Programs & Examples On #Ogg

Ogg is free and open bitstream container format designed for streaming and manipulation of audio, video, and other media.

Method Call Chaining; returning a pointer vs a reference?

Very interesting question.

I don't see any difference w.r.t safety or versatility, since you can do the same thing with pointer or reference. I also don't think there is any visible difference in performance since references are implemented by pointers.

But I think using reference is better because it is consistent with the standard library. For example, chaining in iostream is done by reference rather than pointer.

Two Page Login with Spring Security 3.2.x

There should be three pages here:

  1. Initial login page with a form that asks for your username, but not your password.
  2. You didn't mention this one, but I'd check whether the client computer is recognized, and if not, then challenge the user with either a CAPTCHA or else a security question. Otherwise the phishing site can simply use the tendered username to query the real site for the security image, which defeats the purpose of having a security image. (A security question is probably better here since with a CAPTCHA the attacker could have humans sitting there answering the CAPTCHAs to get at the security images. Depends how paranoid you want to be.)
  3. A page after that that displays the security image and asks for the password.

I don't see this short, linear flow being sufficiently complex to warrant using Spring Web Flow.

I would just use straight Spring Web MVC for steps 1 and 2. I wouldn't use Spring Security for the initial login form, because Spring Security's login form expects a password and a login processing URL. Similarly, Spring Security doesn't provide special support for CAPTCHAs or security questions, so you can just use Spring Web MVC once again.

You can handle step 3 using Spring Security, since now you have a username and a password. The form login page should display the security image, and it should include the user-provided username as a hidden form field to make Spring Security happy when the user submits the login form. The only way to get to step 3 is to have a successful POST submission on step 1 (and 2 if applicable).

500 Error on AppHarbor but downloaded build works on my machine

Just a wild guess: (not much to go on) but I have had similar problems when, for example, I was using the IIS rewrite module on my local machine (and it worked fine), but when I uploaded to a host that did not have that add-on module installed, I would get a 500 error with very little to go on - sounds similar. It drove me crazy trying to find it.

So make sure whatever options/addons that you might have and be using locally in IIS are also installed on the host.

Similarly, make sure you understand everything that is being referenced/used in your web.config - that is likely the problem area.

error: This is probably not a problem with npm. There is likely additional logging output above

Check if port you want to run your app is free. For me, it was the problem.

react hooks useEffect() cleanup for only componentWillUnmount?

instead of creating too many complicated functions and methods what I do is I create an event listener and automatically have mount and unmount done for me without having to worry about doing it manually. Here is an example.

useEffect( () => {

    window.addEventListener("load",  pageLoad);

    //component will unmount
    return () => {
        window.removeEventListener("load", pageLoad);


now that this part is done I just run anything I want from the pageLoad function like this.

const pageLoad = () =>{
console.log(I was mounted and unmounted automatically :D)}

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

I upgraded my IntelliJ Version from 2018.1 to 2018.3.6. It works !

How to post query parameters with Axios?

axios signature for post is[, data[, config]]). So you want to send params object within the third argument:

.post(`/mails/users/sendVerificationMail`, null, { params: {
.then(response => response.status)
.catch(err => console.warn(err));

This will POST an empty body with the two query params:

POST http://localhost:8000/api/mails/users/sendVerificationMail?

ERROR Error: Uncaught (in promise), Cannot match any routes. URL Segment

When you use routerLink like this, then you need to pass the value of the route it should go to. But when you use routerLink with the property binding syntax, like this: [routerLink], then it should be assigned a name of the property the value of which will be the route it should navigate the user to.

So to fix your issue, replace this routerLink="['/about']" with routerLink="/about" in your HTML.

There were other places where you used property binding syntax when it wasn't really required. I've fixed it and you can simply use the template syntax below:

<nav class="main-nav>
    [ngClass]=" ? 'Navbar__ToggleShow' : ''">
    <li class="main-nav__item" routerLinkActive="active">
      <a class="main-nav__link" routerLink="/">Home</a>
    <li class="main-nav__item" routerLinkActive="active"> 
      <a class="main-nav__link" routerLink="/about">About us</a>

It also needs to know where exactly should it load the template for the Component corresponding to the route it has reached. So for that, don't forget to add a <router-outlet></router-outlet>, either in your template provided above or in a parent component.

There's another issue with your AppRoutingModule. You need to export the RouterModule from there so that it is available to your AppModule when it imports it. To fix that, export it from your AppRoutingModule by adding it to the exports array.

import { NgModule } from '@angular/core';
import { CommonModule } from '@angular/common';
import { RouterModule, Routes } from '@angular/router';
import { MainLayoutComponent } from './layout/main-layout/main-layout.component';
import { AboutComponent } from './components/about/about.component';
import { WhatwedoComponent } from './components/whatwedo/whatwedo.component';
import { FooterComponent } from './components/footer/footer.component';
import { ProjectsComponent } from './components/projects/projects.component';
const routes: Routes = [
  { path: 'about', component: AboutComponent },
  { path: 'what', component: WhatwedoComponent },
  { path: 'contacts', component: FooterComponent },
  { path: 'projects', component: ProjectsComponent},

  imports: [
  exports: [RouterModule],
  declarations: []
export class AppRoutingModule { }

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 to resolve Unable to load authentication plugin 'caching_sha2_password' issue

I am using mysql 8.0.12 and updating the mysql connector to mysql-connector-java-8.0.12 resolved the issue for me.

Hope it helps somebody.

Local package.json exists, but node_modules missing

Just had the same error message, but when I was running a package.json with:

"scripts": {
    "build": "tsc -p ./src",

tsc is the command to run the TypeScript compiler.

I never had any issues with this project because I had TypeScript installed as a global module. As this project didn't include TypeScript as a dev dependency (and expected it to be installed as global), I had the error when testing in another machine (without TypeScript) and running npm install didn't fix the problem. So I had to include TypeScript as a dev dependency (npm install typescript --save-dev) to solve the problem.

ApplicationContextException: Unable to start ServletWebServerApplicationContext due to missing ServletWebServerFactory bean

In case you're using IntelliJ and this is happening to you (like it did to my noob-self), ensure the Run setting has Spring Boot Application and NOT plain Application.

Uncaught (in promise): Error: StaticInjectorError(AppModule)[options]

Faced the same error. In my case , what i did wrong was that i injected the service(named DataService in my case) inside the constructor within the Component but I simply forgot to import it within the component.

 constructor(private dataService:DataService ) {
    console.log("constructor called");

I missed the below import code.

import { DataService } from '../../services/data.service';

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

Add your dependencies like mongodb,web,jpa. Delete/clear the remainings.


Error : Program type already present:$Behavior

As android latest update doesn't support 'compile' keyword use 'implementation' in place inside your module build.gradle file.

And check thoroughly in build.gradle for dependancy with + sign like this.

implementation ''

If there are any dependencies like this, just update them with a specific version. After that:

  1. Sync gradle.
  2. Clean your project.
  3. Rebuild the project.

After Spring Boot 2.0 migration: jdbcUrl is required with driverClassName

Your can use DataSourceBuilder for this purpose.

@Bean(name = "dataSource")
@ConfigurationProperties(prefix = "spring.datasource")
public DataSource dataSource(Environment env) {
    final String datasourceUsername = env.getRequiredProperty("spring.datasource.username");
    final String datasourcePassword = env.getRequiredProperty("spring.datasource.password");
    final String datasourceUrl = env.getRequiredProperty("spring.datasource.url");
    final String datasourceDriver = env.getRequiredProperty("spring.datasource.driver-class-name");
    return DataSourceBuilder

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

In IntelliJ:

  1. Open Project Structure (?;) > Modules > YOUR MODULE -> Language level: set 9, in your case.
  2. Repeat for each module.


ReactJS: Maximum update depth exceeded error

You should pass the event object when calling the function :

{<td><span onClick={(e) => this.toggle(e)}>Details</span></td>}

If you don't need to handle onClick event you can also type :

{<td><span onClick={(e) => this.toggle()}>Details</span></td>}

Now you can also add your parameters within the function.

Execution failed for task ':app:compileDebugJavaWithJavac' Android Studio 3.1 Update

I had the same issue, I could solve it by switching fom JDK 11 to JDK 8.

How to start up spring-boot application via command line?

Spring Boot provide the plugin with maven.

So you can go to your project directory and run

mvn spring-boot:run

This command line run will be easily when you're using spring-boot-devs-tool with auto reload/restart when you have changed you application.

No authenticationScheme was specified, and there was no DefaultChallengeScheme found with default authentification and custom authorization

When I used policy before I set the default authentication scheme into it as well. I had modified the DefaultPolicy so it was slightly different. However the same should work for add policy as well.

services.AddAuthorization(options =>
            options.AddPolicy(DefaultAuthorizedPolicy, policy =>
                policy.Requirements.Add(new TokenAuthRequirement());
                policy.AuthenticationSchemes = new List<string>()

Do take into consideration that by Default AuthenticationSchemes property uses a read only list. I think it would be better to implement that instead of List as well.

No provider for HttpClient

I was facing the same problem, then in my app.module.ts I updated the file this way,

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

and in the same file (app.module.ts) in my @NgModule imports[]array I wrote this way,


How to use log4net in core 2.0

Following on Irfan's answer, I have the following XML configuration on OSX with .NET Core 2.1.300 which correctly logs and appends to a ./log folder and also to the console. Note the log4net.config must exist in the solution root (whereas in my case, my app root is a subfolder).

<?xml version="1.0" encoding="utf-8" ?>
  <appender name="ConsoleAppender" type="log4net.Appender.ConsoleAppender" >
      <layout type="log4net.Layout.PatternLayout">
      <conversionPattern value="%date %-5level %logger - %message%newline" />
  <appender name="RollingLogFileAppender" type="log4net.Appender.RollingFileAppender">
    <lockingModel type="log4net.Appender.FileAppender+MinimalLock"/>
    <file value="logs/" />
    <datePattern value="yyyy-MM-dd.'txt'"/>
    <staticLogFileName value="false"/>
    <appendToFile value="true"/>
    <rollingStyle value="Date"/>
    <maxSizeRollBackups value="100"/>
    <maximumFileSize value="15MB"/>
    <layout type="log4net.Layout.PatternLayout">
      <conversionPattern value="%date [%thread] %-5level App  %newline %message %newline %newline"/>
      <level value="ALL"/>
      <appender-ref ref="RollingLogFileAppender"/>
      <appender-ref ref="ConsoleAppender"/>

Another note, the traditional way of setting the XML up within app.config did not work:

<?xml version="1.0" encoding="utf-8"?>
    <section name="log4net" type="log4net.Config.Log4NetConfigurationSectionHandler, log4net" />
  <log4net> ...

For some reason, the log4net node was not found when accessing the XMLDocument via log4netConfig["log4net"].

Vuex - passing multiple parameters to mutation

Mutations expect two arguments: state and payload, where the current state of the store is passed by Vuex itself as the first argument and the second argument holds any parameters you need to pass.

The easiest way to pass a number of parameters is to destruct them:

mutations: {
    authenticate(state, { token, expiration }) {
        localStorage.setItem('token', token);
        localStorage.setItem('expiration', expiration);

Then later on in your actions you can simply

store.commit('authenticate', {

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

"A requires a peer of B but none was installed". Consider it as "A requires one of B's peers but that peer was not installed and we're not telling you which of B's peers you need."

The automatic installation of peer dependencies was explicitly removed with npm 3.

NPM Blog

Release notes of v3

So you cannot install peer dependencies automatically with npm 3 and upwards.

Updated Solution:

Use following for each peer dependency to install that and remove the error

npm install --save-dev xxxxx

Deprecated Solution:

  1. You can use npm-install-peers to find and install required peer dependencies.

    npm install -g npm-install-peers


  2. If you are getting this error after updating any package's version then remove node_modules directory and reinstall packages by npm install or npm cache clean and npm install.

How to Update a Component without refreshing full page - Angular

One of many solutions is to create an @Injectable() class which holds data that you want to show in the header. Other components can also access this class and alter this data, effectively changing the header.

Another option is to set up @Input() variables and @Output() EventEmitters which you can use to alter the header data.

Edit Examples as you requested:

export class HeaderService {
    private _data;
    set data(value) {
        this._data = value;
    get data() {
        return this._data;

in other component:

constructor(private headerService: HeaderService) {}

// Somewhere = 'abc';

in header component:

let headerData;

constructor(private headerService: HeaderService) {
    this.headerData =;

I haven't actually tried this. If the get/set doesn't work you can change it to use a Subject();

// Simple Subject() example:
let subject = new Subject();
this.subject.subscribe(response => {
  console.log(response); // Logs 'hello'

Bootstrap 4 Dropdown Menu not working?

You need to enqueue the script bootstrap.js or bootstrap.min.js. I had the same problem with bootstrap 4.5.3 and the menu worked when I enqueued one of the above scripts. It can be either.

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

In my case, what I did was a mistake in the url tag in the respective template. So, in my url tag I had something like

{% url 'polls:details' %}

while in the views, I had written something like:

def details(request, question_id): code here

So, the first thing you might wanna check is whether things are spelled as they shoould be. The next thing then you can do is as the people above have suggested.

If condition inside of map() React

There are two syntax errors in your ternary conditional:

  1. remove the keyword if. Check the correct syntax here.
  2. You are missing a parenthesis in your code. If you format it like this:

    {(this.props.schema.collectionName.length < 0 ? 
       : (<h1>hejsan</h1>) 

Hope this works!

Android dependency has different version for the compile and runtime

In my case, I was having two different versions of the below implementation in two different modules, So i changed both implementation to versions ie : 6.0.2 and it worked. You may also need to write dependency resolution see the accepted answer.

app module

implementation 'com.karumi:dexter:5.0.0'

commons module

implementation 'com.karumi:dexter:6.0.2'

Angular ngClass and click event for toggling class

Instead of having to create a function in the ts file you can toggle a variable from the template itself. You can then use the variable to apply a specific class to the element. Like so-

<div (click)="status=!status"  
    [ngClass]="status ? 'success' : 'danger'">                
     Some content

So when status is true the class success is applied. When it is false danger class is applied.

This will work without any additional code in the ts file.

Bootstrap 4: Multilevel Dropdown Inside Navigation

Using official HTML without adding extra CSS styles and classes, it's like native support.

Just add the following code:

$.fn.dropdown = (function() {
    var $bsDropdown = $.fn.dropdown;
    return function(config) {
        if (typeof config === 'string' && config === 'toggle') { // dropdown toggle trigged
        var ret = $$(this), config);
        $(this).off(''); // Turn off dropdown.js click event, it will call 'this.toggle()' internal
        return ret;

$(function() {
    $('.dropdown [data-toggle="dropdown"]').on('click', function(e) {
    $('.dropdown').on('', function(e) {
        if ($(this).is('.has-child-dropdown-show')) {

Dropdown of bootstrap can be easily changed to infinite level. It's a pity that they didn't do it.

BTW, a hover version:

Here is a perfect demo: (works well with Bootstrap v4.4.1)

Cannot find control with name: formControlName in angular reactive form

I also had this error, and you helped me solve it. If formGroup or formGroupName are not written with the good case, then the name of the control is not found. Correct the case of formGroup or formGroupName and it is OK.

How to enable CORS in Core WebAPI

In launchSettings.json, under iisSettings, set anonymousAuthentication to true:

"iisSettings": {
    "windowsAuthentication": true,
    "anonymousAuthentication": true,
    "iisExpress": {
      "applicationUrl": "http://localhost:4200/",
      "sslPort": 0

Then, in Startup.cs, under ConfigureServices, before services.AddMvc, add:

services.AddCors(options => options.AddPolicy("ApiCorsPolicy", builder =>
        .WithHeaders(HeaderNames.AccessControlAllowHeaders, "Content-Type")

and then, in configure method, before app.UseMvc() add:


The use of Swift 3 @objc inference in Swift 4 mode is deprecated?

The use of Swift 3 @objc inference in Swift 4 mode is deprecated?

use func call @objc

func call(){



@objc func foo() {


More than one file was found with OS independent path 'META-INF/LICENSE'

I have read all the answers related to getting this message in Android Studio:

More than one file was found with OS independent path 'META-INF/LICENSE'

but in this case excluding classes is no neccessary, we only need to exclude 'META-INF/DEPENDENCIES', this can be done inside the /app/build.gradle:

    packagingOptions {
        exclude 'META-INF/DEPENDENCIES'


Angular 2 ngfor first, last, index loop

Here is how its done in Angular 6

<li *ngFor="let user of userObservable ; first as isFirst">
   <span *ngIf="isFirst">default</span>

Note the change from let first = first to first as isFirst

How to solve "sign_and_send_pubkey: signing failed: agent refused operation"?

quick note for those recently upgrading to "modern" ssh version [OpenSSH_8.1p1, OpenSSL 1.1.1d FIPS 10 Sep 2019] - supplied with fedora 31, seems not to be anymore accepting old DSA SHA256 keys (mine are dated 2006!) - created a new rsa key, public added to authorized, private on client, and everything works perfectly.

thanks for previous suggestions, especially the ssh -v has been very useful

React navigation goBack() and update parent state

I was facing a similar issue, so here is how I solved it by going more into details.

Option one is to navigate back to parent with parameters, just define a callback function in it like this in parent component:

updateData = data => {
  alert("come back status: " + data);
  // some other stuff

and navigate to the child:

onPress = () => {
  this.props.navigation.navigate("ParentScreen", {
    name: "from parent",
    updateData: this.updateData

Now in the child it can be called:


Option two. In order to get data from any component, as the other answer explained, AsyncStorage can be used either synchronously or not.

Once data is saved it can be used anywhere.

// to get
  .then(item => {
    item = JSON.parse(item);
    this.setState({ mystate: item });
// to set
AsyncStorage.setItem("@item", JSON.stringify(someData));

or either use an async function to make it self-update when it gets new value doing like so.

this.state = { item: this.dataUpdate() };
async function dataUpdate() {
  try {
    let item = await AsyncStorage.getItem("@item");
    return item;
  } catch (e) {

See the AsyncStorage docs for more details.

TypeError: can't pickle _thread.lock objects

I had the same problem with Pool() in Python 3.6.3.

Error received: TypeError: can't pickle _thread.RLock objects

Let's say we want to add some number num_to_add to each element of some list num_list in parallel. The code is schematically like this:

class DataGenerator:
    def __init__(self, num_list, num_to_add)
        self.num_list = num_list # e.g. [4,2,5,7]
        self.num_to_add = num_to_add # e.g. 1 

    def run(self):
        new_num_list = Manager().list()

        pool = Pool(processes=50)
        results = [pool.apply_async(run_parallel, (num, new_num_list)) 
                      for num in num_list]
        roots = [r.get() for r in results]

    def run_parallel(self, num, shared_new_num_list):
        new_num = num + self.num_to_add # uses class parameter

The problem here is that self in function run_parallel() can't be pickled as it is a class instance. Moving this parallelized function run_parallel() out of the class helped. But it's not the best solution as this function probably needs to use class parameters like self.num_to_add and then you have to pass it as an argument.


def run_parallel(num, shared_new_num_list, to_add): # to_add is passed as an argument
    new_num = num + to_add

class DataGenerator:
    def __init__(self, num_list, num_to_add)
        self.num_list = num_list # e.g. [4,2,5,7]
        self.num_to_add = num_to_add # e.g. 1

    def run(self):
        new_num_list = Manager().list()

        pool = Pool(processes=50)
        results = [pool.apply_async(run_parallel, (num, new_num_list, self.num_to_add)) # num_to_add is passed as an argument
                      for num in num_list]
        roots = [r.get() for r in results]

Other suggestions above didn't help me.

How to print a Groovy variable in Jenkins?

The following code worked for me:

echo userInput

Error:Execution failed for task ':app:compileDebugKotlin'. > Compilation error. See log for more details

My scenario:

old Kotlin dataclass:

data class AddHotelParams(val destination: Place?, val checkInDate: LocalDate,
                      val checkOutDate: LocalDate?): JsonObject

new Kotlin dataclass:

data class AddHotelParams(val destination: Place?, val checkInDate: LocalDate,
                      val checkOutDate: LocalDate?, val roundTrip: Boolean): JsonObject

The problem was that I forgot to change the object initialization in some parts of the code. I got a generic "compileInternalDebugKotlin" error instead of being told where I needed to change the initialization.

changing initialization to all parts of the code resolved the error.

How can I manually set an Angular form field as invalid?

in component:

formData.form.controls['email'].setErrors({'incorrect': true});

and in HTML:

<input mdInput placeholder="Email" type="email" name="email" required [(ngModel)]="email"  #email="ngModel">
<div *ngIf="!email.valid">{{email.errors| json}}</div>

Bootstrap 4 navbar color

Update 2019

Remember that whatever CSS overrides you define must be the same CSS specificity or greater in order to properly override Bootstrap's CSS.

Bootstrap 4.1+

The Navbar is transparent by default. If you only want to change the background color, it can be done simply by applying the color to the <navbar class="bg-custom">, but remember that won't change the other colors such as the links, hover and dropdown menu colors.

Here's CSS that will change any relevant Navbar colors in Bootstrap 4...

/* change the background color */
.navbar-custom {
    background-color: #ff5500;
/* change the brand and text color */
.navbar-custom .navbar-brand,
.navbar-custom .navbar-text {
    color: rgba(255,255,255,.8);
/* change the link color */
.navbar-custom .navbar-nav .nav-link {
    color: rgba(255,255,255,.5);
/* change the color of active or hovered links */
.navbar-custom .nav-link,
.navbar-custom .nav-item:focus .nav-link,
.navbar-custom .nav-item:hover .nav-link {
    color: #ffffff;


Override Navbar Light or Dark

If you're using the Bootstrap 4 Navbar navbar-light or navbar-dark classes, then use this in the overrides. For example, changing the Navbar link colors...

.navbar-light .nav-link,
.navbar-light .nav-item:focus .nav-link,
.navbar-light .nav-item:hover .nav-link {
        color: #ffffff;

When making any Bootstrap customizations, you need to understand CSS Specificity. Overrides in your custom CSS need to use selectors that are as specific as the bootstrap.css. Read more

Transparent Navbar

Notice that the Bootstrap 4 Navbar is transparent by default. Use navbar-dark for dark/bold background colors, and use navbar-light if the navbar is a lighter color. This will effect the color of the text and color of the toggler icon as explained here.


Hibernate Error executing DDL via JDBC Statement

First thing you need to do here is correct the hibernate dialect version like @JavaLearner has explained. Then you have make sure that all the versions of hibernate dependencies you are using are upto date. Typically you would need: database driver like mysql-connector-java, hibernate dependency: hibernate-core and hibernate entity manager: hibernate-entitymanager. Lastly don't forget to check that the database tables you are using are not the reserved words like order, group, limit, etc. It might save you a lot of headache.

How to implement authenticated routes in React Router 4?

The accepted answer is good, but it does NOT solve the problem when we need our component to reflect changes in URL.

Say, your component's code is something like:

export const Customer = (props) => {

   const history = useHistory();


And you change URL:

const handleGoToPrev = () => {

The component will not reload!

A better solution:

import React from 'react';
import { Redirect, Route } from 'react-router-dom';
import store from '../store/store';

export const PrivateRoute = ({ component: Component, }) => {

  let isLoggedIn = !!store.getState().data.user;

  return (
    <Route {} render={props => isLoggedIn
      ? (
        <Component key={ || 'empty'} {...props} />
      ) : (
        <Redirect to={{ pathname: '/login', state: { from: props.location } }} />
    } />


<PrivateRoute exact path="/app/customer/:id" component={Customer} />

Entity Framework Core: DbContextOptionsBuilder does not contain a definition for 'usesqlserver' and no extension method 'usesqlserver'

I had same issue but problem went off after going back and fixing DbContext incorrect syntax issue such as it should have been ExampleDbContextClass: DbContext whereas I had missed DbContext part in Context Class where you define your DbSet. Also, I verified following dependencies are needed in order to achieve connection to SqlServer. <PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer" Version="3.1.0" /> <PackageReference Include="Microsoft.EntityFrameworkCore.SqlServer.Design" Version="1.1.6" /> Also verify that Version you install is less than your project's current version to be on safe side. Such as if your project is using 3.1 do not try to use newer one which would be for example 3.1.9. I had issue with that too.

Attach Authorization header for all axios requests

The point is to set the token on the interceptors for each request

import axios from "axios";
const httpClient = axios.create({
    baseURL: "http://youradress",
    // baseURL: process.env.APP_API_BASE_URL,

httpClient.interceptors.request.use(function (config) {
    const token = localStorage.getItem('token');
    config.headers.Authorization =  token ? `Bearer ${token}` : '';
    return config;

Golang read request body

I could use the GetBody from Request package.

Look this comment in source code from request.go in net/http:

GetBody defines an optional func to return a new copy of Body. It is used for client requests when a redirect requires reading the body more than once. Use of GetBody still requires setting Body. For server requests it is unused."

GetBody func() (io.ReadCloser, error)

This way you can get the body request without make it empty.


getBody := request.GetBody
copyBody, err := getBody()
if err != nil {
    // Do something return err

How to resolve Unneccessary Stubbing exception

As others pointed out it is usually the simplest to remove the line that is unnecessarily stubbing a method call.

In my case it was in a @BeforeEach and it was relevant most of the time. In the only test where that method was not used I reset the mock, e.g.:


Hope this helps others with the same problem.

(Note that if there are multiple mocked calls on the same mock this could be inconvenient as well since you'll have to mock all the other methods except the one that isn't called.)

Unsupported Media Type in postman

You need to set the content-type in postman as JSON (application/json).

Go to the body inside your POST request, there you will find the raw option.

Right next to it, there will be a drop down, select JSON (application.json).

REACT - toggle class onclick

you can add toggle class or toggle state on click

class Test extends Component(){
  toggleClass() {

    render() {
      <div onClick={this.toggleClass.bind(this)}>


Bootstrap 4 Change Hamburger Toggler Color

One simplest way to encounter this is to use font awesome for example

 <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarCollapse" aria-controls="navbarCollapse" aria-expanded="false" aria-label="Toggle navigation">
       <span><i class="fas fa-bars"></i></span>

Then u can change the i element like you change any other ielement.

Maven build Compilation error : Failed to execute goal org.apache.maven.plugins:maven-compiler-plugin:3.1:compile (default-compile) on project Maven

I had the same problem and I Changed this


here 1.7 is my JDK was solved.

How to hide collapsible Bootstrap 4 navbar on click

With trying out above solutions, I was missing a solution for Dropdown toggles, so here you go! Also opens submenu items.

Maybe you have to tweak it a bit if your toggle class is different.

