Programs & Examples On #Viewwillappear

UIViewController instance method that notifies the view controller that its view is about to be added to a view hierarchy.

UIViewController viewDidLoad vs. viewWillAppear: What is the proper division of labor?

viewDidLoad is things you have to do once. viewWillAppear gets called every time the view appears. You should do things that you only have to do once in viewDidLoad - like setting your UILabel texts. However, you may want to modify a specific part of the view every time the user gets to view it, e.g. the iPod application scrolls the lyrics back to the top every time you go to the "Now Playing" view.

However, when you are loading things from a server, you also have to think about latency. If you pack all of your network communication into viewDidLoad or viewWillAppear, they will be executed before the user gets to see the view - possibly resulting a short freeze of your app. It may be good idea to first show the user an unpopulated view with an activity indicator of some sort. When you are done with your networking, which may take a second or two (or may even fail - who knows?), you can populate the view with your data. Good examples on how this could be done can be seen in various twitter clients. For example, when you view the author detail page in Twitterrific, the view only says "Loading..." until the network queries have completed.

Why does viewWillAppear not get called when an app comes back from the background?


Short answer

Use a NotificationCenter observer rather than viewWillAppear.

override func viewDidLoad() {

    // set observer for UIApplication.willEnterForegroundNotification
    NotificationCenter.default.addObserver(self, selector: #selector(willEnterForeground), name: UIApplication.willEnterForegroundNotification, object: nil)


// my selector that was defined above
@objc func willEnterForeground() {
    // do stuff

Long answer

To find out when an app comes back from the background, use a NotificationCenter observer rather than viewWillAppear. Here is a sample project that shows which events happen when. (This is an adaptation of this Objective-C answer.)

import UIKit
class ViewController: UIViewController {

    // MARK: - Overrides

    override func viewDidLoad() {
        print("view did load")

        // add notification observers
        NotificationCenter.default.addObserver(self, selector: #selector(didBecomeActive), name: UIApplication.didBecomeActiveNotification, object: nil)
        NotificationCenter.default.addObserver(self, selector: #selector(willEnterForeground), name: UIApplication.willEnterForegroundNotification, object: nil)


    override func viewWillAppear(_ animated: Bool) {
        print("view will appear")

    override func viewDidAppear(_ animated: Bool) {
        print("view did appear")

    // MARK: - Notification oberserver methods

    @objc func didBecomeActive() {
        print("did become active")

    @objc func willEnterForeground() {
        print("will enter foreground")


On first starting the app, the output order is:

view did load
view will appear
did become active
view did appear

After pushing the home button and then bringing the app back to the foreground, the output order is:

will enter foreground
did become active 

So if you were originally trying to use viewWillAppear then UIApplication.willEnterForegroundNotification is probably what you want.


As of iOS 9 and later, you don't need to remove the observer. The documentation states:

If your app targets iOS 9.0 and later or macOS 10.11 and later, you don't need to unregister an observer in its dealloc method.

How do I download code using SVN/Tortoise from Google Code?

  • Download the svn binaries
  • unpack them somewhere and add the bin folder to your PATH environment variable
  • open a command line console (cmd.exe)
  • enter than "svn checkout ...." command there
    • make sure to first cd to the place where you want to download (i.e checkout) the projects' code.

Easiest way to activate PHP and MySQL on Mac OS 10.6 (Snow Leopard), 10.7 (Lion), 10.8 (Mountain Lion)?

There's a great guide here:

However, it didn't work for me first try. I found this tip: run "httpd -t" in Terminao to check the syntax of your config files. Turns out using copy & paste from the tutorial introduced some strange characters. After fixing this, it worked great. There are some links from the guide for adding MySQL as well.

This worked much better for me than MAMP. With MAMP, I was having delays of about 20 seconds or so before changes to the .php file would be reflected in the browser when you refresh, even if you cleared the cache, history, cookies, etc.

This problem was resolved in MAMP PRO, but MAMP PRO had a new issue of its own: the .php files would be downloaded instead of being rendered as a page in the browser! I contacted support and they didn't know what was going on.

The built-in Apache server didn't have any of these issues. Definitely the way to go. The guide below is almost identical to the one above, but it has user comments that are helpful:

Delete file from internal storage

This is an old topic, but I will add my experience, maybe someone finds this helpful

>     2019-11-12 20:05:50.178 27764-27764/com.strba.myapplicationx I/File: /storage/emulated/0/Android/data/com.strba.myapplicationx/files/Readings/JPEG_20191112_200550_4444350520538787768.jpg//file when it was created

2019-11-12 20:05:58.801 27764-27764/com.strba.myapplicationx I/File: content://com.strba.myapplicationx.fileprovider/my_images/JPEG_20191112_200550_4444350520538787768.jpg //same file when trying to delete it


              Uri uriDelete=Uri.parse (adapter.getNoteAt (viewHolder.getAdapterPosition ()).getImageuri ());//getter getImageuri on my object from adapter that returns String with content uri

here I initialize Content resolver and delete it with a passed parameter of that URI

            ContentResolver contentResolver = getContentResolver ();
            contentResolver.delete (uriDelete,null ,null );

solution2(my first solution-from head in this time I do know that ): content resolver exists...

              String path = "/storage/emulated/0/Android/data/com.strba.myapplicationx/files/Readings/" +
                    adapter.getNoteAt (viewHolder.getAdapterPosition ()).getImageuri ().substring (58);

            File file = new File (path);
            if (file != null) {
                file.delete ();

Hope that this will be helpful to someone happy coding

How to get param from url in angular 4?

