eclipse will run Junit 5 tests as expected, but the configuration you added won't pollute other builds or other IDE

How to sign in kubernetes dashboard?

If you don't want to grant admin permission to dashboard service account, you can create cluster admin service account.

$ kubectl create serviceaccount cluster-admin-dashboard-sa
$ kubectl create clusterrolebinding cluster-admin-dashboard-sa \
  --clusterrole=cluster-admin \

And then, you can use the token of just created cluster admin service account.

$ kubectl get secret | grep cluster-admin-dashboard-sa
cluster-admin-dashboard-sa-token-6xm8l   3         18m
$ kubectl describe secret cluster-admin-dashboard-sa-token-6xm8l

I quoted it from giantswarm guide -

How to import cv2 in python3?

Your screenshot shows you doing a pip install from the python terminal which is wrong. Do that outside the python terminal. Also the package I believe you want is:

pip install opencv-python

Since you're running on Windows, I might look at the official install manual:

opencv2 is ONLY compatible with Python3 if you do so by compiling the source code. See the section under opencv supported python versions:

MongoError: connect ECONNREFUSED

I was facing the same issue on windows 10. I just uninstall MongoDB and installed it again and it started working. It solved my problem.

Can't create project on Netbeans 8.2

EDIT: The solution is to install JDK 8, as JDK 9 and beyond are currently not supported.

If however, you already have installed JDK 8, then kindly follow the steps outlined below.

The reason is that there is a conflict with the base JDK that NetBeans starts with. You have to set it to a lower version.

  1. Go to the folder "C:\Program Files\NetBeans 8.2\etc", or wherever NetBeans is installed.
  2. Open the netbeans.conf file.
  3. Locate netbeans_jdkhome and replace the JDK path there with "C:\Program Files\Java\jdk1.8.0_152", or wherever your JDK is installed. Be sure to use the right path, or you will run into problems. Here, JDK 1.8.0_152 is installed.
  4. Save the file, and restart NetBeans. It worked for me, should do for you too.

Ajax LARAVEL 419 POST error

419 error happens when you don`t post csrf_token. in your post method you must add this token along other variables.

How to see local history changes in Visual Studio Code?

Basic Functionality

  • Automatically saved local edit history is available with the Local History extension.
  • Manually saved local edit history is available with the Checkpoints extension (this is the IntelliJ equivalent to adding tags to the local history).

Advanced Functionality

  • None of the extensions mentioned above support edit history when a file is moved or renamed.
  • The extensions above only support edit history. They do not support move/delete history, for example, like IntelliJ does.

Open Request

If you'd like to see this feature added natively, along with all of the advanced functionality, I'd suggest upvoting the open GitHub issue here.

TypeScript error TS1005: ';' expected (II)

I was injecting service like this:

private messageShowService MessageShowService

instead of:

private messageShowService: MessageShowService

and that was the reason of error, despite nothing related with ',' was there.

How to view Plugin Manager in Notepad++

A direct process to install / configure Plugin Manager :

  1. Download the latest version of NotepadPlus Plugin Manager from the official Github handle.
  2. Extract the zip file.
  3. Copy the pluginmanager.dll file and paste in C:\Program Files\Notepad++\Plugins\PluginManager directory.
  4. Restart the Notepad++

Note: Create the PluginManager directory if it is not present.

Set cookies for cross origin requests

For express, upgrade your express library to 4.17.1 which is the latest stable version. Then;

In CorsOption: Set origin to your localhost url or your frontend production url and credentials to true e.g

  const corsOptions = {
    origin: config.get("origin"),
    credentials: true,

I set my origin dynamically using config npm module.

Then , in res.cookie:

For localhost: you do not need to set sameSite and secure option at all, you can set httpOnly to true for http cookie to prevent XSS attack and other useful options depending on your use case.

For production environment, you need to set sameSite to none for cross-origin request and secure to true. Remember sameSite works with express latest version only as at now and latest chrome version only set cookie over https, thus the need for secure option.

Here is how I made mine dynamic

    .cookie("access_token", token, {
      httpOnly: true,
      sameSite: app.get("env") === "development" ? true : "none",
      secure: app.get("env") === "development" ? false : true,

intellij idea - Error: java: invalid source release 1.9

Gradle I had the same issue and changing all the settings given in the earlier solutions made no difference. Than I went to the build.gradle and found this line and deleted it.

sourceCompatibility = '11'

and it worked! :)

Iterate over array of objects in Typescript

In Typescript and ES6 you can also use for..of:

for (var product of products) {

which will be transcoded to javascript:

for (var _i = 0, products_1 = products; _i < products_1.length; _i++) {
    var product = products_1[_i];

npm WARN ... requires a peer of ... but none is installed. You must install peer dependencies yourself

I had a similar issue and solved after running these instructions!

npm install npm -g
npm install --save-dev @angular/cli@latest
npm install
npm start

webpack: Module not found: Error: Can't resolve (with relative path)

I had a different problem. some of my includes were set to 'app/src/xxx/yyy' instead of '../xxx/yyy'

Fixing a systemd service 203/EXEC failure (no such file or directory)

I actually used the answer from How do I run a node.js app as a background service? combined with what dwrz said above. In my case, I was creating a Discord bot that needed to be able to run when I was not around.

With this service in place, I initially got the same error that the initial poster did, which brought me here. I was missing the #!/usr/bin/env node at the top of my executed node.js script.

Since then, no problems, although I intend to see what else can be extended to the service itself.

Django - Reverse for '' not found. '' is not a valid view function or pattern name

In my case, I don't put namespace_name in the url tag ex: {% url 'url_name or pattern name' %}. you have to specify the namespace_name like: {% url 'namespace_name:url_name or pattern name' %}.

Explanation: In project path('', include('blog.urls',namespace='blog')), and in app's you have to specify the app_name. like app_name = 'blog'. namespace_name is the app_name.

Angular4 - No value accessor for form control

You should use formControlName="surveyType" on an input and not on a div

bash: npm: command not found?

I know it's an old question. But it keeps showing in google first position and all it says it's "install node.js". For a newbie this is not obvious, so all you have to do is go to the node.js website and search for the command for your linux distribution version or any other operating system. Here is the link:

In this page you have to choose your operating system and you'll find your command. Then you just log into your console as a root (using putty for instance) and execute that command.

After that, you log as normal user and go again inside your laravel application folder and run again npm install command, and it should work. Hope it helps.

npm WARN enoent ENOENT: no such file or directory, open 'C:\Users\Nuwanst\package.json'

the file path you ran is wrong. So if you are working on windows, go to the correct file location with cd and rerun from there.

Getting Image from API in Angular 4/5+?

There is no need to use angular http, you can get with js native functions

// you will ned this function to fetch the image blob._x000D_
async function getImage(url, fileName) {_x000D_
     // on the first then you will return blob from response_x000D_
    return await fetch(url).then(r => r.blob())_x000D_
    .then((blob) => { // on the second, you just create a file from that blob, getting the type and name that intend to inform_x000D_
        return new File([blob], fileName+'.'+   blob.type.split('/')[1]) ;_x000D_
// example url_x000D_
var url = '';_x000D_
// calling the function_x000D_
getImage(url, 'your-name-image').then(function(file) {_x000D_
    // with file reader you will transform the file in a data url file;_x000D_
    var reader = new FileReader();_x000D_
    reader.onloadend = () => {_x000D_
    // just putting the data url to img element_x000D_
        document.querySelector('#image').src = reader.result ;_x000D_
<img src="" id="image"/>

Is there a Google Sheets formula to put the name of the sheet into a cell?

if you want to use build-in functions:


Explanation: cell("address";'Sheet1'!A1) gives you the address of the sheet, output is 'Sheet1'!$A$1. Now we need to extract the actual sheet name from this output. I'm using REGEXEXTRACT to match it by regex ^'(.*)'!\$A\$1$, but you can either use more/less specific regex or use functions like SUBSTITUTE or REPLACE

Typescript Date Type?

Typescript recognizes the Date interface out of the box - just like you would with a number, string, or custom type. So Just use:

myDate : Date;

How to perform string interpolation in TypeScript?

In JavaScript you can use template literals:

let value = 100;
console.log(`The size is ${ value }`);

Refused to load the font 'data:font/woff.....'it violates the following Content Security Policy directive: "default-src 'self'". Note that 'font-src'

In my case, I deleted src/registerServiceWorker file from create-react-app generated app. I added it and now it's all working.

Typescript empty object for a typed variable

Note that using const user = {} as UserType just provides intellisense but at runtime user is empty object {} and has no property inside. that means user.Email will give undefined instead of ""

type UserType = {
    Username: string;
    Email: string;

So, use class with constructor for actually creating objects with default properties.

type UserType = {
  Username: string;
  Email: string;

class User implements UserType {
  constructor() {
    this.Username = "";
    this.Email = "";

  Username: string;
  Email: string;

const myUser = new User();
console.log(myUser); // output: {Username: "", Email: ""}
console.log("val: "+myUser.Email); // output: ""

You can also use interface instead of type

interface UserType {
  Username: string;
  Email: string;

...and rest of code remains same.

Actually, you can even skip the constructor part and use it like this:

class User implements UserType {
      Username = ""; // will be added to new obj
      Email: string; // will not be added

const myUser = new User();
console.log(myUser); // output: {Username: ""}

How to format JSON in notepad++

Here are the steps to install JSToolNPP plugin on your Notepad++.

  1. Download 64bit version from Sourceforge or the 32bit version if you are on a 32-bit OS.

    64bit - Download from
  2. Notepad++ before installation

does not show JSTool in the Plugins menu.

  1. Unzip the downloaded JSToolNPP.1.21.0.uni.64 and copy the JSMinNPP.dll and place it under C:\Program Files\Notepad++\plugins.

  2. Close Notepad++ and reopen it. If you have downloaded an incompatible dll, then it will complain, else it will open successfully. If it complains about incompatibility, go back to STEP 1 and download the correct bit version as per your OS. Check Plugins in Notepad++.

JSTool is now located in the Plugins menu.

  1. Paste a sample unformatted but valid JSON data in Notepad++.

  2. Select all text in Notepad++ (CTRL+A) and format using Plugins -> JSTool -> JSFormat.

NOTE: On side note, if you do not want to install any plugins like this, I would recommend using the following 2 best online formatters.

convert array into DataFrame in Python

In general you can use pandas rename function here. Given your dataframe you could change to a new name like this. If you had more columns you could also rename those in the dictionary. The 0 is the current name of your column

import pandas as pd    
import numpy as np   
e = np.random.normal(size=100)  
e_dataframe = pd.DataFrame(e)      

e_dataframe.rename(index=str, columns={0:'new_column_name'})

Constraint Layout Vertical Align Center


Edit seaborn legend

If legend_out is set to True then legend is available thought g._legend property and it is a part of a figure. Seaborn legend is standard matplotlib legend object. Therefore you may change legend texts like:

import seaborn as sns

tips = sns.load_dataset("tips")
g = sns.lmplot(x="total_bill", y="tip", hue="smoker",
 data=tips, markers=["o", "x"], legend_out = True)

# title
new_title = 'My title'
# replace labels
new_labels = ['label 1', 'label 2']
for t, l in zip(g._legend.texts, new_labels): t.set_text(l)

enter image description here

Another situation if legend_out is set to False. You have to define which axes has a legend (in below example this is axis number 0):

import seaborn as sns

tips = sns.load_dataset("tips")
g = sns.lmplot(x="total_bill", y="tip", hue="smoker",
 data=tips, markers=["o", "x"], legend_out = False)

# check axes and find which is have legend
leg = g.axes.flat[0].get_legend()
new_title = 'My title'
new_labels = ['label 1', 'label 2']
for t, l in zip(leg.texts, new_labels): t.set_text(l)

enter image description here

Moreover you may combine both situations and use this code:

import seaborn as sns

tips = sns.load_dataset("tips")
g = sns.lmplot(x="total_bill", y="tip", hue="smoker",
 data=tips, markers=["o", "x"], legend_out = True)

# check axes and find which is have legend
for ax in g.axes.flat:
    leg = g.axes.flat[0].get_legend()
    if not leg is None: break
# or legend may be on a figure
if leg is None: leg = g._legend

# change legend texts
new_title = 'My title'
new_labels = ['label 1', 'label 2']
for t, l in zip(leg.texts, new_labels): t.set_text(l)

This code works for any seaborn plot which is based on Grid class.

How do I update Anaconda?

This can update the Python instance only:

conda update python

How to import Angular Material in project?

Import all Angular Material modules in Angular 9.

Create material.module.ts file in your_project/src/app/ directory and paste this code.

import { NgModule } from '@angular/core';
import { CommonModule } from '@angular/common';

import { BrowserAnimationsModule } from '@angular/platform-browser/animations';
import { MatCheckboxModule } from '@angular/material/checkbox';
import { MatButtonModule } from '@angular/material/button';
import { MatInputModule } from '@angular/material/input';
import { MatAutocompleteModule } from '@angular/material/autocomplete';
import { MatDatepickerModule } from '@angular/material/datepicker';
import { MatFormFieldModule } from '@angular/material/form-field';
import { MatRadioModule } from '@angular/material/radio';
import { MatSelectModule } from '@angular/material/select';
import { MatSliderModule } from '@angular/material/slider';
import { MatSlideToggleModule } from '@angular/material/slide-toggle';
import { MatMenuModule } from '@angular/material/menu';
import { MatSidenavModule } from '@angular/material/sidenav';
import { MatBadgeModule } from '@angular/material/badge';
import { MatToolbarModule } from '@angular/material/toolbar';
import { MatListModule } from '@angular/material/list';
import { MatGridListModule } from '@angular/material/grid-list';
import { MatCardModule } from '@angular/material/card';
import { MatStepperModule } from '@angular/material/stepper';
import { MatTabsModule } from '@angular/material/tabs';
import { MatExpansionModule } from '@angular/material/expansion';
import { MatButtonToggleModule } from '@angular/material/button-toggle';
import { MatChipsModule } from '@angular/material/chips';
import { MatIconModule } from '@angular/material/icon';
import { MatProgressSpinnerModule } from '@angular/material/progress-spinner';
import { MatProgressBarModule } from '@angular/material/progress-bar';
import { MatDialogModule } from '@angular/material/dialog';
import { MatTooltipModule } from '@angular/material/tooltip';
import { MatSnackBarModule } from '@angular/material/snack-bar';
import { MatTableModule } from '@angular/material/table';
import { MatSortModule } from '@angular/material/sort';
import { MatPaginatorModule } from '@angular/material/paginator';

@NgModule( {
    imports: [

    exports: [
    providers: [
} )

export class AngularMaterialModule { }

Specifying onClick event type with Typescript and React.Konva

You're probably out of luck without some hack-y workarounds

You could try

onClick={(event: React.MouseEvent<HTMLElement>) => {
 makeMove(ownMark, ( as any).index)

I'm not sure how strict your linter is - that might shut it up just a little bit

I played around with it for a bit, and couldn't figure it out, but you can also look into writing your own augmented definitions:

edit: please use the implementation in this reply it is the proper way to solve this issue (and also upvote him, while you're at it).

No signing certificate "iOS Distribution" found

You need to have the private key of the signing certificate in the keychain along with the public key. Have you created the certificate using the same Mac (keychain) ?

Solution #1:

  • Revoke the signing certificate (reset) from apple developer portal
  • Create the signing certificate again on the same mac (keychain). Then you will have the private key for the signing certificate!

Solution #2:

  • Export the signing identities from the origin xCode
  • Import the signing on your xCode

Apple documentation:

Why does "npm install" rewrite package-lock.json?

You probably have something like:


in your package.json which npm updates to the latest minor version, in your case being 2.4.1

Edit: Question from OP

But that doesn't explain why "npm install" would change the lock file. Isn't the lock file meant to create a reproducible build? If so, regardless of the semver value, it should still use the same 2.1.6 version.


This is intended to lock down your full dependency tree. Let's say typescript v2.4.1 requires widget ~v1.0.0. When you npm install it grabs widget v1.0.0. Later on your fellow developer (or CI build) does an npm install and gets typescript v2.4.1 but widget has been updated to widget v1.0.1. Now your node module are out of sync. This is what package-lock.json prevents.

Or more generally:

As an example, consider

package A:

{ "name": "A", "version": "0.1.0", "dependencies": { "B": "<0.1.0" } }

package B:

{ "name": "B", "version": "0.0.1", "dependencies": { "C": "<0.1.0" } }

and package C:

{ "name": "C", "version": "0.0.1" }

If these are the only versions of A, B, and C available in the registry, then a normal npm install A will install:

[email protected] -- [email protected] -- [email protected]

However, if [email protected] is published, then a fresh npm install A will install:

[email protected] -- [email protected] -- [email protected] assuming the new version did not modify B's dependencies. Of course, the new version of B could include a new version of C and any number of new dependencies. If such changes are undesirable, the author of A could specify a dependency on [email protected]. However, if A's author and B's author are not the same person, there's no way for A's author to say that he or she does not want to pull in newly published versions of C when B hasn't changed at all.

OP Question 2: So let me see if I understand correctly. What you're saying is that the lock file specifies the versions of the secondary dependencies, but still relies on the fuzzy matching of package.json to determine the top-level dependencies. Is that accurate?

Answer: No. package-lock locks the entire package tree, including the root packages described in package.json. If typescript is locked at 2.4.1 in your package-lock.json, it should remain that way until it is changed. And lets say tomorrow typescript releases version 2.4.2. If I checkout your branch and run npm install, npm will respect the lockfile and install 2.4.1.

More on package-lock.json:

package-lock.json is automatically generated for any operations where npm modifies either the node_modules tree, or package.json. It describes the exact tree that was generated, such that subsequent installs are able to generate identical trees, regardless of intermediate dependency updates.

This file is intended to be committed into source repositories, and serves various purposes:

Describe a single representation of a dependency tree such that teammates, deployments, and continuous integration are guaranteed to install exactly the same dependencies.

Provide a facility for users to "time-travel" to previous states of node_modules without having to commit the directory itself.

To facilitate greater visibility of tree changes through readable source control diffs.

And optimize the installation process by allowing npm to skip repeated metadata resolutions for previously-installed packages.

iOS 11, 12, and 13 installed certificates not trusted automatically (self signed)

I've been struggling with this for 3 days now while attempting to connect to a local API running Laravel valet. I finally figured it out. In my case I had to drag and drop over the LaravelValetCASelfSigned.pem file from ~/.config/valet/CA/LaravelValetCASelfSigned.pem

After verifying the installing within the simulator I had to go to Settings > About > Certificate Trust Settings > and Enable the Laravel Valet VA Self Signed CN

Finally working!!!

How to convert Observable<any> to array[]

//Component. home.ts :


ionViewDidLoad() {
.subscribe( res=> this.contacts= res as IContacts[]) ;

// reorderArray. accepts only Arrays

  reorderArray(this.contacts, indexes)

// Service . res.ts

getContacts(): Observable<IContacts[]> {
return this.http.get<IContacts[]>(this.apiUrl+"?results=5")

And it works fine

Selection with .loc in python

It's a pandas data-frame and it's using label base selection tool with df.loc and in it, there are two inputs, one for the row and the other one for the column, so in the row input it's selecting all those row values where the value saved in the column class is versicolor, and in the column input it's selecting the column with label class, and assigning Iris-versicolor value to them. So basically it's replacing all the cells of column class with value versicolor with Iris-versicolor.

How to add empty spaces into MD markdown readme on GitHub?

Markdown gets converted into HTML/XHMTL.

John Gruber created the Markdown language in 2004 in collaboration with Aaron Swartz on the syntax, with the goal of enabling people to write using an easy-to-read, easy-to-write plain text format, and optionally convert it to structurally valid HTML (or XHTML).

HTML is completely based on using &nbsp; for adding extra spaces if it doesn't externally define/use JavaScript or CSS for elements.

Markdown is a lightweight markup language with plain text formatting syntax. It is designed so that it can be converted to HTML and many other formats using a tool by the same name.

If you want to use »

  1. only one space » either use &nbsp; or just hit Spacebar (2nd one is good choice in this case)

  2. more than one space » use &nbsp;+space (for 2 consecutive spaces)

eg. If you want to add 10 spaces contiguously then you should use

&nbsp;   &nbsp;   &nbsp;   &nbsp;   &nbsp;  


instead of using 10 &nbsp; one after one as the below one


For more details check

  1. Adding multiple spaces between text in Markdown,
  2. How to create extra space in HTML or web page.

Cloning an array in Javascript/Typescript

I have the same issue with primeNg DataTable. After trying and crying, I've fixed the issue by using this code.

private deepArrayCopy(arr: SelectItem[]): SelectItem[] {
    const result: SelectItem[] = [];
    if (!arr) {
      return result;
    const arrayLength = arr.length;
    for (let i = 0; i <= arrayLength; i++) {
      const item = arr[i];
      if (item) {
        result.push({ label: item.label, value: item.value });
    return result;

For initializing backup value

backupData = this.deepArrayCopy(genericItems);

For resetting changes

genericItems = this.deepArrayCopy(backupData);

The magic bullet is to recreate items by using {} instead of calling constructor. I've tried new SelectItem(item.label, item.value) which doesn't work.

EF Core add-migration Build Failed

maybe it cause because of you did not add this in YOUR_PROJECT.csproj


<DotNetCliToolReference Include="Microsoft.EntityFrameworkCore.Tools.Dotnet" Version="2.0.2" />

Keras input explanation: input_shape, units, batch_size, dim, etc


The amount of "neurons", or "cells", or whatever the layer has inside it.