$('.navbar-nav li a').on('click', function(){
    if(!$( this ).hasClass('dropdown-toggle')){

All libraries must use the exact same version specification

I had the exact same problem after updating to Android Studio 2.3

Adding this line to dependencies solved my problem:

compile ''

Job for mysqld.service failed See "systemctl status mysqld.service"

  1. open my.cnf and copy the log-error path

  2. then check the permission for the copied log file using
    $ ls -l /var/log/mysql.log

  3. if any log file permission may changed from mysql:mysql, please change the file permission to
    $ chown -R mysql:mysql /var/log/mysql.log

  4. then restart the mysql server
    $ service mysql restart || systemctl restart mysqld

note: this kind of errors formed by the permission issues. all the mysql service start commands using the log file for writing the status of mysql. If the permission has been changed, the service can't be write anything into the log files. If it happens it will stopped to run the service

How to solve npm error "npm ERR! code ELIFECYCLE"

Usually killall node command fixes mine.

Tomcat: java.lang.IllegalArgumentException: Invalid character found in method name. HTTP method names must be tokens

I was getting the same exception, whenever a page was getting loaded,

NFO: Error parsing HTTP request header
 Note: further occurrences of HTTP header parsing errors will be logged at DEBUG level.
java.lang.IllegalArgumentException: Invalid character found in method name. HTTP method names must be tokens
    at org.apache.coyote.http11.InternalInputBuffer.parseRequestLine(
    at org.apache.coyote.http11.AbstractHttp11Processor.process(
    at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(
    at java.util.concurrent.ThreadPoolExecutor.runWorker(
    at java.util.concurrent.ThreadPoolExecutor$
    at org.apache.tomcat.util.threads.TaskThread$

I found that one of my page URL was https instead of http, when I changed the same, error was gone.

How to implement a Navbar Dropdown Hover in Bootstrap v4?

Andrei's "complete" jQuery+CSS solution has the right intent, but it's verbose and still incomplete. Incomplete because while it probably covers all the necessary DOM changes, it's missing the firing of custom events. Verbose because it's wheel-reinventing when Bootstrap already provides the dropdown() method, which does everything.

So the correct, DRY solution, which does not rely on the CSS hack often repeated among other answers, is just jQuery:

$('body').on('mouseover mouseout', '.dropdown', function(e) {

mysqld_safe Directory '/var/run/mysqld' for UNIX socket file don't exists

You may try the following if your database does not have any data OR you have another away to restore that data. You will need to know the Ubuntu server root password but not the mysql root password.

It is highly probably that many of us have installed "mysql_secure_installation" as this is a best practice. Navigate to bin directory where mysql_secure_installation exist. It can be found in the /bin directory on Ubuntu systems. By rerunning the installer, you will be prompted about whether to change root database password.

How to Pass data from child to parent component Angular

Hello you can make use of input and output. Input let you to pass variable form parent to child. Output the same but from child to parent.

The easiest way is to pass "startdate" and "endDate" as input

<calendar [startDateInCalendar]="startDateInSearch" [endDateInCalendar]="endDateInSearch" ></calendar>

In this way you have your startdate and enddate directly in search page. Let me know if it works, or think another way. Thanks

Uncaught TypeError: (intermediate value)(...) is not a function

To make semicolon rules simple

Every line that begins with a (, [, `, or any operator (/, +, - are the only valid ones), must begin with a semicolon.


This prevents a



Additional Note

To mention what will happen: brackets will index, parentheses will be treated as function parameters. The backtick would transform into a tagged template, and regex or explicitly signed integers will turn into operators. Of course, you can just add a semicolon to the end of every line. It's good to keep mind though when you're quickly prototyping and are dropping your semicolons.

Also, adding semicolons to the end of every line won't help you with the following, so keep in mind statements like

return // Will automatically insert semicolon, and return undefined.
i // Adds a semicolon
   ++ // But, if you really intended i++ here, your codebase needs help.

The above case will happen to return/continue/break/++/--. Any linter will catch this with dead-code or ++/-- syntax error (++/-- will never realistically happen).

Finally, if you want file concatenation to work, make sure each file ends with a semicolon. If you're using a bundler program (recommended), it should do this automatically.

Bootstrap 4 responsive tables won't take up 100% width

The solution compliant with the v4 of the framework is to set the proper breakpoint. Rather than using .table-responsive, you should be able to use .table-responsive-sm (to be just responsive on small devices)

You can use any of the available endpoints: table-responsive{-sm|-md|-lg|-xl}

Clearing input in vuejs form


<template lang="pug">
    input.input(type='text', v-model='formData.firstName')
    input.input(type='text', v-model='formData.lastName')
    button(@click='resetForm', value='Reset Form') Reset Form


  const initFromData = { firstName: '', lastName: '' };

  export default {
    data() {
      return {
        formData: Object.assign({}, initFromData),
    methods: {
      resetForm() {
        // if shallow copy
        this.formData = Object.assign({}, initFromData);

        // if deep copy
        // this.formData = JSON.parse(JSON.stringify(this.initFromData));

Read the difference between a deep copy and a shallow copy HERE.

Bootstrap 4 align navbar items to the right

Use this code to move items to the right.

<div class="collapse navbar-collapse justify-content-end">

Composer: file_put_contents(./composer.json): failed to open stream: Permission denied

In my case, .composer was owned by root, so I did sudo rm -fr .composer and then my global require worked.

Be warned! You don't wanna use that command if you are not sure what you are doing.

Caused by: org.flywaydb.core.api.FlywayException: Validate failed. Migration Checksum mismatch for migration 2

simple solution will be change spring.datasource.url=jdbc:h2:file:~/dasboot in to new file name like : spring.datasource.url=jdbc:h2:file:~/dasboots

In Chrome 55, prevent showing Download button for HTML 5 video

Google has added a new feature since the last answer was posted here. You can now add the controlList attribute as shown here:

<video width="512" height="380" controls controlsList="nodownload">
    <source data-src="mov_bbb.ogg" type="video/mp4">

You can find all options of the controllist attribute here:

ASP.NET Core Dependency Injection error: Unable to resolve service for type while attempting to activate

I had problems trying to inject from my Program.cs file, by using the CreateDefaultBuilder like below, but ended up solving it by skipping the default binder. (see below).

var host = Host.CreateDefaultBuilder(args)
.ConfigureWebHostDefaults(webBuilder =>
    webBuilder.ConfigureServices(servicesCollection => { servicesCollection.AddSingleton<ITest>(x => new Test()); });

It seems like the Build should have been done inside of ConfigureWebHostDefaults to get it work, since otherwise the configuration will be skipped, but correct me if I am wrong.

This approach worked fine:

var host = new WebHostBuilder()
.ConfigureServices(servicesCollection =>
    var serviceProvider = servicesCollection.BuildServiceProvider();
    IConfiguration configuration = (IConfiguration)serviceProvider.GetService(typeof(IConfiguration));
    servicesCollection.AddSingleton<ISendEmailHandler>(new SendEmailHandler(configuration));

This also shows how to inject an already predefined dependency in .net core (IConfiguration) from

Bootstrap footer at the bottom of the page

In my case for Bootstrap4:

<body class="d-flex flex-column min-vh-100">
    <div class="wrapper flex-grow-1"></div>

What's the difference between ngOnInit and ngAfterViewInit of Angular2?

ngOnInit() is called after ngOnChanges() was called the first time. ngOnChanges() is called every time inputs are updated by change detection.

ngAfterViewInit() is called after the view is initially rendered. This is why @ViewChild() depends on it. You can't access view members before they are rendered.

Console logging for react?

If you want to log inside JSX you can create a dummy component
which plugs where you wish to log:

const Console = prop => (
  ,null // ? React components must return something 

// Some component with JSX and a logger inside
const App = () => 
    <p>imagine this is some component</p>
    <Console log='foo' />
    <p>imagine another component</p>
    <Console warn='bar' />

// Render 
  <App />,
<script src=""></script>
<script src=""></script>
<div id="react"></div>

How to change the integrated terminal in visual studio code or VSCode

From Official Docs

Correctly configuring your shell on Windows is a matter of locating the right executable and updating the setting. Below is a list of common shell executables and their default locations.

There is also the convenience command Select Default Shell that can be accessed through the command palette which can detect and set this for you.

So you can open a command palette using ctrl+shift+p, use the command Select Default Shell, then it displays all the available command line interfaces, select whatever you want, VS code sets that as default integrated terminal for you automatically.

If you want to set it manually find the location of executable of your cli and open user settings of vscode(ctrl+,) then set


Example for gitbash on windows7:


Consider defining a bean of type 'package' in your configuration [Spring-Boot]

If you use interface you can extends CrudRepository<Applicant,Long> with @Repository annotation.

How to toggle boolean state of react component?

Depending on your context; this will allow you to update state given the mouseEnter function. Either way, by setting a state value to either true:false you can update that state value given any function by setting it to the opposing value with !this.state.variable

state = {
  hover: false

onMouseEnter = () => {
    hover: !this.state.hover

Reload child component when variables on parent component changes. Angular2

In case, when we have no control over child component, like a 3rd party library component.

We can use *ngIf and setTimeout to reset the child component from parent without making any change in child component.



show:boolean = true

resetChildForm(){ = false;

   setTimeout(() => { = true
    }, 100);

Getting an object array from an Angular service

Take a look at your code :

 getUsers(): Observable<User[]> {
        return Observable.create(observer => {
            this.http.get('').map(response => response.json();

and code from (BTW. really good tutorial, you should check it out)

 getHeroes(): Promise<Hero[]> {
    return this.http.get(this.heroesUrl)
               .then(response => response.json().data as Hero[])

The HttpService inside Angular2 already returns an observable, sou don't need to wrap another Observable around like you did here:

   return Observable.create(observer => {
        this.http.get('').map(response => response.json()

Try to follow the guide in link that I provided. You should be just fine when you study it carefully.


First of all WHERE you log the this.users variable? JavaScript isn't working that way. Your variable is undefined and it's fine, becuase of the code execution order!

Try to do it like this:

  getUsers(): void {
            .then(users => {
               this.users = users
               console.log('this.users=' + this.users);


See where the console.log(...) is!

Try to resign from toPromise() it's seems to be just for ppl with no RxJs background.

Catch another link: Build your service once again with RxJs observables.

Angular 2 Checkbox Two Way Data Binding

A workaround to achieve the same specially if you want to use checkbox with for loop is to store the state of the checkbox inside an array and change it based on the index of the *ngFor loop. This way you can change the state of the checkbox in your component.


<div *ngFor="let item of items; index as i"> <input type="checkbox" [checked]="category[i]" (change)="checkChange(i)"> {{}} </div>


items = [

  category= []

    if (this.category[i]){  
      this.category[i] = !this.category[i];
      this.category[i] = true;

Align nav-items to right side in bootstrap-4

Navbar expanded

Navbar collapsed

I have a working codepen with left- and right-aligned nav links that all collapse into a responsive menu together using .justify-content-between on the parent tag:

<nav class="navbar navbar-toggleable-sm navbar-inverse bg-inverse">
  <button class="navbar-toggler navbar-toggler-right" type="button" data-toggle="collapse" data-target="#navbar"     aria-controls="navbarNavAltMarkup" aria-expanded="false" aria-label="Toggle navigation">
    <span class="navbar-toggler-icon"></span>
  <a class="navbar-brand" href="#">Acme</a>
  <div class="collapse navbar-collapse justify-content-between" id="navbar">
    <div class="navbar-nav">
      <a class="nav-item nav-link" href="#">Ball Bearings</a>
      <a class="nav-item nav-link" href="#">TNT Boxes</a>
    <div class="navbar-nav">
      <a class="nav-item nav-link" href="#">Logout</a>

if else condition in blade file (laravel 5.3)

I think you are putting one too many curly brackets. Try this

            <td><a href="#" class="viewPopLink btn btn-default1" role="button" data-id="{!! $user->travel_id !!}" data-toggle="modal" data-target="#myModal">Approve/Reject</a> </td>
            <td>{!! $user->status !!}</td>

Unit testing click event in Angular

My objective is to check if the 'onEditButtonClick' is getting invoked when the user clicks the edit button and not checking just the console.log being printed.

You will need to first set up the test using the Angular TestBed. This way you can actually grab the button and click it. What you will do is configure a module, just like you would an @NgModule, just for the testing environment

import { TestBed, async, ComponentFixture } from '@angular/core/testing';

describe('', () => {
  let fixture: ComponentFixture<TestComponent>;
  let component: TestComponent;

  beforeEach(async(() => {
      imports: [ ],
      declarations: [ TestComponent ],
      providers: [  ]
    }).compileComponents().then(() => {
      fixture = TestBed.createComponent(TestComponent);
      component = fixture.componentInstance;

Then you need to spy on the onEditButtonClick method, click the button, and check that the method was called

it('should', async(() => {
  spyOn(component, 'onEditButtonClick');

  let button = fixture.debugElement.nativeElement.querySelector('button');;

  fixture.whenStable().then(() => {

Here we need to run an async test as the button click contains asynchronous event handling, and need to wait for the event to process by calling fixture.whenStable()


It is now preferred to use fakeAsync/tick combo as opposed to the async/whenStable combo. The latter should be used if there is an XHR call made, as fakeAsync does not support it. So instead of the above code, refactored, it would look like

it('should', fakeAsync(() => {
  spyOn(component, 'onEditButtonClick');

  let button = fixture.debugElement.nativeElement.querySelector('button');;


Don't forget to import fakeAsync and tick.

See also:

npm start error with create-react-app

This occurs when the node_modules gets out of sync with package.json.

Run the following at the root and any sub service /sub-folder that might have node_modules folder within it.

rd node_modules /S /Q
npm install

How to use aria-expanded="true" to change a css property

If you were open to using JQuery, you could modify the background color for any link that has the property aria-expanded set to true by doing the following...

$("a[aria-expanded='true']").css("background-color", "#42DCA3");

Depending on how specific you want to be regarding which links this applies to, you may have to slightly modify your selector.

Keyboard shortcut to clear cell output in Jupyter notebook

Add following at start of cell and run it:

from IPython.display import clear_output

Use JsonReader.setLenient(true) to accept malformed JSON at line 1 column 1 path $

In my case ; what solved my issue was.....

You may had json like this, the keys without " double quotations....

{ name: "test", phone: "2324234" }

So try any online Json Validator to make sure you have right syntax...

Json Validator Online

How to add the text "ON" and "OFF" to toggle button

Square version of the toggle can be added by modifying the border radius

.switch {
  position: relative;
  display: inline-block;
  width: 90px;
  height: 36px;

.switch input {display:none;}

.slider {
  position: absolute;
  cursor: pointer;
  top: 0;
  left: 0;
  right: 0;
  bottom: 0;
  background-color: #ca2222;
  -webkit-transition: .4s;
  transition: .4s;
  border-radius: 6px;

.slider:before {
  position: absolute;
  content: "";
  height: 34px;
  width: 32px;
  top: 1px;
  left: 1px;
  right: 1px;
  bottom: 1px;
  background-color: white;
  transition: 0.4s;
  border-radius: 6px;

input:checked + .slider {
  background-color: #2ab934;

input:focus + .slider {
  box-shadow: 0 0 1px #2196F3;

input:checked + .slider:before {
  -webkit-transform: translateX(26px);
  -ms-transform: translateX(26px);
  transform: translateX(55px);

.slider:after {
  color: white;
  display: block;
  position: absolute;
  transform: translate(-50%,-50%);
  top: 50%;
  left: 50%;
  font-size: 10px;
  font-family: Verdana, sans-serif;
input:checked + .slider:after {
<label class="switch">
  <input type="checkbox" id="togBtn">
  <div class="slider"></div>

enter image description here

Error: Cannot invoke an expression whose type lacks a call signature

The function that it returns has a call signature, but you told Typescript to completely ignore that by adding : any in its signature.

What is mapDispatchToProps?

mapStateToProps receives the state and props and allows you to extract props from the state to pass to the component.

mapDispatchToProps receives dispatch and props and is meant for you to bind action creators to dispatch so when you execute the resulting function the action gets dispatched.

I find this only saves you from having to do dispatch(actionCreator()) within your component thus making it a bit easier to read.

How do I access Configuration in any class in ASP.NET Core?

In ASP.NET Core, there are configuration providers for reading configurations from almost anywhere such as files e.g. JSON, INI or XML, environment variables, Azure key vault, command-line arguments, etc. and many more sources. I have written a step by step guide to show you how can you configure your application settings in various files such as JSON, INI or XML and how can you read those settings from your application code. I will also demonstrate how can you read application settings as custom .NET types (classes) and how can you use the built-in ASP.NET Core dependency injection to read your configuration settings in multiple classes, services or even projects available in your solution.

Read A Step by Step Guide for ASP.NET Core Configuration

How to read connection string in .NET Core?

Too late, but after reading all helpful answers and comments, I ended up using Microsoft.Extensions.Configuration.Binder extension package and play a little around to get rid of hardcoded configuration keys.

My solution:


public interface IConfigSection


public static class ConfigurationExtensions
    public static TConfigSection GetConfigSection<TConfigSection>(this IConfiguration configuration) where TConfigSection : IConfigSection, new()
        var instance = new TConfigSection();
        var typeName = typeof(TConfigSection).Name;

        return instance;


   "AppConfigSection": {
      "IsLocal": true
   "ConnectionStringsConfigSection": {
      "LocalConnectionString":"Data Source=MyDb.db",

To access a strongly typed config, you just need to create a class for that, which implements IConfigSection interface(Note: class names and field names should exactly match section in appsettings.json)


public class AppConfigSection: IConfigSection
    public bool IsLocal { get; set; }


public class ConnectionStringsConfigSection : IConfigSection
    public string ServerConnectionString { get; set; }
    public string LocalConnectionString { get; set; }

    public ConnectionStringsConfigSection()
        // set default values to avoid null reference if
        // section is not present in appsettings.json
        ServerConnectionString = string.Empty;
        LocalConnectionString = string.Empty;

And finally, a usage example:


public class Startup
    public Startup(IConfiguration configuration)
        Configuration = configuration;

    public IConfiguration Configuration { get; }

    public void ConfigureServices(IServiceCollection services)
        // some stuff

        var app = Configuration.GetConfigSection<AppConfigSection>();
        var connectionStrings = Configuration.GetConfigSection<ConnectionStringsConfigSection>();

        services.AddDbContext<AppDbContext>(options =>
            if (app.IsLocal)

        // other stuff

To make it neat, you can move above code into an extension method.

That's it, no hardcoded configuration keys.

React js change child component's state from parent component

Above answer is partially correct for me, but In my scenario, I want to set the value to a state, because I have used the value to show/toggle a modal. So I have used like below. Hope it will help someone.

class Child extends React.Component {
  state = {

  handleCancel = (e) => {
      this.setState({ visible: false });

  componentDidMount() {

  componentWillUnmount() {

  method() {
    this.setState({ visible: true });

  render() {
    return (<Modal title="My title?" visible={this.state.visible} onCancel={this.handleCancel}>

class Parent extends React.Component {
  onClick = () => {
    this.child.method() // do stuff
  render() {
    return (
        <Child onRef={ref => (this.child = ref)} />
        <button onClick={this.onClick}>Child.method()</button>

Reference -

How to get `DOM Element` in Angular 2?

Update (using renderer):

Note that the original Renderer service has now been deprecated in favor of Renderer2

as on Renderer2 official doc.

Furthermore, as pointed out by @GünterZöchbauer:

Actually using ElementRef is just fine. Also using ElementRef.nativeElement with Renderer2 is fine. What is discouraged is accessing properties of directly.

You can achieve this by using elementRef as well as by ViewChild. however it's not recommendable to use elementRef due to:

  • security issue
  • tight coupling

as pointed out by official ng2 documentation.

1. Using elementRef (Direct Access):

export class MyComponent {    
constructor (private _elementRef : ElementRef) {

2. Using ViewChild (better approach):

<textarea  #tasknote name="tasknote" [(ngModel)]="taskNote" placeholder="{{ notePlaceholder }}" 
style="background-color: pink" (blur)="updateNote() ; noteEditMode = false " (click)="noteEditMode = false"> {{ todo.note }} </textarea> // <-- changes id to local var

export class MyComponent implements AfterViewInit {
  @ViewChild('tasknote') input: ElementRef;

   ngAfterViewInit() {


3. Using renderer:

export class MyComponent implements AfterViewInit {
      @ViewChild('tasknote') input: ElementRef;
         constructor(private renderer: Renderer2){           

       ngAfterViewInit() {
       //using selectRootElement instead of depreaced invokeElementMethod


Create a global variable in TypeScript

I'm using this:

interface Window {
    globalthing: any;

declare var globalthing: any;

ASP.NET Core Identity - get current user

For context, I created a project using the ASP.NET Core 2 Web Application template. Then, select the Web Application (MVC) then hit the Change Authentication button and select Individual User accounts.

There is a lot of infrastructure built up for you from this template. Find the ManageController in the Controllers folder.

This ManageController class constructor requires this UserManager variable to populated:

private readonly UserManager<ApplicationUser> _userManager;

Then, take a look at the the [HttpPost] Index method in this class. They get the current user in this fashion:

var user = await _userManager.GetUserAsync(User);

As a bonus note, this is where you want to update any custom fields to the user Profile you've added to the AspNetUsers table. Add the fields to the view, then submit those values to the IndexViewModel which is then submitted to this Post method. I added this code after the default logic to set the email address and phone number:

user.FirstName = model.FirstName;
user.LastName = model.LastName;
user.Address1 = model.Address1;
user.Address2 = model.Address2;
user.City = model.City;
user.State = model.State;
user.Zip = model.Zip;
user.Company = model.Company;
user.Country = model.Country;

_dbContext.Attach(user).State = EntityState.Modified;

React - how to pass state to another component

Move all of your state and your handleClick function from Header to your MainWrapper component.

Then pass values as props to all components that need to share this functionality.

class MainWrapper extends React.Component {
    constructor() {
        this.state = {
            sidbarPushCollapsed: false,
            profileCollapsed: false
        this.handleClick = this.handleClick.bind(this);
    handleClick() {
            sidbarPushCollapsed: !this.state.sidbarPushCollapsed,
            profileCollapsed: !this.state.profileCollapsed

    render() {
        return (
               profileCollapsed={this.state.profileCollapsed} />

Then in your Header's render() method, you'd use this.props:

<button type="button" id="sidbarPush" onClick={this.props.handleClick} profile={this.props.profileCollapsed}>

ASP.NET Core 1.0 on IIS error 502.5

Open command prompt with Administrator credentials

Type following command and hit enter



Open Visual Studio 2017 with Administrator credentials

Type following command in Package Manager Console and hit enter


Attempting stop...
Internet services successfully stopped
Attempting start...
Internet services successfully restarted

Vue equivalent of setTimeout?

please use setInterval like below:


'No database provider has been configured for this DbContext' on SignInManager.PasswordSignInAsync

Override constructor of DbContext Try this :-

public DataContext(DbContextOptions<DataContext> option):base(option) {}

How do I access store state in React Redux?

Import connect from react-redux and use it to connect the component with the state connect(mapStates,mapDispatch)(component)

import React from "react";
import { connect } from "react-redux";

const MyComponent = (props) => {
    return (

Finally you need to map the states to the props to access them with this.props

const mapStateToProps = state => {
  return {
    title: state.title
export default connect(mapStateToProps)(MyComponent);

Only the states that you map will be accessible via props

Check out this answer:

For further reading :

How to unapply a migration in ASP.NET Core with EF Core

You should delete migration '20160703192724_MyFirstMigration' record from '_EFMigrationsHistory' table.

otherwise this command will remove migration and delete migrations folder:

PMC Command:

   > remove-migration -force

CLI Command:

   > dotnet ef migrations remove -f

Link About CLI Commands

Link About PMC Commands

Spring Resttemplate exception handling

A very simple solution can be:

try {
     requestEntity = RequestEntity
     .get(new URI("user String"));
    return, String.class);
} catch (RestClientResponseException e) {
        return ResponseEntity.status(e.getRawStatusCode()).body(e.getResponseBodyAsString());

How to install and run Typescript locally in npm?

It took me a while to figure out the solution to this problem - it's in the original question. You need to have a script that calls tsc in your package.json file so that you can run:

npm run tsc 

Include -- before you pass in options (or just include them in the script):

npm run tsc -- -v

Here's an example package.json:

  "name": "foo",
  "scripts": {
    "tsc": "tsc"
  "dependencies": {
    "typescript": "^1.8.10"

Could not load file or assembly 'CrystalDecisions.ReportAppServer.CommLayer, Version=13.0.2000.0

I faced the same issue and used the following steps to solve it

1) go Right side in solution explorer
2) Click on your Project Name
3) click on Reference
4) you can see yellow symbol on some DLL
5) Right click on that DLL and go to Property
6) Find Specific Version = True replace it with Specific Version = False

and also change Copy Local = False to Copy Local = True

How to dynamically add and remove form fields in Angular 2

add and remove text input element dynamically any one can use this this will work Type of Contact Balance Fund Equity Fund Allocation Allocation % is required! Remove Add Contact

userForm: FormGroup;
  public contactList: FormArray;
  // returns all form groups under contacts
  get contactFormGroup() {
    return this.userForm.get('funds') as FormArray;
  ngOnInit() {
  constructor(public fb: FormBuilder,private router: Router,private ngZone: NgZone,private userApi: ApiService) { }
  // contact formgroup
  createContact(): FormGroup {
      fundName: ['', Validators.compose([Validators.required])], // i.e Email, Phone
      allocation: [null, Validators.compose([Validators.required])]

  // triggered to change validation of value field type
  changedFieldType(index) {
    let validators = null;

    validators = Validators.compose([
      Validators.pattern(new RegExp('^\\+[0-9]?()[0-9](\\d[0-9]{9})$')) // pattern for validating international phone number



  // get the formgroup under contacts form array
  getContactsFormGroup(index): FormGroup {
    // this.contactList = this.form.get('contacts') as FormArray;
    const formGroup = this.contactList.controls[index] as FormGroup;
    return formGroup;

  submitUser() {
    this.userForm ={
      first_name: ['', [Validators.required]],
      last_name: [''],
      email: ['', [Validators.required]],
      company_name: ['', [Validators.required]],
      license_start_date: ['', [Validators.required]],
      license_end_date: ['', [Validators.required]],
      gender: ['Male'],
      funds: this.fb.array([this.createContact()])
    this.contactList = this.userForm.get('funds') as FormArray;
  addContact() {
  removeContact(index) {

How do I detect if a user is already logged in Firebase?