It's a property of each layer, and yes, it's related to the output shape (as we will see later). In your picture, except for the input layer, which is conceptually different from other layers, you have:

  • Hidden layer 1: 4 units (4 neurons)
  • Hidden layer 2: 4 units
  • Last layer: 1 unit


Shapes are consequences of the model's configuration. Shapes are tuples representing how many elements an array or tensor has in each dimension.

Ex: a shape (30,4,10) means an array or tensor with 3 dimensions, containing 30 elements in the first dimension, 4 in the second and 10 in the third, totaling 30*4*10 = 1200 elements or numbers.

The input shape

What flows between layers are tensors. Tensors can be seen as matrices, with shapes.

In Keras, the input layer itself is not a layer, but a tensor. It's the starting tensor you send to the first hidden layer. This tensor must have the same shape as your training data.

Example: if you have 30 images of 50x50 pixels in RGB (3 channels), the shape of your input data is (30,50,50,3). Then your input layer tensor, must have this shape (see details in the "shapes in keras" section).

Each type of layer requires the input with a certain number of dimensions:

  • Dense layers require inputs as (batch_size, input_size)
    • or (batch_size, optional,...,optional, input_size)
  • 2D convolutional layers need inputs as:
    • if using channels_last: (batch_size, imageside1, imageside2, channels)
    • if using channels_first: (batch_size, channels, imageside1, imageside2)
  • 1D convolutions and recurrent layers use (batch_size, sequence_length, features)

Now, the input shape is the only one you must define, because your model cannot know it. Only you know that, based on your training data.

All the other shapes are calculated automatically based on the units and particularities of each layer.

Relation between shapes and units - The output shape

Given the input shape, all other shapes are results of layers calculations.

The "units" of each layer will define the output shape (the shape of the tensor that is produced by the layer and that will be the input of the next layer).

Each type of layer works in a particular way. Dense layers have output shape based on "units", convolutional layers have output shape based on "filters". But it's always based on some layer property. (See the documentation for what each layer outputs)

Let's show what happens with "Dense" layers, which is the type shown in your graph.

A dense layer has an output shape of (batch_size,units). So, yes, units, the property of the layer, also defines the output shape.

  • Hidden layer 1: 4 units, output shape: (batch_size,4).
  • Hidden layer 2: 4 units, output shape: (batch_size,4).
  • Last layer: 1 unit, output shape: (batch_size,1).


Weights will be entirely automatically calculated based on the input and the output shapes. Again, each type of layer works in a certain way. But the weights will be a matrix capable of transforming the input shape into the output shape by some mathematical operation.

In a dense layer, weights multiply all inputs. It's a matrix with one column per input and one row per unit, but this is often not important for basic works.

In the image, if each arrow had a multiplication number on it, all numbers together would form the weight matrix.

Shapes in Keras

Earlier, I gave an example of 30 images, 50x50 pixels and 3 channels, having an input shape of (30,50,50,3).

Since the input shape is the only one you need to define, Keras will demand it in the first layer.

But in this definition, Keras ignores the first dimension, which is the batch size. Your model should be able to deal with any batch size, so you define only the other dimensions:

input_shape = (50,50,3)
    #regardless of how many images I have, each image has this shape        

Optionally, or when it's required by certain kinds of models, you can pass the shape containing the batch size via batch_input_shape=(30,50,50,3) or batch_shape=(30,50,50,3). This limits your training possibilities to this unique batch size, so it should be used only when really required.

Either way you choose, tensors in the model will have the batch dimension.

So, even if you used input_shape=(50,50,3), when keras sends you messages, or when you print the model summary, it will show (None,50,50,3).

The first dimension is the batch size, it's None because it can vary depending on how many examples you give for training. (If you defined the batch size explicitly, then the number you defined will appear instead of None)

Also, in advanced works, when you actually operate directly on the tensors (inside Lambda layers or in the loss function, for instance), the batch size dimension will be there.

  • So, when defining the input shape, you ignore the batch size: input_shape=(50,50,3)
  • When doing operations directly on tensors, the shape will be again (30,50,50,3)
  • When keras sends you a message, the shape will be (None,50,50,3) or (30,50,50,3), depending on what type of message it sends you.


And in the end, what is dim?

If your input shape has only one dimension, you don't need to give it as a tuple, you give input_dim as a scalar number.

So, in your model, where your input layer has 3 elements, you can use any of these two:

  • input_shape=(3,) -- The comma is necessary when you have only one dimension
  • input_dim = 3

But when dealing directly with the tensors, often dim will refer to how many dimensions a tensor has. For instance a tensor with shape (25,10909) has 2 dimensions.

Defining your image in Keras

Keras has two ways of doing it, Sequential models, or the functional API Model. I don't like using the sequential model, later you will have to forget it anyway because you will want models with branches.

PS: here I ignored other aspects, such as activation functions.

With the Sequential model:

from keras.models import Sequential  
from keras.layers import *  

model = Sequential()    

#start from the first hidden layer, since the input is not actually a layer   
#but inform the shape of the input, with 3 elements.    
model.add(Dense(units=4,input_shape=(3,))) #hidden layer 1 with input

#further layers:    
model.add(Dense(units=4)) #hidden layer 2
model.add(Dense(units=1)) #output layer   

With the functional API Model:

from keras.models import Model   
from keras.layers import * 

#Start defining the input tensor:
inpTensor = Input((3,))   

#create the layers and pass them the input tensor to get the output tensor:    
hidden1Out = Dense(units=4)(inpTensor)    
hidden2Out = Dense(units=4)(hidden1Out)    
finalOut = Dense(units=1)(hidden2Out)   

#define the model's start and end points    
model = Model(inpTensor,finalOut)

Shapes of the tensors

Remember you ignore batch sizes when defining layers:

  • inpTensor: (None,3)
  • hidden1Out: (None,4)
  • hidden2Out: (None,4)
  • finalOut: (None,1)

Hide header in stack navigator React navigation

Just add this into your class/component code snippet and Header will be hidden

 static navigationOptions = { header: null }

'ng' is not recognized as an internal or external command, operable program or batch file

I just installed angular cli and it solved my issue, simply run:

npm install -g @angular/cli

AttributeError: module 'cv2.cv2' has no attribute 'createLBPHFaceRecognizer'

Check your OpenCV version

import cv2

If your are running Python v3.x and OpenCV v4 and above:

pip install opencv-contrib-python

Try running your program again. This should now work.

How to fix Cannot find module 'typescript' in Angular 4?

I had a very similar problem after moving a working project to a new subdirectory on my file system. It turned out I had failed to move the file named .angular-cli.json to the subfolder along with everything else. After noticing that and moving the file into the subdirectory, all was back to normal.

Flutter - Wrap text on overflow, like insert ellipsis or fade

First, wrap your Row or Column in Expanded widget


    'your long text here',
    overflow: TextOverflow.fade,
    maxLines: 1,
    softWrap: false,
    style: Theme.of(context).textTheme.body1,

How to hide the Google Invisible reCAPTCHA badge

this does not disable the spam checking

div.g-recaptcha > div.grecaptcha-badge {
    width:0 !important;

'router-outlet' is not a known element

Try this:

Import RouterModule into your app.module.ts

import { RouterModule } from '@angular/router';

Add RouterModule into your imports []

like this:

 imports: [    RouterModule,  ]

Angular ForEach in Angular4/Typescript?

arrayData.forEach((key : any, val: any) => {
                        key['index'] = val + 1;

                        arrayData2.forEach((keys : any, vals :any) => {
                            if (key.group_id == {
                                key.group_name = keys.group_name;

Safe Area of Xcode 9

Apple introduced the topLayoutGuide and bottomLayoutGuide as properties of UIViewController way back in iOS 7. They allowed you to create constraints to keep your content from being hidden by UIKit bars like the status, navigation or tab bar. These layout guides are deprecated in iOS 11 and replaced by a single safe area layout guide.

Refer link for more information.

Failed to load AppCompat ActionBar with unknown error in android studio

Try this:

Just change:

compile ''


compile ''


Cannot find control with name: formControlName in angular reactive form

you're missing group nested controls with formGroupName directive

<div class="panel-body" formGroupName="address">
  <div class="form-group">
    <label for="address" class="col-sm-3 control-label">Business Address</label>
    <div class="col-sm-8">
      <input type="text" class="form-control" formControlName="street" placeholder="Business Address">
  <div class="form-group">
    <label for="website" class="col-sm-3 control-label">Website</label>
    <div class="col-sm-8">
      <input type="text" class="form-control" formControlName="website" placeholder="website">
  <div class="form-group">
    <label for="telephone" class="col-sm-3 control-label">Telephone</label>
    <div class="col-sm-8">
      <input type="text" class="form-control" formControlName="mobile" placeholder="telephone">
  <div class="form-group">
    <label for="email" class="col-sm-3 control-label">Email</label>
    <div class="col-sm-8">
      <input type="text" class="form-control" formControlName="email" placeholder="email">
  <div class="form-group">
    <label for="page id" class="col-sm-3 control-label">Facebook Page ID</label>
    <div class="col-sm-8">
      <input type="text" class="form-control" formControlName="pageId" placeholder="facebook page id">
  <div class="form-group">
    <label for="about" class="col-sm-3  control-label"></label>
    <div class="col-sm-3">
      <!--span class="btn btn-success form-control" (click)="openGeneralPanel()">Back</span-->
    <label for="about" class="col-sm-2  control-label"></label>
    <div class="col-sm-3">
      <button class="btn btn-success form-control" [disabled]="companyCreatForm.invalid" (click)="openContactInfo()">Continue</button>

How to specify legend position in matplotlib in graph coordinates

In addition to @ImportanceOfBeingErnest's post, I use the following line to add a legend at an absolute position in a plot.


For unknown reasons, bbox_transform=fig.transFigure does not work with me.

Read file from resources folder in Spring Boot

Spent way too much time coming back to this page so just gonna leave this here:

File file = new ClassPathResource("data/data.json").getFile();

Property 'value' does not exist on type EventTarget in TypeScript

Try code below:


it works for me :-)

React navigation goBack() and update parent state

You can pass a callback function as parameter when you call navigate like this:

  const DEMO_TOKEN = await AsyncStorage.getItem('id_token');
  if (DEMO_TOKEN === null) {
    this.props.navigation.navigate('Login', {
      onGoBack: () => this.refresh(),
    return -3;
  } else {

And define your callback function:

refresh() {

Then in the login/registration view, before goBack, you can do this:

await AsyncStorage.setItem('id_token', myId);

Update for React Navigation v5:

await AsyncStorage.setItem('id_token', myId);

Home does not contain an export named Home

We also can use

import { Home } from './layouts/Home'; 

using export keyword before class keyword.

export class Home extends React.Component{

For default

 import Home from './layouts/Home'; 

Default export class

 export default class Home extends React.Component{

Both case don't need to write

export default Home;

after class.

Android Studio - Failed to notify project evaluation listener error

In my case, I had to do -

File -> Sync Project with Gradle Files

Sync Project with Gradle Files

Jersey stopped working with InjectionManagerFactory not found

Add this dependency:



Make sure not to mix your Jersey dependency versions. This answer says version "2.28", but use whatever version your other Jersey dependency versions are.

Load json from local file with http.get() in angular 2

If you are using Angular CLI: 7.3.3 What I did is, On my assets folder I put my fake json data then on my services I just did this.

const API_URL = './assets/data/db.json';

getAllPassengers(): Observable<PassengersInt[]> {
    return this.http.get<PassengersInt[]>(API_URL);

enter image description here

Disable Button in Angular 2

I tried use [disabled]="!editmode" but it not work in my case.

This is my solution [disabled]="!editmode ? 'disabled': null" , I share for whom concern.

<button [disabled]="!editmode ? 'disabled': null" 
            <div class="btn-primary">Load Chart</div>


How to use jQuery Plugin with Angular 4?

Install jquery with npm

npm install jquery --save

Add typings

npm install --save-dev @types/jquery

Add scripts to angular-cli.json

"apps": [{
  "scripts": [

Build project and serve

ng build

Hope this helps! Enjoy coding

The origin server did not find a current representation for the target resource or is not willing to disclose that one exists

Accessing webpages issues

I added yellow highlighted package and now my view page is accessible. in eclipse when we deploy our war it only deploy those stuff mention in the deployment assessment.

We set Deployment Assessment from right click on project --> Properties --> Apply and Close....

Get keys of a Typescript interface as array of strings

// declarations.d.ts
export interface IMyTable {
      id: number;
      title: string;
      createdAt: Date;
      isDeleted: boolean
declare var Tes: IMyTable;
// call in annother page

Cast object to interface in TypeScript

If it helps anyone, I was having an issue where I wanted to treat an object as another type with a similar interface. I attempted the following:

Didn't pass linting

const x = new Obj(a as b);

The linter was complaining that a was missing properties that existed on b. In other words, a had some properties and methods of b, but not all. To work around this, I followed VS Code's suggestion:

Passed linting and testing

const x = new Obj(a as unknown as b);

Note that if your code attempts to call one of the properties that exists on type b that is not implemented on type a, you should realize a runtime fault.

Returning a promise in an async function in TypeScript

It's complicated.

First of all, in this code

const p = new Promise((resolve) => {

the type of p is inferred as Promise<{}>. There is open issue about this on typescript github, so arguably this is a bug, because obviously (for a human), p should be Promise<number>.

Then, Promise<{}> is compatible with Promise<number>, because basically the only property a promise has is then method, and then is compatible in these two promise types in accordance with typescript rules for function types compatibility. That's why there is no error in whatever1.

But the purpose of async is to pretend that you are dealing with actual values, not promises, and then you get the error in whatever2 because {} is obvioulsy not compatible with number.

So the async behavior is the same, but currently some workaround is necessary to make typescript compile it. You could simply provide explicit generic argument when creating a promise like this:

const whatever2 = async (): Promise<number> => {
    return new Promise<number>((resolve) => {

How to print a Groovy variable in Jenkins?

The following code worked for me:

echo userInput

How to import image (.svg, .png ) in a React Component

You can use require as well to render images like

//then in the render function of Jsx insert the mainLogo variable

class NavBar extends Component {
  render() {
    return (
      <nav className="nav" style={nbStyle}>
        <div className="container">
          //right below here
          <img src={require('./logoWhite.png')} style={nbStyle.logo} alt="fireSpot"/>

How do I set the background color of my main screen in Flutter?

I still cannot make this work. Any other ideas?

Check if value exists in enum in TypeScript

For anyone who comes here looking to validate if a string is one of the values of an enum and type convert it, I wrote this function that returns the proper type and returns undefined if the string is not in the enum.

function keepIfInEnum<T>(
  value: string,
  enumObject: { [key: string]: T }
) {
  if (Object.values(enumObject).includes((value as unknown) as T)) {
    return (value as unknown) as T;
  } else {
    return undefined;

As an example:

enum StringEnum {
  value1 = 'FirstValue',
  value2 = 'SecondValue',
keepIfInEnum<StringEnum>('FirstValue', StringEnum)  // 'FirstValue'
keepIfInEnum<StringEnum>('OtherValue', StringEnum)  // undefined

How to extract svg as file from web page

Here's a three step solution:

  1. Copy the SVG code snippet, and paste it into a new HTML page.
  2. Save the HTML page as (for example) "logo.html", and then open that HTML page in Chrome hitting > File > Print > "Save as pdf"
  3. This PDF can now be opened in Illustrator - extracting the vector element.

How to set combobox default value?

Suppose you bound your combobox to a List<Person>

List<Person> pp = new List<Person>();
pp.Add(new Person() {id = 1, name="Steve"});
pp.Add(new Person() {id = 2, name="Mark"});
pp.Add(new Person() {id = 3, name="Charles"});

cbo1.DisplayMember = "name";
cbo1.ValueMember = "id";
cbo1.DataSource = pp;

At this point you cannot set the Text property as you like, but instead you need to add an item to your list before setting the datasource

pp.Insert(0, new Person() {id=-1, name="--SELECT--"});
cbo1.DisplayMember = "name";
cbo1.ValueMember = "id";
cbo1.DataSource = pp;
cbo1.SelectedIndex = 0;

Of course this means that you need to add a checking code when you try to use the info from the combobox

if(cbo1.SelectedValue != null && Convert.ToInt32(cbo1.SelectedValue) == -1)
    MessageBox.Show("Please select a person name");

The code is the same if you use a DataTable instead of a list. You need to add a fake row at the first position of the Rows collection of the datatable and set the initial index of the combobox to make things clear. The only thing you need to look at are the name of the datatable columns and which columns should contain a non null value before adding the row to the collection

In a table with three columns like ID, FirstName, LastName with ID,FirstName and LastName required you need to

DataRow row = datatable.NewRow();
row["ID"] = -1;
row["FirstName"] = "--Select--";    
row["LastName"] = "FakeAddress";
dataTable.Rows.InsertAt(row, 0);

How to loop through a JSON object with typescript (Angular2)

Assuming your json object from your GET request looks like the one you posted above simply do:

let list: string[] = [];

json.Results.forEach(element => {

Or am I missing something that prevents you from doing it this way?

How to check undefined in Typescript

Adding this late answer to check for object.propertie that can help in some cases:

Using a juggling-check, you can test both null and undefined in one hit:

if ( == null) {

If you use a strict-check, it will only be true for values set to null and won't evaluate as true for undefined variables:

if ( === null) {

Typescript does NOT have a function to check if a variable is defined.

Update October 2020

You can now also use the nullish coallesing operator introduced in Typescript.

let neverNullOrUndefined = someValue ?? anotherValue;

Here, anotherValue will only be returned if someValue is null or undefined.

How to fix the error "Windows SDK version 8.1" was not found?

I faced this problem too. Re-ran the Visual Studio 2017 Installer, go to 'Individual Components' and select Windows 8.1 SDK. Go back to to the project > Right click and Re-target to match the SDK required as shown below:enter image description here

Error: Cannot match any routes. URL Segment: - Angular 2

please modify your router.module.ts as:

const routes: Routes = [
    path: '',
    redirectTo: 'one',
    pathMatch: 'full'
    path: 'two',
    component: ClassTwo, children: [
            path: 'three',
            component: ClassThree,
            outlet: 'nameThree',
            path: 'four',
            component: ClassFour,
            outlet: 'nameFour'
           path: '',
           redirectTo: 'two',
           pathMatch: 'full'

and in your component1.html

<h3>In One</h3>

    <a routerLink="/two" class="dash-item">...Go to Two...</a>
    <a routerLink="/two/three" class="dash-item">... Go to THREE...</a>
    <a routerLink="/two/four" class="dash-item">...Go to FOUR...</a>

<router-outlet></router-outlet>                   // Successfully loaded component2.html
<router-outlet name="nameThree" ></router-outlet> // Error: Cannot match any routes. URL Segment: 'three'
<router-outlet name="nameFour" ></router-outlet>  // Error: Cannot match any routes. URL Segment: 'three'

General error: 1364 Field 'user_id' doesn't have a default value

Here's how I did it:

This is my PostsController


    'title' => request('title'),
    'body' => request('body'),
    'user_id' => auth()->id() 

And this is my Post Model.

protected $fillable = ['title', 'body','user_id'];

And try refreshing the migration if its just on test instance

$ php artisan migrate:refresh

Note: migrate: refresh will delete all the previous posts, users

Module AppRegistry is not registered callable module (calling runApplication)

If you are using windows and running yarn open cmd on admin mode' terminate and Restart the node process by typing this command.

Find the node: killall -9 node force to kill : taskkill /f /im node.exe Reset the cache : yarn start --reset-cache

Navigate to your project directory: cd myapp Re-Run your App : yarn android

Visual Studio Code pylint: Unable to import 'protorpc'

I had same problem for pyodbc , I had two version of python on my Ubuntu (python3.8 and python3.9), problem was: package installed on python3.8 location but my interpreter was for python3.9. i installed python3.8 interpreter in command palette and it fixed.

Sort an array of objects in React and render them

Chrome browser considers integer value as return type not boolean value so,, b) => a.item.timeM > b.item.timeM ? 1:-1).map(
    (item, i) => <div key={i}> {item.matchID} {item.timeM} {item.description}</div>

How to uninstall an older PHP version from centOS7

yum -y remove php* to remove all php packages then you can install the 5.6 ones.

Error: the entity type requires a primary key

Removed and added back in the table using Scaffold-DbContext and the error went away

Check if a string contains a number

This too will work.

if any(i.isdigit() for i in s):

How to run Selenium WebDriver test cases in Chrome

On Ubuntu, you can simply install the chromium-chromedriver package:

apt install chromium-chromedriver

Be aware that this also installs an outdated Selenium version. To install the latest Selenium:

pip install selenium

How to store arrays in MySQL?

In MySQL, use the JSON type.

Contra the answers above, the SQL standard has included array types for almost twenty years; they are useful, even if MySQL has not implemented them.

In your example, however, you'll likely want to create three tables: person and fruit, then person_fruit to join them.