First import the following

import Firebase
import FirebaseAuth


    // Check if logged in
    if (Auth.auth().currentUser != null) {
      // User is logged in   
      // User is not logged in

org.gradle.api.tasks.TaskExecutionException: Execution failed for task ':app:transformClassesWithDexForDebug'

I had the same issue and I could solve it like this:

1) If your minSdkVersion is set to 21 or a higher value, the only thing you need to do is to set multiDexEnabled in your build.gradle file at the module level, as shown below:

android {
    defaultConfig {
        minSdkVersion 21 
        targetSdkVersion 28
        multiDexEnabled true

2) However, if your minSdkVersion is set to 20 or less, you should use the MultiDex compatibility library, as follows:

2.1) Modify the module-level build.gradle file to enable MultiDex and add the MultiDex library as dependency, as shown below

android {
    defaultConfig {
        minSdkVersion 15 
        targetSdkVersion 28
        multiDexEnabled true

dependencies {
  implementation ''

2.2) According to the Application class or not, do one of the following actions:

2.2.1) If you do not cancel the Application class, modify your manifest file to set android: name in the <application> tag as shown below:

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android=""
            android:name="" >

2.2.2) If you cancel the Application class, you must change it to extend MultiDexApplication (if possible) as shown below:

public class MyApplication extends MultiDexApplication { ... }

2.2.3) Also, if you override the Application class and can not change the base class, alternatively you can override the attachBaseContext () method and invoke MultiDex.install (this) to enable MultiDex:

public class MyApplication extends SomeOtherApplication {
  protected void attachBaseContext(Context base) {

Please use this link, it was really useful for me!

How to set the max size of upload file

To avoid this exception you can take help of VM arguments just as I used in Spring 1.5.8.RELEASE:


Where are logs located?

In Laravel 6, by default the logs are in:


Error:Execution failed for task ':app:transformClassesWithDexForDebug' in android studio

In my case I had 2 projects A and B. And I upgraded to gradle 4.5.

A was dependent on B but both had references of my 3rd party jar

I was getting this error Program type already present: com.mnox.webservice.globals.WebServiceLightErrorHashCode

Program type already present: com.mnox.webservice.globals.WebServiceLightErrorHashCode

To fix it

  1. I removed the duplicate jar's
  2. I used api in the B build.gradle file so that it gets referred to in A.

The other root cause can be if you have upgraded to gradle 4.5 and used implementation instead of api in your commons build.gradle

Firebase FCM force onTokenRefresh() to be called

Try to implement FirebaseInstanceIdService to get refresh token.

Access the registration token:

You can access the token's value by extending FirebaseInstanceIdService. Make sure you have added the service to your manifest, then call getToken in the context of onTokenRefresh, and log the value as shown:

public void onTokenRefresh() {
    // Get updated InstanceID token.
    String refreshedToken = FirebaseInstanceId.getInstance().getToken();
    Log.d(TAG, "Refreshed token: " + refreshedToken);

    // TODO: Implement this method to send any registration to your app's servers.

Full Code:

   import android.util.Log;


public class MyFirebaseInstanceIDService extends FirebaseInstanceIdService {

    private static final String TAG = "MyFirebaseIIDService";

     * Called if InstanceID token is updated. This may occur if the security of
     * the previous token had been compromised. Note that this is called when the InstanceID token
     * is initially generated so this is where you would retrieve the token.
    // [START refresh_token]
    public void onTokenRefresh() {
        // Get updated InstanceID token.
        String refreshedToken = FirebaseInstanceId.getInstance().getToken();
        Log.d(TAG, "Refreshed token: " + refreshedToken);

        // TODO: Implement this method to send any registration to your app's servers.
    // [END refresh_token]

     * Persist token to third-party servers.
     * Modify this method to associate the user's FCM InstanceID token with any server-side account
     * maintained by your application.
     * @param token The new token.
    private void sendRegistrationToServer(String token) {
        // Add custom implementation, as needed.

See my answer here.


You shouldn't be starting a FirebaseInstanceIdService yourself.

It will Called when the system determines that the tokens need to be refreshed. The application should call getToken() and send the tokens to all application servers.

This will not be called very frequently, it is needed for key rotation and to handle Instance ID changes due to:

  • App deletes Instance ID
  • App is restored on a new device User
  • uninstalls/reinstall the app
  • User clears app data

The system will throttle the refresh event across all devices to avoid overloading application servers with token updates.

Try below way:

you'd call FirebaseInstanceID.getToken() anywhere off your main thread (whether it is a service, AsyncTask, etc), store the returned token locally and send it to your server. Then whenever onTokenRefresh() is called, you'd call FirebaseInstanceID.getToken() again, get a new token, and send that up to the server (probably including the old token as well so your server can remove it, replacing it with the new one).

Firebase cloud messaging notification not received by device

I had a similar problem, but in my case I was missing the google-services plugin from my Gradle build (I was adding Firebase to an existing project).

I added the following to my root build.gradle:

classpath ''

and the following to the end of my app-level build.gradle:

apply plugin: ''

I then had to download the google-services.json file from the Firebase Console (having originally imported an existing Google Cloud project) and copy it to my app directory`.

Android Studio: /dev/kvm device permission denied

Type in terminal:

sudo apt install qemu-kvm -y
sudo chown $USER /dev/kvm

Add Favicon with React and Webpack

The correct answer in the present if you dont use Create React App is the next:

new HtmlWebpackPlugin({
   favicon: "./public/fav-icon.ico"

If you use CRA then you can modificate the manifest.json in the public directory

Pip - Fatal error in launcher: Unable to create process using '"'

I got the same error when installed both python2 and python3 on my Windows 7.

You can use python3 -m pip install xxxxxx to install your package.

Or, fix it completely:

  1. Try to run python3 -m pip install --upgrade pip in cmd.

  2. If failed in step 1, try python3  -m pip install --upgrade --force-reinstall pip

How to get current value of RxJS Subject or Observable?

The only way you should be getting values "out of" an Observable/Subject is with subscribe!

If you're using getValue() you're doing something imperative in declarative paradigm. It's there as an escape hatch, but 99.9% of the time you should NOT use getValue(). There are a few interesting things that getValue() will do: It will throw an error if the subject has been unsubscribed, it will prevent you from getting a value if the subject is dead because it's errored, etc. But, again, it's there as an escape hatch for rare circumstances.

There are several ways of getting the latest value from a Subject or Observable in a "Rx-y" way:

  1. Using BehaviorSubject: But actually subscribing to it. When you first subscribe to BehaviorSubject it will synchronously send the previous value it received or was initialized with.
  2. Using a ReplaySubject(N): This will cache N values and replay them to new subscribers.
  3. A.withLatestFrom(B): Use this operator to get the most recent value from observable B when observable A emits. Will give you both values in an array [a, b].
  4. A.combineLatest(B): Use this operator to get the most recent values from A and B every time either A or B emits. Will give you both values in an array.
  5. shareReplay(): Makes an Observable multicast through a ReplaySubject, but allows you to retry the observable on error. (Basically it gives you that promise-y caching behavior).
  6. publishReplay(), publishBehavior(initialValue), multicast(subject: BehaviorSubject | ReplaySubject), etc: Other operators that leverage BehaviorSubject and ReplaySubject. Different flavors of the same thing, they basically multicast the source observable by funneling all notifications through a subject. You need to call connect() to subscribe to the source with the subject.

The instance of entity type cannot be tracked because another instance of this type with the same key is already being tracked

I faced the same problem but the issue was very silly, By mistake I have given wrong relationship I have given relationship between 2 Ids.

Bootstrap $('#myModal').modal('show') is not working

jQuery lib has to be loaded first. In my case, i was loading bootstrap lib first, also tried tag with target and firing a click trigger. But the main issue was - jquery has to be loaded first.

List of swagger UI alternatives

Yes, there are a few of them.

Hosted solutions that support swagger:

Check the following articles for more details:

Nginx upstream prematurely closed connection while reading response header from upstream, for large requests

I solved this by setting a higher timeout value for the proxy:

location / {
    proxy_read_timeout 300s;
    proxy_connect_timeout 75s;
    proxy_pass http://localhost:3000;


How to redirect to another page in node.js

If the user successful login into your Node app, I'm thinking that you are using Express, isn't ? Well you can redirect easy by using res.redirect. Like:'/auth', function(req, res) {
  // Your logic and then redirect

Failed to execute goal org.apache.maven.plugins:maven-surefire-plugin:2.12:test (default-test) on project.

The problem is not in your dependencies.... you should open detail error on this path

Please refer to D:\Masters\thesis related papers and tools\junitcategorizer\junitcategorizer.instrument\target\surefire-reports for the individual test results.

the detail error's in there, maybe your service class or serviceImpl class or something missing like @anotation or else... i got error same with you,...u should try

angular 2 ngIf and CSS transition/animation

One way is to use a setter for the ngIf property and set the state as part of updating the value.

StackBlitz example


 import {
  } from '@angular/animations';
  import { ChangeDetectionStrategy, Component, Input } from '@angular/core';

  export type FadeState = 'visible' | 'hidden';

    selector: 'app-fade',
    templateUrl: './fade.component.html',
    styleUrls: ['./fade.component.scss'],
    animations: [
      trigger('state', [
            opacity: '1'
            opacity: '0'
        transition('* => visible', [animate('500ms ease-out')]),
        transition('visible => hidden', [animate('500ms ease-out')])
    changeDetection: ChangeDetectionStrategy.OnPush
  export class FadeComponent {
    state: FadeState;
    // tslint:disable-next-line: variable-name
    private _show: boolean;
    get show() {
      return this._show;
    set show(value: boolean) {
      if (value) {
        this._show = value;
        this.state = 'visible';
      } else {
        this.state = 'hidden';

    animationDone(event: AnimationEvent) {
      if (event.fromState === 'visible' && event.toState === 'hidden') {
        this._show = false;


    <button mat-raised-button color="primary">test</button>


:host {
  display: block;
.fade {
  opacity: 0;

Toggle Class in React

Toggle function in react

At first you should create constructor like this

constructor(props) {
        this.state = {
            close: true,

Then create a function like this

yourFunction = () => {
            close: !this.state.close,

then use this like

render() {
        const {close} = this.state;
        return (


                 <div onClick={() => this.yourFunction()}></div>

                 <div className={close ? "isYourDefaultClass" : "isYourOnChangeClass"}></div>


Please give better solutions

Uncaught TypeError: $(...).datepicker is not a function(anonymous function)

Including more than one reference to Jquery library is the reason for the error Only Include one reference to the Jquery library and that will resolve the issue

How do I create a singleton service in Angular 2?

  1. If you want to make service singleton at application level you should define it in app.module.ts

    providers: [ MyApplicationService ] (you can define the same in child module as well to make it that module specific)

    • Do not add this service in provider which creates an instance for that component which breaks the singleton concept, just inject through constructor.
  2. If you want to define singleton service at component level create service, add that service in app.module.ts and add in providers array inside specific component as shown in below snipet.

    @Component({ selector: 'app-root', templateUrl: './test.component.html', styleUrls: ['./test.component.scss'], providers : [TestMyService] })

  3. Angular 6 provide new way to add service at application level. Instead of adding a service class to the providers[] array in AppModule , you can set the following config in @Injectable() :

    @Injectable({providedIn: 'root'}) export class MyService { ... }

The "new syntax" does offer one advantage though: Services can be loaded lazily by Angular (behind the scenes) and redundant code can be removed automatically. This can lead to a better performance and loading speed - though this really only kicks in for bigger services and apps in general.

ReactJS - Add custom event listener to component

You could use componentDidMount and componentWillUnmount methods:

import React, { Component } from 'react';
import ReactDOM from 'react-dom';

class MovieItem extends Component
    _handleNVEvent = event => {

    componentDidMount() {
        ReactDOM.findDOMNode(this).addEventListener('nv-event', this._handleNVEvent);

    componentWillUnmount() {
        ReactDOM.findDOMNode(this).removeEventListener('nv-event', this._handleNVEvent);



export default MovieItem;

How to set default values for Angular 2 component properties?

That is interesting subject. You can play around with two lifecycle hooks to figure out how it works: ngOnChanges and ngOnInit.

Basically when you set default value to Input that's mean it will be used only in case there will be no value coming on that component. And the interesting part it will be changed before component will be initialized.

Let's say we have such components with two lifecycle hooks and one property coming from input.

  selector: 'cmp',
export class Login implements OnChanges, OnInit {
  @Input() property: string = 'default';

  ngOnChanges(changes) {

  ngOnInit() {


Situation 1

Component included in html without defined property value

As result we will see in console: Init default

That's mean onChange was not triggered. Init was triggered and property value is default as expected.

Situation 2

Component included in html with setted property <cmp [property]="'new value'"></cmp>

As result we will see in console:

Changed new value Object {}

Init new value

And this one is interesting. Firstly was triggered onChange hook, which setted property to new value, and previous value was empty object! And only after that onInit hook was triggered with new value of property.

How to know if docker is already logged in to a docker registry server

At least in "Docker for Windows" you can see if you are logged in to docker hub over the UI. Just right click the docker icon in the windows notification area: Docker Logged in

Angular2 get clicked element id

For TypeScript users:

    toggle(event: Event): void {
        let elementId: string = ( as Element).id;
        // do something with the id... 

The request was rejected because no multipart boundary was found in springboot

The problem is that you are setting the Content-Type by yourself, let it be blank. Google Chrome will do it for you. The multipart Content-Type needs to know the file boundary, and when you remove the Content-Type, Postman will do it automagically for you.

Android- Error:Execution failed for task ':app:transformClassesWithDexForRelease'

Well, I believe the question is answered and has already been accepted. But I am going to write what I faced and how I solved it.

I did receive also the same error:

Error:Execution failed for task ':app:transformClassesWithDexForDebug'. java.lang.RuntimeException: java.util.concurrent.ExecutionException: org.gradle.process.internal.ExecException: Process 'command 'C:\Program Files\Java\jdk1.8.0_60\bin\java.exe'' finished with non-zero exit value 1

I wasn't fortunate to apply all the settings and got success. But when I tried to Debug the project again. This time I got Three Error (including above):

Error:Java HotSpot(TM) 64-Bit Server VM warning: CodeCache is full. Compiler has been disabled.


Error:Java HotSpot(TM) 64-Bit Server VM warning: Try increasing the code cache size using -XX:ReservedCodeCacheSize=

So what I did? I just go to Android Studio:

File > Invalidate Caches / Restart.. > Invalidate & Restart

Quick Fix!

Extra Note:

What I found in Gradle Console:

:app:incrementalDebugTasks :app:prePackageMarkerForDebug :app:fastDeployDebugExtractor :app:generateDebugInstantRunAppInfo :app:transformClassesWithDexForDebug To run dex in process, the Gradle daemon needs a larger heap. It currently has approximately 910 MB. For faster builds, increase the maximum heap size for the Gradle daemon to more than 2048 MB. To do this set org.gradle.jvmargs=-Xmx2048M in the project For more information see :app:transformClassesWithDexForDebug FAILED

Read More about it Here on Oracle Blog

ASP.NET 5 MVC: unable to connect to web server 'IIS Express'

The issue may be because [v] Enabled SSL was selected for your project (see the Debug tab in the project settings window), but Visual Studio decides to be dumb and setup something like http://localhost:32396. The reason it fails is because 1. it is not HTTPS, and 2. the cert is not valid. To force it, you need to use a port in the range 44300-44398.


Docker: unable to prepare context: unable to evaluate symlinks in Dockerfile path: GetFileAttributesEx

I erroneously created Dockerfile.txt in my working directory leading to the above-mentioned error while build

The fix was to remove the .txt extension from the file.

The file name should be Dockerfile only without any extension.

java.lang.RuntimeException: Unable to instantiate org.apache.hadoop.hive.ql.metadata.SessionHiveMetaStoreClient

I did below modifications and I am able to start the Hive Shell without any errors:

1. ~/.bashrc

Inside bashrc file add the below environment variables at End Of File : sudo gedit ~/.bashrc

#Java Home directory configuration
export JAVA_HOME="/usr/lib/jvm/java-9-oracle"
export PATH="$PATH:$JAVA_HOME/bin"

# Hadoop home directory configuration
export HADOOP_HOME=/usr/local/hadoop

export HIVE_HOME=/usr/lib/hive
export PATH=$PATH:$HIVE_HOME/bin

2. hive-site.xml

You have to create this file(hive-site.xml) in conf directory of Hive and add the below details

<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<?xml-stylesheet type="text/xsl" href="configuration.xsl"?>









3. You also need to put the jar file(mysql-connector-java-5.1.28.jar) in the lib directory of Hive

4. Below installations required on your Ubuntu to Start the Hive Shell:

  1. MySql
  2. Hadoop
  3. Hive
  4. Java

5. Execution Part:

  1. Start all services of Hadoop:

  2. Enter the jps command to check whether all Hadoop services are up and running: jps

  3. Enter the hive command to enter into hive shell: hive

How to use code to open a modal in Angular 2?

@ng-bootstrap/ng-bootstrap npm I m using for this as in the project bootstrap is used, for material, we used dialog


  <span (click)="openModal(modalRef)" class="form-control input-underline pl-3 ">Open Abc Modal

Modal template

<ng-template class="custom-modal"  #modalRef let-c="close" let-d="dismiss">
   <div class="modal-header custom-modal-head"><h4 class="modal-title">List of Countries</h4>
     <button type="button" class="close" aria-label="Close" (click)="d('Cross click')">
         <img src="assets/actor/images/close.png" alt="">
  <div class="modal-body country-select">
       <div class="serch-field">
           <div class="row">
               <div class="col-md-12">
                 <input type="text"  class="form-control input-underline pl-3" placeholder="Search Country"
                    [(ngModel)]="countryWorkQuery" [ngModelOptions]="{standalone: true}">
                 <ul *ngIf="countries" class="ng-star-inserted">
                   <li (click)="setSelectedCountry(cntry, 'work');d('Cross click');" class="cursor-pointer"
                   *ngFor="let cntry of countries | filterNames:countryWorkQuery ">{{}}</li>
                 <span *ngIf="!modalSpinner && (!countries || countries.length<=0)">No country found</span>
                 <span *ngIf="modalSpinner" class="loader">
                     <img src="assets/images/loader.gif" alt="loader">

Ts File

import {NgbModal, ModalDismissReasons} from '@ng-bootstrap/ng-bootstrap';

    private modalService: NgbModal
  ) { }

  openModal(modalContent){, { centered: true});

Laravel 5.2 Missing required parameters for [Route: user.profile] [URI: user/{nickname}/profile]

You have to pass the route parameters to the route method, for example:

<li><a href="{{ route('user.profile', $nickname) }}">Profile</a></li>
<li><a href="{{ route('user.settings', $nickname) }}">Settings</a></li>

It's because, both routes have a {nickname} in the route declaration. I've used $nickname for example but make sure you change the $nickname to appropriate value/variable, for example, it could be something like the following:

<li><a href="{{ route('user.settings', auth()->user()->nickname) }}">Settings</a></li>

How to get current route in react-router 2.0.0-rc5

You can get the current route using

const currentRoute = this.props.routes[this.props.routes.length - 1];

...which gives you access to the props from the lowest-level active <Route ...> component.


<Route path="childpath" component={ChildComponent} />

currentRoute.path returns 'childpath' and currentRoute.component returns function _class() { ... }.

Forward X11 failed: Network error: Connection refused

fill in the "X display location" did not work for me. but install MobaXterm did the job.

configuring project ':app' failed to find Build Tools revision

I found out that it also happens if you uninstalled some packages from your react-native project and there is still packages in your build gradle dependencies in the bottom of page like:


JavaFX FXML controller - constructor vs initialize method

In Addition to the above answers, there probably should be noted that there is a legacy way to implement the initialization. There is an interface called Initializable from the fxml library.

import javafx.fxml.Initializable;

class MyController implements Initializable {
    @FXML private TableView<MyModel> tableView;

    public void initialize(URL location, ResourceBundle resources) {


location - The location used to resolve relative paths for the root object, or null if the location is not known.
resources - The resources used to localize the root object, or null if the root object was not localized. 

And the note of the docs why the simple way of using @FXML public void initialize() works:

NOTE This interface has been superseded by automatic injection of location and resources properties into the controller. FXMLLoader will now automatically call any suitably annotated no-arg initialize() method defined by the controller. It is recommended that the injection approach be used whenever possible.

HTML 5 Video "autoplay" not automatically starting in CHROME

Try this when i tried giving muted , check this demo in codpen

    <video width="320" height="240" controls autoplay muted id="videoId">
  <source src="" type="video/mp4">
  Your browser does not support the video tag.


function toggleMute() {

  var video=document.getElementById("videoId");

    video.muted = false;
  } else {
    video.muted = true;



edited attribute content

autoplay muted playsinline

Can't push image to Amazon ECR - fails with "no basic auth credentials"

In my case this was a bug with Docker for Windows and their support for the Windows Credential Manager.

Open your ~/.docker/config.json and remove the "credsStore": "wincred" entry.

This will cause credentials to be written to the config.json directly. You'll have to log in again afterwards.

You can track this bug through the tickets #22910 and #24968 on GitHub.

*ngIf and *ngFor on same element causing error

You can also use ng-template (instead of template. See the note for the caveat of using template tag) for applying both *ngFor and ngIf on the same HTML element. Here is an example where you can use both *ngIf and *ngFor for the same tr element in the angular table.

<tr *ngFor = "let fruit of fruiArray">
    <ng-template [ngIf] = "fruit=='apple'>
        <td> I love apples!</td>

where fruiArray = ['apple', 'banana', 'mango', 'pineapple'].


The caveat of using just the template tag instead of ng-template tag is that it throws StaticInjectionError in some places.

Can't run Curl command inside my Docker Container

Ran into this same issue while using the CURL command inside my Dockerfile. As Gilles pointed out, we have to install curl first. These are the commands to be added in the 'Dockerfile'.

FROM ubuntu:16.04

# Install prerequisites
RUN apt-get update && apt-get install -y \
CMD /bin/bash

How to fix the error; 'Error: Bootstrap tooltips require Tether ('

An additional note. If you check uncompressed javascript file, you will find the condition:

if(window.Tether === undefined) {
     throw new Error('Bootstrap tooltips require Tether (')

So the error message contains the required information.

You can download the archive from that link.

Uncompressed version:

Angular 2 router no base href set

With angular 4 you can fix this issue by updating app.module.ts file as follows:

Add import statement at the top as below:

import {APP_BASE_HREF} from '@angular/common';

And add below line inside @NgModule

providers: [{provide: APP_BASE_HREF, useValue: '/my/app'}]


Jquery to open Bootstrap v3 modal of remote url

A different perspective to the same problem away from Javascript and using php:

<a data-toggle="modal" href="#myModal">LINK</a>

<div class="modal fade" tabindex="-1" aria-labelledby="gridSystemModalLabel" id="myModal" role="dialog" style="max-width: 90%;">
    <div class="modal-dialog" style="text-align: left;">
        <div class="modal-content">
            <div class="modal-header">
                <button type="button" class="close" data-dismiss="modal">&times;</button>
                <h4 class="modal-title">Title</h4>
            <div class="modal-body">
                <?php include( 'remotefile.php'); ?>
            <div class="modal-footer">
                <button type="button" class="btn btn-default" data-dismiss="modal">Close</button>

and put in the remote.php file your basic html source.

Angular - Set headers for every request

In Angular 2.1.2 I approached this by extending the angular Http:

import {Injectable} from "@angular/core";
import {Http, Headers, RequestOptionsArgs, Request, Response, ConnectionBackend, RequestOptions} from "@angular/http";
import {Observable} from 'rxjs/Observable';

export class HttpClient extends Http {

  constructor(protected _backend: ConnectionBackend, protected _defaultOptions: RequestOptions) {

    super(_backend, _defaultOptions);

  _setCustomHeaders(options?: RequestOptionsArgs):RequestOptionsArgs{
    if(!options) {
      options = new RequestOptions({});
    if(localStorage.getItem("id_token")) {

      if (!options.headers) {

        options.headers = new Headers();

      options.headers.set("Authorization", localStorage.getItem("id_token"))
    return options;

  request(url: string|Request, options?: RequestOptionsArgs): Observable<Response> {
    options = this._setCustomHeaders(options);
    return super.request(url, options)

then in my App Providers I was able to use a custom Factory to provide 'Http'

import { RequestOptions, Http, XHRBackend} from '@angular/http';
import {HttpClient} from './httpClient';
import { RequestOptions, Http, XHRBackend} from '@angular/http';
import {HttpClient} from './httpClient';//above snippet

function httpClientFactory(xhrBackend: XHRBackend, requestOptions: RequestOptions): Http {
  return new HttpClient(xhrBackend, requestOptions);

  declarations: APP_DECLARATIONS,
     { provide: Http, useFactory: httpClientFactory, deps: [XHRBackend, RequestOptions]}
export class AppModule {


now I don't need to declare every Http method and can use http as normal throughout my application.

Angular2 QuickStart npm start is not working correctly

In order to get npm start running for me, I had to make sure I had globally installed some of the devDependencies. Have you tried:

  • npm install -g concurrently
  • npm install -g lite-server
  • npm install -g typescript

React: "this" is undefined inside a component function

If you call your created method in the lifecycle methods like componentDidMount... then you can only use the this.onToggleLoop = this.onToogleLoop.bind(this) and the fat arrow function onToggleLoop = (event) => {...}.

The normal approach of the declaration of a function in the constructor wont work because the lifecycle methods are called earlier.

Vue.js toggle class on click

Without the need of a method:

// html element, will display'active' class if showMobile is true
//clicking on the elment will toggle showMobileMenu to true and false alternatively
<div id="mobile-toggle"
 :class="{ active: showMobileMenu }"
 @click="showMobileMenu = !showMobileMenu">

//in your vue.js app
data: {
    showMobileMenu: false

How to use Bootstrap modal using the anchor tag for Register?

Here is a link to W3Schools that answers your question

Note: For anchor tag elements, omit data-target, and use href="#modalID" instead:

I hope that helps

Angular 2 - How to navigate to another route using this.router.parent.navigate('/about')?

You should use


As well as specifying the route path, you can also specify your route's name:

{ path:'/About', name: 'About',   ... }


In android how to set navigation drawer header image and name programmatically in class file?

I know this is an old post but i am sure that this might help someone down the road.

You can simply get the headerView element of the Navigation view by doing this:

 NavigationView mView = ( NavigationView ) findViewById( );

 if( mView != null ){
     LinearLayout mParent = ( LinearLayout ) mView.getHeaderView( 0 );

     if( mParent != null ){
        // Set your values to the image and text view by declaring and setting as you need to here. 

I hope that this helps someone.

How to detect a route change in Angular?

Angular 4.x and above :

This can be achieved using url property of ActivatedRoute class as below,

this.activatedRoute.url.subscribe(url =>{

Note: That you need to import and inject the provider from angular/router package

import { ActivatedRoute } from '@angular/router`


constructor(private activatedRoute : ActivatedRoute){  }

How to change the MySQL root account password on CentOS7?