DROP TABLE IF EXISTS person_fruit;

  person_id   INT           NOT NULL AUTO_INCREMENT,
  person_name VARCHAR(1000) NOT NULL,
  PRIMARY KEY (person_id)

  fruit_id    INT           NOT NULL AUTO_INCREMENT,
  fruit_name  VARCHAR(1000) NOT NULL,
  fruit_color VARCHAR(1000) NOT NULL,
  fruit_price INT           NOT NULL,
  PRIMARY KEY (fruit_id)

CREATE TABLE person_fruit (
  pf_person INT NOT NULL,
  pf_fruit  INT NOT NULL,
  PRIMARY KEY (pf_id),
  FOREIGN KEY (pf_person) REFERENCES person (person_id),
  FOREIGN KEY (pf_fruit) REFERENCES fruit (fruit_id)

INSERT INTO person (person_name)
  ('John'); -- again

INSERT INTO fruit (fruit_name, fruit_color, fruit_price)
  ('apple', 'red', 1),
  ('orange', 'orange', 2),
  ('pineapple', 'yellow', 3);

INSERT INTO person_fruit (pf_person, pf_fruit)
  (1, 1),
  (1, 2),
  (2, 2),
  (2, 3),
  (3, 1),
  (3, 2),
  (3, 3);

If you wish to associate the person with an array of fruits, you can do so with a view:

DROP VIEW IF EXISTS person_fruit_summary;
CREATE VIEW person_fruit_summary AS
    person_id                                                                                              AS pfs_person_id,
    max(person_name)                                                                                       AS pfs_person_name,
    cast(concat('[', group_concat(json_quote(fruit_name) ORDER BY fruit_name SEPARATOR ','), ']') as json) AS pfs_fruit_name_array
    INNER JOIN person_fruit
      ON person.person_id = person_fruit.pf_person
    INNER JOIN fruit
      ON person_fruit.pf_fruit = fruit.fruit_id

The view shows the following data:

| pfs_person_id | pfs_person_name | pfs_fruit_name_array             |
|             1 | John            | ["apple", "orange"]              |
|             2 | Mary            | ["orange", "pineapple"]          |
|             3 | John            | ["apple", "orange", "pineapple"] |

In 5.7.22, you'll want to use JSON_ARRAYAGG, rather than hack the array together from a string.

Python: instance has no attribute

Your class doesn't have a __init__(), so by the time it's instantiated, the attribute atoms is not present. You'd have to do C.setdata('something') so C.atoms becomes available.

>>> C = Residues()
>>> C.atoms.append('thing')

Traceback (most recent call last):
  File "<pyshell#84>", line 1, in <module>
AttributeError: Residues instance has no attribute 'atoms'

>>> C.setdata('something')
>>> C.atoms.append('thing')   # now it works

Unlike in languages like Java, where you know at compile time what attributes/member variables an object will have, in Python you can dynamically add attributes at runtime. This also implies instances of the same class can have different attributes.

To ensure you'll always have (unless you mess with it down the line, then it's your own fault) an atoms list you could add a constructor:

def __init__(self):
    self.atoms = []

add a string prefix to each value in a string column using Pandas

Another solution with .loc:

df = pd.DataFrame({'col': ['a', 0]})
df.loc[df.index, 'col'] = 'string' + df['col'].astype(str)

This is not as quick as solutions above (>1ms per loop slower) but may be useful in case you need conditional change, like:

mask = (df['col'] == 0)
df.loc[mask, 'col'] = 'string' + df['col'].astype(str)

"Comparison method violates its general contract!"

Java does not check consistency in a strict sense, only notifies you if it runs into serious trouble. Also it does not give you much information from the error.

I was puzzled with what's happening in my sorter and made a strict consistencyChecker, maybe this will help you:

 * @param dailyReports
 * @param comparator
public static <T> void checkConsitency(final List<T> dailyReports, final Comparator<T> comparator) {
  final Map<T, List<T>> objectMapSmallerOnes = new HashMap<T, List<T>>();

  iterateDistinctPairs(dailyReports.iterator(), new IPairIteratorCallback<T>() {
     * @param o1
     * @param o2
    public void pair(T o1, T o2) {
      final int diff =, o2);
      if (diff < Compare.EQUAL) {
        checkConsistency(objectMapSmallerOnes, o1, o2);
        getListSafely(objectMapSmallerOnes, o2).add(o1);
      } else if (Compare.EQUAL < diff) {
        checkConsistency(objectMapSmallerOnes, o2, o1);
        getListSafely(objectMapSmallerOnes, o1).add(o2);
      } else {
        throw new IllegalStateException("Equals not expected?");

 * @param objectMapSmallerOnes
 * @param o1
 * @param o2
static <T> void checkConsistency(final Map<T, List<T>> objectMapSmallerOnes, T o1, T o2) {
  final List<T> smallerThan = objectMapSmallerOnes.get(o1);

  if (smallerThan != null) {
    for (final T o : smallerThan) {
      if (o == o2) {
        throw new IllegalStateException(o2 + "  cannot be smaller than " + o1 + " if it's supposed to be vice versa.");
      checkConsistency(objectMapSmallerOnes, o, o2);

 * @param keyMapValues 
 * @param key 
 * @param <Key> 
 * @param <Value> 
 * @return List<Value>
public static <Key, Value> List<Value> getListSafely(Map<Key, List<Value>> keyMapValues, Key key) {
  List<Value> values = keyMapValues.get(key);

  if (values == null) {
    keyMapValues.put(key, values = new LinkedList<Value>());

  return values;

 * @author Oku
 * @param <T>
public interface IPairIteratorCallback<T> {
   * @param o1
   * @param o2
  void pair(T o1, T o2);

 * Iterates through each distinct unordered pair formed by the elements of a given iterator
 * @param it
 * @param callback
public static <T> void iterateDistinctPairs(final Iterator<T> it, IPairIteratorCallback<T> callback) {
  List<T> list = Convert.toMinimumArrayList(new Iterable<T>() {

    public Iterator<T> iterator() {
      return it;


  for (int outerIndex = 0; outerIndex < list.size() - 1; outerIndex++) {
    for (int innerIndex = outerIndex + 1; innerIndex < list.size(); innerIndex++) {
      callback.pair(list.get(outerIndex), list.get(innerIndex));

Formula px to dp, dp to px android

Below funtions worked well for me across devices.

It is taken from

public static float convertPixelsToDp(float px){
    DisplayMetrics metrics = Resources.getSystem().getDisplayMetrics();
    float dp = px / (metrics.densityDpi / 160f);
    return Math.round(dp);

public static float convertDpToPixel(float dp){
    DisplayMetrics metrics = Resources.getSystem().getDisplayMetrics();
    float px = dp * (metrics.densityDpi / 160f);
    return Math.round(px);

TypeError: 'list' object is not callable while trying to access a list

You are attempting to call wordlists here:

print  wordlists(len(words)) <--- Error here.


print wordlists[len(words)]

How do I update a GitHub forked repository?

rm -rf oldrepository
git clone ...

There may be subtler options, but it is the only way that I have any confidence that my local repository is the same as upstream.

Javascript - How to show escape characters in a string?

You have to escape the backslash, so try this:

str = "Hello\\nWorld";

Here are more escaped characters in Javascript.

Merge two json/javascript arrays in to one array

Try the code below, using jQuery extend method:

var json1 = {"name":"ramesh","age":"12"};

var json2 = {"member":"true"};


Adding images to an HTML document with javascript

This works:

var img = document.createElement('img');
img.src = 'img/eqp/' + this.apparel + '/' + this.facing + '_idle.png';

Or using jQuery:

.attr('src','img/eqp/' + this.apparel + '/' + this.facing + '_idle.png')

modal View controllers - how to display and dismiss

I have solved the issue by using UINavigationController when presenting. In MainVC, when presenting VC1

let vc1 = VC1()
let navigationVC = UINavigationController(rootViewController: vc1)
self.present(navigationVC, animated: true, completion: nil)

In VC1, when I would like to show VC2 and dismiss VC1 in same time (just one animation), I can have a push animation by

let vc2 = VC2()
self.navigationController?.setViewControllers([vc2], animated: true)

And in VC2, when close the view controller, as usual we can use:

self.dismiss(animated: true, completion: nil)

In jQuery how can I set "top,left" properties of an element with position values relative to the parent and not the document?

Code offset dynamic for dynamic page

var pos=$('#send').offset().top;
$('#loading').offset({ top : pos-220});

Move textfield when keyboard appears swift

Swift 4.1,

Use TPKeyBoardAvoiding class for achieving this. This works fine with UIScrollView, UICollectionView, UITableView.

Just assign this class to your scrollview, collectionview or tableview in storyboard or create its object programmatically. All textfield or textviews inside TPKeyboardAvoiding scrollview will adjust automatically when the keyboard appears and disappears.

Here is the link for TPKeyboardAvoiding

TPKeyboardAvoiding for Swift 4.1,

import Foundation
import UIKit

// MARK: - TableView
class TPKeyboardAvoidingTableView:UITableView,UITextFieldDelegate, UITextViewDelegate {

    override var frame:CGRect{
            super.frame = frame

            if hasAutomaticKeyboardAvoidingBehaviour() {return}

    override var contentSize:CGSize{
            if hasAutomaticKeyboardAvoidingBehaviour() {
                super.contentSize = newValue

            if newValue.equalTo(self.contentSize)

            super.contentSize = newValue

        //        didSet{
        //            self.TPKeyboardAvoiding_updateContentInset()
        //        }

    override init(frame: CGRect, style: UITableViewStyle) {
        super.init(frame: frame, style: style)

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)

    override func awakeFromNib() {


    func hasAutomaticKeyboardAvoidingBehaviour()->Bool
        if #available(iOS 8.3, *) {
            if self.delegate is UITableViewController
                return true

        return false

    func focusNextTextField()->Bool
        return self.TPKeyboardAvoiding_focusNextTextField()

    @objc func scrollToActiveTextField()
        return self.TPKeyboardAvoiding_scrollToActiveTextField()

    override func willMove(toSuperview newSuperview: UIView?) {
        super.willMove(toSuperview: newSuperview)
        if newSuperview != nil {
            NSObject.cancelPreviousPerformRequests(withTarget: self, selector: #selector(TPKeyboardAvoiding_assignTextDelegateForViewsBeneathView(_:)), object: self)

    override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
        super.touchesEnded(touches, with: event)

    func textFieldShouldReturn(_ textField: UITextField) -> Bool {
        if !self.focusNextTextField()
        return true

    override func layoutSubviews() {
        NSObject.cancelPreviousPerformRequests(withTarget: self, selector: #selector(TPKeyboardAvoiding_assignTextDelegateForViewsBeneathView(_:)), object: self)

        Timer.scheduledTimer(timeInterval: 0.1, target: self, selector: #selector(TPKeyboardAvoiding_assignTextDelegateForViewsBeneathView(_:)), userInfo: nil, repeats: false)

private extension TPKeyboardAvoidingTableView
    func setup()
        if self.hasAutomaticKeyboardAvoidingBehaviour() { return }

                                               selector: #selector(TPKeyboardAvoiding_keyboardWillShow(_:)),
                                               name: NSNotification.Name.UIKeyboardWillChangeFrame,
                                               object: nil)

                                               selector: #selector(TPKeyboardAvoiding_keyboardWillHide(_:)),
                                               name: NSNotification.Name.UIKeyboardWillHide,
                                               object: nil)

                                               selector: #selector(scrollToActiveTextField),
                                               name: NSNotification.Name.UITextViewTextDidBeginEditing,
                                               object: nil)

                                               selector: #selector(scrollToActiveTextField),
                                               name: NSNotification.Name.UITextFieldTextDidBeginEditing,
                                               object: nil)

// MARK: - CollectionView
class TPKeyboardAvoidingCollectionView:UICollectionView,UITextViewDelegate {

    override var contentSize:CGSize{
            if newValue.equalTo(self.contentSize)

            super.contentSize = newValue

        //        didSet{
        //            self.TPKeyboardAvoiding_updateContentInset()
        //        }

    override var frame:CGRect{
            super.frame = frame


    //    override init(frame: CGRect) {
    //        super.init(frame: frame)
    //    }

    override init(frame: CGRect, collectionViewLayout layout: UICollectionViewLayout) {
        super.init(frame: frame, collectionViewLayout: layout)

    required init?(coder aDecoder: NSCoder) {
        //        fatalError("init(coder:) has not been implemented")
        super.init(coder: aDecoder)


    override func awakeFromNib() {


    func focusNextTextField()->Bool
        return self.TPKeyboardAvoiding_focusNextTextField()

    @objc func scrollToActiveTextField()
        return self.TPKeyboardAvoiding_scrollToActiveTextField()

    override func willMove(toSuperview newSuperview: UIView?) {
        super.willMove(toSuperview: newSuperview)
        if newSuperview != nil {
            NSObject.cancelPreviousPerformRequests(withTarget: self, selector: #selector(TPKeyboardAvoiding_assignTextDelegateForViewsBeneathView(_:)), object: self)

    override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
        super.touchesEnded(touches, with: event)

    func textFieldShouldReturn(_ textField: UITextField) -> Bool {
        if !self.focusNextTextField()
        return true

    override func layoutSubviews() {
        NSObject.cancelPreviousPerformRequests(withTarget: self, selector: #selector(TPKeyboardAvoiding_assignTextDelegateForViewsBeneathView(_:)), object: self)

        Timer.scheduledTimer(timeInterval: 0.1, target: self, selector: #selector(TPKeyboardAvoiding_assignTextDelegateForViewsBeneathView(_:)), userInfo: nil, repeats: false)

private extension TPKeyboardAvoidingCollectionView
    func setup()
                                               selector: #selector(TPKeyboardAvoiding_keyboardWillShow(_:)),
                                               name: NSNotification.Name.UIKeyboardWillChangeFrame,
                                               object: nil)

                                               selector: #selector(TPKeyboardAvoiding_keyboardWillHide(_:)),
                                               name: NSNotification.Name.UIKeyboardWillHide,
                                               object: nil)

                                               selector: #selector(scrollToActiveTextField),
                                               name: NSNotification.Name.UITextViewTextDidBeginEditing,
                                               object: nil)

                                               selector: #selector(scrollToActiveTextField),
                                               name: NSNotification.Name.UITextFieldTextDidBeginEditing,
                                               object: nil)

// MARK: - ScrollView
class TPKeyboardAvoidingScrollView:UIScrollView,UITextFieldDelegate,UITextViewDelegate
    override var contentSize:CGSize{

    override var frame:CGRect{

    override init(frame: CGRect) {
        super.init(frame: frame)

    override func awakeFromNib() {

    func contentSizeToFit()
        self.contentSize = self.TPKeyboardAvoiding_calculatedContentSizeFromSubviewFrames()

    func focusNextTextField() ->Bool
        return self.TPKeyboardAvoiding_focusNextTextField()

    @objc func scrollToActiveTextField()
        return self.TPKeyboardAvoiding_scrollToActiveTextField()

    required init?(coder aDecoder: NSCoder) {
        super.init(coder: aDecoder)


    override func willMove(toSuperview newSuperview: UIView?) {
        super.willMove(toSuperview: newSuperview)
        if newSuperview != nil {
            NSObject.cancelPreviousPerformRequests(withTarget: self, selector: #selector(TPKeyboardAvoiding_assignTextDelegateForViewsBeneathView(_:)), object: self)

    override func touchesEnded(_ touches: Set<UITouch>, with event: UIEvent?) {
        super.touchesEnded(touches, with: event)

    func textFieldShouldReturn(_ textField: UITextField) -> Bool {
        if !self.focusNextTextField()
        return true

    override func layoutSubviews() {
        NSObject.cancelPreviousPerformRequests(withTarget: self, selector: #selector(TPKeyboardAvoiding_assignTextDelegateForViewsBeneathView(_:)), object: self)

        Timer.scheduledTimer(timeInterval: 0.1, target: self, selector: #selector(TPKeyboardAvoiding_assignTextDelegateForViewsBeneathView(_:)), userInfo: nil, repeats: false)

private extension TPKeyboardAvoidingScrollView
    func setup()
                                               selector: #selector(TPKeyboardAvoiding_keyboardWillShow(_:)),
                                               name: NSNotification.Name.UIKeyboardWillChangeFrame,
                                               object: nil)

                                               selector: #selector(TPKeyboardAvoiding_keyboardWillHide(_:)),
                                               name: NSNotification.Name.UIKeyboardWillHide,
                                               object: nil)

                                               selector: #selector(scrollToActiveTextField),
                                               name: NSNotification.Name.UITextViewTextDidBeginEditing,
                                               object: nil)

                                               selector: #selector(scrollToActiveTextField),
                                               name: NSNotification.Name.UITextFieldTextDidBeginEditing,
                                               object: nil)

// MARK: - Process Event
let kCalculatedContentPadding:CGFloat = 10;
let kMinimumScrollOffsetPadding:CGFloat = 20;

extension UIScrollView
    @objc func TPKeyboardAvoiding_keyboardWillShow(_ notification:Notification)
        guard let userInfo = notification.userInfo else { return }
        guard let rectNotification = notification.userInfo?[UIKeyboardFrameEndUserInfoKey] as? NSValue else

        let keyboardRect = self.convert(rectNotification.cgRectValue , from: nil)
        if keyboardRect.isEmpty

        let state = self.keyboardAvoidingState()

        guard let firstResponder = self.TPKeyboardAvoiding_findFirstResponderBeneathView(self) else { return}
        state.keyboardRect = keyboardRect
        if !state.keyboardVisible
            state.priorInset = self.contentInset
            state.priorScrollIndicatorInsets = self.scrollIndicatorInsets
            state.priorPagingEnabled = self.isPagingEnabled

        state.keyboardVisible = true
        self.isPagingEnabled = false

        if self is TPKeyboardAvoidingScrollView
            state.priorContentSize = self.contentSize
            if self.contentSize.equalTo(
                self.contentSize = self.TPKeyboardAvoiding_calculatedContentSizeFromSubviewFrames()

        let duration = userInfo[UIKeyboardAnimationDurationUserInfoKey] as? Float ?? 0.0
        let curve = userInfo[UIKeyboardAnimationCurveUserInfoKey] as? Int ?? 0
        let options = UIViewAnimationOptions(rawValue: UInt(curve))

        UIView.animate(withDuration: TimeInterval(duration),
                       delay: 0,
                       options: options,
                       animations: { [weak self]() -> Void in
                        if let actualSelf = self
                            actualSelf.contentInset = actualSelf.TPKeyboardAvoiding_contentInsetForKeyboard()
                            let viewableHeight = actualSelf.bounds.size.height - - actualSelf.contentInset.bottom
                            let point = CGPoint(x: actualSelf.contentOffset.x, y: actualSelf.TPKeyboardAvoiding_idealOffsetForView(firstResponder, viewAreaHeight: viewableHeight))
                            actualSelf.setContentOffset(point, animated: false)

                            actualSelf.scrollIndicatorInsets = actualSelf.contentInset

        }) { (finished) -> Void in


    @objc func TPKeyboardAvoiding_keyboardWillHide(_ notification:Notification)
        guard let userInfo = notification.userInfo else { return }

        guard let rectNotification = userInfo[UIKeyboardFrameEndUserInfoKey] as? NSValue else
        let keyboardRect = self.convert(rectNotification.cgRectValue , from: nil)
        if keyboardRect.isEmpty
        let state = self.keyboardAvoidingState()

        if !state.keyboardVisible
        state.keyboardRect =
        state.keyboardVisible = false

        let duration = userInfo[UIKeyboardAnimationDurationUserInfoKey] as? Float ?? 0.0
        let curve = userInfo[UIKeyboardAnimationCurveUserInfoKey] as? Int ?? 0
        let options = UIViewAnimationOptions(rawValue: UInt(curve))

        UIView.animate(withDuration: TimeInterval(duration),
                       delay: 0,
                       options: options,
                       animations: { [weak self]() -> Void in
                        if let actualSelf = self
                            if actualSelf is TPKeyboardAvoidingScrollView {
                                actualSelf.contentSize = state.priorContentSize
                                actualSelf.contentInset = state.priorInset
                                actualSelf.scrollIndicatorInsets = state.priorScrollIndicatorInsets
                                actualSelf.isPagingEnabled = state.priorPagingEnabled

        }) { (finished) -> Void in


    func TPKeyboardAvoiding_updateFromContentSizeChange()
        let state = self.keyboardAvoidingState()
        if state.keyboardVisible
            state.priorContentSize = self.contentSize

    func TPKeyboardAvoiding_focusNextTextField() ->Bool
        guard let firstResponder = self.TPKeyboardAvoiding_findFirstResponderBeneathView(self) else { return false}
        guard let view = self.TPKeyboardAvoiding_findNextInputViewAfterView(firstResponder, beneathView: self) else { return false}
        Timer.scheduledTimer(timeInterval: 0.1, target: view, selector: #selector(becomeFirstResponder), userInfo: nil, repeats: false)

        return true


    func TPKeyboardAvoiding_scrollToActiveTextField()
        let state = self.keyboardAvoidingState()

        if !state.keyboardVisible { return }

        let visibleSpace = self.bounds.size.height - - self.contentInset.bottom

        let idealOffset = CGPoint(x: 0,
                                  y: self.TPKeyboardAvoiding_idealOffsetForView(self.TPKeyboardAvoiding_findFirstResponderBeneathView(self),
                                                                                viewAreaHeight: visibleSpace))

        DispatchQueue.main.asyncAfter(deadline: + Double((Int64)(0 * NSEC_PER_SEC)) / Double(NSEC_PER_SEC)) {[weak self] () -> Void in
            self?.setContentOffset(idealOffset, animated: true)

    func TPKeyboardAvoiding_findFirstResponderBeneathView(_ view:UIView) -> UIView?
        for childView in view.subviews
            if childView.responds(to: #selector(getter: isFirstResponder)) && childView.isFirstResponder
                return childView
            let result = TPKeyboardAvoiding_findFirstResponderBeneathView(childView)
            if result != nil
                return result
        return nil

    func TPKeyboardAvoiding_updateContentInset()
        let state = self.keyboardAvoidingState()
        if state.keyboardVisible
            self.contentInset = self.TPKeyboardAvoiding_contentInsetForKeyboard()

    func TPKeyboardAvoiding_calculatedContentSizeFromSubviewFrames() ->CGSize
        let wasShowingVerticalScrollIndicator = self.showsVerticalScrollIndicator
        let wasShowingHorizontalScrollIndicator = self.showsHorizontalScrollIndicator

        self.showsVerticalScrollIndicator = false
        self.showsHorizontalScrollIndicator = false

        var rect =

        for view in self.subviews
            rect = rect.union(view.frame)

        rect.size.height += kCalculatedContentPadding
        self.showsVerticalScrollIndicator = wasShowingVerticalScrollIndicator
        self.showsHorizontalScrollIndicator = wasShowingHorizontalScrollIndicator

        return rect.size

    func TPKeyboardAvoiding_idealOffsetForView(_ view:UIView?,viewAreaHeight:CGFloat) -> CGFloat
        let contentSize = self.contentSize

        var offset:CGFloat = 0.0
        let subviewRect =  view != nil ? view!.convert(view!.bounds, to: self) :

        var padding = (viewAreaHeight - subviewRect.height)/2
        if padding < kMinimumScrollOffsetPadding
            padding = kMinimumScrollOffsetPadding

        offset = subviewRect.origin.y - padding -

        if offset > (contentSize.height - viewAreaHeight)
            offset = contentSize.height - viewAreaHeight

        if offset <
            offset =

        return offset

    func TPKeyboardAvoiding_contentInsetForKeyboard() -> UIEdgeInsets
        let state = self.keyboardAvoidingState()
        var newInset = self.contentInset;

        let keyboardRect = state.keyboardRect
        newInset.bottom = keyboardRect.size.height - max(keyboardRect.maxY - self.bounds.maxY, 0)

        return newInset


    func TPKeyboardAvoiding_viewIsValidKeyViewCandidate(_ view:UIView)->Bool
        if view.isHidden || !view.isUserInteractionEnabled {return false}

        if view is UITextField
            if (view as! UITextField).isEnabled {return true}

        if view is UITextView
            if (view as! UITextView).isEditable {return true}

        return false

    func TPKeyboardAvoiding_findNextInputViewAfterView(_ priorView:UIView,beneathView view:UIView, candidateView bestCandidate: inout UIView?)
        let priorFrame = self.convert(priorView.frame, to: priorView.superview)
        let candidateFrame = bestCandidate == nil ? : self.convert(bestCandidate!.frame, to: bestCandidate!.superview)

        var bestCandidateHeuristic = -sqrt(candidateFrame.origin.x*candidateFrame.origin.x + candidateFrame.origin.y*candidateFrame.origin.y) + ( Float(fabs(candidateFrame.minY - priorFrame.minY))<Float.ulpOfOne ? 1e6 : 0)

        for childView in view.subviews
            if TPKeyboardAvoiding_viewIsValidKeyViewCandidate(childView)
                let frame = self.convert(childView.frame, to: view)
                let heuristic = -sqrt(frame.origin.x*frame.origin.x + frame.origin.y*frame.origin.y)
                    + (Float(fabs(frame.minY - priorFrame.minY)) < Float.ulpOfOne ? 1e6 : 0)

                if childView != priorView && (Float(fabs(frame.minY - priorFrame.minY)) < Float.ulpOfOne
                    && frame.minX > priorFrame.minX
                    || frame.minY > priorFrame.minY)
                    && (bestCandidate == nil || heuristic > bestCandidateHeuristic)
                    bestCandidate = childView
                    bestCandidateHeuristic = heuristic
                self.TPKeyboardAvoiding_findNextInputViewAfterView(priorView, beneathView: view, candidateView: &bestCandidate)

    func TPKeyboardAvoiding_findNextInputViewAfterView(_ priorView:UIView,beneathView view:UIView) ->UIView?
        var candidate:UIView?
        self.TPKeyboardAvoiding_findNextInputViewAfterView(priorView, beneathView: view, candidateView: &candidate)
        return candidate

    @objc func TPKeyboardAvoiding_assignTextDelegateForViewsBeneathView(_ obj: AnyObject)
        func processWithView(_ view: UIView) {
            for childView in view.subviews
                if childView is UITextField || childView is UITextView

        if let timer = obj as? Timer, let view = timer.userInfo as? UIView {
        else if let view = obj as? UIView {

    func TPKeyboardAvoiding_initializeView(_ view:UIView)
        if let textField = view as? UITextField,
            let delegate = self as? UITextFieldDelegate, textField.returnKeyType == UIReturnKeyType.default &&
            textField.delegate !== delegate
            textField.delegate = delegate
            let otherView = self.TPKeyboardAvoiding_findNextInputViewAfterView(view, beneathView: self)
            textField.returnKeyType = otherView != nil ? .next : .done


    func keyboardAvoidingState()->TPKeyboardAvoidingState
        var state = objc_getAssociatedObject(self, &AssociatedKeysKeyboard.DescriptiveName) as? TPKeyboardAvoidingState
        if state == nil
            state = TPKeyboardAvoidingState()
            self.state = state

        return self.state!


// MARK: - Internal object observer
internal class TPKeyboardAvoidingState:NSObject
    var priorInset =
    var priorScrollIndicatorInsets =

    var keyboardVisible = false
    var keyboardRect =
    var priorContentSize =

    var priorPagingEnabled = false

internal extension UIScrollView
    fileprivate struct AssociatedKeysKeyboard {
        static var DescriptiveName = "KeyBoard_DescriptiveName"

    var state:TPKeyboardAvoidingState?{
            let optionalObject:AnyObject? = objc_getAssociatedObject(self, &AssociatedKeysKeyboard.DescriptiveName) as AnyObject?
            if let object:AnyObject = optionalObject {
                return object as? TPKeyboardAvoidingState
            } else {
                return nil
            objc_setAssociatedObject(self, &AssociatedKeysKeyboard.DescriptiveName, newValue, objc_AssociationPolicy.OBJC_ASSOCIATION_RETAIN_NONATOMIC)

Javascript Thousand Separator / string format

You can use ngx-format-field. It is a directive to format the input value which will appear in the view. It will not manipulate the Input value which will be saved in the backend. See link here!



<input type="text" formControlName="currency" [appFormatFields]="CURRENCY"


onChangeCurrency() {

To see the demo: here!

100% width in React Native Flexbox

Simply add alignSelf: "stretch" to your item's stylesheet.

line1: {
    backgroundColor: '#FDD7E4',
    alignSelf: 'stretch',
    textAlign: 'center',

Android Studio: Drawable Folder: How to put Images for Multiple dpi?

Simply go to project Explorer and change your View from Android to project from drop Down and you are good to go.There you can simply create folder like we do in Eclipse. And in android project view it is hidden but when you switch to project. You can create folder like drawable-hdpi,drawable-xhdpi.

enter image description here

how to check if a datareader is null or empty



objCar.StrDescription = (objSqlDataReader["fieldDescription"].GetType() != typeof(DBNull)) ? (String)objSqlDataReader["fieldDescription"] : "";

cannot download, $GOPATH not set

I found easier to do it like this:

export GOROOT=$HOME/go
export GOPATH=$GOROOT/bin

Visual Studio replace tab with 4 spaces?

For VS2010 and above (VS2010 needs a plugin). If you have checked/set the options of the tab size in Visual Studio but it still won't work. Then check if you have a .editorconfig file in your project! This will override the Visual Studio settings. Edit the tab-size in that file.

This can happen if you install an Angular application in your project with the Angular-Cli.

See MSDN blog

Escaping backslash in string - javascript

Slightly hacky, but it works:

const input = '\text';_x000D_
const output = JSON.stringify(input).replace(/((^")|("$))/g, "").trim();_x000D_
console.log({ input, output });_x000D_
// { input: '\text', output: '\\text' }

jQuery: Return data after ajax call success

Note: This answer was written in February 2010.
See updates from 2015, 2016 and 2017 at the bottom.

You can't return anything from a function that is asynchronous. What you can return is a promise. I explained how promises work in jQuery in my answers to those questions:

If you could explain why do you want to return the data and what do you want to do with it later, then I might be able to give you a more specific answer how to do it.

Generally, instead of:

function testAjax() {
    url: "getvalue.php",  
    success: function(data) {
      return data; 

you can write your testAjax function like this:

function testAjax() {
  return $.ajax({
      url: "getvalue.php"

Then you can get your promise like this:

var promise = testAjax();

You can store your promise, you can pass it around, you can use it as an argument in function calls and you can return it from functions, but when you finally want to use your data that is returned by the AJAX call, you have to do it like this:

promise.success(function (data) {

(See updates below for simplified syntax.)

If your data is available at this point then this function will be invoked immediately. If it isn't then it will be invoked as soon as the data is available.

The whole point of doing all of this is that your data is not available immediately after the call to $.ajax because it is asynchronous. Promises is a nice abstraction for functions to say: I can't return you the data because I don't have it yet and I don't want to block and make you wait so here's a promise instead and you'll be able to use it later, or to just give it to someone else and be done with it.

See this DEMO.

UPDATE (2015)

Currently (as of March, 2015) jQuery Promises are not compatible with the Promises/A+ specification which means that they may not cooperate very well with other Promises/A+ conformant implementations.

However jQuery Promises in the upcoming version 3.x will be compatible with the Promises/A+ specification (thanks to Benjamin Gruenbaum for pointing it out). Currently (as of May, 2015) the stable versions of jQuery are 1.x and 2.x.

What I explained above (in March, 2011) is a way to use jQuery Deferred Objects to do something asynchronously that in synchronous code would be achieved by returning a value.

But a synchronous function call can do two things - it can either return a value (if it can) or throw an exception (if it can't return a value). Promises/A+ addresses both of those use cases in a way that is pretty much as powerful as exception handling in synchronous code. The jQuery version handles the equivalent of returning a value just fine but the equivalent of complex exception handling is somewhat problematic.

In particular, the whole point of exception handling in synchronous code is not just giving up with a nice message, but trying to fix the problem and continue the execution, or possibly rethrowing the same or a different exception for some other parts of the program to handle. In synchronous code you have a call stack. In asynchronous call you don't and advanced exception handling inside of your promises as required by the Promises/A+ specification can really help you write code that will handle errors and exceptions in a meaningful way even for complex use cases.

For differences between jQuery and other implementations, and how to convert jQuery promises to Promises/A+ compliant, see Coming from jQuery by Kris Kowal et al. on the Q library wiki and Promises arrive in JavaScript by Jake Archibald on HTML5 Rocks.

How to return a real promise

The function from my example above:

function testAjax() {
  return $.ajax({
      url: "getvalue.php"

returns a jqXHR object, which is a jQuery Deferred Object.

To make it return a real promise, you can change it to - using the method from the Q wiki:

function testAjax() {
  return Q($.ajax({
      url: "getvalue.php"

or, using the method from the HTML5 Rocks article:

function testAjax() {
  return Promise.resolve($.ajax({
      url: "getvalue.php"

This Promise.resolve($.ajax(...)) is also what is explained in the promise module documentation and it should work with ES6 Promise.resolve().

To use the ES6 Promises today you can use es6-promise module's polyfill() by Jake Archibald.

To see where you can use the ES6 Promises without the polyfill, see: Can I use: Promises.

For more info see:

Future of jQuery

Future versions of jQuery (starting from 3.x - current stable versions as of May 2015 are 1.x and 2.x) will be compatible with the Promises/A+ specification (thanks to Benjamin Gruenbaum for pointing it out in the comments). "Two changes that we've already decided upon are Promise/A+ compatibility for our Deferred implementation [...]" (jQuery 3.0 and the future of Web development). For more info see: jQuery 3.0: The Next Generations by Dave Methvin and jQuery 3.0: More interoperability, less Internet Explorer by Paul Krill.

Interesting talks

UPDATE (2016)

There is a new syntax in ECMA-262, 6th Edition, Section 14.2 called arrow functions that may be used to further simplify the examples above.

Using the jQuery API, instead of:

promise.success(function (data) {

you can write:

promise.success(data => alert(data));

or using the Promises/A+ API:

promise.then(data => alert(data));

Remember to always use rejection handlers either with:

promise.then(data => alert(data), error => alert(error));

or with:

promise.then(data => alert(data)).catch(error => alert(error));

See this answer to see why you should always use rejection handlers with promises:

Of course in this example you could use just promise.then(alert) because you're just calling alert with the same arguments as your callback, but the arrow syntax is more general and lets you write things like:

promise.then(data => alert("x is " + data.x));

Not every browser supports this syntax yet, but there are certain cases when you're sure what browser your code will run on - e.g. when writing a Chrome extension, a Firefox Add-on, or a desktop application using Electron, NW.js or AppJS (see this answer for details).

For the support of arrow functions, see:

UPDATE (2017)

There is an even newer syntax right now called async functions with a new await keyword that instead of this code:

    .then(data => console.log('Data:', data))
    .catch(error => console.log('Error:', error));

lets you write:

try {
    let data = await functionReturningPromise();
    console.log('Data:', data);
} catch (error) {
    console.log('Error:', error);

You can only use it inside of a function created with the async keyword. For more info, see:

For support in browsers, see:

For support in Node, see:

In places where you don't have native support for async and await you can use Babel:

or with a slightly different syntax a generator based approach like in co or Bluebird coroutines:

More info

Some other questions about promises for more details:

How to break out of the IF statement

just want to add another variant to update this wonderful "how to" list. Though, It may be really useful in more complicated cases:

try {
    if (something)
        //some code
        if (something2)
            throw new Exception("Weird-01.");
            // now You will go to the catch statement
        if (something3)
            throw new Exception("Weird-02.");
            // now You will go to the catch statement
        //some code
catch (Exception ex)
    Console.WriteLine(ex); // you will get your Weird-01 or Weird-02 here
// The code i want to go if the second or third if is true

Batch file to delete files older than N days

Gosh, a lot of answers already. A simple and convenient route I found was to execute ROBOCOPY.EXE twice in sequential order from a single Windows command line instruction using the & parameter.


In this example it works by picking all files (.) that are older than 30 days old and moving them to the target folder. The second command does the same again with the addition of the PURGE command which means remove files in the target folder that don’t exist in the source folder. So essentially, the first command MOVES files and the second DELETES because they no longer exist in the source folder when the second command is invoked.

Consult ROBOCOPY's documentation and use the /L switch when testing.

How to get height of Keyboard?

The method by ZAFAR007 updated for Swift 5 in Xcode 10

override func viewDidLoad() {

    NotificationCenter.default.addObserver(self, selector: #selector(keyboardWillShow), name: UIResponder.keyboardWillShowNotification, object: nil)


@objc func keyboardWillShow(notification: NSNotification) {

    if let keyboardSize = (notification.userInfo?[UIResponder.keyboardFrameBeginUserInfoKey] as? NSValue)?.cgRectValue {
        let keyboardHeight : Int = Int(keyboardSize.height)


m2e lifecycle-mapping not found

You can use this dummy plugin:

mvn archetype:generate -DgroupId=org.eclipse.m2e -DartifactId=lifecycle-mapping -Dversion=1.0.0 -DarchetypeArtifactId=maven-archetype-mojo

After generating the project install/deploy it.

"Could not find the main class" error when running jar exported by Eclipse

I ran into the same issues the other day and it took me days to make it work. The error message was "Could not find the main class", but I can run the executable jar exported from Eclipse in other Windows machines without any problem.

The solution was to install both x64 and x86 version of the same version of JRE. The path environment variable was pointed to the x64 version. No idea why, but it worked for me.

How to make a dropdown readonly using jquery?

It´s work very well

$('#cf_1268591 option:not(:selected)').prop('disabled', true);

With this I can see the options but I can't select it

Can I use a min-height for table, tr or td?

The solution without div is used a pseudo element like ::after into first td in row with min-height. Save your HTML clean.

table tr td:first-child::after {
   content: "";
   display: inline-block;
   vertical-align: top;
   min-height: 60px;

Plotting histograms from grouped data in a pandas DataFrame

I'm on a roll, just found an even simpler way to do it using the by keyword in the hist method:


That's a very handy little shortcut for quickly scanning your grouped data!

For future visitors, the product of this call is the following chart: enter image description here

Rollback transaction after @Test

Aside: attempt to amend Tomasz Nurkiewicz's answer was rejected:

This edit does not make the post even a little bit easier to read, easier to find, more accurate or more accessible. Changes are either completely superfluous or actively harm readability.

Correct and permanent link to the relevant section of documentation about integration testing.

To enable support for transactions, you must configure a PlatformTransactionManager bean in the ApplicationContext that is loaded via @ContextConfiguration semantics.

public class Persistence {
    Environment env;

    DataSource dataSource() {
        return new DriverManagerDataSource(

    PlatformTransactionManager transactionManager() {
        return new DataSourceTransactionManager(dataSource());

In addition, you must declare Spring’s @Transactional annotation either at the class or method level for your tests.

@ContextConfiguration(classes = {Persistence.class, SomeRepository.class})
public class SomeRepositoryTest { ... }

Annotating a test method with @Transactional causes the test to be run within a transaction that will, by default, be automatically rolled back after completion of the test. If a test class is annotated with @Transactional, each test method within that class hierarchy will be run within a transaction.

how to insert value into DataGridView Cell?

You can access any DGV cell as follows :

dataGridView1.Rows[rowIndex].Cells[columnIndex].Value = value;

But usually it's better to use databinding : you bind the DGV to a data source (DataTable, collection...) through the DataSource property, and only work on the data source itself. The DataGridView will automatically reflect the changes, and changes made on the DataGridView will be reflected on the data source

I can't install python-ldap

On Fedora 22, you need to do this instead:

sudo dnf install python-devel
sudo dnf install openldap-devel

Make code in LaTeX look *nice*

It turns out that lstlisting is able to format code nicely, but requires a lot of tweaking.

Wikibooks has a good example for the parameters you can tweak.

append new row to old csv file python

If you use pandas, you can append your dataframes to an existing CSV file this way:

df.to_csv('log.csv', mode='a', index=False, header=False)

With mode='a' we ensure that we append, rather than overwrite, and with header=False we ensure that we append only the values of df rows, rather than header + values.

Android Fatal signal 11 (SIGSEGV) at 0x636f7d89 (code=1). How can it be tracked down?

In my case the issue was being caused by the Android Profiler. In Android Studio, click on "Android Profiler" and "end session".

Ironically, it was also causing extreme performance issues in the application.

"Templates can be used only with field access, property access, single-dimension array index, or single-parameter custom indexer expressions" error

The ...For extension methods on the HtmlHelper (e.g., DisplayFor, TextBoxFor, ElementFor, etc...) take a property and nothing else. If you don't have a property, use the non-For method (e.g., Display, TextBox, Element, etc...).

The ...For extension methods provides a way of simplifying postback by naming the control after the property. This is why it takes an expression and not simply a value. If you are not interested in this postback facilitation then do not use the ...For methods at all.

Note: You should not be doing things like calling ToString inside the view. This should be done inside the view model. I realize that a lot of demo projects put domain objects straight into the view. In my experience, this rarely works because it assumes that you do not want any formatting on the data in the domain entity. Best practice is to create a view model that wraps the entity into something that can be directly consumed by the view. Most of the properties in this view model should be strings that are already formatted or data for which you have element or display templates created.

Why is synchronized block better than synchronized method?

Difference between synchronized block and synchronized method are following:

  1. synchronized block reduce scope of lock, but synchronized method's scope of lock is whole method.
  2. synchronized block has better performance as only the critical section is locked but synchronized method has poor performance than block.
  3. synchronized block provide granular control over lock but synchronized method lock either on current object represented by this or class level lock.
  4. synchronized block can throw NullPointerException but synchronized method doesn't throw.
  5. synchronized block: synchronized(this){}

    synchronized method: public synchronized void fun(){}

What are all the possible values for HTTP "Content-Type" header?

If you are using jaxrs or any other, then there will be a class called mediatype.User interceptor before sending the request and compare it against this.

Jquery/Ajax call with timer

If you want to set something on a timer, you can use JavaScript's setTimeout or setInterval methods:

setTimeout ( expression, timeout );
setInterval ( expression, interval );

Where expression is a function and timeout and interval are integers in milliseconds. setTimeout runs the timer once and runs the expression once whereas setInterval will run the expression every time the interval passes.

So in your case it would work something like this:

setInterval(function() {
    //call $.ajax here
}, 5000); //5 seconds

As far as the Ajax goes, see jQuery's ajax() method. If you run an interval, there is nothing stopping you from calling the same ajax() from other places in your code.

If what you want is for an interval to run every 30 seconds until a user initiates a form submission...and then create a new interval after that, that is also possible:

setInterval() returns an integer which is the ID of the interval.

var id = setInterval(function() {
    //call $.ajax here
}, 30000); // 30 seconds

If you store that ID in a variable, you can then call clearInterval(id) which will stop the progression.

Then you can reinstantiate the setInterval() call after you've completed your ajax form submission.

Unprotect workbook without password

No longer works for spreadsheets Protected with Excel 2013 or later -- they improved the pw hash. So now need to unzip .xlsx and hack the internals.

how to concatenate two dictionaries to create a new one in Python?