Here a little bit twist with mysql-community-server 5.7 I share some steps, how to reset mysql5.7 root password or set password. it will work centos7 and RHEL7 as well.

step1. 1st stop your databases

service mysqld stop

step2. 2nd modify /etc/my.cnf file add "skip-grant-tables"

vi /etc/my.cnf

[mysqld] skip-grant-tables

step3. 3rd start mysql

service mysqld start

step4. select mysql default database

mysql -u root

mysql>use mysql;

step4. set a new password

mysql> update user set authentication_string=PASSWORD("yourpassword") where User='root';

step5 restart mysql database

service mysqld restart

 mysql -u root -p

enjoy :)

`node-pre-gyp install --fallback-to-build` failed during MeanJS installation on OSX

Alright so after some debugging the following dependencies are using an older version of touch:

./node_modules/bower/node_modules/decompress-zip/package.json:    "touch": "0.0.3"
./node_modules/bower/node_modules/lockfile/package.json:    "touch": "0"
./node_modules/gulp-nodemon/node_modules/nodemon/package.json:    "touch": "1.0.0",
./node_modules/gulp-nodemon/node_modules/touch/package.json:    "touch": "./bin/touch.js"
./node_modules/nodemon/package.json:    "touch": "~0.0.3",

With that I was able to get meanJS working with node 5.

Here is the history on the commands I ran:

git clone
cd mean
nvm install 5
nvm use 5
npm install
which node-gyp
npm install -g node-pre-gyp
sudo xcodebuild -license
npm install

Had some issues and then:

I added the following line:

#!/usr/bin/env node

To the top of the file ./mean/node_modules/.bin/touch

And then:

npm install

And of course maybe throw in a sudo rm -rf ./node_modules && npm cache clean before retrying.

Boto3 Error: botocore.exceptions.NoCredentialsError: Unable to locate credentials

I had the same issue and found out that the format of my ~/.aws/credentials file was wrong.

It worked with a file containing:


Note that the profile name must be "[default]". Some official documentation make reference to a profile named "[credentials]", which did not work for me.

What is the difference between putting a property on application.yml or bootstrap.yml in spring boot?

This answer has been very beautifully explained in book "Microservices Interview Questions, For Java Developers (Spring Boot, Spring Cloud, Cloud Native Applications) by Munish Chandel, Version 1.30, 25.03.2018.

The following content has been taken from this book, and total credit for this answer goes to the Author of the book i.e. Munish Chandel


application.yml/ file is specific to Spring Boot applications. Unless you change the location of external properties of an application, spring boot will always load application.yml from the following location:


You can store all the external properties for your application in this file. Common properties that are available in any Spring Boot project can be found at: You can customize these properties as per your application needs. Sample file is shown below:

        name: foobar
        driverClassName: com.mysql.jdbc.Driver
        url: jdbc:mysql://localhost/test
    port: 9000


bootstrap.yml on the other hand is specific to spring-cloud-config and is loaded before the application.yml

bootstrap.yml is only needed if you are using Spring Cloud and your microservice configuration is stored on a remote Spring Cloud Config Server.

Important points about bootstrap.yml

  1. When used with Spring Cloud Config server, you shall specify the application-name and config git location using below properties. "application-name" "git-uri-config"

  1. When used with microservices (other than cloud config server), we need to specify the application name and location of config server using below properties 
  1. This properties file can contain other configuration relevant to Spring Cloud environment for e.g. eureka server location, encryption/decryption related properties.

Upon startup, Spring Cloud makes an HTTP(S) call to the Spring Cloud Config Server with the name of the application and retrieves back that application’s configuration.

application.yml contains the default configuration for the microservice and any configuration retrieved (from cloud config server) during the bootstrap process will override configuration defined in application.yml

How do I "shake" an Android device within the Android emulator to bring up the dev menu to debug my React Native app

It might be not direct solution, but I've created a lib that allows you to use 3 fingers touch instead of shake to open dev menu, when in development mode

You only have to wrap your app inside:

import DevMenuOnTouch from 'react-native-dev-menu-on-touch'; // or: import { DevMenuOnTouch } from 'react-native-dev-menu-on-touch'

class YourRootApp extends Component {
  render() {
    return (
        <YourApp />

It's really useful when you have to debug on real device and you have co-workers sitting next to you.

The resource could not be loaded because the App Transport Security policy requires the use of a secure connection

For iOS 10.x and Swift 3.x [below versions are also supported] just add the following lines in 'info.plist'


Logging with Retrofit 2

hey guys,i already find solution:

  public static <T> T createApi(Context context, Class<T> clazz, String host, boolean debug) {
    if (singleton == null) {
        synchronized (RetrofitUtils.class) {
            if (singleton == null) {
                RestAdapter.Builder builder = new RestAdapter.Builder();
                        .setClient(new OkClient(OkHttpUtils.getInstance(context)))
                        .setConverter(new GsonConverter(GsonUtils.newInstance()))
                        .setErrorHandler(new ErrorHandlers())
                        .setLogLevel(debug ? RestAdapter.LogLevel.FULL : RestAdapter.LogLevel.NONE)/*LogLevel.BASIC will cause response.getBody().in() close*/
                        .setLog(new RestAdapter.Log() {
                            public void log(String message) {
                                if (message.startsWith("{") || message.startsWith("["))
                                else {
                singleton =;
    return singleton.create(clazz);

CORS with spring-boot and angularjs not working

This works for me:

public class MyConfig extends WebSecurityConfigurerAdapter  {
   protected void configure(HttpSecurity http) throws Exception {


       http.cors().configurationSource(new CorsConfigurationSource() {

        public CorsConfiguration getCorsConfiguration(HttpServletRequest request) {
            CorsConfiguration config = new CorsConfiguration();
            return config;





How to solve ERR_CONNECTION_REFUSED when trying to connect to localhost running IISExpress - Error 502 (Cannot debug from Visual Studio)?

While probably not related to your problem, I had the same issue today. As it turns out, I had enabled an URL Rewrite module to force my site to use HTTPS instead of HTTP and on my production environment, this worked just fine. But on my development system, where it runs as an application within my default site, it failed...
As it turns out, my default site had no binding for HTTPS so the rewrite module would send me from HTTP to HTTPS, yet nothing was listening to the HTTPS port...
There's a chance that you have this issue for a similar reason. This error seems to occur if there's no proper binding for the site you're trying to access...

Deploying Maven project throws invalid LOC header (bad signature)

I was facing this issue while deploying my ear to my local weblogic instance. Clearing the local repository and building the ear again resolved the issue for me.

ASP.NET Web API : Correct way to return a 401/unauthorised response

Just return the following:

return Unauthorized();

Android Studio - Device is connected but 'offline'

I had this issue on a device with USB-C using a microUSB cable with a USB-C adapter. After switching to a USB-C cable without any adapter it worked. I only saw this issue on a LeEco.

Maven- No plugin found for prefix 'spring-boot' in the current project and in the plugin groups

In my case, my maven variable environment was M2_HOME, so I've changed to MAVEN_HOME and worked.

Where is the kibana error log? Is there a kibana error log?

Kibana 4 logs to stdout by default. Here is an excerpt of the config/kibana.yml defaults:

# Enables you specify a file where Kibana stores log output.
# logging.dest: stdout

So when invoking it with service, use the log capture method of that service. For example, on a Linux distribution using Systemd / systemctl (e.g. RHEL 7+):

journalctl -u kibana.service

One way may be to modify init scripts to use the --log-file option (if it still exists), but I think the proper solution is to properly configure your instance YAML file. For example, add this to your config/kibana.yml:

logging.dest: /var/log/kibana.log

Note that the Kibana process must be able to write to the file you specify, or the process will die without information (it can be quite confusing).

As for the --log-file option, I think this is reserved for CLI operations, rather than automation.

How do I enable logging for Spring Security?

Spring security logging for webflux reactive apps is now available starting with version 5.4.0-M2 (as mentionned by @bzhu in comment How do I enable logging for Spring Security?)

Until this gets into a GA release, here is how to get this milestone release in gradle

repositories {
    if (!version.endsWith('RELEASE')) {
        maven { url "" }

// Force earlier milestone release to get securing logging preview
dependencyManagement {
    imports {
        mavenBom "${springCloudVersion}"


How to customize the configuration file of the official PostgreSQL Docker image?

I looked through all answers and there is another option left. You can change your CMD value in docker file (it is not the best one, but still possible way to achieve your goal).

Basically we need to

  • Copy config file in docker container
  • Override postgres start options

Docker file example:

FROM postgres:9.6
USER postgres

# Copy postgres config file into container
COPY postgresql.conf /etc/postgresql

# Override default postgres config file
CMD ["postgres", "-c", "config_file=/etc/postgresql/postgresql.conf"]

Though I think using command: postgres -c config_file=/etc/postgresql/postgresql.confin your docker-compose.yml file proposed by Matthias Braun is the best option.

What does the ELIFECYCLE Node.js error mean?

This issue can also occur when you pull code from git and not yet installed node modules "npm install".

How to get the current logged in user Id in ASP.NET Core

Although Adrien's answer is correct, you can do this all in single line. No need for extra function or mess.

It works I checked it in ASP.NET Core 1.0

var user = await _userManager.GetUserAsync(HttpContext.User);

then you can get other properties of the variable like user.Email. I hope this helps someone.

How does the data-toggle attribute work? (What's its API?)

The data-* attributes is used to store custom data private to the page or application

So Bootstrap uses these attributes for saving states of objects

W3School data-* description

Oracle SQL - DATE greater than statement

You need to convert the string to date using the to_date() function

SELECT * FROM OrderArchive
WHERE OrderDate <= to_date('31-Dec-2014','DD-MON-YYYY');


SELECT * FROM OrderArchive
WHERE OrderDate <= to_date('31 Dec 2014','DD MON YYYY');


SELECT * FROM OrderArchive
WHERE OrderDate <= to_date('2014-12-31','yyyy-MM-dd');

This will work only if OrderDate is stored in Date format. If it is Varchar you should apply to_date() func on that column also like

 SELECT * FROM OrderArchive
    WHERE to_date(OrderDate,'yyyy-Mm-dd') <= to_date('2014-12-31','yyyy-MM-dd');

React Js conditionally applying class attributes


React is lake a lot of utilities. But you don't need any npm package for that . just create somewhere the function classnames and call it when you need;

function classnames(obj){
  return Object.entries(obj).filter( e => e[1] ).map( e=>e[0] ).join(' ');


function classnames(obj){
 return Object.entries(obj).map( ([k,v]) => v?k:'' ).join(' ');


  stateClass= {
  classnames(stateClass) // return 'foo pony'

 <div className="foo bar {classnames(stateClass)}"> some content </div>

Just For Inspiration

declare helper element and used it toggle method



const classes = document.createElement('span').classList; 

function classstate(obj){
  for( let n in obj) classes.toggle(n,obj[n]);
 return classes; 

How to access a value defined in the file in Spring Boot

Another way is injecting org.springframework.core.env.Environment to your bean.

private Environment env;

public void method() {
    String path = env.getProperty("userBucket.path");

Plugin org.apache.maven.plugins:maven-clean-plugin:2.5 or one of its dependencies could not be resolved

This is what worked for me in IntelliJIdea:

Go to File -> Build, Execution, Deployment -> Build Tools -> Maven -> Repositories

Check that there are two repositories:  (Remote)
C:/Users/_user_/.m2/repository   (Local)

And then click on Update for both repos. The update of remote repository will take a while, but in the end click on OK and that's all.

Using both Python 2.x and Python 3.x in IPython Notebook

  • If you are running anaconda in virtual environment.
  • And when you create a new notebook but i's not showing to select the virtual environment kernel.
  • Then you have to set it into the ipykernel using the following command
$ pip install --user ipykernel
$ python -m ipykernel install --user --name=test2

No tests found for given includes Error, when running Parameterized Unit test in Android Studio

If you are using intellij and want to use gradle you need to add this to the dependencies section of build.gradle file:


How to disable spring security for particular url

If you want to ignore multiple API endpoints you can use as follow:

    protected void configure(HttpSecurity httpSecurity) throws Exception {

How to log SQL statements in Spring Boot?

If you want to view the actual parameters used to query you can use

Then notice that actual parameter value is shown as binding parameter......

   2018-08-07 14:14:36.079 DEBUG 44804 --- [           main] org.hibernate.SQL                        : select as id1_0_, employee0_.department as departme2_0_, employee0_.joining_date as joining_3_0_, as name4_0_ from employee employee0_ where employee0_.joining_date=?
    2018-08-07 14:14:36.079 TRACE 44804 --- [           main] o.h.type.descriptor.sql.BasicBinder      : binding parameter [1] as [TIMESTAMP] - [Tue Aug 07 00:00:00 SGT 2018]

How to do logging in React Native?

There is normally two scenarios where we need debugging.

  1. When we facing issues related to data and we want to check our data and debugging related to data in that case console.log('data::',data)

    and debug js remotely is the best option.

  2. Other case is the UI and styles related issues where we need to check styling of the component in that case react-dev-tools is the best option.

    both of the methods mention here.

How to add jQuery code into HTML Page

1) Best practice is to make new javascript file like my.js. Make this file into your js folder in root directory -> js/my.js . 2) In my.js file add your code inside of $(document).ready(function(){}) scope.

    $(".icon-bg").click(function () {

    $(".button").click(function () {

    $(".iconmelon").click(function () {

    $(".private").click(function () {

3) add your new js file into your html

<script src=""></script>
<script src="/js/my.js"></script>

Manage toolbar's navigation and back button from fragment in android

You have to manage your back button pressed action on your main Activity because your main Activity is container for your fragment.

First, add your all fragment to transaction.addToBackStack(null) and now navigation back button call will be going on main activity. I hope following code will help you...

    public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()) {
    return super.onOptionsItemSelected(item);

you can also use

Fragment fragment =fragmentManager.findFragmentByTag(Constant.TAG); 
if(fragment!=null) {          
      FragmentTransaction transaction = fragmentManager.beginTransaction();

And to change the title according to fragment name from fragment you can use the following code:

activity.getSupportActionBar().setTitle("Keyword Report Detail");

unable to dequeue a cell with identifier Cell - must register a nib or a class for the identifier or connect a prototype cell in a storyboard

Match the identifier name at both places

This error occurs when the identifier name of the Tablecell is different in the Swift file and in the Storyboard.

For example, the identifier is placecellIdentifier in my case.

1) The Swift File

override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {

    let cell = tableView.dequeueReusableCell(withIdentifier: "placecellIdentifier", for: indexPath)
    // Your code 

    return cell

###2) The Storyboard enter image description here

command/usr/bin/codesign failed with exit code 1- code sign error

I had the same error on January 2018 with xcode 8.2.1

Before I try to open xcode I couldn't because the system was updating. I tried sometime later and it let me working on it, and then I got the same error.

I followed most of the solutions described in this article but they didn't work for me.

Then I remembered the message about the system updating and I tried to reboot the machine.

And that did the magic. It worked for me.

How to execute logic on Optional if not present?

You will have to split this into multiple statements. Here is one way to do that:

if (!obj.isPresent()) {
  logger.fatal("Object not available");

obj.ifPresent(o -> o.setAvailable(true));
return obj;

Another way (possibly over-engineered) is to use map:

if (!obj.isPresent()) {
  logger.fatal("Object not available");

return -> {o.setAvailable(true); return o;});

If obj.setAvailable conveniently returns obj, then you can simply the second example to:

if (!obj.isPresent()) {
  logger.fatal("Object not available");

return -> o.setAvailable(true));

jQuery DataTables Getting selected row values

You can iterate over the row data

$('#button').click(function () {
    var ids = $.map(table.rows('.selected').data(), function (item) {
        return item[0]
    alert(table.rows('.selected').data().length + ' row(s) selected');

Demo: Fiddle

recyclerview No adapter attached; skipping layout

For those who use the RecyclerView within a fragment and inflate it from other views: when inflating the whole fragment view, make sure that you bind the RecyclerView to its root view.

I was connecting and doing everything for the adapter correctly, but I never did the binding. This answer by @Prateek Agarwal has it all for me, but here is more elaboration.


    override fun onCreateView(inflater: LayoutInflater?, container: ViewGroup?, savedInstanceState: Bundle?): View? {

    val rootView =  inflater?.inflate(R.layout.fragment_layout, container, false)
    recyclerView = rootView?.findViewById(
    // rest of my stuff
    recyclerView?.layoutManager = viewManager
    recyclerView?.adapter = viewAdapter
    // return the root view
    return rootView


public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {

    View rootView= inflater.inflate(R.layout.fragment_layout,container,false);
    recyclerview= rootView.findViewById(;
    return rootView;

Error:Execution failed for task ':ProjectName:mergeDebugResources'. > Crunching Cruncher *some file* failed, see logs

I was also stuck by this problem.But in my case I delete all .png images from drawable folder ,clean and rebuild application and then paste all .png images to my drawable, rebuild again. It worked fine for me.

Asp.Net WebApi2 Enable CORS not working with AspNet.WebApi.Cors 5.2.3

I've created a pared-down demo project for you.

You can try the above API Link from your local Fiddler to see the headers. Here is an explanation.


All this does is call the WebApiConfig. It's nothing but code organization.

public class WebApiApplication : System.Web.HttpApplication
    protected void Application_Start()


The key method for your here is the EnableCrossSiteRequests method. This is all that you need to do. The EnableCorsAttribute is a globally scoped CORS attribute.

public static class WebApiConfig
    public static void Register(HttpConfiguration config)

    private static void AddRoutes(HttpConfiguration config)
            name: "Default",
            routeTemplate: "api/{controller}/"

    private static void EnableCrossSiteRequests(HttpConfiguration config)
        var cors = new EnableCorsAttribute(
            origins: "*", 
            headers: "*", 
            methods: "*");

Values Controller

The Get method receives the EnableCors attribute that we applied globally. The Another method overrides the global EnableCors.

public class ValuesController : ApiController
    // GET api/values
    public IEnumerable<string> Get()
        return new string[] { 
            "This is a CORS response.", 
            "It works from any origin." 

    // GET api/values/another
    [EnableCors(origins:"", headers:"*", methods: "*")]
    public IEnumerable<string> Another()
        return new string[] { 
            "This is a CORS response. ", 
            "It works only from two origins: ",
            "1. ",
            "2. the same origin." 


You do not need to add anything special into web.config. In fact, this is what the demo's web.config looks like - it's empty.

<?xml version="1.0" encoding="utf-8"?>


var url = ""_x000D_
$.get(url, function(data) {_x000D_
  console.log("We expect this to succeed.");_x000D_
var url = ""_x000D_
$.get(url, function(data) {_x000D_
}).fail(function(xhr, status, text) {_x000D_
  console.log("We expect this to fail.");_x000D_
<script src=""></script>

Is it possible to ignore one single specific line with Pylint?

Pylint message control is documented in the Pylint manual:

Is it possible to locally disable a particular message?

Yes, this feature has been added in Pylint 0.11. This may be done by adding # pylint: disable=some-message,another-one at the desired block level or at the end of the desired line of code.

You can use the message code or the symbolic names.

For example,

def test():
    # Disable all the no-member violations in this function
    # pylint: disable=no-member
global VAR # pylint: disable=global-statement

The manual also has further examples.

There is a wiki that documents all Pylint messages and their codes.

Spring boot - Not a managed type

I think replacing @ComponentScan with @ComponentScan("com.nervy.dialer.domain") will work.

Edit :

I have added a sample application to demonstrate how to set up a pooled datasource connection with BoneCP.

The application has the same structure with yours. I hope this will help you to resolve your configuration problems

Hadoop cluster setup - Connection refused

Hi Edit your conf/core-site.xml and change localhost to Use the conf below. That should work.


How to change Toolbar home icon color

This answer maybe too late, but here is how I do it. Styling the toolbar will do the trick. Create toolbar.xml with following code.

<?xml version="1.0" encoding="utf-8"?>
local:popupTheme="@style/ThemeOverlay.AppCompat.Light" />

and in the styles.xml

<style name="AppBaseTheme" parent="Theme.AppCompat.Light.NoActionBar">

<!-- Application theme. -->
<style name="AppTheme" parent="AppBaseTheme">
    <item name="windowNoTitle">true</item>
    <item name="windowActionBar">false</item>
    <item name="colorPrimary">@color/colorPrimary</item>
    <item name="colorPrimaryDark">@color/colorPrimaryDark</item>

Finally, include the toolbar inside layout

        layout="@layout/toolbar" />

Fatal error: Call to a member function prepare() on null

It looks like your $pdo variable is not initialized. I can't see in the code you've uploaded where you are initializing it.

Make sure you create a new PDO object in the global scope before calling the class methods. (You should declare it in the global scope because of how you implemented the methods inside the Category class).

$pdo = new PDO('mysql:host=localhost;dbname=test', $user, $pass);

No log4j2 configuration file found. Using default configuration: logging only errors to the console

Tested with: log4j-ap 2.13.2, log4j-core 2.13.2.

  1. Keep XML file directly under below folder structure. src/main/java
  2. In the POM:
  1. Clean and build.

Why do we use volatile keyword?

Consider this code,

int some_int = 100;

while(some_int == 100)
   //your code

When this program gets compiled, the compiler may optimize this code, if it finds that the program never ever makes any attempt to change the value of some_int, so it may be tempted to optimize the while loop by changing it from while(some_int == 100) to something which is equivalent to while(true) so that the execution could be fast (since the condition in while loop appears to be true always). (if the compiler doesn't optimize it, then it has to fetch the value of some_int and compare it with 100, in each iteration which obviously is a little bit slow.)

However, sometimes, optimization (of some parts of your program) may be undesirable, because it may be that someone else is changing the value of some_int from outside the program which compiler is not aware of, since it can't see it; but it's how you've designed it. In that case, compiler's optimization would not produce the desired result!

So, to ensure the desired result, you need to somehow stop the compiler from optimizing the while loop. That is where the volatile keyword plays its role. All you need to do is this,

volatile int some_int = 100; //note the 'volatile' qualifier now!

In other words, I would explain this as follows:

volatile tells the compiler that,

"Hey compiler, I'm volatile and, you know, I can be changed by some XYZ that you're not even aware of. That XYZ could be anything. Maybe some alien outside this planet called program. Maybe some lightning, some form of interrupt, volcanoes, etc can mutate me. Maybe. You never know who is going to change me! So O you ignorant, stop playing an all-knowing god, and don't dare touch the code where I'm present. Okay?"

Well, that is how volatile prevents the compiler from optimizing code. Now search the web to see some sample examples.

Quoting from the C++ Standard ($

[..] volatile is a hint to the implementation to avoid aggressive optimization involving the object because the value of the object might be changed by means undetectable by an implementation.[...]

Related topic:

Does making a struct volatile make all its members volatile?

Using the passwd command from within a shell script

Sometimes it is useful to set a password which nobody knows. This seems to work:

tr -dc A-Za-z0-9 < /dev/urandom | head -c44 | passwd --stdin $user

How to chain scope queries with OR instead of AND?

This would be a good candidate for MetaWhere if you're using Rails 3.0+, but it doesn't work on Rails 3.1. You might want to try out squeel instead. It's made by the same author. Here's how'd you'd perform an OR based chain:

Person.where{(name == "John") | (lastname == "Smith")}

You can mix and match AND/OR, among many other awesome things.

Python: call a function from string name

You can use a dictionary too.

def install():
    print "In install"

methods = {'install': install}

method_name = 'install' # set by the command line options
if method_name in methods:
    methods[method_name]() # + argument list of course
    raise Exception("Method %s not implemented" % method_name)

Mongoose's find method with $or condition does not work properly

I implore everyone to use Mongoose's query builder language and promises instead of callbacks:

User.find().or([{ name: param }, { nickname: param }])
    .then(users => { /*logic here*/ })
    .catch(error => { /*error logic here*/ })

Read more about Mongoose Queries.

Including external HTML file to another HTML file

You can use jquery load for that.

<script type="text/javascript">
$(document).ready(function(e) {

Don't forget to include jquery library befor above code.

ORA-28000: the account is locked error getting frequently

I have faced this similar issue and resolved it by using following steps :

  1. Open windows command prompt.
  2. Login using the command sqlplus "/ as sysdba"
  3. Then executed the command alter user HR identified by password account unlock

    Please note, the password is the password that I have used.

    By using above steps you can connect to Oracle Database as user HR with the password password.

Removing trailing newline character from fgets() input

The steps to remove the newline character in the perhaps most obvious way:

  1. Determine the length of the string inside NAME by using strlen(), header string.h. Note that strlen() does not count the terminating \0.
size_t sl = strlen(NAME);

  1. Look if the string begins with or only includes one \0 character (empty string). In this case sl would be 0 since strlen() as I said above doesn´t count the \0 and stops at the first occurrence of it:
if(sl == 0)
   // Skip the newline replacement process.

  1. Check if the last character of the proper string is a newline character '\n'. If this is the case, replace \n with a \0. Note that index counts start at 0 so we will need to do NAME[sl - 1]:
if(NAME[sl - 1] == '\n')
   NAME[sl - 1] = '\0';

Note if you only pressed Enter at the fgets() string request (the string content was only consisted of a newline character) the string in NAME will be an empty string thereafter.

  1. We can combine step 2. and 3. together in just one if-statement by using the logic operator &&:
if(sl > 0 && NAME[sl - 1] == '\n')
   NAME[sl - 1] = '\0';

  1. The finished code:
size_t sl = strlen(NAME);
if(sl > 0 && NAME[sl - 1] == '\n')
   NAME[sl - 1] = '\0';

If you rather like a function for use this technique by handling fgets output strings in general without retyping each and every time, here is fgets_newline_kill:

void fgets_newline_kill(char a[])
    size_t sl = strlen(a);

    if(sl > 0 && a[sl - 1] == '\n')
       a[sl - 1] = '\0';

In your provided example, it would be:

printf("Enter your Name: ");

if (fgets(Name, sizeof Name, stdin) == NULL) {
    fprintf(stderr, "Error reading Name.\n");
else {

Note that this method does not work if the input string has embedded \0s in it. If that would be the case strlen() would only return the amount of characters until the first \0. But this isn´t quite a common approach, since the most string-reading functions usually stop at the first \0 and take the string until that null character.

Aside from the question on its own. Try to avoid double negations that make your code unclearer: if (!(fgets(Name, sizeof Name, stdin) != NULL) {}. You can simply do if (fgets(Name, sizeof Name, stdin) == NULL) {}.

How to get a thread and heap dump of a Java process on Windows that's not running in a console

Maybe jcmd?

Jcmd utility is used to send diagnostic command requests to the JVM, where these requests are useful for controlling Java Flight Recordings, troubleshoot, and diagnose JVM and Java Applications.

The jcmd tool was introduced with Oracle's Java 7 and is particularly useful in troubleshooting issues with JVM applications by using it to identify Java processes' IDs (akin to jps), acquiring heap dumps (akin to jmap), acquiring thread dumps (akin to jstack), viewing virtual machine characteristics such as system properties and command-line flags (akin to jinfo), and acquiring garbage collection statistics (akin to jstat). The jcmd tool has been called "a swiss-army knife for investigating and resolving issues with your JVM application" and a "hidden gem."