  1. Slowest and doesn't work in Python3: concatenate the items and call dict on the resulting list:

    $ python -mtimeit -s'd1={1:2,3:4}; d2={5:6,7:9}; d3={10:8,13:22}' \
    'd4 = dict(d1.items() + d2.items() + d3.items())'
    100000 loops, best of 3: 4.93 usec per loop
  2. Fastest: exploit the dict constructor to the hilt, then one update:

    $ python -mtimeit -s'd1={1:2,3:4}; d2={5:6,7:9}; d3={10:8,13:22}' \
    'd4 = dict(d1, **d2); d4.update(d3)'
    1000000 loops, best of 3: 1.88 usec per loop
  3. Middling: a loop of update calls on an initially-empty dict:

    $ python -mtimeit -s'd1={1:2,3:4}; d2={5:6,7:9}; d3={10:8,13:22}' \
    'd4 = {}' 'for d in (d1, d2, d3): d4.update(d)'
    100000 loops, best of 3: 2.67 usec per loop
  4. Or, equivalently, one copy-ctor and two updates:

    $ python -mtimeit -s'd1={1:2,3:4}; d2={5:6,7:9}; d3={10:8,13:22}' \
    'd4 = dict(d1)' 'for d in (d2, d3): d4.update(d)'
    100000 loops, best of 3: 2.65 usec per loop

I recommend approach (2), and I particularly recommend avoiding (1) (which also takes up O(N) extra auxiliary memory for the concatenated list of items temporary data structure).

Truststore and Keystore Definitions

In a SSL handshake the purpose of trustStore is to verify credentials and the purpose of keyStore is to provide credential.


keyStore in Java stores private key and certificates corresponding to their public keys and require if you are SSL Server or SSL requires client authentication.


TrustStore stores certificates from third party, your Java application communicate or certificates signed by CA(certificate authorities like Verisign, Thawte, Geotrust or GoDaddy) which can be used to identify third party.


TrustManager determines whether remote connection should be trusted or not i.e. whether remote party is who it claims to and KeyManager decides which authentication credentials should be sent to the remote host for authentication during SSL handshake.

If you are an SSL Server you will use private key during key exchange algorithm and send certificates corresponding to your public keys to client, this certificate is acquired from keyStore. On SSL client side, if its written in Java, it will use certificates stored in trustStore to verify identity of Server. SSL certificates are most commonly comes as .cer file which is added into keyStore or trustStore by using any key management utility e.g. keytool.


I need an unordered list without any bullets

 <div class="custom-control custom-checkbox left">
    <ul class="list-unstyled">
         <label class="btn btn-secondary text-left" style="width:100%;text-align:left;padding:2px;">
           <input type="checkbox" style="zoom:1.7;vertical-align:bottom;" asp-for="@Model[i].IsChecked" class="custom-control-input" /> @Model[i].Title

How to load assemblies in PowerShell?

LoadWithPartialName has been deprecated. The recommended solution for PowerShell V3 is to use the Add-Type cmdlet e.g.:

Add-Type -Path 'C:\Program Files\Microsoft SQL Server\110\SDK\Assemblies\Microsoft.SqlServer.Smo.dll'

There are multiple different versions and you may want to pick a particular version. :-)

How do you do a deep copy of an object in .NET?

Maybe you only need a shallow copy, in that case use Object.MemberWiseClone().

There are good recommendations in the documentation for MemberWiseClone() for strategies to deep copy: -

Does reading an entire file leave the file handle open?

You can use pathlib.

For Python 3.5 and above:

from pathlib import Path
contents = Path(file_path).read_text()

For older versions of Python use pathlib2:

$ pip install pathlib2


from pathlib2 import Path
contents = Path(file_path).read_text()

This is the actual read_text implementation:

def read_text(self, encoding=None, errors=None):
    Open the file in text mode, read it, and close the file.
    with'r', encoding=encoding, errors=errors) as f:

Getting Access Denied when calling the PutObject operation with bucket-level permission

I was having the same error message for a mistake I made: Make sure you use a correct s3 uri such as: s3://my-bucket-name/

(If my-bucket-name is at the root of your aws s3 obviously)

I insist on that because when copy pasting the s3 bucket from your browser you get something like

Thus I made the mistake to use s3://buckets/my-bucket-name which raises:

An error occurred (AccessDenied) when calling the PutObject operation: Access Denied

How to add image in Flutter

  1. Create images folder in root level of your project.

    enter image description here

    enter image description here

  2. Drop your image in this folder, it should look like

    enter image description here

  3. Go to your pubspec.yaml file, add assets header and pay close attention to all the spaces.

      uses-material-design: true
      # add this
        - images/profile.jpg
  4. Tap on Packages get at the top right corner of the IDE.

    enter image description here

  5. Now you can use your image anywhere using


How do I find the parent directory in C#?


If you clear the "bin\Debug\" in the Project properties -> Build -> Output path, then you can just use AppDomain.CurrentDomain.BaseDirectory

Zip folder in C#

There's nothing in the BCL to do this for you, but there are two great libraries for .NET which do support the functionality.

I've used both and can say that the two are very complete and have well-designed APIs, so it's mainly a matter of personal preference.

I'm not sure whether they explicitly support adding Folders rather than just individual files to zip files, but it should be quite easy to create something that recursively iterated over a directory and its sub-directories using the DirectoryInfo and FileInfo classes.

Copy mysql database from remote server to local computer

Assuming the following command works successfully:

mysql -u username -p -h

The syntax for mysqldump is identical, and outputs the database dump to stdout. Redirect the output to a local file on the computer:

mysqldump -u username -p -h DBNAME > backup.sql

Replace DBNAME with the name of the database you'd like to download to your computer.

How to update and delete a cookie?

update would just be resetting it using createCookie

function createCookie(name,value,days) {
    if (days) {
        var date = new Date();
        date.setTime(date.getTime() + (days * 24 * 60 * 60 *1000));
        var expires = "; expires=" + date.toGMTString();
    } else {
        var expires = "";
    document.cookie = name + "=" + value + expires + "; path=/";

function readCookie(name) {
    var nameEQ = name + "=";
    var ca = document.cookie.split(';');
    for(var i=0;i < ca.length;i++) {
        var c = ca[i];
        while (c.charAt(0)==' ') {
            c = c.substring(1,c.length);
        if (c.indexOf(nameEQ) == 0) {
            return c.substring(nameEQ.length,c.length);
    return null;

function eraseCookie(name) {

How can I get Git to follow symlinks?

I used to add files beyond symlinks for quite some time now. This used to work just fine, without making any special arrangements. Since I updated to Git 1.6.1, this does not work any more.

You may be able to switch to Git 1.6.0 to make this work. I hope that a future version of Git will have a flag to git-add allowing it to follow symlinks again.

Calculating and printing the nth prime number

int counter = 0;

for(int i = 1; ; i++) {

    if(counter == userInput) {

Edit: Your prime function could use a bit of work. Here's one that I have written:

private static boolean isPrime(long n) {
    if(n < 2)
        return false;

    for (long i = 2; i * i <= n; i++) {
        if (n % i == 0)
            return false;
    return true;

Note - you only need to go up to sqrt(n) when looking at factors, hence the i * i <= n

Why do I get a "permission denied" error while installing a gem?

I wanted to share the steps that I followed that fixed this issue for me in the hopes that it can help someone else (and also as a reminder for me in case something like this happens again)

The issues I'd been having (which were the same as OP's) may have to do with using homebrew to install Ruby.

To fix this, first I updated homebrew:

brew update && brew upgrade
brew doctor

(If brew doctor comes up with any issues, fix them first.) Then I uninstalled ruby

brew uninstall ruby

If rbenv is NOT installed at this point, then

brew install rbenv
brew install ruby-build
echo 'export RBENV_ROOT=/usr/local/var/rbenv' >> ~/.bash_profile
echo 'if which rbenv > /dev/null; then eval "$(rbenv init -)"; fi' >> ~/.bash_profile

Then I used rbenv to install ruby. First, find the desired version:

rbenv install -l

Install that version (e.g. 2.2.2)

rbenv install 2.2.2

Then set the global version to the desired ruby version:

rbenv global 2.2.2

At this point you should see the desired version set for the following commands:

rbenv versions


ruby --version

Now you should be able to install bundler:

gem install bundler

And once in the desired project folder, you can install all the required gems:

bundle install

Is there a way to use two CSS3 box shadows on one element?

Box shadows can use commas to have multiple effects, just like with background images (in CSS3).

Project has no file! Edit the project properties to set one

Project has no file! Edit the project properties to set one

best option is create new workspace import the project ,fix the project its work

fatal: Unable to create temporary file '/home/username/git/myrepo.git/./objects/pack/tmp_pack_XXXXXX': Permission denied

One of the principal issues with pushing to a GIT is that the material you push will appear as your material, and will block submissions from other people on a team. As a GIT repository administrator, you will have to manage the hooks to prevent Alice's push from blocking Bob from pushing. To do that, you will want to ensure that your developers all belong to a group, lets call it 'developers' and that the repository is owned by root:developers, and then add this to the hooks/post-update script:

sudo chown -R root:developers $GIT_DIR
sudo chmod -R g+w $GIT_DIR

That will make it so that team members are able to push to the repository without stepping on each other's toes.

How to find a string inside a entire database?

Here are couple more free tools that can be used for this. Both work as SSMS addins.

ApexSQL Search – 100% free - searches both schema and data in tables. Has couple more useful options such as dependency tracking…

SSMS Tools pack – free for all versions except SQL 2012 – doesn’t look as advanced as previous one but has a lot of other cool features.

Is there a way to get LaTeX to place figures in the same page as a reference to that figure?

Yes, include float package into the top of your document and H (capital H) as a figure specifier:



struct in class

You should define the struct out of the class like this:

#include <iostream>
using namespace std;
struct X
        int v;
class E
      X var;

int main(){

E object;

return 0;

How to upload a file to directory in S3 bucket using boto

import boto
from boto.s3.key import Key

END_POINT = ''                          # eg. us-east-1
S3_HOST = ''                            # eg.
BUCKET_NAME = 'test'        
FILENAME = 'upload.txt'                
UPLOADED_FILENAME = 'dumps/upload.txt'
# include folders in file path. If it doesn't exist, it will be created

s3 = boto.s3.connect_to_region(END_POINT,

bucket = s3.get_bucket(BUCKET_NAME)
k = Key(bucket)

How to catch an Exception from a thread

Also from Java 8 you can write Dan Cruz answer as:

Thread t = new Thread(()->{
            System.out.println("Sleeping ...");
            try {
            } catch (InterruptedException e) {
            System.out.println("Throwing exception ...");
            throw new RuntimeException(); });

t.setUncaughtExceptionHandler((th, ex)-> log(String.format("Exception in thread %d id: %s", th.getId(), ex)));

Can we call the function written in one JavaScript in another JS file?

The function could be called as if it was in the same JS File as long as the file containing the definition of the function has been loaded before the first use of the function.



function alertNumber(number) {


function alertOne() {


    <script src="File1.js" type="text/javascript"></script> 
    <script src="File2.js" type="text/javascript"></script> 
    <script type="text/javascript">

The other way won't work. As correctly pointed out by Stuart Wakefield. The other way will also work.


    <script src="File2.js" type="text/javascript"></script> 
    <script src="File1.js" type="text/javascript"></script> 
    <script type="text/javascript">

What will not work would be:


    <script src="File2.js" type="text/javascript"></script> 
    <script type="text/javascript">
    <script src="File1.js" type="text/javascript"></script> 

Although alertOne is defined when calling it, internally it uses a function that is still not defined (alertNumber).

PostgreSQL: ERROR: operator does not exist: integer = character varying

I think it is telling you exactly what is wrong. You cannot compare an integer with a varchar. PostgreSQL is strict and does not do any magic typecasting for you. I'm guessing SQLServer does typecasting automagically (which is a bad thing).

If you want to compare these two different beasts, you will have to cast one to the other using the casting syntax ::.

Something along these lines:

create view view1
select table1.col1,table2.col1,table3.col3
from table1 
inner join
inner join 
table1.col4::varchar = table2.col5
/* Here col4 of table1 is of "integer" type and col5 of table2 is of type "varchar" */
/* ERROR: operator does not exist: integer = character varying */

Notice the varchar typecasting on the table1.col4.

Also note that typecasting might possibly render your index on that column unusable and has a performance penalty, which is pretty bad. An even better solution would be to see if you can permanently change one of the two column types to match the other one. Literately change your database design.

Or you could create a index on the casted values by using a custom, immutable function which casts the values on the column. But this too may prove suboptimal (but better than live casting).

Can I recover a branch after its deletion in Git?

Adding to tfe answer: there is also the script in the contrib/ area of the Git sources (in git.git repository), which might help you.

git-resurrect <name> attempts to find traces of a branch tip called <name>, and tries to resurrect it. Currently, the reflog is searched for checkout messages, and with -r also merge messages. With -m and -t, the history of all refs is scanned for Merge <name> into other/Merge <other> into <name> (respectively) commit subjects, which is rather slow but allows you to resurrect other people's topic branches.

How do you check current view controller class in Swift?

For types you can use is and if it is your own viewcontroller class then you need to use isKindOfClass like:

let vcOnTop = self.embeddedNav.viewControllers[self.embeddedNav.viewControllers.count-1]
            if vcOnTop.isKindOfClass(VcShowDirections){

How can I get the current stack trace in Java?

Another solution (only 35 31 characters):

new Exception().printStackTrace();   
new Error().printStackTrace();

Indexes of all occurrences of character in a string

Try the following (Which does not print -1 at the end now!)

int index = word.indexOf(guess);
while(index >= 0) {
   index = word.indexOf(guess, index+1);

Why is this rsync connection unexpectedly closed on Windows?

The trick for me was I had ssh conflict.

I have Git installed on my Windows path, which includes ssh. cwrsync also installs ssh.

The trick is to have make a batch file to set the correct paths:


@echo off
SET CWRSYNCHOME=c:\commands\cwrsync
SET HOME=c:\Users\Petah\
%~dp0\cwrsync\bin\rsync.exe %*

On Windows you can type where ssh to check if this is an issue. You will get something like this:

where ssh
C:\Program Files (x86)\Git\bin\ssh.exe
C:\Program Files\cwRsync\ssh.exe

Get type of all variables

Designed to do essentially the inverse of what you wanted, here's one of my toolkit toys:

if (type=='function') type <-'closure'

Usage of MySQL's "IF EXISTS"

     SELECT count(*) FROM gdata_calendars 
     WHERE `group` =  ? AND id = ?)

For Detail explanation you can visit here

How can I clone a private GitLab repository?

You have your ssh clone statement wrong: git clone username [email protected]:root/test.git

That statement would try to clone a repository named username into the location relative to your current path, [email protected]:root/test.git.

You want to leave out username:

git clone [email protected]:root/test.git

Cannot open database "test" requested by the login. The login failed. Login failed for user 'xyz\ASPNET'

Well, the error is pretty clear, no? You are trying to connect to your SQL Server with user "xyz/ASPNET" - that's the account your ASP.NET app is running under.

This account is not allowed to connect to SQL Server - either create a login on SQL Server for that account, or then specify another valid SQL Server account in your connection string.

Can you show us your connection string (by updating your original question)?

UPDATE: Ok, you're using integrated Windows authentication --> you need to create a SQL Server login for "xyz\ASPNET" on your SQL Server - or change your connection string to something like:

connectionString="Server=.\SQLExpress;Database=IFItest;User ID=xyz;pwd=top$secret"

If you have a user "xyz" with a password of "top$secret" in your database.

Advantages of using display:inline-block vs float:left in CSS

There is one characteristic about inline-block which may not be straight-forward though. That is that the default value for vertical-align in CSS is baseline. This may cause some unexpected alignment behavior. Look at this article.

Instead, when you do a float:left, the divs are independent of each other and you can align them using margin easily.

The specified DSN contains an architecture mismatch between the Driver and Application. JAVA

I ran into this problem when upgrading to a windows 7 server with some legacy CLASP applications. Trying to run a 32bit application on a 64 bit machine.

Try setting the application pools 32bit compatibility to True and/or create dsn's in 32 and 64 bit.

Open the odbc datasource window in both versions from the run box. C:\Windows\SysWOW64\odbcad32.exe C:\Windows\system32\odbcad32.exe

How to convert a string to number in TypeScript?

typescript needs to know that our var a is going to ether be Number || String

export type StringOrNumber = number | string;

export function toString (v: StringOrNumber) {
 return `${v}`;

export function toNumber (v: StringOrNumber) {
 return Number(v);

export function toggle (v: StringOrNumber) {
 return typeof v === "number" ? `${v}` : Number(v);

How can I fill out a Python string with spaces?

A nice trick to use in place of the various print formats:

(1) Pad with spaces to the right:

('hi' + '        ')[:8]

(2) Pad with leading zeros on the left:

('0000' + str(2))[-4:]

Getting an attribute value in xml element

I think I got it. I have to use org.w3c.dom.Element explicitly. I had a different Element field too.

VB.NET: Clear DataGridView

The mistake that you are making is that you seem to be using a dataset object for storing your data. Each time you use the following code to put data into your dataset you add data to the data already in your dataset.


If you assign the table in your dataset to a DataGridView object in your program by the following code you will get duplicate results because you have not cleared data which is already residing in your dataset and in your dataset table.

myDataGridView.DataSource = myDataSet.Tables(0)

To avoid replicating the data you have to call clear method on your dataset object.


An then assign the table in your dataset to your DataGridView object. The code is like this.

myDataGridView.DataSource = myDataSet.Tables(0)

You can try this code:

' clear previous data
DataGridView2.DataSource = Nothing
DataGridView2.DataMember = Nothing
    adapter1 = New SqlDataAdapter(sql, connection)
    ' clear data already in the dataset
    DataGridView2.DataSource = ds1.Tables(0)
Catch ex As Exception
End Try

Cannot connect to MySQL 4.1+ using old authentication

edit: This only applies if you are in control of the MySQL server... if you're not take a look at Mysql password hashing method old vs new

First check with the SQL query

SHOW VARIABLES LIKE 'old_passwords'

(in the MySQL command line client, HeidiSQL or whatever front end you like) whether the server is set to use the old password schema by default. If this returns old_passwords,Off you just happen to have old password entries in the user table. The MySQL server will use the old authentication routine for these accounts. You can simply set a new password for the account and the new routine will be used.

You can check which routine will be used by taking a look at the mysql.user table (with an account that has access to that table)

SELECT `User`, `Host`, Length(`Password`) FROM mysql.user

This will return 16 for accounts with old passwords and 41 for accounts with new passwords (and 0 for accounts with no password at all, you might want to take care of those as well).
Either use the user management tools of the MySQL front end (if there are any) or

SET PASSWORD FOR 'User'@'Host'=PASSWORD('yourpassword');
FLUSH Privileges;

(replace User and Host with the values you got from the previous query.) Then check the length of the password again. It should be 41 now and your client (e.g. mysqlnd) should be able to connect to the server.

see also the MySQL documentation: *

How to select rows from a DataFrame based on column values

More flexibility using .query with Pandas >= 0.25.0:

August 2019 updated answer

Since Pandas >= 0.25.0 we can use the query method to filter dataframes with Pandas methods and even column names which have spaces. Normally the spaces in column names would give an error, but now we can solve that using a backtick (`) - see GitHub:

# Example dataframe
df = pd.DataFrame({'Sender email':['[email protected]', "[email protected]", "[email protected]"]})

     Sender email
0  [email protected]
1  [email protected]
2    [email protected]

Using .query with method str.endswith:

df.query('`Sender email`.str.endswith("")')


     Sender email
1  [email protected]
2    [email protected]

Also we can use local variables by prefixing it with an @ in our query:

domain = ''
df.query('`Sender email`.str.endswith(@domain)')


     Sender email
1  [email protected]
2    [email protected]

what is Array.any? for javascript

What you want is .empty not .empty() to fully mimics Ruby :

     Object.defineProperty( Array.prototype, 'empty', {
           get: function ( ) { return this.length===0 }
      } );    


[].empty //true
[3,2,8].empty //false

For any , see my answer here

Material UI and Grid system

I looked around for an answer to this and the best way I found was to use Flex and inline styling on different components.

For example, to make two paper components divide my full screen in 2 vertical components (in ration of 1:4), the following code works fine.

const styles = {
    display: 'flex',
    flexDirection: 'row wrap',
    padding: 20,
    width: '100%'
    flex: 1,
    height: '100%',
    margin: 10,
    textAlign: 'center',
    padding: 10
    height: 600,
    flex: 4,
    margin: 10,
    textAlign: 'center',

class ExampleComponent extends React.Component {
  render() {
    return (
        <div style={styles.div}>
          <Paper zDepth={3} style={styles.paperLeft}>
            <h4>First Vertical component</h4>
          <Paper zDepth={3} style={styles.paperRight}>
              <h4>Second Vertical component</h4>

Now, with some more calculations, you can easily divide your components on a page.

Further Reading on flex

Warning: Null value is eliminated by an aggregate or other SET operation in Aqua Data Studio

Use ISNULL(field, 0) It can also be used with aggregates:

ISNULL(count(field), 0)

However, you might consider changing count(field) to count(*)



closedcases = ISNULL(
   (select count(closed) from ticket       
    where assigned_to = c.user_id and closed is not null       
    group by assigned_to), 0), 

opencases = ISNULL(
    (select count(closed) from ticket 
     where assigned_to = c.user_id and closed is null 
     group by assigned_to), 0),

How to pick a new color for each plotted line within a figure in matplotlib?

matplotlib 1.5+

You can use axes.set_prop_cycle (example).

matplotlib 1.0-1.4

You can use axes.set_color_cycle (example).

matplotlib 0.x

You can use Axes.set_default_color_cycle.

How do I get milliseconds from epoch (1970-01-01) in Java?

How about System.currentTimeMillis()?

From the JavaDoc:

Returns: the difference, measured in milliseconds, between the current time and midnight, January 1, 1970 UTC

Java 8 introduces the java.time framework, particularly the Instant class which "...models a ... point on the time-line...":

long now =;

Returns: the number of milliseconds since the epoch of 1970-01-01T00:00:00Z -- i.e. pretty much the same as above :-)


How to pass extra variables in URL with WordPress

$edit_post = add_query_arg('c', '123', 'news' );


<a href="<?php echo $edit_post; ?>">Go to New page</a>

You can add any page inplace of "news".

$.widget is not a function

Place your widget.js after core.js, but before any other jquery that calls the widget.js file. (Example: draggable.js) Precedence (order) matters in what javascript/jquery can 'see'. Always position helper code before the code that uses the helper code.

How to draw a circle with given X and Y coordinates as the middle spot of the circle?

The fillOval fits an oval inside a rectangle, with width=r, height = r you get a circle. If you want fillOval(x,y,r,r) to draw a circle with the center at (x,y) you will have to displace the rectangle by half its width and half its height.

public void drawCenteredCircle(Graphics2D g, int x, int y, int r) {
  x = x-(r/2);
  y = y-(r/2);

This will draw a circle with center at x,y

How to open a URL in a new Tab using JavaScript or jQuery?

 var url = "";, '_blank');

Generating random numbers with normal distribution in Excel

As @osknows said in a comment above (rather than an answer which is why I am adding this), the Analysis Pack includes Random Number Generation functions (e.g. NORM.DIST, NORM.INV) to generate a set of numbers. A good summary link is at

JPA: difference between @JoinColumn and @PrimaryKeyJoinColumn?

I normally differentiate these two via this diagram:

Use PrimaryKeyJoinColumn

enter image description here

Use JoinColumn

enter image description here

What is two way binding?

Actually emberjs supports two-way binding, which is one of the most powerful feature for a javascript MVC framework. You can check it out where it mentioning binding in its user guide.

for emberjs, to create two way binding is by creating a new property with the string Binding at the end, then specifying a path from the global scope:

App.wife = Ember.Object.create({
  householdIncome: 80000

App.husband = Ember.Object.create({
  householdIncomeBinding: 'App.wife.householdIncome'

App.husband.get('householdIncome'); // 80000

// Someone gets raise.
App.husband.set('householdIncome', 90000);
App.wife.get('householdIncome'); // 90000

Note that bindings don't update immediately. Ember waits until all of your application code has finished running before synchronizing changes, so you can change a bound property as many times as you'd like without worrying about the overhead of syncing bindings when values are transient.

Hope it helps in extend of original answer selected.

Round to 5 (or other number) in Python

def round_to_next5(n):
    return n + (5 - n) % 5

Python: read all text file lines in loop

You can stop the 2-line separation in the output by using

    with open('t.ini') as f:
       for line in f:
           print line.strip()
           if 'str' in line:

Error when deploying an artifact in Nexus

I had this exact problem today and the problem was that the version I was trying to release:perform was already in the Nexus repo.

In my case this was likely due to a network disconnect during an earlier invocation of release:perform. Even though I lost my connection, it appears the release succeeded.

Remove Trailing Spaces and Update in Columns in SQL Server


SELECT TRIM('   Sample   ');

Result: 'Sample'

UPDATE TableName SET ColumnName = TRIM(ColumnName)

How to return a struct from a function in C++?

As pointed out by others, define studentType outside the function. One more thing, even if you do that, do not create a local studentType instance inside the function. The instance is on the function stack and will not be available when you try to return it. One thing you can however do is create studentType dynamically and return the pointer to it outside the function.

How to lock specific cells but allow filtering and sorting

Here is an article that explains the problem and solution with alot more detail:

Sorting Locked Cells in Protected Worksheets

The thing to understand is that the purpose of locking cells is to prevent them from being changed, and sorting permanently changes cell values. You can write a macro, but a much better solution is to use the "Allow Users to Edit Ranges" feature. This makes the cells editable so sorting can work, but because the cells are still technically locked you can prevent users from selecting them.

Can I use return value of INSERT...RETURNING in another INSERT?

The best practice for this situation. Use RETURNING … INTO.


Note this is for PLPGSQL

No 'Access-Control-Allow-Origin' header is present on the requested resource- AngularJS

I added this and it worked fine for me.



Then you will call the model using cors:

In a controller you will add at the top for global scope or on each class. It's up to you.

 [EnableCorsAttribute("http://localhost:51003/", "*", "*")]

Also, when your pushing this data to Angular it wants to see the .cshtml file being called as well, or it will push the data but not populate your view.

(function () {
    "use strict";
        serverPath: "http://localhost:51003/About"

//Replace URL with the appropriate path from production server.

I hope this helps anyone out, it took me a while to understand Entity Framework, and why CORS is so useful.

Calling a parent window function from an iframe

You can use

see the following.

    function abc() {
    <iframe id="myFrame">
        <a onclick=";" href="#">Click Me</a>

Sum function in VBA

Function is not a property/method from range.

If you want to sum values then use the following:

Range("A1").Value = Application.Sum(Range(Cells(2, 1), Cells(3, 2)))


if you want the formula then use as follows:

Range("A1").Formula = "=SUM(" & Range(Cells(2, 1), Cells(3, 2)).Address(False, False) & ")"

'The two false after Adress is to define the address as relative (A2:B3).
'If you omit the parenthesis clause or write True instead, you can set the address
'as absolute ($A$2:$B$3).

In case you are allways going to use the same range address then you can use as Rory sugested:

Range("A1").Formula ="=Sum(A2:B3)"

How do you dynamically add elements to a ListView on Android?

Create an XML layout first in your project's res/layout/main.xml folder:

<?xml version="1.0" encoding="utf-8"?>
    android:layout_height="fill_parent" >
        android:text="Add New Item"

This is a simple layout with a button on the top and a list view on the bottom. Note that the ListView has the id @android:id/list which defines the default ListView a ListActivity can use.

public class ListViewDemo extends ListActivity {
    ArrayList<String> listItems=new ArrayList<String>();

    ArrayAdapter<String> adapter;

    int clickCounter=0;

    public void onCreate(Bundle icicle) {
        adapter=new ArrayAdapter<String>(this,

    public void addItems(View v) {
        listItems.add("Clicked : "+clickCounter++);

android.R.layout.simple_list_item_1 is the default list item layout supplied by Android, and you can use this stock layout for non-complex things.

listItems is a List which holds the data shown in the ListView. All the insertion and removal should be done on listItems; the changes in listItems should be reflected in the view. That's handled by ArrayAdapter<String> adapter, which should be notified using:


An Adapter is instantiated with 3 parameters: the context, which could be your activity/listactivity; the layout of your individual list item; and lastly, the list, which is the actual data to be displayed in the list.

Execute Stored Procedure from a Function

I have figured out a solution to this problem. We can build a Function or View with "rendered" sql in a stored procedure that can then be executed as normal.

1.Create another sproc

CREATE PROCEDURE [dbo].[usp_FunctionBuilder]

2.Build the dynamic sql that you want to execute in your function (Example: you could use a loop and union, you could read in another sproc, use if statements and parameters for conditional sql, etc.)

SET @innerSql = 'your sql'

3.Wrap the @innerSql in a create function statement and define any external parameters that you have used in the @innerSql so they can be passed into the generated function.

SET @outerSql = 'CREATE FUNCTION [dbo].[fn_GeneratedFunction] ( @Param varchar(10))
' + @innerSql;


This is just pseudocode but the solution solves many problems such as linked server limitations, parameters, dynamic sql in function, dynamic server/database/table name, loops, etc.

You will need to tweak it to your needs, (Example: changing the return in the function)

Convert Date format into DD/MMM/YYYY format in SQL Server

I'm not sure there is an exact match for the format you want. But you can get close with convert() and style 106. Then, replace the spaces:

SELECT replace(convert(NVARCHAR, getdate(), 106), ' ', '/')


Navigate to Run/Debug Configurations

Click Run from the top Tab > Edit Configurations

  • Module: Select your App
  • Installation Options: Deploy Default APK
  • Ok

enter image description here

How to go to a URL using jQuery?

window.location is just what you need. Other thing you can do is to create anchor element and simulate click on it

$("<a href='your url'></a>").click(); 

How to ignore files/directories in TFS for avoiding them to go to central source repository?

I'm going to assume you are using Web Site Projects. These automatically crawl their project directory and throw everything into source control. There's no way to stop them.

However, don't despair. Web Application Projects don't exhibit this strange and rather unexpected (imho: moronic) behavior. WAP is an addon on for VS2005 and comes direct with VS2008.

As an alternative to changing your projects to WAP, you might consider moving the Assets folder out of Source control and into a TFS Document Library. Only do this IF the project itself doesn't directly use the assets files.

YouTube: How to present embed video with sound muted


   <div id="player"></div>

          var tag = document.createElement('script');
          tag.src = "";
          var firstScriptTag = document.getElementsByTagName('script')[0];
          firstScriptTag.parentNode.insertBefore(tag, firstScriptTag);

          var player;
          function onYouTubeIframeAPIReady() {
            player = new YT.Player('player', {
              height: '720',
              width: '1280',
              videoId: 'M7lc1UVf-VE',
              playerVars :{'autoplay':1,'loop':1,'playlist':'M7lc1UVf-VE','vq':'hd720'},
              events: {
                'onReady': onPlayerReady,
                'onStateChange': onPlayerStateChange

          function onPlayerReady(event) {

          var done = false;
          function onPlayerStateChange(event) {
            if ( == YT.PlayerState.PLAYING && !done) {
        //      setTimeout(stopVideo, 6000);
                      done = true;

How to differentiate single click event and double click event?

I know this is old, but below is a JS only example of a basic loop counter with a single timer to determine a single vs double click. Hopefully this helps someone.

var count = 0;
var ele = document.getElementById("my_id");
ele.addEventListener('click', handleSingleDoubleClick, false); 

function handleSingleDoubleClick()
  if(!count) setTimeout(TimerFcn, 400); // 400 ms click delay
  count += 1;
function TimerFcn() 
  if(count > 1) console.log('you double clicked!')
  else console.log('you single clicked')
  count = 0;

Angular 2 Show and Hide an element

This is a good use case for a directive. Something like this is surprisingly useful.

  selector: '[removeAfter]'
export class RemoveAfter {
  constructor(readonly element: ElementRef<HTMLElement>) { }
   * Removes the attributed element after the specified number of milliseconds. 
   * @default `1000`
  @Input() removeAfter = 1000;

  ngOnInit() {
    setTimeout(() => {
    }, this.removeAfter);

Mysql - How to quit/exit from stored procedure

If you want an "early exit" for a situation in which there was no error, then use the accepted answer posted by @piotrm. Most typically, however, you will be bailing due to an error condition (especially in a SQL procedure).

As of MySQL v5.5 you can throw an exception. Negating exception handlers, etc. that will achieve the same result, but in a cleaner, more precise manner.

Here's how:


IF <Some Error Condition> THEN      
    SET MESSAGE_TEXT = 'Your Custom Error Message';
END IF;     

Note SQLSTATE '45000' equates to "Unhandled user-defined exception condition". By default, this will produce an error code of 1644 (which has that same meaning). Note that you can throw other condition codes or error codes if you want (plus additional details for exception handling).

For more on this subject, check out:

How to raise an error within a MySQL function


As I'm re-reading this post of mine, I realized I had something additional to add. Prior to MySQL v5.5, there was a way to emulate throwing an exception. It's not the same thing exactly, but this was the analogue: Create an error via calling a procedure which does not exist. Call the procedure by a name which is meaningful in order to get a useful means by which to determine what the problem was. When the error occurs, you'll get to see the line of failure (depending on your execution context).

For example:

CALL AttemptedToInsertSomethingInvalid;

Note that when you create a procedure, there is no validation performed on such things. So while in something like a compiled language, you could never call a function that wasn't there, in a script like this it will simply fail at runtime, which is exactly what is desired in this case!

WHERE IS NULL, IS NOT NULL or NO WHERE clause depending on SQL Server parameter value

WHERE MyColumn = COALESCE(@value,MyColumn) 
  • If @value is NULL, it will compare MyColumn to itself, ignoring @value = no where clause.

  • IF @value has a value (NOT NULL) it will compare MyColumn to @value.

Reference: COALESCE (Transact-SQL).

How to implement __iter__(self) for a container object (Python)

example for inhert from dict, modify its iter, for example, skip key 2 when in for loop

# method 1
class Dict(dict):
    def __iter__(self):
        keys = self.keys()
        for i in keys:
            if i == 2:
            yield i

# method 2
class Dict(dict):
    def __iter__(self):
        for i in super(Dict, self).__iter__():
            if i == 2:
            yield i

Recommended method for escaping HTML in Java

org.apache.commons.lang3.StringEscapeUtils is now deprecated. You must now use org.apache.commons.text.StringEscapeUtils by


How to refresh Gridview after pressed a button in

Adding the GridView1.DataBind() to the button click event did not work for me. However, adding it to the SqlDataSource1_Updated event did though.

Protected Sub SqlDataSource1_Updated(sender As Object, e As SqlDataSourceStatusEventArgs) Handles SqlDataSource1.Updated
End Sub

How to display errors on laravel 4?

Just go to your app/storage/logs there logs of error available. Go to filename of today's date time and you will find latest error in your application.


Open app/config/app.php and change setting

'debug' => false,


'debug' => true, 


Go to .env file to your application and change the configuratuion


How to secure RESTful web services?

If choosing between OAuth versions, go with OAuth 2.0.

OAuth bearer tokens should only be used with a secure transport.

OAuth bearer tokens are only as secure or insecure as the transport that encrypts the conversation. HTTPS takes care of protecting against replay attacks, so it isn't necessary for the bearer token to also guard against replay.

While it is true that if someone intercepts your bearer token they can impersonate you when calling the API, there are plenty of ways to mitigate that risk. If you give your tokens a long expiration period and expect your clients to store the tokens locally, you have a greater risk of tokens being intercepted and misused than if you give your tokens a short expiration, require clients to acquire new tokens for every session, and advise clients not to persist tokens.

If you need to secure payloads that pass through multiple participants, then you need something more than HTTPS/SSL, since HTTPS/SSL only encrypts one link of the graph. This is not a fault of OAuth.

Bearer tokens are easy to for clients to obtain, easy for clients to use for API calls and are widely used (with HTTPS) to secure public facing APIs from Google, Facebook, and many other services.

How do I execute a file in Cygwin?

Thomas wrote:

Apparently, gcc doesn't behave like the one described in The C Programming language

It does in general. For your program to run on Windows it needs to end in .exe, "the C Programming language" was not written with Windows programmers in mind. As you've seen, cygwin emulates many, but not all, features of a POSIX environment.

jQuery DataTables: control table width

This is my way of doing it..

    processing: true,
    serverSide: true,
    ajax: 'customer/data',
    columns: [
        { data: 'id', name: 'id' , width: '50px', class: 'text-right' },
        { data: 'name', name: 'name' width: '50px', class: 'text-right' }

HttpUtility does not exist in the current context

After following the answers above , and did

Project -> Properties -> Application -> Target Framework -> select ".Net Framework 4"

It still didn't work until I went to
Project -> Add Reference
And selected System.web. And everything worked link a charm.

using jQuery .animate to animate a div from right to left?

If you know the width of the child element you are animating, you can use and animate a margin offset as well. For example, this will animate from left:0 to right:0





$( "#itemToMove" ).animate({
"margin-right": "0",
"right": "0"
}, 1000 );

SQL Server convert string to datetime

UPDATE MyTable SET MyDate = CONVERT(datetime, '2009/07/16 08:28:01', 120)

For a full discussion of CAST and CONVERT, including the different date formatting options, see the MSDN Library Link below:

length and length() in Java

Let me first highlight three different ways for similar purpose.

length -- arrays (int[], double[], String[]) -- to know the length of the arrays

length() -- String related Object (String, StringBuilder, etc) -- to know the length of the String

size() -- Collection Object (ArrayList, Set, etc) -- to know the size of the Collection

Now forget about length() consider just length and size().

length is not a method, so it completely makes sense that it will not work on objects. It only works on arrays.
size() its name describes it better and as it is a method, it will be used in the case of those objects who work with collection (collection frameworks) as I said up there.

Now come to length():
String is not a primitive array (so we can't use .length) and also not a Collection (so we cant use .size()) that's why we also need a different one which is length() (keep the differences and serve the purpose).

As answer to Why?
I find it useful, easy to remember and use and friendly.

React : difference between <Route exact path="/" /> and <Route path="/" />

In short, if you have multiple routes defined for your app's routing, enclosed with Switch component like this;


  <Route exact path="/" component={Home} />
  <Route path="/detail" component={Detail} />

  <Route exact path="/functions" component={Functions} />
  <Route path="/functions/:functionName" component={FunctionDetails} />


Then you have to put exact keyword to the Route which it's path is also included by another Route's path. For example home path / is included in all paths so it needs to have exact keyword to differentiate it from other paths which start with /. The reason is also similar to /functions path. If you want to use another route path like /functions-detail or /functions/open-door which includes /functions in it then you need to use exact for the /functions route.

How to access global variables

I suggest use the common way of import.

First I will explain the way it called "relative import" maybe this way cause of some error

Second I will explain the common way of import.


In go version >= 1.12 there is some new tips about import file and somethings changed.

1- You should put your file in another folder for example I create a file in "model" folder and the file's name is "example.go"

2- You have to use uppercase when you want to import a file!

3- Use Uppercase for variables, structures and functions that you want to import in another files

Notice: There is no way to import the main.go in another file.

file directory is:


this is a example.go:

package model

import (

var StartTime = time.Now()

and this is main.go you should use uppercase when you want to import a file. "Mod" started with uppercase

package main

import (
    Mod "./model"

func main() {


NOTE: I don't recommend this this type of import!


(normal import)

the better way import file is:

your structure should be like this:

         |                |__________Your-project-name
         |                                |________main.go
         |                                |________handlers
         |                                |________models

and this is a example:

package main

import (

func main(){
     //you can use sessions here

so you can import "" in every where that you want...just import it.

Angular HttpPromise: difference between `success`/`error` methods and `then`'s arguments

Official Notice: success and error have been deprecated, please use the standard then method instead.

Deprecation Notice: The $http legacy promise methods success and error have been deprecated. Use the standard then method instead. If $httpProvider.useLegacyPromiseExtensions is set to false then these methods will throw $http/legacy error.


screenshot: view the screenshot

Calling a PHP function from an HTML form in the same file

Here is a full php script to do what you're describing, though pointless. You need to read up on server-side vs. client-side. PHP can't run on the client-side, you have to use javascript to interact with the server, or put up with a page refresh. If you can't understand that, there is no way you'll be able to use my code (or anyone else's) to your benefit.

The following code performs AJAX call without jQuery, and calls the same script to stream XML to the AJAX. It then inserts your username and a <br/> in a div below the user box.

Please go back to learning the basics before trying to pursue something as advanced as AJAX. You'll only be confusing yourself in the end and potentially wasting other people's money.

    function test() {
        header("Content-Type: text/xml");
        echo "<?xml version=\"1.0\" standalone=\"yes\"?><user>".$_GET["user"]."</user>"; //output an xml document.
    } else {
        <script type="text/javascript">
            function do_ajax() {
                    xmlhttp=new XMLHttpRequest();
                } else {
                    xmlhttp=new ActiveXObject("Microsoft.XMLHTTP");
                xmlhttp.onreadystatechange = function(){
                    if (xmlhttp.readyState==4 && xmlhttp.status==200)
                        var xmlDoc = xmlhttp.responseXML;
                        mydiv = document.getElementById("Test");
      "GET","<?php echo $_SERVER["PHP_SELF"]; ?>?user="+document.getElementById('username').value,true);
        <form action="test.php" method="post">
            <input type="text" name="user" placeholder="enter a text" id="username"/>
            <input type="button" value="submit" onclick="do_ajax()" />
        <div id="Test"></div>
</html><?php } ?>

How to align an input tag to the center without specifying the width?

You can use the following CSS for your input field:

.center-block {
  display: block;
  margin-right: auto;
  margin-left: auto;

Then,update your input field as following:

<input class="center-block" type="button" value="Some Button">

Why am I getting an error "Object literal may only specify known properties"?

As of TypeScript 1.6, properties in object literals that do not have a corresponding property in the type they're being assigned to are flagged as errors.

Usually this error means you have a bug (typically a typo) in your code, or in the definition file. The right fix in this case would be to fix the typo. In the question, the property callbackOnLoactionHash is incorrect and should have been callbackOnLocationHash (note the mis-spelling of "Location").