Here’s the process you’ll need to use in invoking the jcmd:

  1. Go to jcmd <pid> GC.heap_dump <file-path>
  2. In which
  3. pid: is a Java Process Id, for which the heap dump will be captured Also, the
  4. file-path: is a file path in which the heap dump is be printed.

Check it out for more information about taking Java heap dump.

Focus Next Element In Tab Index

A word of advice: Don’t try to control where the focus lands during a tab event. Instead try to control which element are and aren’t tabbable by setting the tabIndex of the elements you don’t want to receive focus to -1. E.g.

// `tabContainer` is a container where we want only
// element at a time to be tabbable, e.g. a radio menu.

tabContainer.addEventListener("focusin", () => {
  const desired = findDesiredFocusElement();

  if (!desired) {
    // Just leave the focus be. We have no preference
    // at the moment.

  // Move the focus to the correct element.

  // Remove all undesired elements from the tab order.
  for (const undesired of findUndesiredFocusElements()) {
    // Make it untabbable.
    undesired.tabIndex = -1;

tabContainer.addEventListener("focusout", (event) => {
  for (const element of findRelevantFocusElements()) {
    // Give each element back their focus capability.
    element.tabIndex = 0;

Note: This might not be what is best in your situation, e.g. in your case it might be better to control the tab index in some change events or not to reset the tabIndex state on focusout etc.

More info here.

Do standard windows .ini files allow comments?

I have seen comments in INI files, so yes. Please refer to this Wikipedia article. I could not find an official specification, but that is the correct syntax for comments, as many game INI files had this as I remember.


The API returns the Value and the Comment (forgot to mention this in my reply), just construct and example INI file and call the API on this (with comments) and you can see how this is returned.

Column calculated from another column?

Generated Column is one of the good approach for MySql version which is 5.7.6 and above.

There are two kinds of Generated Columns:

  • Virtual (default) - column will be calculated on the fly when a record is read from a table
  • Stored - column will be calculated when a new record is written/updated in the table

Both types can have NOT NULL restrictions, but only a stored Generated Column can be a part of an index.

For current case, we are going to use stored generated column. To implement I have considered that both of the values required for calculation are present in table

CREATE TABLE order_details (price DOUBLE, quantity INT, amount DOUBLE AS (price * quantity));

INSERT INTO order_details (price, quantity) VALUES(100,1),(300,4),(60,8);

amount will automatically pop up in table and you can access it directly, also please note that whenever you will update any of the columns, amount will also get updated.

Opening popup windows in HTML

HTML alone does not support this. You need to use some JS.

And also consider nowadays people use popup blocker in browsers.

<a href="'document.aspx','mypopuptitle','width=600,height=400')">open popup</a>

Merge (Concat) Multiple JSONObjects in Java

In addition to @erel's answer, I had to make this edit (I'm using org.json.simple) to the outer else for dealing with JSONArray's:

            // existing value for "key" - recursively deep merge:
            if (value instanceof JSONObject) {
                JSONObject valueJson = (JSONObject)value;
                deepMerge(valueJson, (JSONObject) target.get(key));

            // insert each JSONArray's JSONObject in place
            if (value instanceof JSONArray) {
                ((JSONArray) value).forEach(
                    jsonobj ->
                    ((JSONArray) target.get(key)).add(jsonobj));
            else {
                target.put(key, value);

close fxml window by code, javafx

I implemented this in the following way after receiving a NullPointerException from the accepted answer.

In my FXML:

<Button onMouseClicked="#onMouseClickedCancelBtn" text="Cancel">

In my Controller class:

@FXML public void onMouseClickedCancelBtn(InputEvent e) {
    final Node source = (Node) e.getSource();
    final Stage stage = (Stage) source.getScene().getWindow();

In Rails, how do you render JSON using a view?

Im new to RoR this is what I found out. you can directly render a json format

  users = User.all
  render json: {allUsers: users} # ! rendering all users

How to set a variable to current date and date-1 in linux?

you should man date first

date +%Y-%m-%d
date +%Y-%m-%d -d yesterday

UTF-8 all the way through

I'd like to add one thing to chazomaticus' excellent answer:

Don't forget the META tag either (like this, or the HTML4 or XHTML version of it):

<meta charset="utf-8">

That seems trivial, but IE7 has given me problems with that before.

I was doing everything right; the database, database connection and Content-Type HTTP header were all set to UTF-8, and it worked fine in all other browsers, but Internet Explorer still insisted on using the "Western European" encoding.

It turned out the page was missing the META tag. Adding that solved the problem.


The W3C actually has a rather large section dedicated to I18N. They have a number of articles related to this issue – describing the HTTP, (X)HTML and CSS side of things:

They recommend using both the HTTP header and HTML meta tag (or XML declaration in case of XHTML served as XML).

Who sets response content-type in Spring MVC (@ResponseBody)

Simple declaration of the StringHttpMessageConverter bean is not enough, you need to inject it into AnnotationMethodHandlerAdapter:

<bean class = "org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter">
    <property name="messageConverters">
            <bean class = "org.springframework.http.converter.StringHttpMessageConverter">
                <property name="supportedMediaTypes" value = "text/plain;charset=UTF-8" />

However, using this method you have to redefine all HttpMessageConverters, and also it doesn't work with <mvc:annotation-driven />.

So, perhaps the most convenient but ugly method is to intercept instantiation of the AnnotationMethodHandlerAdapter with BeanPostProcessor:

public class EncodingPostProcessor implements BeanPostProcessor {
    public Object postProcessBeforeInitialization(Object bean, String name)
            throws BeansException {
        if (bean instanceof AnnotationMethodHandlerAdapter) {
            HttpMessageConverter<?>[] convs = ((AnnotationMethodHandlerAdapter) bean).getMessageConverters();
            for (HttpMessageConverter<?> conv: convs) {
                if (conv instanceof StringHttpMessageConverter) {
                    ((StringHttpMessageConverter) conv).setSupportedMediaTypes(
                        Arrays.asList(new MediaType("text", "html", 
        return bean;

    public Object postProcessAfterInitialization(Object bean, String name)
            throws BeansException {
        return bean;


<bean class = "EncodingPostProcessor " />

How to get disk capacity and free space of remote computer

I created a PowerShell advanced function (script cmdlet) a while back that allows you to query multiple computers.

The code for the function is a little over 100 lines long, so you can find it here: PowerShell version of the df command

Check out the Usage section for examples. The following usage example queries a set of remote computers (input from the PowerShell pipeline) and displays the output in a table format with numeric values in human-readable form:

PS> $cred = Get-Credential -Credential 'example\administrator'
PS> 'db01','dc01','sp01' | Get-DiskFree -Credential $cred -Format | Format-Table -GroupBy Name -AutoSize

   Name: DB01

Name Vol Size  Used  Avail Use% FS   Type
---- --- ----  ----  ----- ---- --   ----
DB01 C:  39.9G 15.6G 24.3G   39 NTFS Local Fixed Disk
DB01 D:  4.1G  4.1G  0B     100 CDFS CD-ROM Disc

   Name: DC01

Name Vol Size  Used  Avail Use% FS   Type
---- --- ----  ----  ----- ---- --   ----
DC01 C:  39.9G 16.9G 23G     42 NTFS Local Fixed Disk
DC01 D:  3.3G  3.3G  0B     100 CDFS CD-ROM Disc
DC01 Z:  59.7G 16.3G 43.4G   27 NTFS Network Connection

   Name: SP01

Name Vol Size   Used   Avail Use% FS   Type
---- --- ----   ----   ----- ---- --   ----
SP01 C:  39.9G  20G    19.9G   50 NTFS Local Fixed Disk
SP01 D:  722.8M 722.8M 0B     100 UDF  CD-ROM Disc

Web scraping with Java

If you wish to automate scraping of large amount pages or data, then you could try Gotz ETL.

It is completely model driven like a real ETL tool. Data structure, task workflow and pages to scrape are defined with a set of XML definition files and no coding is required. Query can be written either using Selectors with JSoup or XPath with HtmlUnit.

Replacing a 32-bit loop counter with 64-bit introduces crazy performance deviations with _mm_popcnt_u64 on Intel CPUs

TL;DR: Use __builtin intrinsics instead; they might happen to help.

I was able to make gcc 4.8.4 (and even 4.7.3 on generate optimal code for this by using __builtin_popcountll which uses the same assembly instruction, but gets lucky and happens to make code that doesn't have an unexpectedly long loop-carried dependency because of the false dependency bug.

I am not 100% sure of my benchmarking code, but objdump output seems to share my views. I use some other tricks (++i vs i++) to make the compiler unroll loop for me without any movl instruction (strange behaviour, I must say).


Count: 20318230000  Elapsed: 0.411156 seconds   Speed: 25.503118 GB/s

Benchmarking code:

#include <stdint.h>
#include <stddef.h>
#include <time.h>
#include <stdio.h>
#include <stdlib.h>

uint64_t builtin_popcnt(const uint64_t* buf, size_t len){
  uint64_t cnt = 0;
  for(size_t i = 0; i < len; ++i){
    cnt += __builtin_popcountll(buf[i]);
  return cnt;

int main(int argc, char** argv){
  if(argc != 2){
    printf("Usage: %s <buffer size in MB>\n", argv[0]);
    return -1;
  uint64_t size = atol(argv[1]) << 20;
  uint64_t* buffer = (uint64_t*)malloc((size/8)*sizeof(*buffer));

  // Spoil copy-on-write memory allocation on *nix
  for (size_t i = 0; i < (size / 8); i++) {
    buffer[i] = random();
  uint64_t count = 0;
  clock_t tic = clock();
  for(size_t i = 0; i < 10000; ++i){
    count += builtin_popcnt(buffer, size/8);
  clock_t toc = clock();
  printf("Count: %lu\tElapsed: %f seconds\tSpeed: %f GB/s\n", count, (double)(toc - tic) / CLOCKS_PER_SEC, ((10000.0*size)/(((double)(toc - tic)*1e+9) / CLOCKS_PER_SEC)));
  return 0;

Compile options:

gcc --std=gnu99 -mpopcnt -O3 -funroll-loops -march=native bench.c -o bench

GCC version:

gcc (Ubuntu 4.8.4-2ubuntu1~14.04.1) 4.8.4

Linux kernel version:


CPU information:

processor   : 0
vendor_id   : GenuineIntel
cpu family  : 6
model       : 70
model name  : Intel(R) Core(TM) i7-4870HQ CPU @ 2.50 GHz
stepping    : 1
microcode   : 0xf
cpu MHz     : 2494.226
cache size  : 6144 KB
physical id : 0
siblings    : 1
core id     : 0
cpu cores   : 1
apicid      : 0
initial apicid  : 0
fpu     : yes
fpu_exception   : yes
cpuid level : 13
wp      : yes
flags       : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ss ht syscall nx rdtscp lm constant_tsc nopl xtopology nonstop_tsc eagerfpu pni pclmulqdq ssse3 fma cx16 pcid sse4_1 sse4_2 x2apic movbe popcnt tsc_deadline_timer aes xsave avx f16c rdrand hypervisor lahf_lm abm arat pln pts dtherm fsgsbase tsc_adjust bmi1 hle avx2 smep bmi2 invpcid xsaveopt
bugs        :
bogomips    : 4988.45
clflush size    : 64
cache_alignment : 64
address sizes   : 36 bits physical, 48 bits virtual
power management:

Powershell: count members of a AD group

The Get-ADGroupMember cmdlet would solve this in a much more efficient way than you're tying.

As an example:

$users = Get-ADGroupMember -Identity 'Group Name'


In order to clarify things, and to make your script simpler. Here's a generic script that will work for your environment that outputs the user count for each group matching your filters.

$groups = Get-ADGroup -filter {(name -like "WA*") -or (name -like "workstation*")}
foreach($group in $groups){
  $countUser = (Get-ADGroupMember $group.DistinguishedName).count
  Write-Host "The group $($group.Name) has $countUser user(s)."

How to add minutes to current time in swift

NSDate.init with timeIntervalSinceNow:

 let dateAfterMin = NSDate.init(timeIntervalSinceNow: (minutes * 60.0))

Using If/Else on a data frame

Use ifelse:

frame$twohouses <- ifelse(frame$data>=2, 2, 1)
   data twohouses
1     0         1
2     1         1
3     2         2
4     3         2
5     4         2
16    0         1
17    2         2
18    1         1
19    2         2
20    0         1
21    4         2

The difference between if and ifelse:

  • if is a control flow statement, taking a single logical value as an argument
  • ifelse is a vectorised function, taking vectors as all its arguments.

The help page for if, accessible via ?"if" will also point you to ?ifelse

Insert data using Entity Framework model

[HttpPost] // it use when you write logic on button click event

public ActionResult DemoInsert(EmployeeModel emp)
    Employee emptbl = new Employee();    // make object of table
    emptbl.EmpName = emp.EmpName;
    emptbl.EmpAddress = emp.EmpAddress;  // add if any field you want insert
    dbc.Employees.Add(emptbl);           // pass the table object 

    return View();

Pip "Could not find a that satisfies the requirement"

pygame is not distributed via pip. See this link which provides windows binaries ready for installation.

  1. Install python
  2. Make sure you have python on your PATH
  3. Download the appropriate wheel from this link
  4. Install pip using this tutorial
  5. Finally, use these commands to install pygame wheel with pip

    • Python 2 (usually called pip)

      • pip install file.whl
    • Python 3 (usually called pip3)

      • pip3 install file.whl

Another tutorial for installing pygame for windows can be found here. Although the instructions are for 64bit windows, it can still be applied to 32bit

How to convert seconds to time format?

Maybe the simplest way is:

gmdate('H:i:s', $your_time_in_seconds);

TimePicker Dialog from clicking EditText

For me the dialogue appears more than one if I click the dpFlightDate edit text more than one time same for the timmer dialog . how can I avoid this dialog to appear only once and if the user click's 2nd time the dialog must not appear again ie if dialog is on the screen ?

          // perform click event on edit text
            dpFlightDate.setOnClickListener(new View.OnClickListener() {
                public void onClick(View v) {
                    // calender class's instance and get current date , month and year from calender
                    final Calendar c = Calendar.getInstance();
                    int mYear = c.get(Calendar.YEAR); // current year
                    int mMonth = c.get(Calendar.MONTH); // current month
                    int mDay = c.get(Calendar.DAY_OF_MONTH); // current day
                    // date picker dialog
                    datePickerDialog = new DatePickerDialog(frmFlightDetails.this,
                            new DatePickerDialog.OnDateSetListener() {
                                public void onDateSet(DatePicker view, int year,
                                                      int monthOfYear, int dayOfMonth) {
                                    // set day of month , month and year value in the edit text
                                    dpFlightDate.setText(dayOfMonth + "/"
                                            + (monthOfYear + 1) + "/" + year);

                            }, mYear, mMonth, mDay);
            tpFlightTime.setOnClickListener(new View.OnClickListener() {
                public void onClick(View view) {
                    // Use the current time as the default values for the picker
                    final Calendar c = Calendar.getInstance();
                    int hour = c.get(Calendar.HOUR_OF_DAY);
                    int minute = c.get(Calendar.MINUTE);
                    // Create a new instance of TimePickerDialog
                    timePickerDialog = new TimePickerDialog(frmFlightDetails.this, new TimePickerDialog.OnTimeSetListener() {
                        public void onTimeSet(TimePicker timePicker, int selectedHour, int selectedMinute) {
                            tpFlightTime.setText( selectedHour + ":" + selectedMinute);
                    }, hour, minute, true);//Yes 24 hour time
                    timePickerDialog.setTitle("Select Time");

"installation of package 'FILE_PATH' had non-zero exit status" in R

I have had the same problem with a specific package in R and the solution was I should install in the ubuntu terminal libcurl. Look at the information that appears above explaining to us that curl package has error installation.

I knew this about the message:

Configuration failed because libcurl was not found. Try installing:
 * deb: libcurl4-openssl-dev (Debian, Ubuntu, etc)
 * rpm: libcurl-devel (Fedora, CentOS, RHEL)
 * csw: libcurl_dev (Solaris)
If libcurl is already installed, check that 'pkg-config' is in your
PATH and PKG_CONFIG_PATH contains a libcurl.pc file. If pkg-config
is unavailable you can set INCLUDE_DIR and LIB_DIR manually via:
R CMD INSTALL --configure-vars='INCLUDE_DIR=... LIB_DIR=...'

To install it I used the net command:

sudo apt-get install libcurl4-openssl-dev

Sometimes we can not install a specific package in R because we have problems with packages that must be installed previously as curl package. To know if we should install it we should check the warning errors such as: installation of package ‘curl’ had non-zero exit status.

I hope I have been helpful

Check if $_POST exists

if( isset($_POST['fromPerson']) ) is right.

You can use a function and return, better then directing echo.

Set start value for column with autoincrement

Also note that you cannot normally set a value for an IDENTITY column. You can, however, specify the identity of rows if you set IDENTITY_INSERT to ON for your table. For example:


-- do inserts here


This insert will reset the identity to the last inserted value. From MSDN:

If the value inserted is larger than the current identity value for the table, SQL Server automatically uses the new inserted value as the current identity value.

How do I save a String to a text file using Java?

You can use the ArrayList to put all the contents of the TextArea for exemple, and send as parameter by calling the save, as the writer just wrote string lines, then we use the "for" line by line to write our ArrayList in the end we will be content TextArea in txt file. if something does not make sense, I'm sorry is google translator and I who do not speak English.

Watch the Windows Notepad, it does not always jump lines, and shows all in one line, use Wordpad ok.

private void SaveActionPerformed(java.awt.event.ActionEvent evt) {

    String NameFile = Name.getText();
    ArrayList< String > Text = new ArrayList< String >();


    SaveFile(NameFile, Text);

public void SaveFile(String name, ArrayList< String> message) {

    path = "C:\\Users\\Paulo Brito\\Desktop\\" + name + ".txt";

    File file1 = new File(path);

    try {

        if (!file1.exists()) {


        File[] files = file1.listFiles();

        FileWriter fw = new FileWriter(file1, true);

        BufferedWriter bw = new BufferedWriter(fw);

        for (int i = 0; i < message.size(); i++) {



        FileReader fr = new FileReader(file1);

        BufferedReader br = new BufferedReader(fr);

        fw = new FileWriter(file1, true);

        bw = new BufferedWriter(fw);

        while (br.ready()) {

            String line = br.readLine();




    } catch (IOException ex) {
        JOptionPane.showMessageDialog(null, "Error in" + ex);     

Delete entire row if cell contains the string X

This is not necessarily a VBA task - This specific task is easiest sollowed with Auto filter.

1.Insert Auto filter (In Excel 2010 click on home-> (Editing) Sort & Filter -> Filter)
2. Filter on the 'Websites' column
3. Mark the 'none' and delete them
4. Clear filter

Why aren't Xcode breakpoints functioning?

Solution for me with XCode 9.4.1 (did not stop at any breakpoint):

Under build Target -> Build Settings -> Optimization Level: Switched from "Optimize for speed" -> "No optimization" (now it's slower but works)

JFrame Maximize window

If you're using a JFrame, try this

JFrame frame = new JFrame();

Express.js Response Timeout

In case you would like to use timeout middleware and exclude a specific route:

var timeout = require('connect-timeout');
app.use(timeout('5s')); //set 5s timeout for all requests

app.use('/my_route', function(req, res, next) {
    req.clearTimeout(); // clear request timeout
    req.setTimeout(20000); //set a 20s timeout for this request
}).get('/my_route', function(req, res) {
    //do something that takes a long time

How do I monitor the computer's CPU, memory, and disk usage in Java?

Have a look at this very detailled article:

To get the percentage of CPU used, all you need is some simple maths:

MBeanServerConnection mbsc = ManagementFactory.getPlatformMBeanServer();

OperatingSystemMXBean osMBean = ManagementFactory.newPlatformMXBeanProxy(
mbsc, ManagementFactory.OPERATING_SYSTEM_MXBEAN_NAME, OperatingSystemMXBean.class);

long nanoBefore = System.nanoTime();
long cpuBefore = osMBean.getProcessCpuTime();

// Call an expensive task, or sleep if you are monitoring a remote process

long cpuAfter = osMBean.getProcessCpuTime();
long nanoAfter = System.nanoTime();

long percent;
if (nanoAfter > nanoBefore)
 percent = ((cpuAfter-cpuBefore)*100L)/
else percent = 0;

System.out.println("Cpu usage: "+percent+"%");

Note: You must import and not

How do I make a Windows batch script completely silent?

Copies a directory named html & all its contents to a destination directory in silent mode. If the destination directory is not present it will still create it.

@echo off
TITLE Copy Folder with Contents

set SOURCE=C:\labs
set DESTINATION=C:\Users\MyUser\Desktop\html

xcopy %SOURCE%\html\* %DESTINATION%\* /s /e /i /Y >NUL

  1. /S Copies directories and subdirectories except empty ones.

  2. /E Copies directories and subdirectories, including empty ones. Same as /S /E. May be used to modify /T.

  3. /I If destination does not exist and copying more than one file, assumes that destination must be a directory.

  4. /Y Suppresses prompting to confirm you want to overwrite an existing destination file.

How to retrieve checkboxes values in jQuery

I have had a similar problem and this is how i solved it using the examples above:

 $(".ms-drop").click(function () {
        $(function showSelectedValues() {
            alert($(".ms-drop input[type=checkbox]:checked").map(
               function () { return this.value; }).get().join(","));

System.BadImageFormatException: Could not load file or assembly (from installutil.exe)

After trying all the mentioned solutions I found the PlatformTarget somehow added to AnyCPU configuration in my project .csproj.

<PropertyGroup Condition=" '$(Configuration)|$(Platform)' == 'Release|AnyCPU' ">

Removing the line worked for me.

How to convert List to Json in Java

Use GSONBuilder with setPrettyPrinting and disableHtml for nice output.

String json = new GsonBuilder().setPrettyPrinting().disableHtmlEscaping().
                            create().toJson(outputList  );

How do I erase an element from std::vector<> by index?

The erase method will be used in two ways:

  1. Erasing single element:

    vector.erase( vector.begin() + 3 ); // Deleting the fourth element
  2. Erasing range of elements:

    vector.erase( vector.begin() + 3, vector.begin() + 5 ); // Deleting from fourth element to sixth element

Angularjs $q.all

$http is a promise too, you can make it simpler:

return $q.all({
        return $'upload/tasks',d).then(someProcessCallback, onErrorCallback);

How do I get the value of a textbox using jQuery?

Per Jquery docs

The .val() method is primarily used to get the values of form elements such as input, select and textarea. When called on an empty collection, it returns undefined.

In order to retrieve the value store in the text box with id txtEmail, you can use


Python update a key in dict if it doesn't exist

According to the above answers setdefault() method worked for me.

old_attr_name = mydict.setdefault(key, attr_name)
if attr_name != old_attr_name:
    raise RuntimeError(f"Key '{key}' duplication: "
                       f"'{old_attr_name}' and '{attr_name}'.")

Though this solution is not generic. Just suited me in this certain case. The exact solution would be checking for the key first (as was already advised), but with setdefault() we avoid one extra lookup on the dictionary, that is, though small, but still a performance gain.

Is it acceptable and safe to run pip install under sudo?

Your original problem is that pip cannot write the logs to the folder.

IOError: [Errno 13] Permission denied: '/Users/markwalker/Library/Logs/pip.log'

You need to cd into a folder in which the process invoked can write like /tmp so a cd /tmp and re invoking the command will probably work but is not what you want.

BUT actually for this particular case (you not wanting to use sudo for installing python packages) and no need for global package installs you can use the --user flag like this :

pip install --user <packagename>

and it will work just fine.

I assume you have a one user python python installation and do not want to bother with reading about virtualenv (which is not very userfriendly) or pipenv.

As some people in the comments section have pointed out the next approach is not a very good idea unless you do not know what to do and got stuck:

Another approach for global packages like in your case you want to do something like :

chown -R $USER /Library/Python/2.7/site-packages/

or more generally

chown -R $USER <path to your global pip packages>

Android Error - Open Failed ENOENT

With sdk, you can't write to the root of internal storage. This cause your error.

Edit :

Based on your code, to use internal storage with sdk:

final File dir = new File(context.getFilesDir() + "/nfs/guille/groce/users/nicholsk/workspace3/SQLTest");
dir.mkdirs(); //create folders where write files
final File file = new File(dir, "BlockForTest.txt");

Difference between `constexpr` and `const`

First of all, both are qualifiers in c++. A variable declared const must be initialized and cannot be changed in the future. Hence generally a variable declared as a const will have a value even before compiling.

But, for constexpr it is a bit different.

For constexpr, you can give an expression that could be evaluated during the compilation of the program.

Obviously, the variable declared as constexper cannot be changed in the future just like const.

Angular.js ng-repeat filter by property having one of multiple values (OR of values)

Here is a way to do it while passing in an extra argument: (thanks to Denis Pshenov)

<div ng-repeat="group in groups">
    <li ng-repeat="friend in friends | filter:weDontLike(">

With the backend:

$scope.weDontLike = function(name) {
    return function(friend) {
        return != name;


And yet another way with an in-template filter only: (thanks to mikel)

<div ng:app>
  <div ng-controller="HelloCntl">
       <li ng-repeat="friend in friends | filter:{name:'!Adam'}">

C++ delete vector, objects, free memory

vector::clear() does not free memory allocated by the vector to store objects; it calls destructors for the objects it holds.

For example, if the vector uses an array as a backing store and currently contains 10 elements, then calling clear() will call the destructor of each object in the array, but the backing array will not be deallocated, so there is still sizeof(T) * 10 bytes allocated to the vector (at least). size() will be 0, but size() returns the number of elements in the vector, not necessarily the size of the backing store.

As for your second question, anything you allocate with new you must deallocate with delete. You typically do not maintain a pointer to a vector for this reason. There is rarely (if ever) a good reason to do this and you prevent the vector from being cleaned up when it leaves scope. However, calling clear() will still act the same way regardless of how it was allocated.

Push commits to another branch

It's very simple. Suppose that you have made changes to your Branch A which resides on both place locally and remotely but you want to push these changes to Branch B which doesn't exist anywhere.

Step-01: create and switch to the new branch B

git checkout -b B

Step-02: Add changes in the new local branch

git add . //or specific file(s)

Step-03: Commit the changes

git commit -m "commit_message"

Step-04: Push changes to the new branch B. The below command will create a new branch B as well remotely

git push origin B

Now, you can verify from bitbucket that the branch B will have one more commit than branch A. And when you will checkout the branch A these changes won't be there as these have been pushed into the branch B.