This change also required some updates in definition files, so you should get the latest version of the .d.ts for any libraries you're using.


interface TextOptions {
    alignment?: string;
    color?: string;
    padding?: number;
function drawText(opts: TextOptions) { ... }
drawText({ align: 'center' }); // Error, no property 'align' in 'TextOptions'

But I meant to do that

There are a few cases where you may have intended to have extra properties in your object. Depending on what you're doing, there are several appropriate fixes

Type-checking only some properties

Sometimes you want to make sure a few things are present and of the correct type, but intend to have extra properties for whatever reason. Type assertions (<T>v or v as T) do not check for extra properties, so you can use them in place of a type annotation:

interface Options {
    x?: string;
    y?: number;

// Error, no property 'z' in 'Options'
let q1: Options = { x: 'foo', y: 32, z: 100 };
// OK
let q2 = { x: 'foo', y: 32, z: 100 } as Options;
// Still an error (good):
let q3 = { x: 100, y: 32, z: 100 } as Options;

These properties and maybe more

Some APIs take an object and dynamically iterate over its keys, but have 'special' keys that need to be of a certain type. Adding a string indexer to the type will disable extra property checking


interface Model {
  name: string;
function createModel(x: Model) { ... }

// Error
createModel({name: 'hello', length: 100});


interface Model {
  name: string;
  [others: string]: any;
function createModel(x: Model) { ... }

// OK
createModel({name: 'hello', length: 100});

This is a dog or a cat or a horse, not sure yet

interface Animal { move; }
interface Dog extends Animal { woof; }
interface Cat extends Animal { meow; }
interface Horse extends Animal { neigh; }

let x: Animal;
if(...) {
  x = { move: 'doggy paddle', woof: 'bark' };
} else if(...) {
  x = { move: 'catwalk', meow: 'mrar' };
} else {
  x = { move: 'gallop', neigh: 'wilbur' };

Two good solutions come to mind here

Specify a closed set for x

// Removes all errors
let x: Dog|Cat|Horse;

or Type assert each thing

// For each initialization
  x = { move: 'doggy paddle', woof: 'bark' } as Dog;

This type is sometimes open and sometimes not

A clean solution to the "data model" problem using intersection types:

interface DataModelOptions {
  name?: string;
  id?: number;
interface UserProperties {
  [key: string]: any;
function createDataModel(model: DataModelOptions & UserProperties) {
 /* ... */
// findDataModel can only look up by name or id
function findDataModel(model: DataModelOptions) {
 /* ... */
// OK
createDataModel({name: 'my model', favoriteAnimal: 'cat' });
// Error, 'ID' is not correct (should be 'id')
findDataModel({ ID: 32 });

See also

How do I use dataReceived event of the SerialPort Port Object in C#?

I believe this won't work because you are using a console application and there is no Event Loop running. An Event Loop / Message Pump used for event handling is setup automatically when a Winforms application is created, but not for a console app.

Find all files with name containing string

grep -R "somestring" | cut -d ":" -f 1

Jquery select change not firing

You can fire chnage event by these methods:


$('#selectid').change(function () {
    alert('This works');


$(document).on('change', '#selectid', function() {
    alert('This Works');


    alert('This Works');

If this methods not working, check your jQuery working or not:

$(document).ready(function($) {
   alert('Jquery Working');

Invalid http_host header

The error log is straightforward. As it suggested,You need to add to your ALLOWED_HOSTS setting.

In your project file,set ALLOWED_HOSTS like this :

ALLOWED_HOSTS = ['', 'localhost', '']

For further reading read from here.

Using the last-child selector

If the number of list items is fixed you can use the adjacent selector, e.g. if you only have three <li> elements, you can select the last <li> with:

#nav li+li+li {
    border-bottom: 1px solid #b5b5b5;

jQuery: Get selected element tag name

nodeName will give you the tag name in uppercase, while localName will give you the lower case.


will give you : yourelement instead of YOURELEMENT

How to get ELMAH to work with ASP.NET MVC [HandleError] attribute?

There is now an ELMAH.MVC package in NuGet that includes an improved solution by Atif and also a controller that handles the elmah interface within MVC routing (no need to use that axd anymore)
The problem with that solution (and with all the ones here) is that one way or another the elmah error handler is actually handling the error, ignoring what you might want to set up as a customError tag or through ErrorHandler or your own error handler
The best solution IMHO is to create a filter that will act at the end of all the other filters and log the events that have been handled already. The elmah module should take care of loging the other errors that are unhandled by the application. This will also allow you to use the health monitor and all the other modules that can be added to to look at error events

I wrote this looking with reflector at the ErrorHandler inside elmah.mvc

public class ElmahMVCErrorFilter : IExceptionFilter
   private static ErrorFilterConfiguration _config;

   public void OnException(ExceptionContext context)
       if (context.ExceptionHandled) //The unhandled ones will be picked by the elmah module
           var e = context.Exception;
           var context2 = context.HttpContext.ApplicationInstance.Context;
           //TODO: Add additional variables to context.HttpContext.Request.ServerVariables for both handled and unhandled exceptions
           if ((context2 == null) || (!_RaiseErrorSignal(e, context2) && !_IsFiltered(e, context2)))
            _LogException(e, context2);

   private static bool _IsFiltered(System.Exception e, System.Web.HttpContext context)
       if (_config == null)
           _config = (context.GetSection("elmah/errorFilter") as ErrorFilterConfiguration) ?? new ErrorFilterConfiguration();
       var context2 = new ErrorFilterModule.AssertionHelperContext((System.Exception)e, context);
       return _config.Assertion.Test(context2);

   private static void _LogException(System.Exception e, System.Web.HttpContext context)
       ErrorLog.GetDefault((System.Web.HttpContext)context).Log(new Elmah.Error((System.Exception)e, (System.Web.HttpContext)context));

   private static bool _RaiseErrorSignal(System.Exception e, System.Web.HttpContext context)
       var signal = ErrorSignal.FromContext((System.Web.HttpContext)context);
       if (signal == null)
           return false;
       signal.Raise((System.Exception)e, (System.Web.HttpContext)context);
       return true;

Now, in your filter config you want to do something like this:

    public static void RegisterGlobalFilters(GlobalFilterCollection filters)
        //These filters should go at the end of the pipeline, add all error handlers before
        filters.Add(new ElmahMVCErrorFilter());

Notice that I left a comment there to remind people that if they want to add a global filter that will actually handle the exception it should go BEFORE this last filter, otherwise you run into the case where the unhandled exception will be ignored by the ElmahMVCErrorFilter because it hasn't been handled and it should be loged by the Elmah module but then the next filter marks the exception as handled and the module ignores it, resulting on the exception never making it into elmah.

Now, make sure the appsettings for elmah in your webconfig look something like this:

<add key="elmah.mvc.disableHandler" value="false" /> <!-- This handles elmah controller pages, if disabled elmah pages will not work -->
<add key="elmah.mvc.disableHandleErrorFilter" value="true" /> <!-- This uses the default filter for elmah, set to disabled to use our own -->
<add key="elmah.mvc.requiresAuthentication" value="false" /> <!-- Manages authentication for elmah pages -->
<add key="elmah.mvc.allowedRoles" value="*" /> <!-- Manages authentication for elmah pages -->
<add key="elmah.mvc.route" value="errortracking" /> <!-- Base route for elmah pages -->

The important one here is "elmah.mvc.disableHandleErrorFilter", if this is false it will use the handler inside elmah.mvc that will actually handle the exception by using the default HandleErrorHandler that will ignore your customError settings

This setup allows you to set your own ErrorHandler tags in classes and views, while still loging those errors through the ElmahMVCErrorFilter, adding a customError configuration to your web.config through the elmah module, even writing your own Error Handlers. The only thing you need to do is remember to not add any filters that will actually handle the error before the elmah filter we've written. And I forgot to mention: no duplicates in elmah.

Is it possible to execute multiple _addItem calls asynchronously using Google Analytics?

From the docs:

_trackTrans() Sends both the transaction and item data to the Google Analytics server. This method should be called after _trackPageview(), and used in conjunction with the _addItem() and addTrans() methods. It should be called after items and transaction elements have been set up.

So, according to the docs, the items get sent when you call trackTrans(). Until you do, you can add items, but the transaction will not be sent.

Edit: Further reading led me here:

Where it clearly says you can start another transaction with an existing ID. When you commit it, the new items you listed will be added to that transaction.

Can I call a constructor from another constructor (do constructor chaining) in C++?

C++11: Yes!

C++11 and onwards has this same feature (called delegating constructors).

The syntax is slightly different from C#:

class Foo {
  Foo(char x, int y) {}
  Foo(int y) : Foo('a', y) {}

C++03: No

Unfortunately, there's no way to do this in C++03, but there are two ways of simulating this:

  1. You can combine two (or more) constructors via default parameters:

    class Foo {
      Foo(char x, int y=0);  // combines two constructors (char) and (char, int)
      // ...
  2. Use an init method to share common code:

    class Foo {
      Foo(char x);
      Foo(char x, int y);
      // ...
      void init(char x, int y);
    Foo::Foo(char x)
      init(x, int(x) + 7);
      // ...
    Foo::Foo(char x, int y)
      init(x, y);
      // ...
    void Foo::init(char x, int y)
      // ...

See the C++FAQ entry for reference.

How to hide a <option> in a <select> menu with CSS?

I would suggest that you do not use the solutions that use a <span> wrapper because it isn't valid HTML, which could cause problems down the road. I think the preferred solution is to actually remove any options that you wish to hide, and restore them as needed. Using jQuery, you'll only need these 3 functions:

The first function will save the original contents of the select. Just to be safe, you may want to call this function when you load the page.

function setOriginalSelect ($select) {
    if ($"originalHTML") == undefined) {
        $"originalHTML", $select.html());
    } // If it's already there, don't re-set it

This next function calls the above function to ensure that the original contents have been saved, and then simply removes the options from the DOM.

function removeOptions ($select, $options) {

The last function can be used whenever you want to "reset" back to all the original options.

function restoreOptions ($select) {
    var ogHTML = $"originalHTML");
    if (ogHTML != undefined) {

Note that all these functions expect that you're passing in jQuery elements. For example:

// in your search function...
var $s = $('select.someClass');
var $optionsThatDontMatchYourSearch= $s.find('options.someOtherClass');
restoreOptions($s); // Make sure you're working with a full deck
removeOptions($s, $optionsThatDontMatchYourSearch); // remove options not needed

Here is a working example:

Get the value in an input text box

You can get the value like this:


Where this refers to the form that contains the input.

Converting HTML string into DOM elements?

You can do it like this:

  var d=document
  return b;

var foo="<img src='//'>foo<i>bar</i>".toDOM();

ReactJS - Does render get called any time "setState" is called?

Yes. It calls the render() method every time we call setState only except when "shouldComponentUpdate" returns false.

Check if current directory is a Git repository

# check if git repo

if [ $(git rev-parse --is-inside-work-tree) = true ]; then
    echo "yes, is a git repo"
    git pull
    echo "no, is not a git repo"
    git clone url --depth 1

Android - R cannot be resolved to a variable

I've fixed the problem in my case very easy:
go to Build- Path->Configure Build Path->Order and Export and ensure that <project name>/gen folder is above <project name>/src
After fixing the order the error disappears.

Parsing CSV / tab-delimited txt file with Python

Although there is nothing wrong with the other solutions presented, you could simplify and greatly escalate your solutions by using python's excellent library pandas.

Pandas is a library for handling data in Python, preferred by many Data Scientists.

Pandas has a simplified CSV interface to read and parse files, that can be used to return a list of dictionaries, each containing a single line of the file. The keys will be the column names, and the values will be the ones in each cell.

In your case:

    import pandas

    def create_dictionary(filename):
        my_data = pandas.DataFrame.from_csv(filename, sep='\t', index_col=False)
        # Here you can delete the dataframe columns you don't want!
        del my_data['B']
        del my_data['D']
        # ...
        # Now you transform the DataFrame to a list of dictionaries
        list_of_dicts = [item for item in my_data.T.to_dict().values()]
        return list_of_dicts

# Usage:
x = create_dictionary("myfile.csv")

How do I uninstall a Windows service if the files do not exist anymore?

If you wish to use a tool for it you could use Process Hacker

Form to create the service:

Process Hacker Create Service

Context menu on a service to delete it:

Process Hacker Delete Service

I find Process Hacker a more convient tool to manage Windows processes and services than Windows's own Taskmgr.exe. Especially on Windows XP, where you can't access services at all from task manager.

What is the best (and safest) way to merge a Git branch into master?

I would first make the to-be-merged branch as clean as possible. Run your tests, make sure the state is as you want it. Clean up the new commits by git squash.

Besides KingCrunches answer, I suggest to use

git checkout master
git pull origin master
git merge --squash test
git commit
git push origin master

You might have made many commits in the other branch, which should only be one commit in the master branch. To keep the commit history as clean as possible, you might want to squash all your commits from the test branch into one commit in the master branch (see also: Git: To squash or not to squash?). Then you can also rewrite the commit message to something very expressive. Something that is easy to read and understand, without digging into the code.

edit: You might be interested in

So on GitHub, I end up doing the following for a feature branch mybranch:

Get the latest from origin

$ git checkout master
$ git pull origin master

Find the merge base hash:

$ git merge-base mybranch master

$ git checkout mybranch
$ git rebase -i c193ea5e11f5699ae1f58b5b7029d1097395196f

Now make sure only the first is pick, the rest is s:

pick 00f1e76 Add first draft of the Pflichtenheft
s d1c84b6 Update to two class problem
s 7486cd8 Explain steps better

Next choose a very good commit message and push to GitHub. Make the pull request then.

After the merge of the pull request, you can delete it locally:

$ git branch -d mybranch

and on GitHub

$ git push origin :mybranch

React router nav bar example

Note The accepted is perfectly fine - but wanted to add a version4 example because they are different enough.


  import React from 'react';
  import { Link } from 'react-router';

  export default class Nav extends React.Component {
    render() {    
      return (
        <nav className="Nav">
          <div className="Nav__container">
            <Link to="/" className="Nav__brand">
              <img src="logo.svg" className="Nav__logo" />

            <div className="Nav__right">
              <ul className="Nav__item-wrapper">
                <li className="Nav__item">
                  <Link className="Nav__link" to="/path1">Link 1</Link>
                <li className="Nav__item">
                  <Link className="Nav__link" to="/path2">Link 2</Link>
                <li className="Nav__item">
                  <Link className="Nav__link" to="/path3">Link 3</Link>


  import React from 'react';
  import { Link, Switch, Route } from 'react-router';
  import Nav from './nav';
  import Page1 from './page1';
  import Page2 from './page2';
  import Page3 from './page3';

  export default class App extends React.Component {
    render() {    
      return (
        <div className="App">
              <Nav />
                <Route exactly component={Landing} pattern="/" />
                <Route exactly component={Page1} pattern="/path1" />
                <Route exactly component={Page2} pattern="/path2" />
                <Route exactly component={Page3} pattern="/path3" />
                <Route component={Page404} />

Alternatively, if you want a more dynamic nav, you can look at the excellent v4 docs:


A few people have asked about a page without the Nav, such as a login page. I typically approach it with a wrapper Route component

  import React from 'react';
  import { Link, Switch, Route } from 'react-router';
  import Nav from './nav';
  import Page1 from './page1';
  import Page2 from './page2';
  import Page3 from './page3';

  const NavRoute = ({exact, path, component: Component}) => (
    <Route exact={exact} path={path} render={(props) => (
        <Component {...props}/>

  export default class App extends React.Component {
    render() {    
      return (
        <div className="App">
                <NavRoute exactly component={Landing} pattern="/" />
                <Route exactly component={Login} pattern="/login" />
                <NavRoute exactly component={Page1} pattern="/path1" />
                <NavRoute exactly component={Page2} pattern="/path2" />
                <NavRoute component={Page404} />

Immutable array in Java

If you want to avoid both mutability and boxing, there is no way out of the box. But you can create a class which holds primitive array inside and provides read-only access to elements via method(s).

Calling a function when ng-repeat has finished

If you’re not averse to using double-dollar scope props and you’re writing a directive whose only content is a repeat, there is a pretty simple solution (assuming you only care about the initial render). In the link function:

const dereg = scope.$watch('$$childTail.$last', last => {
    if (last) {
        // do yr stuff -- you may still need a $timeout here

This is useful for cases where you have a directive that needs to do DOM manip based on the widths or heights of the members of a rendered list (which I think is the most likely reason one would ask this question), but it’s not as generic as the other solutions that have been proposed.

Join String list elements with a delimiter in one step

If you are using Spring you can use StringUtils.join() method which also allows you to specify prefix and suffix.

String s = StringUtils.collectionToDelimitedString(fieldRoles.keySet(),
                "\n", "<value>", "</value>");

Alter table to modify default value of column

Your belief about what will happen is not correct. Setting a default value for a column will not affect the existing data in the table.

I create a table with a column col2 that has no default value

SQL> create table foo(
  2    col1 number primary key,
  3    col2 varchar2(10)
  4  );

Table created.

SQL> insert into foo( col1 ) values (1);

1 row created.

SQL> insert into foo( col1 ) values (2);

1 row created.

SQL> insert into foo( col1 ) values (3);

1 row created.

SQL> select * from foo;

      COL1 COL2
---------- ----------

If I then alter the table to set a default value, nothing about the existing rows will change

SQL> alter table foo
  2    modify( col2 varchar2(10) default 'foo' );

Table altered.

SQL> select * from foo;

      COL1 COL2
---------- ----------

SQL> insert into foo( col1 ) values (4);

1 row created.

SQL> select * from foo;

      COL1 COL2
---------- ----------
         4 foo

Even if I subsequently change the default again, there will still be no change to the existing rows

SQL> alter table foo
  2    modify( col2 varchar2(10) default 'bar' );

Table altered.

SQL> select * from foo;

      COL1 COL2
---------- ----------
         4 foo

SQL> insert into foo( col1 ) values (5);

1 row created.

SQL> select * from foo;

      COL1 COL2
---------- ----------
         4 foo
         5 bar

String delimiter in string.split method

StringTokenizer st = new StringTokenizer("1||1||Abdul-Jabbar||Karim||1996||1974",

Answer will print

1 1 Abdul-Jabbar Karim 1996 1974

How to convert View Model into JSON object in ASP.NET MVC?

Andrew had a great response but I wanted to tweek it a little. The way this is different is that I like my ModelViews to not have overhead data in them. Just the data for the object. It seem that ViewData fits the bill for over head data, but of course I'm new at this. I suggest doing something like this.


virtual public ActionResult DisplaySomeWidget(int id)
    SomeModelView returnData = someDataMapper.getbyid(1);
    var serializer = new JavaScriptSerializer();
    ViewData["JSON"] = serializer.Serialize(returnData);
    return View(myview, returnData);


//create base js object;
var myWidget= new Widget(); //Widget is a class with a public member variable called data. <%= ViewData["JSON"] %>;

What This does for you is it gives you the same data in your JSON as in your ModelView so you can potentially return the JSON back to your controller and it would have all the parts. This is similar to just requesting it via a JSONRequest however it requires one less call so it saves you that overhead. BTW this is funky for Dates but that seems like another thread.

How can I strip first and last double quotes?

Below function will strip the empty spces and return the strings without quotes. If there are no quotes then it will return same string(stripped)

def removeQuote(str):
str = str.strip()
    str = str[1:-1]
    print("Removed Quotes",str)
    print("Same String",str)
return str

PHP Echo a large block of text

To expand on @hookedonwinter's answer, here's an alternate (cleaner, in my opinion) syntax:

<?php if (is_single()): ?>
    <p>This will be shown if "is_single()" is true.</p>
<?php else: ?>
    <p>This will be shown otherwise.</p>
<?php endif; ?>

Reduce size of legend area in barplot

The cex parameter will do that for you.

a <- c(3, 2, 2, 2, 1, 2 )
barplot(a, beside = T,
        col = 1:6, space = c(0, 2))
       legend = c("a", "b", "c", "d", "e", "f"), 
       fill = 1:6, ncol = 2,
       cex = 0.75)

The plot

How to rotate portrait/landscape Android emulator?

See the Android documentation on controlling the emulator; it's Ctrl + F11 / Ctrl + F12.

On ThinkPad running Ubuntu, you may try CTRL + Left Arrow Key or Right Arrow Key

How to create standard Borderless buttons (like in the design guideline mentioned)?

This is how you create a borderless (flat) button programmatically without using XML

ContextThemeWrapper myContext = new ContextThemeWrapper(this.getActivity(),;

Button myButton = new Button(myContext, null,;

AngularJS sorting by property

You should really improve your JSON structure to fix your problem:

$scope.testData = [
   {name:"CData", order: 1},
   {name:"BData", order: 2},
   {name:"AData", order: 3},

Then you could do

<li ng-repeat="test in testData | orderBy:order">...</li>

The problem, I think, is that the (key, value) variables are not available to the orderBy filter, and you should not be storing data in your keys anyways

How to change the name of an iOS app?

  1. Select Target

    Target selected in Xcode sidebar.

  2. Select Info

    Info tab selected.

  3. Insert Bundle Display Name and set App Title

    Dropdown showing Application Category highlighted.

check / uncheck checkbox using jquery?

For jQuery 1.6+ :

.attr() is deprecated for properties; use the new .prop() function instead as:

$('#myCheckbox').prop('checked', true); // Checks it
$('#myCheckbox').prop('checked', false); // Unchecks it

For jQuery < 1.6:

To check/uncheck a checkbox, use the attribute checked and alter that. With jQuery you can do:

$('#myCheckbox').attr('checked', true); // Checks it
$('#myCheckbox').attr('checked', false); // Unchecks it

Cause you know, in HTML, it would look something like:

<input type="checkbox" id="myCheckbox" checked="checked" /> <!-- Checked -->
<input type="checkbox" id="myCheckbox" /> <!-- Unchecked -->

However, you cannot trust the .attr() method to get the value of the checkbox (if you need to). You will have to rely in the .prop() method.

importing go files in same folder

No import is necessary as long as you declare both a.go and b.go to be in the same package. Then, you can use go run to recognize multiple files with:

$ go run a.go b.go

What rules does software version numbering follow?