Note: If you have commited your changes into the branch A and after that you want to shift those changes into the new branch B then you will have to reset those changes first. #HappyLearning

Difference between numpy.array shape (R, 1) and (R,)

The data structure of shape (n,) is called a rank 1 array. It doesn't behave consistently as a row vector or a column vector which makes some of its operations and effects non intuitive. If you take the transpose of this (n,) data structure, it'll look exactly same and the dot product will give you a number and not a matrix. The vectors of shape (n,1) or (1,n) row or column vectors are much more intuitive and consistent.

Print a list in reverse order with range()?

[9, 8, 7, 6, 5, 4, 3, 2, 1, 0]

DirectX SDK (June 2010) Installation Problems: Error Code S1023

I've had the same problem twice already and the easiest and most concise solution that I found is located here (in MSDN Blogs -> Games for Windows and the DirectX SDK). However, just in case that page goes down, here's the method:

  1. Remove the Visual C++ 2010 Redistributable Package version 10.0.40219 (Service Pack 1) from the system (both x86 and x64 if applicable). This can be easily done via a command-line with administrator rights:

    MsiExec.exe /passive /X{F0C3E5D1-1ADE-321E-8167-68EF0DE699A5}
    MsiExec.exe /passive /X{1D8E6291-B0D5-35EC-8441-6616F567A0F7}
  2. Install the DirectX SDK (June 2010)

  3. Reinstall the Visual C++ 2010 Redistributable Package version 10.0.40219 (Service Pack 1). On an x64 system, you should install both the x86 and x64 versions of the C++ REDIST. Be sure to install the most current version available, which at this point is the KB 2565063 with a security fix.

Note: This issue does not affect earlier version of the DirectX SDK which deploy the VS 2005 / VS 2008 CRT REDIST and do not deploy the VS 2010 CRT REDIST. This issue does not affect the DirectX End-User Runtime web or stand-alone installer as those packages do not deploy any version of the VC++ CRT.

File Checksum Integrity Verifier: This of course assumes you actually have an uncorrupted copy of the DirectX SDK setup package. The best way to validate this it to run

fciv -sha1 DXSDK_Jun10.exe

and verify you get

8fe98c00fde0f524760bb9021f438bd7d9304a69 dxsdk_jun10.exe

Java System.out.print formatting

Since you're using formatters for the rest of it, just use DecimalFormat:

import java.text.DecimalFormat;

DecimalFormat xFormat = new DecimalFormat("000")
System.out.print(xFormat.format(x + 1) + " ");

Alternative you could do whole job in whole line using printf:

System.out.printf("%03d %s  %s    %s    \n",  x + 1, // the payment number
formatter.format(monthlyInterest),  // round our interest rate

Fluid width with equally spaced DIVs

If css3 is an option, this can be done using the css calc() function.

Case 1: Justifying boxes on a single line ( FIDDLE )

Markup is simple - a bunch of divs with some container element.

CSS looks like this:

    height: 100px;
    float: left;
    width: 50px;
    margin-right: calc((100% - 300px) / 5 - 1px); 

where -1px to fix an IE9+ calc/rounding bug - see here

Case 2: Justifying boxes on multiple lines ( FIDDLE )

Here, in addition to the calc() function, media queries are necessary.

The basic idea is to set up a media query for each #columns states, where I then use calc() to work out the margin-right on each of the elements (except the ones in the last column).

This sounds like a lot of work, but if you're using LESS or SASS this can be done quite easily

(It can still be done with regular css, but then you'll have to do all the calculations manually, and then if you change your box width - you have to work out everything again)

Below is an example using LESS: (You can copy/paste this code here to play with it, [it's also the code I used to generate the above mentioned fiddle])

@min-margin: 15px;
@div-width: 150px;

@3divs: (@div-width * 3);
@4divs: (@div-width * 4);
@5divs: (@div-width * 5);
@6divs: (@div-width * 6);
@7divs: (@div-width * 7);

@3divs-width: (@3divs + @min-margin * 2);
@4divs-width: (@4divs + @min-margin * 3);
@5divs-width: (@5divs + @min-margin * 4);
@6divs-width: (@6divs + @min-margin * 5);
@7divs-width: (@7divs + @min-margin * 6);


    overflow: auto;
    display: block;
    min-width: @3divs-width;
.container > div
    margin-bottom: 20px;
    width: @div-width;
    height: 100px;
    background: blue;
    color: #fff;
    text-align: center;

@media (max-width: @3divs-width) {
    .container > div {  
        margin-right: @min-margin;
    .container > div:nth-child(3n) {  
        margin-right: 0;

@media (min-width: @3divs-width) and (max-width: @4divs-width) {
    .container > div {  
        margin-right: ~"calc((100% - @{3divs})/2 - 1px)";
    .container > div:nth-child(3n) {  
        margin-right: 0;

@media (min-width: @4divs-width) and (max-width: @5divs-width) {
    .container > div {  
        margin-right: ~"calc((100% - @{4divs})/3 - 1px)";
    .container > div:nth-child(4n) {  
        margin-right: 0;

@media (min-width: @5divs-width) and (max-width: @6divs-width) {
    .container > div {  
        margin-right: ~"calc((100% - @{5divs})/4 - 1px)";
    .container > div:nth-child(5n) {  
        margin-right: 0;

@media (min-width: @6divs-width){
    .container > div {  
        margin-right: ~"calc((100% - @{6divs})/5 - 1px)";
    .container > div:nth-child(6n) {  
        margin-right: 0;

So basically you first need to decide a box-width and a minimum margin that you want between the boxes.

With that, you can work out how much space you need for each state.

Then, use calc() to calcuate the right margin, and nth-child to remove the right margin from the boxes in the final column.

The advantage of this answer over the accepted answer which uses text-align:justify is that when you have more than one row of boxes - the boxes on the final row don't get 'justified' eg: If there are 2 boxes remaining on the final row - I don't want the first box to be on the left and the next one to be on the right - but rather that the boxes follow each other in order.

Regarding browser support: This will work on IE9+,Firefox,Chrome,Safari6.0+ - (see here for more details) However i noticed that on IE9+ there's a bit of a glitch between media query states. [if someone knows how to fix this i'd really like to know :) ] <-- FIXED HERE

How to filter multiple values (OR operation) in angularJS

My solution

ng-repeat="movie in movies | filter: {'Action'} + filter: {'Comedy}"

How can I group data with an Angular filter?

First do a loop using a filter that will return only unique teams, and then a nested loop that returns all players per current team:


<div ng-app ng-controller="Main">
    <div ng-repeat="playerPerTeam in playersToFilter() | filter:filterTeams">
        <li ng-repeat="player in players | filter:{team:}">{{}}</li>        


function Main($scope) {
    $scope.players = [{name: 'Gene', team: 'team alpha'},
                    {name: 'George', team: 'team beta'},
                    {name: 'Steve', team: 'team gamma'},
                    {name: 'Paula', team: 'team beta'},
                    {name: 'Scruath of the 5th sector', team: 'team gamma'}];

    var indexedTeams = [];

    // this will reset the list of indexed teams each time the list is rendered again
    $scope.playersToFilter = function() {
        indexedTeams = [];
        return $scope.players;

    $scope.filterTeams = function(player) {
        var teamIsNew = indexedTeams.indexOf( == -1;
        if (teamIsNew) {
        return teamIsNew;

Bootstrap 4 Dropdown Menu not working?

include them with this order this will work i dont know why :D

<!-- jQuery -->
<script src="js/jquery-3.4.1.min.js"></script>

<!-- Popper -->
<script src="js/popper.min.js"></script>

<!-- Bootstrap js -->
<script src="js/bootstrap.min.js"></script>

Printing pointers in C

You have used:

char s[] = "asd";

Here s actually points to the bytes "asd". The address of s, would also point to this location.

If you used:

char *s = "asd";

the value of s and &s would be different, as s would actually be a pointer to the bytes "asd".

You used:

char s[] = "asd";
char **p = &s;

Here s points to the bytes "asd". p is a pointer to a pointer to characters, and has been set to a the address of characters. In other words you have too many indirections in p. If you used char *s = "asd", you could use this additional indirection.

IF statement: how to leave cell blank if condition is false ("" does not work)

The formula in C1


is either giving an answer of "" (which isn't treated as blank) or the contents of B1.

If you want the formula in D1 to show TRUE if C1 is "" and FALSE if C1 has something else in then use the formula


instead of ISBLANK

Should I check in folder "node_modules" to Git when creating a Node.js app on Heroku?

Instead of checking in folder node_modules, make a package.json file for your application.

The package.json file specifies the dependencies of your application. Heroku can then tell npm to install all of those dependencies. The tutorial you linked to contains a section on package.json files.

How to import JSON File into a TypeScript file?

As stated in this reddit post, after Angular 7, you can simplify things to these 2 steps:

  1. Add those three lines to compilerOptions in your tsconfig.json file:
"resolveJsonModule": true,
"esModuleInterop": true,
"allowSyntheticDefaultImports": true
  1. Import your json data:
import myData from '../assets/data/my-data.json';

And that's it. You can now use myDatain your components/services.

How to calculate the difference between two dates using PHP?

// If you just want to see the year difference then use this function.
// Using the logic I've created you may also create month and day difference
// which I did not provide here so you may have the efforts to use your brain.
// :)
echo getYearDifference ($date1,$date2);
function getYearDifference($date1=strtotime($date1),$date2=strtotime($date2)){
    $year = 0;
    while($date2 > $date1 = strtotime('+1 year', $date1)){
    return $year;

How to send a model in jQuery $.ajax() post request to MVC controller method

This can be done by building a javascript object to match your mvc model. The names of the javascript properties have to match exactly to the mvc model or else the autobind won't happen on the post. Once you have your model on the server side you can then manipulate it and store the data to the database.

I am achieving this either by a double click event on a grid row or click event on a button of some sort.

@model TestProject.Models.TestModel


function testButton_Click(){
  var javaModel ={
  ModelId: '@Model.TestId',
  CreatedDate: '@Model.CreatedDate.ToShortDateString()',
  TestDescription: '@Model.TestDescription',
  //Here I am using a Kendo editor and I want to bind the text value to my javascript
  //object. This may be different for you depending on what controls you use.
  TestStatus: ($('#StatusTextBox'))[0].value, 
  TestType: '@Model.TestType'

  //Now I did for some reason have some trouble passing the ENUM id of a Kendo ComboBox 
    //selected value. This puzzled me due to the conversion to Json object in the Ajax call. 
  //By parsing the Type to an int this worked.

  javaModel.TestType = parseInt(javaModel.TestType);

      //This is where you want to post to.
      contentType: 'application/json',
      data: JSON.stringify(javaModel)

//This is your controller action on the server, and it will autobind your values 
//to the newTestModel on post.

public ActionResult TestModelUpdate(TestModel newTestModel)
 return //do some return action;

White spaces are required between publicId and systemId

If you're working from some network that requires you to use a proxy in your browser to connect to the internet (likely an office building), that might be it. I had the same issue and adding the proxy configs to the network settings solved it.

  • Go to your preferences (Eclipse -> Preferences on a Mac, or Window -> Preferences on a Windows)
  • Then -> General -> expand to view the list underneath -> Select Network Connections (don't expand)
  • At the top of the page that appears there is a drop down, select "Manual."
  • Then select "HTTP" in the list directly below the drop down (which now should have all it's options checked) and then click the "Edit" button to the right of the list.
  • Enter in the proxy url and port you need to connect to the internet in your web browser normally.
  • Repeat for "HTTPS."

If you don't know the proxy url and port, talk to your network admin.

How can I set a proxy server for gem?

You need to add http_proxy and https_proxy environment variables as described here.

How to find the lowest common ancestor of two nodes in any binary tree?

Nick Johnson is correct that a an O(n) time complexity algorithm is the best you can do if you have no parent pointers.) For a simple recursive version of that algorithm see the code in Kinding's post which runs in O(n) time.

But keep in mind that if your nodes have parent pointers, an improved algorithm is possible. For both nodes in question construct a list containing the path from root to the node by starting at the node, and front inserting the parent.

So for 8 in your example, you get (showing steps): {4}, {2, 4}, {1, 2, 4}

Do the same for your other node in question, resulting in (steps not shown): {1, 2}

Now compare the two lists you made looking for the first element where the list differ, or the last element of one of the lists, whichever comes first.

This algorithm requires O(h) time where h is the height of the tree. In the worst case O(h) is equivalent to O(n), but if the tree is balanced, that is only O(log(n)). It also requires O(h) space. An improved version is possible that uses only constant space, with code shown in CEGRD's post

Regardless of how the tree is constructed, if this will be an operation you perform many times on the tree without changing it in between, there are other algorithms you can use that require O(n) [linear] time preparation, but then finding any pair takes only O(1) [constant] time. For references to these algorithms, see the the lowest common ancestor problem page on Wikipedia. (Credit to Jason for originally posting this link)

Selenium Finding elements by class name in python

Use nth-child, for example:

driver.find_element(By.CSS_SELECTOR, 'p.content:nth-child(1)')


driver.find_element(By.CSS_SELECTOR, 'p.content:first-child')

How do I auto-submit an upload form when a file is selected?

Try bellow code with jquery :

    <script src=""></script>

    $('#myForm').on('change', "input#MyFile", function (e) {
    <div id="content">
        <form id="myForm" action="action.php" method="POST" enctype="multipart/form-data">
            <input type="file" id="MyFile" value="Upload" />

Can we make unsigned byte in Java

Although it may seem annoying (coming from C) that Java did not include unsigned byte in the language it really is no big deal since a simple "b & 0xFF" operation yields the unsigned value for (signed) byte b in the (rare) situations that it is actually needed. The bits don't actually change -- just the interpretation (which is important only when doing for example some math operations on the values).

What is the fastest/most efficient way to find the highest set bit (msb) in an integer in C?

Another poster provided a lookup-table using a byte-wide lookup. In case you want to eke out a bit more performance (at the cost of 32K of memory instead of just 256 lookup entries) here is a solution using a 15-bit lookup table, in C# 7 for .NET.

The interesting part is initializing the table. Since it's a relatively small block that we want for the lifetime of the process, I allocate unmanaged memory for this by using Marshal.AllocHGlobal. As you can see, for maximum performance, the whole example is written as native:

readonly static byte[] msb_tab_15;

// Initialize a table of 32768 bytes with the bit position (counting from LSB=0)
// of the highest 'set' (non-zero) bit of its corresponding 16-bit index value.
// The table is compressed by half, so use (value >> 1) for indexing.
static MyStaticInit()
    var p = new byte[0x8000];

    for (byte n = 0; n < 16; n++)
        for (int c = (1 << n) >> 1, i = 0; i < c; i++)
            p[c + i] = n;

    msb_tab_15 = p;

The table requires one-time initialization via the code above. It is read-only so a single global copy can be shared for concurrent access. With this table you can quickly look up the integer log2, which is what we're looking for here, for all the various integer widths (8, 16, 32, and 64 bits).

Notice that the table entry for 0, the sole integer for which the notion of 'highest set bit' is undefined, is given the value -1. This distinction is necessary for proper handling of 0-valued upper words in the code below. Without further ado, here is the code for each of the various integer primitives:

ulong (64-bit) Version

/// <summary> Index of the highest set bit in 'v', or -1 for value '0' </summary>
public static int HighestOne(this ulong v)
    if ((long)v <= 0)
        return (int)((v >> 57) & 0x40) - 1;      // handles cases v==0 and MSB==63

    int j = /**/ (int)((0xFFFFFFFFU - v /****/) >> 58) & 0x20;
    j |= /*****/ (int)((0x0000FFFFU - (v >> j)) >> 59) & 0x10;
    return j + msb_tab_15[v >> (j + 1)];

uint (32-bit) Version

/// <summary> Index of the highest set bit in 'v', or -1 for value '0' </summary>
public static int HighestOne(uint v)
    if ((int)v <= 0)
        return (int)((v >> 26) & 0x20) - 1;     // handles cases v==0 and MSB==31

    int j = (int)((0x0000FFFFU - v) >> 27) & 0x10;
    return j + msb_tab_15[v >> (j + 1)];

Various overloads for the above

public static int HighestOne(long v) => HighestOne((ulong)v);
public static int HighestOne(int v) => HighestOne((uint)v);
public static int HighestOne(ushort v) => msb_tab_15[v >> 1];
public static int HighestOne(short v) => msb_tab_15[(ushort)v >> 1];
public static int HighestOne(char ch) => msb_tab_15[ch >> 1];
public static int HighestOne(sbyte v) => msb_tab_15[(byte)v >> 1];
public static int HighestOne(byte v) => msb_tab_15[v >> 1];

This is a complete, working solution which represents the best performance on .NET 4.7.2 for numerous alternatives that I compared with a specialized performance test harness. Some of these are mentioned below. The test parameters were a uniform density of all 65 bit positions, i.e., 0 ... 31/63 plus value 0 (which produces result -1). The bits below the target index position were filled randomly. The tests were x64 only, release mode, with JIT-optimizations enabled.

That's the end of my formal answer here; what follows are some casual notes and links to source code for alternative test candidates associated with the testing I ran to validate the performance and correctness of the above code.

The version provided above above, coded as Tab16A was a consistent winner over many runs. These various candidates, in active working/scratch form, can be found here, here, and here.

 1  candidates.HighestOne_Tab16A               622,496
 2  candidates.HighestOne_Tab16C               628,234
 3  candidates.HighestOne_Tab8A                649,146
 4  candidates.HighestOne_Tab8B                656,847
 5  candidates.HighestOne_Tab16B               657,147
 6  candidates.HighestOne_Tab16D               659,650
 7  _highest_one_bit_UNMANAGED.HighestOne_U    702,900
 8  de_Bruijn.IndexOfMSB                       709,672
 9  _old_2.HighestOne_Old2                     715,810
10  _test_A.HighestOne8                        757,188
11  _old_1.HighestOne_Old1                     757,925
12  _test_A.HighestOne5  (unsafe)              760,387
13  _test_B.HighestOne8  (unsafe)              763,904
14  _test_A.HighestOne3  (unsafe)              766,433
15  _test_A.HighestOne1  (unsafe)              767,321
16  _test_A.HighestOne4  (unsafe)              771,702
17  _test_B.HighestOne2  (unsafe)              772,136
18  _test_B.HighestOne1  (unsafe)              772,527
19  _test_B.HighestOne3  (unsafe)              774,140
20  _test_A.HighestOne7  (unsafe)              774,581
21  _test_B.HighestOne7  (unsafe)              775,463
22  _test_A.HighestOne2  (unsafe)              776,865
23  candidates.HighestOne_NoTab                777,698
24  _test_B.HighestOne6  (unsafe)              779,481
25  _test_A.HighestOne6  (unsafe)              781,553
26  _test_B.HighestOne4  (unsafe)              785,504
27  _test_B.HighestOne5  (unsafe)              789,797
28  _test_A.HighestOne0  (unsafe)              809,566
29  _test_B.HighestOne0  (unsafe)              814,990
30  _highest_one_bit.HighestOne                824,345
30  _bitarray_ext.RtlFindMostSignificantBit    894,069
31  candidates.HighestOne_Naive                898,865

Notable is that the terrible performance of ntdll.dll!RtlFindMostSignificantBit via P/Invoke:

[DllImport("ntdll.dll"), SuppressUnmanagedCodeSecurity, SecuritySafeCritical]
public static extern int RtlFindMostSignificantBit(ulong ul);

It's really too bad, because here's the entire actual function:

        bsr rdx, rcx  
        mov eax,0FFFFFFFFh  
        movzx ecx, dl  
        cmovne      eax,ecx  

I can't imagine the poor performance originating with these five lines, so the managed/native transition penalties must be to blame. I was also surprised that the testing really favored the 32KB (and 64KB) short (16-bit) direct-lookup tables over the 128-byte (and 256-byte) byte (8-bit) lookup tables. I thought the following would be more competitive with the 16-bit lookups, but the latter consistently outperformed this:

public static int HighestOne_Tab8A(ulong v)
    if ((long)v <= 0)
        return (int)((v >> 57) & 64) - 1;

    int j;
    j =  /**/ (int)((0xFFFFFFFFU - v) >> 58) & 32;
    j += /**/ (int)((0x0000FFFFU - (v >> j)) >> 59) & 16;
    j += /**/ (int)((0x000000FFU - (v >> j)) >> 60) & 8;
    return j + msb_tab_8[v >> j];

The last thing I'll point out is that I was quite shocked that my deBruijn method didn't fare better. This is the method that I had previously been using pervasively:

const ulong N_bsf64 = 0x07EDD5E59A4E28C2,
            N_bsr64 = 0x03F79D71B4CB0A89;

readonly public static sbyte[]
bsf64 =
    63,  0, 58,  1, 59, 47, 53,  2, 60, 39, 48, 27, 54, 33, 42,  3,
    61, 51, 37, 40, 49, 18, 28, 20, 55, 30, 34, 11, 43, 14, 22,  4,
    62, 57, 46, 52, 38, 26, 32, 41, 50, 36, 17, 19, 29, 10, 13, 21,
    56, 45, 25, 31, 35, 16,  9, 12, 44, 24, 15,  8, 23,  7,  6,  5,
bsr64 =
     0, 47,  1, 56, 48, 27,  2, 60, 57, 49, 41, 37, 28, 16,  3, 61,
    54, 58, 35, 52, 50, 42, 21, 44, 38, 32, 29, 23, 17, 11,  4, 62,
    46, 55, 26, 59, 40, 36, 15, 53, 34, 51, 20, 43, 31, 22, 10, 45,
    25, 39, 14, 33, 19, 30,  9, 24, 13, 18,  8, 12,  7,  6,  5, 63,

public static int IndexOfLSB(ulong v) =>
    v != 0 ? bsf64[((v & (ulong)-(long)v) * N_bsf64) >> 58] : -1;

public static int IndexOfMSB(ulong v)
    if ((long)v <= 0)
        return (int)((v >> 57) & 64) - 1;

    v |= v >> 1; v |= v >> 2;  v |= v >> 4;   // does anybody know a better
    v |= v >> 8; v |= v >> 16; v |= v >> 32;  // way than these 12 ops?
    return bsr64[(v * N_bsr64) >> 58];

There's much discussion of how superior and great deBruijn methods at this SO question, and I had tended to agree. My speculation is that, while both the deBruijn and direct lookup table methods (that I found to be fastest) both have to do a table lookup, and both have very minimal branching, only the deBruijn has a 64-bit multiply operation. I only tested the IndexOfMSB functions here--not the deBruijn IndexOfLSB--but I expect the latter to fare much better chance since it has so many fewer operations (see above), and I'll likely continue to use it for LSB.

Get img src with PHP

Use a HTML parser like DOMDocument and then evaluate the value you're looking for with DOMXpath:

$html = '<img id="12" border="0" src="/images/image.jpg"
         alt="Image" width="100" height="100" />';

$doc = new DOMDocument();
$xpath = new DOMXPath($doc);
$src = $xpath->evaluate("string(//img/@src)"); # "/images/image.jpg"

Or for those who really need to save space:

$xpath = new DOMXPath(@DOMDocument::loadHTML($html));
$src = $xpath->evaluate("string(//img/@src)");

And for the one-liners out there:

$src = (string) reset(simplexml_import_dom(DOMDocument::loadHTML($html))->xpath("//img/@src"));

Rounding float in Ruby

If you just need to display it, I would use the number_with_precision helper. If you need it somewhere else I would use, as Steve Weet pointed, the round method

Can I load a .NET assembly at runtime and instantiate a type knowing only the name?

Yes. I don't have any examples that I've done personally available right now. I'll post later when I find some. Basically you'll use reflection to load the assembly and then to pull whatever types you need for it.

In the meantime, this link should get you started:

Using reflection to load unreferenced assemblies at runtime

How to comment out particular lines in a shell script

You can comment section of a script using a conditional.

For example, the following script:

if ${DEBUG}; then
echo 1
echo 2
echo 3
echo 4
echo 5
echo 6
echo 7

would output:


In order to uncomment the section of the code, you simply need to comment the variable:


(Doing so would print the numbers 1 through 7.)

How to Implement Custom Table View Section Headers and Footers with Storyboard

I know this question was for iOS 5, but for the benefit of future readers, note that effective iOS 6 we can now use dequeueReusableHeaderFooterViewWithIdentifier instead of dequeueReusableCellWithIdentifier.

So in viewDidLoad, call either registerNib:forHeaderFooterViewReuseIdentifier: or registerClass:forHeaderFooterViewReuseIdentifier:. Then in viewForHeaderInSection, call tableView:dequeueReusableHeaderFooterViewWithIdentifier:. You do not use a cell prototype with this API (it's either a NIB-based view or a programmatically created view), but this is the new API for dequeued headers and footers.

In laymans terms, what does 'static' mean in Java?

Above points are correct and I want to add some more important points about Static keyword.

Internally what happening when you are using static keyword is it will store in permanent memory(that is in heap memory),we know that there are two types of memory they are stack memory(temporary memory) and heap memory(permanent memory),so if you are not using static key word then will store in temporary memory that is in stack memory(or you can call it as volatile memory).

so you will get a doubt that what is the use of this right???

example: static int a=10;(1 program)

just now I told if you use static keyword for variables or for method it will store in permanent memory right.

so I declared same variable with keyword static in other program with different value.

example: static int a=20;(2 program)

the variable 'a' is stored in heap memory by program 1.the same static variable 'a' is found in program 2 at that time it won`t create once again 'a' variable in heap memory instead of that it just replace value of a from 10 to 20.

In general it will create once again variable 'a' in stack memory(temporary memory) if you won`t declare 'a' as static variable.

overall i can say that,if we use static keyword
  1.we can save memory
  2.we can avoid duplicates
  3.No need of creating object in-order to access static variable with the help of class name you can access it.

How can I compare two strings in java and define which of them is smaller than the other alphabetically?

Haven't you heard about the Comparable interface being implemented by String ? If no, try to use


And it will output a good root for a solution to your problem.

WPF Datagrid Get Selected Cell Value

These are 2 methods that can be used to take a value from the selected row

    /// <summary>
    /// Take a value from a the selected row of a DataGrid
    /// ATTENTION : The column's index is absolute : if the DataGrid is reorganized by the user,
    /// the index must change
    /// </summary>
    /// <param name="dGrid">The DataGrid where we take the value</param>
    /// <param name="columnIndex">The value's line index</param>
    /// <returns>The value contained in the selected line or an empty string if nothing is selected</returns>
    public static string getDataGridValueAt(DataGrid dGrid, int columnIndex)
        if (dGrid.SelectedItem == null)
            return "";
        string str = dGrid.SelectedItem.ToString(); // Take the selected line
        str = str.Replace("}", "").Trim().Replace("{", "").Trim(); // Delete useless characters
        if (columnIndex < 0 || columnIndex >= str.Split(',').Length) // case where the index can't be used 
            return "";
        str = str.Split(',')[columnIndex].Trim();
        str = str.Split('=')[1].Trim();
        return str;

    /// <summary>
    /// Take a value from a the selected row of a DataGrid
    /// </summary>
    /// <param name="dGrid">The DataGrid where we take the value.</param>
    /// <param name="columnName">The column's name of the searched value. Be careful, the parameter must be the same as the shown on the dataGrid</param>
    /// <returns>The value contained in the selected line or an empty string if nothing is selected or if the column doesn't exist</returns>
    public static string getDataGridValueAt(DataGrid dGrid, string columnName)
        if (dGrid.SelectedItem == null)
            return "";
        for (int i = 0; i < columnName.Length; i++)
            if (columnName.ElementAt(i) == '_')
                columnName = columnName.Insert(i, "_");
        string str = dGrid.SelectedItem.ToString(); // Get the selected Line
        str = str.Replace("}", "").Trim().Replace("{", "").Trim(); // Remove useless characters
        for (int i = 0; i < str.Split(',').Length; i++)
            if (str.Split(',')[i].Trim().Split('=')[0].Trim() == columnName) // Check if the searched column exists in the dataGrid.
                return str.Split(',')[i].Trim().Split('=')[1].Trim();
        return str;

Trigger css hover with JS

If you bind events to the onmouseover and onmouseout events in Jquery, you can then trigger that effect using mouseenter().

What are you trying to accomplish?

How to return a part of an array in Ruby?

You can use slice() for this:

>> foo = [1,2,3,4,5,6]
=> [1, 2, 3, 4, 5, 6]
>> bar = [10,20,30,40,50,60]
=> [10, 20, 30, 40, 50, 60]
>> half = foo.length / 2
=> 3
>> foobar = foo.slice(0, half) + bar.slice(half, foo.length)
=> [1, 2, 3, 40, 50, 60]

By the way, to the best of my knowledge, Python "lists" are just efficiently implemented dynamically growing arrays. Insertion at the beginning is in O(n), insertion at the end is amortized O(1), random access is O(1).

How to make a floated div 100% height of its parent?

A similar case when you need several child elements have the same height can be solved with flexbox:

Set display: flex; for parent and flex: 1; for child elements, they all will have the same height.

Show all tables inside a MySQL database using PHP?



How do I find which application is using up my port?

On the command prompt, do:

netstat -nb

How to get the command line args passed to a running process on unix/linux systems?

Full commandline

For Linux & Unix System you can use ps -ef | grep process_name to get the full command line.

On SunOS systems, if you want to get full command line, you can use

/usr/ucb/ps -auxww | grep -i process_name

To get the full command line you need to become super user.

List of arguments

pargs -a PROCESS_ID

will give a detailed list of arguments passed to a process. It will output the array of arguments in like this:

argv[o]: first argument
argv[1]: second..
argv[*]: and so on..

I didn't find any similar command for Linux, but I would use the following command to get similar output:

tr '\0' '\n' < /proc/<pid>/environ

How to change spinner text size and text color?

To prevent lagging, you need to not only set the text properties in the onItemSelected listener, but also in the Activity's onCreate method (but it's a little tricky).

Specifically, you need to put this in onCreate after setting the adapter:

spinner.setSelection(0, true);
View v = spinner.getSelectedView();

And then put this in onItemSelected:

((TextView) view).setTextColor(backgroundColor);

Here is a full example:

protected void onCreate(Bundle savedInstanceState)
    Spinner spinner = (Spinner) findViewById(; 

    //Set the choices on the spinner by setting the adapter.  
    spinner.setAdapter(new SpinnerAdapter(toolbar.getContext(), new String[]{"Overview", "Story", "Specifications", "Poll", "Video"}, accentColor, backgroundColor));

    //Set the text color of the Spinner's selected view (not a drop down list view) 
    spinner.setSelection(0, true);
    View v = spinner.getSelectedView();

    //Set the listener for when each option is clicked.  
    spinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener()

        public void onItemSelected(AdapterView<?> parent, View view, int position, long id)
           //Change the selected item's text color  
           ((TextView) view).setTextColor(backgroundColor);

        public void onNothingSelected(AdapterView<?> parent)


For more details, see my question.

How do you show animated GIFs on a Windows Form (c#)

I had the same issue and came across different solutions by implementing which I used to face several different issues. Finally, below is what I put some pieces from different posts together which worked for me as expected.

private void btnCompare_Click(object sender, EventArgs e)
    ThreadStart threadStart = new ThreadStart(Execution);
    Thread thread = new Thread(threadStart);

Here is the Execution method that also carries invoking the PictureBox control:

private void Execution()
    btnCompare.Invoke((MethodInvoker)delegate { pictureBox1.Visible = true; });

    // Your main code comes here . . .

    btnCompare.Invoke((MethodInvoker)delegate { pictureBox1.Visible = false; });

Keep in mind, the PictureBox is invisible from Properties Window or do below:

private void ComparerForm_Load(object sender, EventArgs e)
    pictureBox1.Visible = false;

I get conflicting provisioning settings error when I try to archive to submit an iOS app

The problem is in the Cordova settings.

Note this:

iPhone Distribution has been manually specified

This didn’t make any sense to me, since I had set the project to auto sign in xcode. Like you, the check and uncheck didn’t work. But then I read the last file path given and followed it. The file path is APP > Platforms > ios > Cordova > build-release.xconfig

And in the file, iPhone Distribution is explicitly set for CODE_SIGN_IDENTITY.


CODE_SIGN_IDENTITY = iPhone Distribution
CODE_SIGN_IDENTITY[sdk=iphoneos*] = iPhone Distribution


CODE_SIGN_IDENTITY = iPhone Developer
CODE_SIGN_IDENTITY[sdk=iphoneos*] = iPhone Developer

It a simple thing, and the error message does make it clear that iPhone Distribution has been manually specified, but it doesn’t really say where unless you follow the path. I looked and fiddled with xcode for about three hours trying to figure this out. Hopes this helps anyone in the future.

Fixed digits after decimal with f-strings

Adding to Rob?'s answer: in case you want to print rather large numbers, using thousand separators can be a great help (note the comma).

>>> f'{a*1000:,.2f}'

Stop embedded youtube iframe?

One cannot simply overestimate this post and answers thx OP and helpers. My solution with just video_id exchanging:

<div style="pointer-events: none;">
    <iframe id="myVideo" src="" width="560" height="315" frameborder="0"></iframe> </div>

    <button id="play">PLAY</button>

    <button id="pause">PAUSE</button>

        $('#play').click(function() {
                var frame = document.getElementById("myVideo");

        $('#pause').click(function() {
                var frame = document.getElementById("myVideo");

Docker: Copying files from Docker container to host

Create a path where you want to copy the file and then use:

docker run -d -v hostpath:dockerimag

How do I import global modules in Node? I get "Error: Cannot find module <module>"?

I am using Docker. I am trying to create a docker image that has all of my node dependencies installed, but can use my local app directory at container run time (without polluting it with a node_modules directory or link). This causes problems in this scenario. My workaround is to require from the exact path where the module, e.g. require('/usr/local/lib/node_modules/')

HTML 5 video recording and storing a stream

RecordRTC: WebRTC audio/video recording

  • Audio recording both for Chrome and Firefox
  • Video/Gif recording for Chrome; (Firefox has a little bit issues, will be recovered soon)

Demo :

Creating .webm video from getUserMedia()

Demo :

Capturing Audio & Video in HTML5

Determining complexity for recursive functions (Big O notation)

One of the best ways I find for approximating the complexity of the recursive algorithm is drawing the recursion tree. Once you have the recursive tree:

Complexity = length of tree from root node to leaf node * number of leaf nodes
  1. The first function will have length of n and number of leaf node 1 so complexity will be n*1 = n
  2. The second function will have the length of n/5 and number of leaf nodes again 1 so complexity will be n/5 * 1 = n/5. It should be approximated to n

  3. For the third function, since n is being divided by 5 on every recursive call, length of recursive tree will be log(n)(base 5), and number of leaf nodes again 1 so complexity will be log(n)(base 5) * 1 = log(n)(base 5)

  4. For the fourth function since every node will have two child nodes, the number of leaf nodes will be equal to (2^n) and length of the recursive tree will be n so complexity will be (2^n) * n. But since n is insignificant in front of (2^n), it can be ignored and complexity can be only said to be (2^n).

  5. For the fifth function, there are two elements introducing the complexity. Complexity introduced by recursive nature of function and complexity introduced by for loop in each function. Doing the above calculation, the complexity introduced by recursive nature of function will be ~ n and complexity due to for loop n. Total complexity will be n*n.

Note: This is a quick and dirty way of calculating complexity(nothing official!). Would love to hear feedback on this. Thanks.

Simple CSS: Text won't center in a button

What about:

<input type="button" style="width:24px;" value="A"/>

Vue v-on:click does not work on component

From the documentation:

Due to limitations in JavaScript, Vue cannot detect the following changes to an array:

  1. When you directly set an item with the index, e.g. vm.items[indexOfItem] = newValue
  2. When you modify the length of the array, e.g. vm.items.length = newLength

In my case i stumbled on this problem when migrating from Angular to VUE. Fix was quite easy, but really difficult to find:

setValue(index) {
    Vue.set(this.arr, index, !this.arr[index]);
    this.$forceUpdate(); // Needed to force view rerendering

How to get request URL in Spring Boot RestController

Add a parameter of type UriComponentsBuilder to your controller method. Spring will give you an instance that's preconfigured with the URI for the current request, and you can then customize it (such as by using MvcUriComponentsBuilder.relativeTo to point at a different controller using the same prefix).

Youtube API Limitations

Version 3 of the YouTube Data API has concrete quota numbers listed in the Google API Console where you register for your API Key. You can use 10,000 units per day. Projects that had enabled the YouTube Data API before April 20, 2016, have a default quota of 50M/day.

You can read about what a unit is here:

  • A simple read operation that only retrieves the ID of each returned resource has a cost of approximately 1 unit.
  • A write operation has a cost of approximately 50 units.
  • A video upload has a cost of approximately 1600 units.

If you hit the limits, Google will stop returning results until your quota is reset. You can apply for more than 1M requests per day, but you will have to pay for those extra requests.

Also, you can read about why Google has deferred support to StackOverflow on their YouTube blog here:

There are a number of active members on the YouTube Developer Relations team here including Jeff Posnick, Jarek Wilkiewicz, and Ibrahim Ulukaya who all have knowledge of Youtube internals...

UPDATE: Increased the quota numbers to reflect current limits on December 10, 2013.

UPDATE: Decreased the quota numbers from 50M to 1M per day to reflect current limits on May 13, 2016.

UPDATE: Decreased the quota numbers from 1M to 10K per day as of January 11, 2019.

Configure DataSource programmatically in Spring Boot

My project of spring-boot has run normally according to your assistance. The yaml datasource configuration is:

  # (DataSourceAutoConfiguration & DataSourceProperties)
    name: ds-h2
    url: jdbc:h2:D:/work/workspace/fdata;DATABASE_TO_UPPER=false
    username: h2
    password: h2
    driver-class: org.h2.Driver

Custom DataSource

public class DataSourceBean {

    @ConfigurationProperties(prefix = "spring.datasource")
    public DataSource getDataSource() {
        return DataSourceBuilder
//                .url("jdbc:h2:D:/work/workspace/fork/gs-serving-web-content/initial/data/fdata;DATABASE_TO_UPPER=false")
//                .username("h2")
//                .password("h2")
//                .driverClassName("org.h2.Driver")

javascript if number greater than number

Do this.

var x=parseInt(document.forms["frmOrder"]["txtTotal"].value);
var y=parseInt(document.forms["frmOrder"]["totalpoints"].value);

Remove and Replace Printed items

Just use CR to go to beginning of the line.

import time
for x in range (0,5):  
    b = "Loading" + "." * x
    print (b, end="\r")

What is thread Safe in java?

As Seth stated thread safe means that a method or class instance can be used by multiple threads at the same time without any problems occuring.

Consider the following method:

private int myInt = 0;
public int AddOne()
    int tmp = myInt;
    tmp = tmp + 1;
    myInt = tmp;
    return tmp;

Now thread A and thread B both would like to execute AddOne(). but A starts first and reads the value of myInt (0) into tmp. Now for some reason the scheduler decides to halt thread A and defer execution to thread B. Thread B now also reads the value of myInt (still 0) into it's own variable tmp. Thread B finishes the entire method, so in the end myInt = 1. And 1 is returned. Now it's Thread A's turn again. Thread A continues. And adds 1 to tmp (tmp was 0 for thread A). And then saves this value in myInt. myInt is again 1.

So in this case the method AddOne() was called two times, but because the method was not implemented in a thread safe way the value of myInt is not 2, as expected, but 1 because the second thread read the variable myInt before the first thread finished updating it.

Creating thread safe methods is very hard in non trivial cases. And there are quite a few techniques. In Java you can mark a method as synchronized, this means that only one thread can execute that method at a given time. The other threads wait in line. This makes a method thread safe, but if there is a lot of work to be done in a method, then this wastes a lot of time. Another technique is to 'mark only a small part of a method as synchronized' by creating a lock or semaphore, and locking this small part (usually called the critical section). There are even some methods that are implemented as lockless thread safe, which means that they are built in such a way that multiple threads can race through them at the same time without ever causing problems, this can be the case when a method only executes one atomic call. Atomic calls are calls that can't be interrupted and can only be done by one thread at a time.

Magento addFieldToFilter: Two fields, match as OR, not AND

Here is my solution in Enterprise 1.11 (should work in CE 1.6):

                        array('gteq' => 10),
                        array('null' => true),
                        array('gteq' => 9.99),
                        array('null' => true),
                        array('gteq' => 1.5),
                        array('null' => true),

Which results in this SQL:

    SELECT `main_table`.*
    FROM `shipping_method_entity` AS `main_table`
    WHERE (((max_item_count >= 10) OR (max_item_count IS NULL)))
      AND (((max_item_price >= 9.99) OR (max_item_price IS NULL)))
      AND (((max_item_weight >= 1.5) OR (max_item_weight IS NULL)))

Change input value onclick button - pure javascript or jQuery

Another simple solution for this case using jQuery. Keep in mind it's not a good practice to use inline javascript.


I've added IDs to html on the total price and on the buttons. Here is the jQuery.

    $('#total').text('Product price: $1000');

    $('#total').text('Product price: $2000');
}); Invalid Keystore format

I think the keystore file you want to use has a different or unsupported format in respect to your Java version. Could you post some more info of your task?

In general, to solve this issue you might need to recreate the whole keystore (using some other JDK version for example). In export-import the keys between the old and the new one - if you manage to open the old one somewhere else.

If it is simply an unsupported version, try the BouncyCastle crypto provider for example (although I'm not sure If it adds support to Java for more keystore types?).

Edit: I looked at the feature spec of BC.

Get height and width of a layout programmatically

As I just ran into this problem thought I would write it for kotlin,

my_view.viewTreeObserver.addOnGlobalLayoutListener {
       // here your view is measured
       // get height using my_view.height
       // get width using my_view.width

or {
       // here your view is measured
       // get height using my_view.height
       // get width using my_view.width

How to unload a package without restarting R

Note also that you can only use unload() once. If you use it a second time without rerunning library(), y'll get the not very informative error message invalid 'name' argument:

#> Loading required package: permute
#> Loading required package: lattice
#> This is vegan 2.5-6
detach("package:vegan",  unload=TRUE)
detach("package:vegan",  unload=TRUE)
#> Error in detach("package:vegan", unload = TRUE): invalid 'name' argument

Created on 2020-05-09 by the reprex package (v0.3.0)

Position of a string within a string using Linux shell script?

With bash

a="The cat sat on the mat"
strindex() { 
  [[ "$x" = "$1" ]] && echo -1 || echo "${#x}"
strindex "$a" "$b"   # prints 4
strindex "$a" foo    # prints -1

How to use UIVisualEffectView to Blur Image?

Just put this blur view on the imageView. Here is an example in Objective-C:

UIVisualEffect *blurEffect;
blurEffect = [UIBlurEffect effectWithStyle:UIBlurEffectStyleLight];

UIVisualEffectView *visualEffectView;
visualEffectView = [[UIVisualEffectView alloc] initWithEffect:blurEffect];

visualEffectView.frame = imageView.bounds;
[imageView addSubview:visualEffectView];

and Swift:

var visualEffectView = UIVisualEffectView(effect: UIBlurEffect(style: .Light))    

visualEffectView.frame = imageView.bounds


Deserialize a JSON array in C#

This code is working fine for me,

var a = serializer.Deserialize<List<Entity>>(json);

Saving data to a file in C#

Starting with the System.IO namespace (particularly the File or FileInfo objects) should get you started.

Indentation Error in Python

Did you maybe use some <tab> instead of spaces?

Try remove all the spaces before the code and readd them using <space> characters, just to be sure it's not a <tab>.

concatenate two strings

You can use concatenation operator and instead of declaring two variables only use one variable

String finalString =  cursor.getString(numcol) + cursor.getString(cursor.getColumnIndexOrThrow(db.KEY_DESTINATIE));

How can I show line numbers in Eclipse?

On a Mac do this:

cmd + , or ADT -> Preferences 

Expand General -> Editors ->Text Editors

Check box: Show line numbers

enter image description here

Warning: X may be used uninitialized in this function

When you use Vector *one you are merely creating a pointer to the structure but there is no memory allocated to it.

Simply use one = (Vector *)malloc(sizeof(Vector)); to declare memory and instantiate it.

"Error 1067: The process terminated unexpectedly" when trying to start MySQL

Same problem here. After analysing log reports via eventvwr.msc I found, that logging files were placed in folder which requires admin rights to update, so files cannot be created and install and startup process could not proceed.

So checking eventlog was very usefull.

symfony2 twig path with parameter url creation

Make sure your routing.yml file has 'id' specified in it. In other words, it should look like:

    path: /category/{id}

Validation for 10 digit mobile number and focus input field on invalid

$().ready(function () {

            function (value, element) {
                if (value == "")
                    return false;
                return value.match(/^\d{10}$/);
            "Please enter 10 digits Contact # (No spaces or dash)"

        rules: {
            phone: "tendigits"
        messages: {
            phone: "Please enter 10 digits Contact # (No spaces or dash)",




Singleton in Android

You are copying singleton's customVar into a singletonVar variable and changing that variable does not affect the original value in singleton.

// This does not update singleton variable
// It just assigns value of your local variable

// This actually assigns value of variable in singleton
Singleton.customVar = singletonVar;

remove objects from array by object property

You can use filter. This method always returns the element if the condition is true. So if you want to remove by id you must keep all the element that doesn't match with the given id. Here is an example:

arrayOfObjects = arrayOfObjects.filter(obj => != idToRemove)

__init__() missing 1 required positional argument

The problem is with, you

def __init__(self, data):

when you create object from DHT class you should pass parameter the data should be dict type, like


But in your code youshould to change is

if __name__ == '__main__': DHT(data).showData()


if __name__ == '__main__': DHT({'one':1,'two':2,'three':3}).showData()

LINQ's Distinct() on a particular property

Solution first group by your fields then select firstordefault item.

    List<Person> distinctPeople = allPeople
   .GroupBy(p => p.PersonId)
   .Select(g => g.FirstOrDefault())

How to remove the querystring and get only the url?

You can use strtok to get string before first occurence of ?

$url = strtok($_SERVER["REQUEST_URI"], '?');

strtok() represents the most concise technique to directly extract the substring before the ? in the querystring. explode() is less direct because it must produce a potentially two-element array by which the first element must be accessed.

Some other techniques may break when the querystring is missing or potentially mutate other/unintended substrings in the url -- these techniques should be avoided.

A demonstration:

$urls = [

foreach ($urls as $url) {
    var_export(['strtok: ', strtok($url, '?')]);
    echo "\n";
    var_export(['strstr/true: ', strstr($url, '?', true)]); // not reliable
    echo "\n";
    var_export(['explode/2: ', explode('?', $url, 2)[0]]);  // limit allows func to stop searching after first encounter
    echo "\n";
    var_export(['substr/strrpos: ', substr($url, 0, strrpos( $url, "?"))]);  // not reliable; still not with strpos()
    echo "\n---\n";


array (
  0 => 'strtok: ',
  1 => '',
array (
  0 => 'strstr/true: ',
  1 => '',
array (
  0 => 'explode/2: ',
  1 => '',
array (
  0 => 'substr/strrpos: ',
  1 => '',
array (
  0 => 'strtok: ',
  1 => '',
array (
  0 => 'strstr/true: ',
  1 => false,                       // bad news
array (
  0 => 'explode/2: ',
  1 => '',
array (
  0 => 'substr/strrpos: ',
  1 => '',                          // bad news

An existing connection was forcibly closed by the remote host - WCF

I just had this error now in server only and the solution was to set a maxItemsInObjectGraph attribute in wcf web.config under <behavior> tag:

<dataContractSerializer maxItemsInObjectGraph="2147483646"/>

What's the difference between unit, functional, acceptance, and integration tests?

unit test: testing of individual module or independent component in an application is known to be unit testing , the unit testing will be done by developer.

integration test: combining all the modules and testing the application to verify the communication and the data flow between the modules are working properly or not , this testing also performed by developers.

funcional test checking the individual functionality of an application is mean to be functional testing

acceptance testing this testing is done by end user or customer whether the build application is according to the customer requirement , and customer specification this is known to be acceptance testing

Calling a function within a Class method?

  class sampleClass
        public function f1()
           return "f1 run";

        public function f2()
           echo ("f2 run" );
           $result =  $this->f1();
           echo ($result);



output :

f2 run f1 run

Rotating a point about another point (2D)

This is the answer by Nils Pipenbrinck, but implemented in c# fiddle.

using System;

public class Program
    public static void Main()
        var angle = 180 * Math.PI/180;
        Console.WriteLine(rotate_point(0,0,angle,new Point{X=10, Y=10}).Print());

    static Point rotate_point(double cx, double cy, double angle, Point p)
        double s = Math.Sin(angle);
        double c = Math.Cos(angle);
        // translate point back to origin:
        p.X -= cx;
        p.Y -= cy;
        // rotate point
        double Xnew = p.X * c - p.Y * s;
        double Ynew = p.X * s + p.Y * c;
        // translate point back:
        p.X = Xnew + cx;
        p.Y = Ynew + cy;
        return p;

    class Point
        public double X;
        public double Y;

        public string Print(){
            return $"{X},{Y}";

Ps: Apparently I can’t comment, so I’m obligated to post it as an answer ...

Tricks to manage the available memory in an R session

This is a newer answer to this excellent old question. From Hadley's Advanced R:



## 88 B

## 832 B

## 6.74 kB


If list index exists, do X

A lot of answers, not the simple one.

To check if a index 'id' exists at dictionary dict:

dic = {}
dic['name'] = "joao"
dic['age']  = "39"

if 'age' in dic

returns true if 'age' exists.

Angular 2 change event on every keypress

<input type="text" [ngModel]="mymodel" (keypress)="mymodel=$"/>

How to change an element's title attribute using jQuery

I beleive

$("#myElement").attr("title", "new title value")


$("#myElement").prop("title", "new title value")

should do the trick...

I think you can find all the core functions in the jQuery Docs, although I hate the formatting.

Running EXE with parameters

To start the process with parameters, you can use following code:

string filename = Path.Combine(cPath,"HHTCtrlp.exe");
var proc = System.Diagnostics.Process.Start(filename, cParams);

To kill/exit the program again, you can use following code:


Adding a column to a data.frame

In addition to Roman's answer, something like this might be even simpler. Note that I haven't tested it because I do not have access to R right now.

# Note that I use a global variable here
# normally not advisable, but I liked the
# use here to make the code shorter
index <<- 0
new_column = sapply(df$h_no, function(x) {
  if(x == 1) index = index + 1

The function iterates over the values in n_ho and always returns the categorie that the current value belongs to. If a value of 1 is detected, we increase the global variable index and continue.

Accessing last x characters of a string in Bash

1. Generalized Substring

To generalise the question and the answer of gniourf_gniourf (as this is what I was searching for), if you want to cut a range of characters from, say, 7th from the end to 3rd from the end, you can use this syntax:

${string: -7:4}

Where 4 is the length of course (7-3).

2. Alternative using cut

In addition, while the solution of gniourf_gniourf is obviously the best and neatest, I just wanted to add an alternative solution using cut:

echo $string | cut -c $((${#string}-2))-

Here, ${#string} is the length of the string, and the "-" means cut to the end.

3. Alternative using awk

This solution instead uses the substring function of awk to select a substring which has the syntax substr(string, start, length) going to the end if the length is omitted. length($string)-2) thus picks up the last three characters.

echo $string | awk '{print substr($1,length($1)-2) }'

MySQL root password change

Found it! I forgot to hash the password when I changed it. I used this query to solve my problem:

update user set password=PASSWORD('NEW PASSWORD') where user='root';

I forgot the PASSWORD('NEW PASSWORD') and just put in the new password in plain text

Pure CSS scroll animation

And for webkit enabled browsers I've had good results with:

.myElement {
    -webkit-overflow-scrolling: touch;
    scroll-behavior: smooth; // Added in from answer from Felix
    overflow-x: scroll;

This makes scrolling behave much more like the standard browser behavior - at least it works well on the iPhone we were testing on!

Hope that helps,


Get source JARs from Maven repository

If you want find the source jar file for any of the artifact manually, go to maven repository location for the particular artifact and in Files click on 'view All'. You can find source jar file.

How to add a custom button to the toolbar that calls a JavaScript function?

This article may be useful too

There are code samples and step-by-step guide about building your own CKEditor plugin with custom button.

How to run certain task every day at a particular time using ScheduledExecutorService?

As with the present java SE 8 release with it's excellent date time API with java.time these kind of calculation can be done more easily instead of using java.util.Calendar and java.util.Date.

Now as a sample example for scheduling a task with your use case:

ZonedDateTime now ="America/Los_Angeles"));
ZonedDateTime nextRun = now.withHour(5).withMinute(0).withSecond(0);
if(now.compareTo(nextRun) > 0)
    nextRun = nextRun.plusDays(1);

Duration duration = Duration.between(now, nextRun);
long initalDelay = duration.getSeconds();

ScheduledExecutorService scheduler = Executors.newScheduledThreadPool(1);            
scheduler.scheduleAtFixedRate(new MyRunnableTask(),

The initalDelay is computed to ask the scheduler to delay the execution in TimeUnit.SECONDS. Time difference issues with unit milliseconds and below seems to be negligible for this use case. But you can still make use of duration.toMillis() and TimeUnit.MILLISECONDS for handling the scheduling computaions in milliseconds.

And also TimerTask is better for this or ScheduledExecutorService?

NO: ScheduledExecutorService seemingly better than TimerTask. StackOverflow has already an answer for you.

From @PaddyD,

You still have the issue whereby you need to restart this twice a year if you want it to run at the right local time. scheduleAtFixedRate won't cut it unless you are happy with the same UTC time all year.