The usual method I have seen is X.Y.Z, which generally corresponds to major.minor.patch:

  • Major version numbers change whenever there is some significant change being introduced. For example, a large or potentially backward-incompatible change to a software package.
  • Minor version numbers change when a new, minor feature is introduced or when a set of smaller features is rolled out.
  • Patch numbers change when a new build of the software is released to customers. This is normally for small bug-fixes or the like.

Other variations use build numbers as an additional identifier. So you may have a large number for if you have many revisions that are tested between releases. I use a couple of packages that are identified by year/month or year/release. Thus, a release in the month of September of 2010 might be 2010.9 or 2010.3 for the 3rd release of this year.

There are many variants to versioning. It all boils down to personal preference.

For the "1.3v1.1", that may be two different internal products, something that would be a shared library / codebase that is rev'd differently from the main product; that may indicate version 1.3 for the main product, and version 1.1 of the internal library / package.

Basic example for sharing text or image with UIActivityViewController in Swift

I've used the implementation above and just now I came to know that it doesn't work on iPad running iOS 13. I had to add these lines before present() call in order to make it work

//avoiding to crash on iPad
if let popoverController = activityViewController.popoverPresentationController {
     popoverController.sourceRect = CGRect(x: UIScreen.main.bounds.width / 2, y: UIScreen.main.bounds.height / 2, width: 0, height: 0)
     popoverController.sourceView = self.view
     popoverController.permittedArrowDirections = UIPopoverArrowDirection(rawValue: 0)

That's how it works for me

func shareData(_ dataToShare: [Any]){

        let activityViewController = UIActivityViewController(activityItems: dataToShare, applicationActivities: nil)

        //exclude some activity types from the list (optional)
        //activityViewController.excludedActivityTypes = [

        //avoiding to crash on iPad
        if let popoverController = activityViewController.popoverPresentationController {
            popoverController.sourceRect = CGRect(x: UIScreen.main.bounds.width / 2, y: UIScreen.main.bounds.height / 2, width: 0, height: 0)
            popoverController.sourceView = self.view
            popoverController.permittedArrowDirections = UIPopoverArrowDirection(rawValue: 0)

        self.present(activityViewController, animated: true, completion: nil)

How can I undo a mysql statement that I just executed?

Basically: If you're doing a transaction just do a rollback. Otherwise, you can't "undo" a MySQL query.

jQuery lose focus event

blur event: when the element loses focus.

focusout event: when the element, or any element inside of it, loses focus.

As there is nothing inside the filter element, both blur and focusout will work in this case.

$(function() {
  $('#filter').blur(function() {

jsfiddle with blur:

$(function() {
  $('#filter').focusout(function() {

jsfiddle with focusout:

In Firebase, is there a way to get the number of children of a node without loading all the node data?

This is a little late in the game as several others have already answered nicely, but I'll share how I might implement it.

This hinges on the fact that the Firebase REST API offers a shallow=true parameter.

Assume you have a post object and each one can have a number of comments:

 "posts": {
  "$postKey": {
   "comments": {

You obviously don't want to fetch all of the comments, just the number of comments.

Assuming you have the key for a post, you can send a GET request to[the post key]/comments?shallow=true.

This will return an object of key-value pairs, where each key is the key of a comment and its value is true:

 "comment1key": true,
 "comment2key": true,
 "comment9999key": true

The size of this response is much smaller than requesting the equivalent data, and now you can calculate the number of keys in the response to find your value (e.g. commentCount = Object.keys(result).length).

This may not completely solve your problem, as you are still calculating the number of keys returned, and you can't necessarily subscribe to the value as it changes, but it does greatly reduce the size of the returned data without requiring any changes to your schema.

Tuples( or arrays ) as Dictionary keys in C#

The good, clean, fast, easy and readable ways is:

  • generate equality members (Equals() and GetHashCode()) method for the current type. Tools like ReSharper not only creates the methods, but also generates the necessary code for an equality check and/or for calculating hash code. The generated code will be more optimal than Tuple realization.
  • just make a simple key class derived from a tuple.

add something similar like this:

public sealed class myKey : Tuple<TypeA, TypeB, TypeC>
    public myKey(TypeA dataA, TypeB dataB, TypeC dataC) : base (dataA, dataB, dataC) { }

    public TypeA DataA => Item1; 

    public TypeB DataB => Item2;

    public TypeC DataC => Item3;

So you can use it with dictionary:

var myDictinaryData = new Dictionary<myKey, string>()
    {new myKey(1, 2, 3), "data123"},
    {new myKey(4, 5, 6), "data456"},
    {new myKey(7, 8, 9), "data789"}
  • You also can use it in contracts
  • as a key for join or groupings in linq
  • going this way you never ever mistype order of Item1, Item2, Item3 ...
  • you no need to remember or look into to code to understand where to go to get something
  • no need to override IStructuralEquatable, IStructuralComparable, IComparable, ITuple they all alredy here

How to use FormData for AJAX file upload?

<label class="btn btn-info btn-file">
Import <input type="file" style="display: none;">
$(document).ready(function () {
                $(document).on('change', ':file', function () {
                    var fileUpload = $(this).get(0);
                    var files = fileUpload.files;
                    var bid = 0;
                    if (files.length != 0) {
                        var data = new FormData();
                        for (var i = 0; i < files.length ; i++) {
                            data.append(files[i].name, files[i]);
                            xhr: function () {
                                var xhr = $.ajaxSettings.xhr();
                                xhr.upload.onprogress = function (e) {
                                    console.log(Math.floor(e.loaded / * 100) + '%');
                                return xhr;
                            contentType: false,
                            processData: false,
                            type: 'POST',
                            data: data,
                            url: '/ControllerX/' + bid,
                            success: function (response) {
                                location.href = 'xxx/Index/';
        public ActionResult ControllerX(string id)
            var files = Request.Form.Files;

Fastest way to serialize and deserialize .NET objects

The binary serializer included with .net should be faster that the XmlSerializer. Or another serializer for protobuf, json, ...

But for some of them you need to add Attributes, or some other way to add metadata. For example ProtoBuf uses numeric property IDs internally, and the mapping needs to be somehow conserved by a different mechanism. Versioning isn't trivial with any serializer.

How to check if all list items have the same value and return it, or return an “otherValue” if they don’t?

return collection.All(i => i == collection.First())) 
    ? collection.First() : otherValue;.

Or if you're worried about executing First() for each element (which could be a valid performance concern):

var first = collection.First();
return collection.All(i => i == first) ? first : otherValue;

Changing default encoding of Python?

First: reload(sys) and setting some random default encoding just regarding the need of an output terminal stream is bad practice. reload often changes things in sys which have been put in place depending on the environment - e.g. sys.stdin/stdout streams, sys.excepthook, etc.

Solving the encode problem on stdout

The best solution I know for solving the encode problem of print'ing unicode strings and beyond-ascii str's (e.g. from literals) on sys.stdout is: to take care of a sys.stdout (file-like object) which is capable and optionally tolerant regarding the needs:

  • When sys.stdout.encoding is None for some reason, or non-existing, or erroneously false or "less" than what the stdout terminal or stream really is capable of, then try to provide a correct .encoding attribute. At last by replacing sys.stdout & sys.stderr by a translating file-like object.

  • When the terminal / stream still cannot encode all occurring unicode chars, and when you don't want to break print's just because of that, you can introduce an encode-with-replace behavior in the translating file-like object.

Here an example:

#!/usr/bin/env python
# encoding: utf-8
import sys

class SmartStdout:
    def __init__(self, encoding=None, org_stdout=None):
        if org_stdout is None:
            org_stdout = getattr(sys.stdout, 'org_stdout', sys.stdout)
        self.org_stdout = org_stdout
        self.encoding = encoding or \
                        getattr(org_stdout, 'encoding', None) or 'utf-8'
    def write(self, s):
        self.org_stdout.write(s.encode(self.encoding, 'backslashreplace'))
    def __getattr__(self, name):
        return getattr(self.org_stdout, name)

if __name__ == '__main__':
    if sys.stdout.isatty():
        sys.stdout = sys.stderr = SmartStdout()

    us = u'aouäöü?zß²'
    print us

Using beyond-ascii plain string literals in Python 2 / 2 + 3 code

The only good reason to change the global default encoding (to UTF-8 only) I think is regarding an application source code decision - and not because of I/O stream encodings issues: For writing beyond-ascii string literals into code without being forced to always use u'string' style unicode escaping. This can be done rather consistently (despite what anonbadger's article says) by taking care of a Python 2 or Python 2 + 3 source code basis which uses ascii or UTF-8 plain string literals consistently - as far as those strings potentially undergo silent unicode conversion and move between modules or potentially go to stdout. For that, prefer "# encoding: utf-8" or ascii (no declaration). Change or drop libraries which still rely in a very dumb way fatally on ascii default encoding errors beyond chr #127 (which is rare today).

And do like this at application start (and/or via in addition to the SmartStdout scheme above - without using reload(sys):

def set_defaultencoding_globally(encoding='utf-8'):
    assert sys.getdefaultencoding() in ('ascii', 'mbcs', encoding)
    import imp
    _sys_org = imp.load_dynamic('_sys_org', 'sys')

if __name__ == '__main__':
    sys.stdout = sys.stderr = SmartStdout()
    s = 'aouäöü?zß²'
    print s

This way string literals and most operations (except character iteration) work comfortable without thinking about unicode conversion as if there would be Python3 only. File I/O of course always need special care regarding encodings - as it is in Python3.

Note: plains strings then are implicitely converted from utf-8 to unicode in SmartStdout before being converted to the output stream enconding.

How to Navigate from one View Controller to another using Swift

In AppDelegate you can write like this...

var window: UIWindow?

fileprivate let navigationCtrl = UINavigationController()

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplication.LaunchOptionsKey: Any]?) -> Bool {
    // Override point for customization after application launch.


    return true

func createWindow() {
    let screenSize = UIScreen.main.bounds
    self.window = UIWindow(frame: screenSize)
    self.window?.backgroundColor = UIColor.white
    self.window?.rootViewController = navigationCtrl

func showLoginVC() {
    let storyboardBundle = Bundle.main
    // let storyboardBundle = Bundle(for: ClassName.self) // if you are not using main application, means may be you are crating a framework or library you can use this statement instead
    let storyboard = UIStoryboard(name: "LoginVC", bundle: storyboardBundle)
    let loginVC = storyboard.instantiateViewController(withIdentifier: "LoginVC") as! LoginVC
    navigationCtrl.pushViewController(loginVC, animated: false)

String "true" and "false" to boolean

You could add to the String class to have the method of to_boolean. Then you could do 'true'.to_boolean or '1'.to_boolean

class String
  def to_boolean
    self == 'true' || self == '1'

Remove all occurrences of a value from a list?


>>> x = [1, 2, 3, 4, 2, 2, 3]

The simplest and efficient solution as already posted before is

>>> x[:] = [v for v in x if v != 2]
>>> x
[1, 3, 4, 3]

Another possibility which should use less memory but be slower is

>>> for i in range(len(x) - 1, -1, -1):
        if x[i] == 2:
            x.pop(i)  # takes time ~ len(x) - i
>>> x
[1, 3, 4, 3]

Timing results for lists of length 1000 and 100000 with 10% matching entries: 0.16 vs 0.25 ms, and 23 vs 123 ms.

Timing with length 1000

Timing with length 100000 mvc3 return raw html to view

What was working for me (ASP.NET Core), was to set return type ContentResult, then wrap the HMTL into it and set the ContentType to "text/html; charset=UTF-8". That is important, because, otherwise it will not be interpreted as HTML and the HTML language would be displayed as text.

Here's the example, part of a Controller class:

/// <summary>
/// Startup message displayed in browser.
/// </summary>
/// <returns>HTML result</returns>
public ContentResult Get()
    var result = Content("<html><title>DEMO</title><head><h2>Demo started successfully."
      + "<br/>Use <b><a href=\"http://localhost:5000/swagger\">Swagger</a></b>"
      + " to view API.</h2></head><body/></html>");
    result.ContentType = "text/html; charset=UTF-8";
    return result;


I got this same error when installing to an actual device. More information and a solution to loading the missing libraries to the device can be found at the following site:


To set this up correctly, there are 2 key files that need to be copied to the system:

These files are located in the any of these google app packs:

These links no longer work, but you can find the files in the android sdk if you have Google Maps API v1

After unzipping any of these files, you want to copy the files to your system, like-ah-so:

adb remount

adb push system/etc/permissions/ /system/etc/permissions

adb push system/framework/ /system/framework

adb reboot

How to clear all input fields in bootstrap modal when clicking data-dismiss button?

If you are using a form in the modal then you can use


Count number of rows within each group

If you want to include 0 counts for month-years that are missing in the data, you can use a little table magic.

data.frame(with(df1, table(Year, Month)))

For example, the toy data.frame in the question, df1, contains no observations of January 2014.

    x Year Month
1   1 2012   Feb
2   2 2014   Feb
3   3 2013   Mar
4   4 2012   Jan
5   5 2014   Feb
6   6 2014   Feb
7   7 2012   Jan
8   8 2014   Feb
9   9 2013   Mar
10 10 2013   Jan
11 11 2013   Jan
12 12 2012   Jan
13 13 2014   Mar
14 14 2012   Mar
15 15 2013   Feb
16 16 2014   Feb
17 17 2014   Mar
18 18 2012   Jan
19 19 2013   Mar
20 20 2012   Jan

The base R aggregate function does not return an observation for January 2014.

aggregate(x ~ Year + Month, data = df1, FUN = length)
  Year Month x
1 2012   Feb 1
2 2013   Feb 1
3 2014   Feb 5
4 2012   Jan 5
5 2013   Jan 2
6 2012   Mar 1
7 2013   Mar 3
8 2014   Mar 2

If you would like an observation of this month-year with 0 as the count, then the above code will return a data.frame with counts for all month-year combinations:

data.frame(with(df1, table(Year, Month)))
  Year Month Freq
1 2012   Feb    1
2 2013   Feb    1
3 2014   Feb    5
4 2012   Jan    5
5 2013   Jan    2
6 2014   Jan    0
7 2012   Mar    1
8 2013   Mar    3
9 2014   Mar    2

Format numbers to strings in Python

I've tried this in Python 3.6.9

>>> hours, minutes, seconds = 9, 33, 35
>>> time = f'{hours:02}:{minutes:02}:{seconds:02} {"pm" if hours > 12 else "am"}'
>>> print (time)
09:33:35 am
>>> type(time)

<class 'str'>

Where can I set path to make.exe on Windows?

I had issues for a whilst not getting Terraform commands to run unless I was in the directory of the exe, even though I set the path correctly.

For anyone else finding this issue, I fixed it by moving the environment variable higher than others!

Echo tab characters in bash script

Use the verbatim keystroke, ^V (CTRL+V, C-v, whatever).

When you type ^V into the terminal (or in most Unix editors), the following character is taken verbatim. You can use this to type a literal tab character inside a string you are echoing.

Something like the following works:

echo "^V<tab>"     # CTRL+V, TAB

Bash docs (q.v., "quoted-insert")

quoted-insert (C-q, C-v) Add the next character that you type to the line verbatim. This is how to insert key sequences like C-q, for example.

side note: according to this, ALT+TAB should do the same thing, but we've all bound that sequence to window switching so we can't use it

tab-insert (M-TAB) Insert a tab character.


Note: you can use this strategy with all sorts of unusual characters. Like a carriage return:

echo "^V^M"        # CTRL+V, CTRL+M

This is because carriage return is ASCII 13, and M is the 13th letter of the alphabet, so when you type ^M, you get the 13th ASCII character. You can see it in action using ls^M, at an empty prompt, which will insert a carriage return, causing the prompt to act just like you hit return. When these characters are normally interpreted, verbatim gets you get the literal character.

How to return a class object by reference in C++?

You're probably returning an object that's on the stack. That is, return_Object() probably looks like this:

Object& return_Object()
    Object object_to_return;
    // ... do stuff ...

    return object_to_return;

If this is what you're doing, you're out of luck - object_to_return has gone out of scope and been destructed at the end of return_Object, so myObject refers to a non-existent object. You either need to return by value, or return an Object declared in a wider scope or newed onto the heap.

Why do 64-bit DLLs go to System32 and 32-bit DLLs to SysWoW64 on 64-bit Windows?

I should add: You should not be putting your dll's into \system32\ anyway! Modify your code, modify your installer... find a home for your bits that is NOT anywhere under c:\windows\

For example, your installer puts your dlls into:

\program files\<your app dir>\


\program files\common files\<your app name>\

(Note: The way you actually do this is to use the environment var: %ProgramFiles% or %ProgramFiles(x86)% to find where Program Files is.... you do not assume it is c:\program files\ ....)

and then sets a registry tag :

HKLM\software\<your app name>
-- dllLocation

The code that uses your dlls reads the registry, then dynamically links to the dlls in that location.

The above is the smart way to go.

You do not ever install your dlls, or third party dlls into \system32\ or \syswow64. If you have to statically load, you put your dlls in your exe dir (where they will be found). If you cannot predict the exe dir (e.g. some other exe is going to call your dll), you may have to put your dll dir into the search path (avoid this if at all poss!)

system32 and syswow64 are for Windows provided files... not for anyone elses files. The only reason folks got into the bad habit of putting stuff there is because it is always in the search path, and many apps/modules use static linking. (So, if you really get down to it, the real sin is static linking -- this is a sin in native code and managed code -- always always always dynamically link!)

MySQL & Java - Get id of the last inserted value (JDBC)

Alternatively you can do:

Statement stmt = db.prepareStatement(query, Statement.RETURN_GENERATED_KEYS);
numero = stmt.executeUpdate();

ResultSet rs = stmt.getGeneratedKeys();
if ({

But use Sean Bright's answer instead for your scenario.

TCP vs UDP on video stream

Drawbacks of using TCP for live video:

  1. Typically live video-streaming appliances are not designed with TCP streaming in mind. If you use TCP, the OS must buffer the unacknowledged segments for every client. This is undesirable, particularly in the case of live events; presumably your list of simultaneous clients is long due to the singularity of the event. Pre-recorded video-casts typically don't have as much of a problem with this because viewers stagger their replay activity; therefore TCP is more appropriate for replaying a video-on-demand.
  2. IP multicast significantly reduces video bandwidth requirements for large audiences; TCP prevents the use of IP multicast, but UDP is well-suited for IP multicast.
  3. Live video is normally a constant-bandwidth stream recorded off a camera; pre-recorded video streams come off a disk. The loss-backoff dynamics of TCP make it harder to serve live video when the source streams are at a constant bandwidth (as would happen for a live-event). If you buffer to disk off a camera, be sure you have enough buffer for unpredictable network events and variable TCP send/backoff rates. UDP gives you much more control for this application since UDP doesn't care about network transport layer drops.

FYI, please don't use the word "packages" when describing networks. Networks send "packets".

Oracle TNS names not showing when adding new connection to SQL Developer

SQL Developer will look in the following location in this order for a tnsnames.ora file

  1. $HOME/.tnsnames.ora
  2. $TNS_ADMIN/tnsnames.ora
  3. TNS_ADMIN lookup key in the registry
  4. /etc/tnsnames.ora ( non-windows )
  5. $ORACLE_HOME/network/admin/tnsnames.ora

To see which one SQL Developer is using, issue the command show tns in the worksheet

If your tnsnames.ora file is not getting recognized, use the following procedure:

  1. Define an environmental variable called TNS_ADMIN to point to the folder that contains your tnsnames.ora file.

    In Windows, this is done by navigating to Control Panel > System > Advanced system settings > Environment Variables...

    In Linux, define the TNS_ADMIN variable in the .profile file in your home directory.

  2. Confirm the os is recognizing this environmental variable

    From the Windows command line: echo %TNS_ADMIN%

    From linux: echo $TNS_ADMIN

  3. Restart SQL Developer

  4. Now in SQL Developer right click on Connections and select New Connection.... Select TNS as connection type in the drop down box. Your entries from tnsnames.ora should now display here.

How can I set response header on express.js assets

There is at least one middleware on npm for handling CORS in Express: cors.

Eclipse : Failed to connect to remote VM. Connection refused.

I faced the same issue. But i resolved it by changing my port numbers to different one.

Call An Asynchronous Javascript Function Synchronously

What you want is actually possible now. If you can run the asynchronous code in a service worker, and the synchronous code in a web worker, then you can have the web worker send a synchronous XHR to the service worker, and while the service worker does the async things, the web worker's thread will wait. This is not a great approach, but it could work.

CSS to set A4 paper size

I looked into this a bit more and the actual problem seems to be with assigning initial to page width under the print media rule. It seems like in Chrome width: initial on the .page element results in scaling of the page content if no specific length value is defined for width on any of the parent elements (width: initial in this case resolves to width: auto ... but actually any value smaller than the size defined under the @page rule causes the same issue).

So not only the content is now too long for the page (by about 2cm), but also the page padding will be slightly more than the initial 2cm and so on (it seems to render the contents under width: auto to the width of ~196mm and then scale the whole content up to the width of 210mm ~ but strangely exactly the same scaling factor is applied to contents with any width smaller than 210mm).

To fix this problem you can simply in the print media rule assign the A4 paper width and hight to html, body or directly to .page and in this case avoid the initial keyword.


@page {
  size: A4;
  margin: 0;
@media print {
  html, body {
    width: 210mm;
    height: 297mm;
  /* ... the rest of the rules ... */

This seems to keep everything else the way it is in your original CSS and fix the problem in Chrome (tested in different versions of Chrome under Windows, OS X and Ubuntu).