As it is true and @PaddyD already has given a workaround(+1 to him), I am providing a working example with Java8 date time API with ScheduledExecutorService. Using daemon thread is dangerous

class MyTaskExecutor
    ScheduledExecutorService executorService = Executors.newScheduledThreadPool(1);
    MyTask myTask;
    volatile boolean isStopIssued;

    public MyTaskExecutor(MyTask myTask$) 
        myTask = myTask$;


    public void startExecutionAt(int targetHour, int targetMin, int targetSec)
        Runnable taskWrapper = new Runnable(){

            public void run() 
                startExecutionAt(targetHour, targetMin, targetSec);

        long delay = computeNextDelay(targetHour, targetMin, targetSec);
        executorService.schedule(taskWrapper, delay, TimeUnit.SECONDS);

    private long computeNextDelay(int targetHour, int targetMin, int targetSec) 
        LocalDateTime localNow =;
        ZoneId currentZone = ZoneId.systemDefault();
        ZonedDateTime zonedNow = ZonedDateTime.of(localNow, currentZone);
        ZonedDateTime zonedNextTarget = zonedNow.withHour(targetHour).withMinute(targetMin).withSecond(targetSec);
        if(zonedNow.compareTo(zonedNextTarget) > 0)
            zonedNextTarget = zonedNextTarget.plusDays(1);

        Duration duration = Duration.between(zonedNow, zonedNextTarget);
        return duration.getSeconds();

    public void stop()
        try {
            executorService.awaitTermination(1, TimeUnit.DAYS);
        } catch (InterruptedException ex) {
            Logger.getLogger(MyTaskExecutor.class.getName()).log(Level.SEVERE, null, ex);


  • MyTask is an interface with function execute.
  • While stopping ScheduledExecutorService, Always use awaitTermination after invoking shutdown on it: There's always a likelihood your task is stuck / deadlocking and the user would wait forever.

The previous example I gave with Calender was just an idea which I did mention, I avoided exact time calculation and Daylight saving issues. Updated the solution on per the complain of @PaddyD

How to save all files from source code of a web site?

In Chrome, go to options (Customize and Control, the 3 dots/bars at top right) ---> More Tools ---> save page as

save page as  
filename     : any_name.html 
save as type : webpage complete.

Then you will get any_name.html and any_name folder.

What is difference between CrudRepository and JpaRepository interfaces in Spring Data JPA?

Ken's answer is basically right but I'd like to chime in on the "why would you want to use one over the other?" part of your question.


The base interface you choose for your repository has two main purposes. First, you allow the Spring Data repository infrastructure to find your interface and trigger the proxy creation so that you inject instances of the interface into clients. The second purpose is to pull in as much functionality as needed into the interface without having to declare extra methods.

The common interfaces

The Spring Data core library ships with two base interfaces that expose a dedicated set of functionalities:

  • CrudRepository - CRUD methods
  • PagingAndSortingRepository - methods for pagination and sorting (extends CrudRepository)

Store-specific interfaces

The individual store modules (e.g. for JPA or MongoDB) expose store-specific extensions of these base interfaces to allow access to store-specific functionality like flushing or dedicated batching that take some store specifics into account. An example for this is deleteInBatch(…) of JpaRepository which is different from delete(…) as it uses a query to delete the given entities which is more performant but comes with the side effect of not triggering the JPA-defined cascades (as the spec defines it).

We generally recommend not to use these base interfaces as they expose the underlying persistence technology to the clients and thus tighten the coupling between them and the repository. Plus, you get a bit away from the original definition of a repository which is basically "a collection of entities". So if you can, stay with PagingAndSortingRepository.

Custom repository base interfaces

The downside of directly depending on one of the provided base interfaces is two-fold. Both of them might be considered as theoretical but I think they're important to be aware of:

  1. Depending on a Spring Data repository interface couples your repository interface to the library. I don't think this is a particular issue as you'll probably use abstractions like Page or Pageable in your code anyway. Spring Data is not any different from any other general purpose library like commons-lang or Guava. As long as it provides reasonable benefit, it's just fine.
  2. By extending e.g. CrudRepository, you expose a complete set of persistence method at once. This is probably fine in most circumstances as well but you might run into situations where you'd like to gain more fine-grained control over the methods expose, e.g. to create a ReadOnlyRepository that doesn't include the save(…) and delete(…) methods of CrudRepository.

The solution to both of these downsides is to craft your own base repository interface or even a set of them. In a lot of applications I have seen something like this:

interface ApplicationRepository<T> extends PagingAndSortingRepository<T, Long> { }

interface ReadOnlyRepository<T> extends Repository<T, Long> {

  // Al finder methods go here

The first repository interface is some general purpose base interface that actually only fixes point 1 but also ties the ID type to be Long for consistency. The second interface usually has all the find…(…) methods copied from CrudRepository and PagingAndSortingRepository but does not expose the manipulating ones. Read more on that approach in the reference documentation.

Summary - tl;dr

The repository abstraction allows you to pick the base repository totally driven by you architectural and functional needs. Use the ones provided out of the box if they suit, craft your own repository base interfaces if necessary. Stay away from the store specific repository interfaces unless unavoidable.

extract the date part from DateTime in C#

When comparing only the date of the datatimes, use the Date property. So this should work fine for you

datetime1.Date == datetime2.Date

What does .pack() do?

The pack() method is defined in Window class in Java and it sizes the frame so that all its contents are at or above their preferred sizes.

Why and when to use angular.copy? (Deep Copy)

When using angular.copy, instead of updating the reference, a new object is created and assigned to the destination(if a destination is provided). But there's more. There's this cool thing that happens after a deep copy.

Say you have a factory service which has methods which updates factory variables.

angular.module('test').factory('TestService', [function () {
    var o = {
        shallow: [0,1], // initial value(for demonstration)
        deep: [0,2] // initial value(for demonstration)
    o.shallowCopy = function () {
        o.shallow = [1,2,3]
    o.deepCopy = function () {
        angular.copy([4,5,6], o.deep);
    return o;

and a controller which uses this service,

angular.module('test').controller('Ctrl', ['TestService', function (TestService) {
     var shallow = TestService.shallow;
     var deep = TestService.deep;

     console.log('****Printing initial values');


     console.log('****Printing values after service method execution');

     console.log('****Printing service variables directly');

When the above program is run the output will be as follows,

****Printing initial values

****Printing values after service method execution

****Printing service variables directly

Thus the cool thing about using angular copy is that, the references of the destination are reflected with the change of values, without having to re-assign the values manually, again.

What's the difference between xsd:include and xsd:import?

The fundamental difference between include and import is that you must use import to refer to declarations or definitions that are in a different target namespace and you must use include to refer to declarations or definitions that are (or will be) in the same target namespace.


unable to start mongodb local server

Try a different port if you can't find any current running processes or killing them doesn't work. For example, try 27018 because the default is 27017.

mongod  --port 27018

I found this out with the command, mongod --help

Dump all documents of Elasticsearch

The data itself is one or more lucene indices, since you can have multiple shards. What you also need to backup is the cluster state, which contains all sorts of information regarding the cluster, the available indices, their mappings, the shards they are composed of etc.

It's all within the data directory though, you can just copy it. Its structure is pretty intuitive. Right before copying it's better to disable automatic flush (in order to backup a consistent view of the index and avoiding writes on it while copying files), issue a manual flush, disable allocation as well. Remember to copy the directory from all nodes.

Also, next major version of elasticsearch is going to provide a new snapshot/restore api that will allow you to perform incremental snapshots and restore them too via api. Here is the related github issue:

Entity Framework Core: A second operation started on this context before a previous operation completed

I managed to get that error by passing an IQueryable into a method that then used that IQueryable 'list' as part of a another query to the same context.

public void FirstMethod()
    // This is returning an IQueryable
    var stockItems = _dbContext.StockItems
        .Where(st => st.IsSomething);


public void SecondMethod(IEnumerable<Stock> stockItems)
    var grnTrans = _dbContext.InvoiceLines
        .Where(il => stockItems.Contains(il.StockItem))

To stop that happening I used the approach here and materialised that list before passing it the second method, by changing the call to SecondMethod to be SecondMethod(stockItems.ToList()

Access maven properties defined in the pom

You can parse the pom file with JDOM (

How to send email to multiple recipients using python smtplib?

import smtplib
from email.mime.multipart import MIMEMultipart
from email.mime.text import MIMEText

def sender(recipients): 

    body = 'Your email content here'
    msg = MIMEMultipart()

    msg['Subject'] = 'Email Subject'
    msg['From'] = '[email protected]'
    msg['To'] = (', ').join(recipients.split(','))


    server = smtplib.SMTP('', 587)
    server.login('[email protected]', 'yourpassword')

if __name__ == '__main__':
    sender('[email protected],[email protected]')

It only worked for me with send_message function and using the join function in the list whith recipients, python 3.6.

SQL Server replace, remove all after certain character

Could use CASE WHEN to leave those with no ';' alone.

    LEFT(MyText, CHARINDEX(';', MyText)-1) ELSE
    MyText END
    FROM MyTable

Can the jQuery UI Datepicker be made to disable Saturdays and Sundays (and holidays)?

These answers were very helpful. Thank you.

My contribution below adds an array where multiple days can return false (we're closed every Tuesday, Wednesday and Thursday). And I bundled the specific dates plus years and the no-weekends functions.

If you want weekends off, add [Saturday], [Sunday] to the closedDays array.


        beforeShowDay: nonWorkingDates,
        numberOfMonths: 1,
        minDate: '05/01/09',
        maxDate: '+2M',
        firstDay: 1

    function nonWorkingDates(date){
        var day = date.getDay(), Sunday = 0, Monday = 1, Tuesday = 2, Wednesday = 3, Thursday = 4, Friday = 5, Saturday = 6;
        var closedDates = [[7, 29, 2009], [8, 25, 2010]];
        var closedDays = [[Monday], [Tuesday]];
        for (var i = 0; i < closedDays.length; i++) {
            if (day == closedDays[i][0]) {
                return [false];


        for (i = 0; i < closedDates.length; i++) {
            if (date.getMonth() == closedDates[i][0] - 1 &&
            date.getDate() == closedDates[i][1] &&
            date.getFullYear() == closedDates[i][2]) {
                return [false];

        return [true];


How to empty a file using Python

Opening a file creates it and (unless append ('a') is set) overwrites it with emptyness, such as this:

open(filename, 'w').close()

How do I pass data between Activities in Android application?

I recently released Vapor API, a jQuery flavored Android framework that makes all sorts of tasks like this simpler. As mentioned, SharedPreferences is one way you could do this.

VaporSharedPreferences is implemented as Singleton so that is one option, and in Vapor API it has a heavily overloaded .put(...) method so you don't have to explicitly worry about the datatype you are committing - providing it is supported. It is also fluent, so you can chain calls:

$.prefs(...).put("val1", 123).put("val2", "Hello World!").put("something", 3.34);

It also optionally autosaves changes, and unifies the reading and writing process under-the-hood so you don't need to explicitly retrieve an Editor like you do in standard Android.

Alternatively you could use an Intent. In Vapor API you can also use the chainable overloaded .put(...) method on a VaporIntent:

$.Intent().put("data", "myData").put("more", 568)...

And pass it as an extra, as mentioned in the other answers. You can retrieve extras from your Activity, and furthermore if you are using VaporActivity this is done for you automatically so you can use:


To retrieve them at the other end in the Activity you switch to.

Hope that is of interest to some :)

How to copy a file along with directory structure/path using python?

To create all intermediate-level destination directories you could use os.makedirs() before copying:

import os
import shutil

srcfile = 'a/long/long/path/to/'
dstroot = '/home/myhome/new_folder'

assert not os.path.isabs(srcfile)
dstdir =  os.path.join(dstroot, os.path.dirname(srcfile))

os.makedirs(dstdir) # create all directories, raise an error if it already exists
shutil.copy(srcfile, dstdir)

How to tell git to use the correct identity (name and email) for a given project?

As of Git 2.13 you can use an includeIf in your gitconfig to include a file with a different configuration based on the path of the repository where you are running your git commands.

Since a new enough Git comes with Ubuntu 18.04 I've been using this in my ~/.gitconfig quite happily.

  path = ~/.gitconfig.alias # I like to keep global aliases separate
  path = ~/.gitconfig.defaultusername # can maybe leave values unset/empty to get warned if a below path didn't match
# If using multiple identities can use per path user/email
# The trailing / is VERY important, git won't apply the config to subdirectories without it
[includeIf "gitdir:~/projects/azure/"]
  path = ~/ # and for Azure
[includeIf "gitdir:~/projects/gitlab/"]
  path = ~/.gitconfig.gitlab # and for GitLab
[includeIf "gitdir:~/projects/foss/"]
  path = ~/.gitconfig.github # and for GitHub

To use Git 2.13 you will either need to add a PPA (Ubuntu older than 18.04/Debian) or download the binaries and install (Windows/other Linux).

How to install Anaconda on RaspBerry Pi 3 Model B

I was trying to run this on a pi zero. Turns out the pi zero has an armv6l architecture so the above won't work for pi zero or pi one. Alternatively here I learned that miniconda doesn't have a recent version of miniconda. Instead I used the same instructions posted here to install berryconda3

Conda is now working. Hope this helps those of you interested in running conda on the pi zero!

Apache Server (xampp) doesn't run on Windows 10 (Port 80)

I had the same issue and none of the above solutions worked for me.

Apache uses both ports 80 and 443 (for HTTPS) and both must be ready to be used for Apache to start successfully. Only port 80 might not be enough.

I found in my case that when running VMWare Workstation I had the port 443 used by the VMware sharing.

You have to disable sharing in the VMware main Preferences or change the port in this section.

After that as long as you have no other server hooked to the port 80 (see above solutions) then you should be able to start Apache or NGinx on XAMPP or any other Windows stack application.

I hope this will help other users.

How to make a node.js application run permanently?

I recommend use PM2, which is a process manager for Node.js applications. PM2 provides an easy way to manage and daemonize applications (run them as a service).

refer this link -

Measure execution time for a Java method

Check this: System.currentTimeMillis.

With this you can calculate the time of your method by doing:

long start = System.currentTimeMillis();
long time = System.currentTimeMillis() - start;

Check if a number has a decimal place/is a whole number

You can multiply it by 10 and then do a "modulo" operation/divison with 10, and check if result of that two operations is zero. Result of that two operations will give you first digit after the decimal point. If result is equal to zero then the number is a whole number.

if ( (int)(number * 10.0) % 10 == 0 ){
// your code

make bootstrap twitter dialog modal draggable

In my own case, i had to set backdrop and set the top and left properties before i could apply draggable function on the modal dialog. Maybe it might help someone ;)

if (!($('').length)) {       
     top: 0,
     left: 0
  backdrop: false,
   show: true

  handle: ".modal-header"

Postgresql GROUP_CONCAT equivalent?

Try like this:

select field1, array_to_string(array_agg(field2), ',')
from table1
group by field1;

bootstrap jquery event won't fire

In my case, I was missing the .modal-dialog div

Doesn't fire event:

<div id="loadingModal" class="modal fade">

Does fire event:

<div id="loadingModal" class="modal fade">
  <div class="modal-dialog">      

Difference between and e.currentTarget

  • is element, which you f.e. click
  • e.currentTarget is element with added event listener.

If you click on child element of button, its better to use currentTarget to detect buttons attributes, in CH its sometimes problem to use

MySQL string replace

The replace function should work for you.


Returns the string str with all occurrences of the string from_str replaced by the string to_str. REPLACE() performs a case-sensitive match when searching for from_str.

What is the '.well' equivalent class in Bootstrap 4

Card seems to be "discarded" LOL, I found the "well" not working with bootstrap 4.3.1 and jQuery v3.4.1, just working fine with bootstrap 4.3.1 and jQuery v3.3.1. Hope it helps.

Insert Update trigger how to determine if insert or update

just simple way


  select @vars = [column] from inserted 
  IF UPDATE([column]) BEGIN
    -- do update action base on @vars 
    -- do insert action base on @vars 


How to get folder path from file path with CMD

The accepted answer is helpful, but it isn't immediately obvious how to retrieve a filename from a path if you are NOT using passed in values. I was able to work this out from this thread, but in case others aren't so lucky, here is how it is done:

@echo off
setlocal enabledelayedexpansion enableextensions

set myPath=C:\Somewhere\Somewhere\SomeFile.txt
call :file_name_from_path result !myPath!
echo %result%
goto :eof

:file_name_from_path <resultVar> <pathVar>
    set "%~1=%~nx2"
    exit /b


Now the :file_name_from_path function can be used anywhere to retrieve the value, not just for passed in arguments. This can be extremely helpful if the arguments can be passed into the file in an indeterminate order or the path isn't passed into the file at all.

How to store a dataframe using Pandas

Pandas DataFrames have the to_pickle function which is useful for saving a DataFrame:

import pandas as pd

a = pd.DataFrame({'A':[0,1,0,1,0],'B':[True, True, False, False, False]})
print a
#    A      B
# 0  0   True
# 1  1   True
# 2  0  False
# 3  1  False
# 4  0  False


b = pd.read_pickle('my_file.pkl')
print b
#    A      B
# 0  0   True
# 1  1   True
# 2  0  False
# 3  1  False
# 4  0  False

How do I seed a random class to avoid getting duplicate random values

Bit late, but the implementation used by System.Random is Environment.TickCount:

public Random() 
  : this(Environment.TickCount) {

This avoids having to cast DateTime.UtcNow.Ticks from a long, which is risky anyway as it doesn't represent ticks since system start, but "the number of 100-nanosecond intervals that have elapsed since 12:00:00 midnight, January 1, 0001 (0:00:00 UTC on January 1, 0001, in the Gregorian calendar)".

Was looking for a good integer seed for the TestApi's StringFactory.GenerateRandomString

Java - Convert integer to string

There are multiple ways:

  • String.valueOf(number) (my preference)
  • "" + number (I don't know how the compiler handles it, perhaps it is as efficient as the above)
  • Integer.toString(number)

The intel x86 emulator accelerator (HAXM installer) revision 6.0.5 is showing not compatible with windows

Try the following

  1. download HAXM from Intel

  2. Unzip the file and Run intelhaxm-android.exe.

  3. Run silent_install.bat.

In my computer Win10 x64 - VS2015 it worked

Automatically pass $event with ng-click?

Take a peek at the ng-click directive source:

compile: function($element, attr) {
  var fn = $parse(attr[directiveName]);
  return function(scope, element, attr) {
    element.on(lowercase(name), function(event) {
      scope.$apply(function() {
        fn(scope, {$event:event});

It shows how the event object is being passed on to the ng-click expression, using $event as a name of the parameter. This is done by the $parse service, which doesn't allow for the parameters to bleed into the target scope, which means the answer is no, you can't access the $event object any other way but through the callback parameter.

How do I create an executable in Visual Studio 2013 w/ C++?

Do ctrl+F5 to compile and run your project without debugging. Look at the output pane (defaults to "Show output from Build"). If it compiled successfully, the path to the .exe file should be there after {projectname}.vcxproj ->

Adding event listeners to dynamically added elements using jQuery

$(document).on('click', 'selector', handler);

Where click is an event name, and handler is an event handler, like reference to a function or anonymous function function() {}

PS: if you know the particular node you're adding dynamic elements to - you could specify it instead of document.

How can I check whether a radio button is selected with JavaScript?

There is very sophisticated way you can validate whether any of the radio buttons are checked with ECMA6 and method .some().


<input type="radio" name="status" id="marriedId" value="Married" />
<input type="radio" name="status" id="divorcedId" value="Divorced" />

And javascript:

let htmlNodes = document.getElementsByName('status');

let radioButtonsArray = Array.from(htmlNodes);

let isAnyRadioButtonChecked = radioButtonsArray.some(element => element.checked);

isAnyRadioButtonChecked will be true if some of the radio buttons are checked and false if neither of them are checked.

Print a string as hex bytes?

Some complements to Fedor Gogolev answer:

First, if the string contains characters whose 'ASCII code' is below 10, they will not be displayed as required. In that case, the correct format should be {:02x}:

>>> s = "Hello unicode \u0005 !!"
>>> ":".join("{0:x}".format(ord(c)) for c in s)

>>> ":".join("{:02x}".format(ord(c)) for c in s)

Second, if your "string" is in reality a "byte string" -- and since the difference matters in Python 3 -- you might prefer the following:

>>> s = b"Hello bytes \x05 !!"
>>> ":".join("{:02x}".format(c) for c in s)

Please note there is no need for conversion in the above code as a bytes objects is defined as "an immutable sequence of integers in the range 0 <= x < 256".

show all tags in git log

Note: the commit 5e1361c from brian m. carlson (bk2204) (for git 1.9/2.0 Q1 2014) deals with a special case in term of log decoration with tags:

log: properly handle decorations with chained tags

git log did not correctly handle decorations when a tag object referenced another tag object that was no longer a ref, such as when the second tag was deleted.
The commit would not be decorated correctly because parse_object had not been called on the second tag and therefore its tagged field had not been filled in, resulting in none of the tags being associated with the relevant commit.

Call parse_object to fill in this field if it is absent so that the chain of tags can be dereferenced and the commit can be properly decorated.
Include tests as well to prevent future regressions.


git tag -a tag1 -m tag1 &&
git tag -a tag2 -m tag2 tag1 &&
git tag -d tag1 &&
git commit --amend -m shorter &&
git log --no-walk --tags --pretty="%H %d" --decorate=full

Javascript/jQuery detect if input is focused

If you can use JQuery, then using the JQuery :focus selector will do the needful


typeof !== "undefined" vs. != null

if (input == undefined) { ... }

works just fine. It is of course not a null comparison, but I usually find that if I need to distinguish between undefined and null, I actually rather need to distinguish between undefined and just any false value, so

else if (input) { ... }

does it.

If a program redefines undefined it is really braindead anyway.

The only reason I can think of was for IE4 compatibility, it did not understand the undefined keyword (which is not actually a keyword, unfortunately), but of course values could be undefined, so you had to have this:

var undefined;

and the comparison above would work just fine.

In your second example, you probably need double parentheses to make lint happy?

How can I get the current user's username in Bash?

An alternative to whoami is id -u -n.

id -u will return the user id (e.g. 0 for root).

What's the "average" requests per second for a production web application?

That is a very open apples-to-oranges type of question.

You are asking 1. the average request load for a production application 2. what is considered fast

These don't neccessarily relate.

Your average # of requests per second is determined by

a. the number of simultaneous users

b. the average number of page requests they make per second

c. the number of additional requests (i.e. ajax calls, etc)

As to what is considered fast.. do you mean how few requests a site can take? Or if a piece of hardware is considered fast if it can process xyz # of requests per second?

Show "loading" animation on button click


 //show loading gif

   //remove gif
  error:function(){//remove gif}


EDIT: after reading the comments

in case you decide against ajax

     //show loading gif

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)"

Passing event and argument to v-on in Vue.js

Depending on what arguments you need to pass, especially for custom event handlers, you can do something like this:

<div @customEvent='(arg1) => myCallback(arg1, arg2)'>Hello!</div>

Creating a daemon in Linux

A daemon is just a process in the background. If you want to start your program when the OS boots, on linux, you add your start command to /etc/rc.d/rc.local (run after all other scripts) or /etc/

On windows, you make a service, register the service, and then set it to start automatically at boot in administration -> services panel.

How to execute a program or call a system command from Python

To fetch the network id from the OpenStack Neutron:

import os
netid = "nova net-list | awk '/ External / { print $2 }'"
temp = os.popen(netid).read()  /* Here temp also contains new line (\n) */
networkId = temp.rstrip()

Output of nova net-list

| ID                                   | Label      | CIDR |
| 431c9014-5b5d-4b51-a357-66020ffbb123 | test1      | None |
| 27a74fcd-37c0-4789-9414-9531b7e3f126 | External   | None |
| 5a2712e9-70dc-4b0e-9281-17e02f4684c9 | management | None |
| 7aa697f5-0e60-4c15-b4cc-9cb659698512 | Internal   | None |

Output of print(networkId)


"register" keyword in C?

You are messing with the compiler's sophisticated graph-coloring algorithm. This is used for register allocation. Well, mostly. It acts as a hint to the compiler -- that's true. But not ignored in its entirety since you are not allowed to take the address of a register variable (remember the compiler, now on your mercy, will try to act differently). Which in a way is telling you not to use it.

The keyword was used long, long back. When there were only so few registers that could count them all using your index finger.

But, as I said, deprecated doesn't mean you cannot use it.

jQuery using append with effects

Something like:

$('#test').append('<div id="newdiv">Hello</div>').hide().show('slow');

should do it?

Edit: sorry, mistake in code and took Matt's suggestion on board too.

Get first 100 characters from string, respecting full words

All you need to do is use:

$pos=strpos($content, ' ', 200);
substr($content,0,$pos ); 

JavaScript: Class.method vs. Class.prototype.method

Yes, the first function has no relationship with an object instance of that constructor function, you can consider it like a 'static method'.

In JavaScript functions are first-class objects, that means you can treat them just like any object, in this case, you are only adding a property to the function object.

The second function, as you are extending the constructor function prototype, it will be available to all the object instances created with the new keyword, and the context within that function (the this keyword) will refer to the actual object instance where you call it.

Consider this example:

// constructor function
function MyClass () {
  var privateVariable; // private member only available within the constructor fn

  this.privilegedMethod = function () { // it can access private members

// A 'static method', it's just like a normal function 
// it has no relation with any 'MyClass' object instance
MyClass.staticMethod = function () {};

MyClass.prototype.publicMethod = function () {
  // the 'this' keyword refers to the object instance
  // you can access only 'privileged' and 'public' members

var myObj = new MyClass(); // new object instance


How can I add a class to a DOM element in JavaScript?

    document.getElementById('add-Box').addEventListener('click', function (event) {
        let itemParent = document.getElementById('box-Parent');
        let newItem = document.createElement('li');
        newItem.className = 'box';

No resource identifier found for attribute '...' in package ''

I was facing the same problem and solved it using the below steps:

Add this in your app's build.gradle

android {
    defaultConfig {
        vectorDrawables.useSupportLibrary = true

Use namespace:


Then use:


Replace multiple whitespaces with single whitespace in JavaScript string

var x = " Test Test Test ".split(" ").join(""); alert(x);

SyntaxError: expected expression, got '<'

May be this helps someone. The error I was getting was

SyntaxError: expected expression, got '<'

What I did clicked on view source in chrome and there I found this error

Notice: Undefined variable: string in D:\Projects\demo\ge.php on line 66

The issue was this snippet of code,

$string= ''; <---- this should be declared outside the loop

while($row = mysql_fetch_assoc($result))
        $string .= '{ id:'.$row['menu_id'].', pId:'.$row['parent_id'].', name:"'.$row['menu_name'].'"},';

which fixed the problem.