Check parameters from URL string or as :param in your routeConfig


import {Router,ActivatedRoute} from '@angular/router';
export class DownstreamComponent  {
    private route: ActivatedRoute,
    private router: Router
) {
      console.log(this.route.snapshot.params); // e.g. :param1 in routeConfig
      console.log(this.route.snapshot.queryParamMap.get('param1')); // e.g. in URI ?param1=blah


rebase in progress. Cannot commit. How to proceed or stop (abort)?

I got stuck in 'rebase status', I got

On branch master
Your branch is up to date with 'origin/master'.

You are currently rebasing.
  (all conflicts fixed: run "git rebase --continue")

nothing to commit, working tree clean

but running git rebase --skip yielded error: could not read '.git/rebase-apply/head-name': No such file or directory.

Running rm -fr ".git/rebase-apply" helped.

Note: of course, do it only if you don't care about the rebase or if you're stuck on a previous rebase you don't want anymore.

MySQL: Insert datetime into other datetime field

If you don't need the DATETIME value in the rest of your code, it'd be more efficient, simple and secure to use an UPDATE query with a sub-select, something like

UPDATE products SET t=(SELECT f FROM products WHERE id=17) WHERE id=42;

or in case it's in the same row in a single table, just

UPDATE products SET t=f WHERE id=42;

Batch: Remove file extension

In case the file your variable holds doesn't actually exist the FOR approach won't work. One trick you could use, if you know the length of the extension, is taking a substring:


the -4 means that the last 4 digits (presumably .ext) will be truncated.

How to validate phone number using PHP?

I depends heavily on which number formats you aim to support, and how strict you want to enforce number grouping, use of whitespace and other separators etc....

Take a look at this similar question to get some ideas.

Then there is E.164 which is a numbering standard recommendation from ITU-T

How do I make an input field accept only letters in javaScript?

dep and clg alphabets validation is not working

var selectedRow = null;

function validateform() {

  var table = document.getElementById("mytable");
  var rowCount = table.rows.length;

  var x = document.forms["myform"]["usrname"].value;
  if (x == "") {
    alert("name must be filled out");
    return false;

  var y = document.forms["myform"]["usremail"].value;
  if (y == "") {
    alert("email must be filled out");
    return false;
  var mail = /[^@]+@[a-zA-Z]+\.[a-zA-Z]{2,6}/
  if (mail.test(y)) {
    //alert("email must be a valid format");
    //return false ;
  } else {
    alert("not a mail id")
    return false;

  var z = document.forms["myform"]["usrage"].value;
  if (z == "") {
    alert("age must be filled out");
    return false;

  if (isNaN(z) || z < 1 || z > 100) {
    alert("The age must be a number between 1 and 100");
    return false;

  var a = document.forms["myform"]["usrdpt"].value;
  if (a == "") {
    alert("Dept must be filled out");
    return false;

  var dept = "`@#$%^&*()+=-[]\\\';,./{}|\":<>?~_";
  if (dept.match(a)) {
    alert("special charachers found");
    return false;

  var b = document.forms["myform"]["usrclg"].value;
  if (b == "") {
    alert("College must be filled out");
    return false;
  var row = table.insertRow(rowCount);
  row.setAttribute('id', rowCount);
  var cell0 = row.insertCell(0);
  var cell1 = row.insertCell(1);
  var cell2 = row.insertCell(2);
  var cell3 = row.insertCell(3);
  var cell4 = row.insertCell(4);
  var cell5 = row.insertCell(5);
  var cell6 = row.insertCell(6);
  var cell7 = row.insertCell(7);

  cell0.innerHTML = rowCount;
  cell1.innerHTML = x;
  cell2.innerHTML = y;
  cell3.innerHTML = z;
  cell4.innerHTML = a;
  cell5.innerHTML = b;
  cell6.innerHTML = '<Button type="button" onclick=onEdit("' + x + '","' + y + '","' + z + '","' + a + '","' + b + '","' + rowCount + '")>Edit</BUTTON>';
  cell7.innerHTML = '<Button type="button" onclick=deletefunction(' + rowCount + ')>Delete</BUTTON>';


function emptyfunction() {
  document.getElementById("usrname").value = "";
  document.getElementById("usremail").value = "";
  document.getElementById("usrage").value = "";
  document.getElementById("usrdpt").value = "";
  document.getElementById("usrclg").value = "";

function onEdit(x, y, z, a, b, rowCount) {
  selectedRow = rowCount;
  document.forms["myform"]["usrname"].value = x;
  document.forms["myform"]["usremail"].value = y;
  document.forms["myform"]["usrage"].value = z;
  document.forms["myform"]["usrdpt"].value = a;
  document.forms["myform"]["usrclg"].value = b;
  document.getElementById('Add').style.display = 'none';
  document.getElementById('update').style.display = 'block';

function deletefunction(rowCount) {

function onUpdatefunction() {
  var row = document.getElementById(selectedRow);

  var x = document.forms["myform"]["usrname"].value;
  if (x == "") {
    alert("name must be filled out");
    return false;

  var y = document.forms["myform"]["usremail"].value;
  if (y == "") {
    alert("email must be filled out");
    return false;

  var mail = /[^@]+@[a-zA-Z]+\.[a-zA-Z]{2,6}/
  if (mail.test(y)) {
    //alert("email must be a valid format");
    //return false ;
  } else {
    alert("not a mail id");

    return false;

  var z = document.forms["myform"]["usrage"].value;
  if (z == "") {
    alert("age must be filled out");
    return false;
  if (isNaN(z) || z < 1 || z > 100) {
    alert("The age must be a number between 1 and 100");
    return false;

  var a = document.forms["myform"]["usrdpt"].value;
  if (a == "") {
    alert("Dept must be filled out");
    return false;
  var letters = /^[A-Za-z]+$/;
  if (a.test(letters)) {
    //Your logice will be here.
  } else {
    alert("Please enter only alphabets");
    return false;

  var b = document.forms["myform"]["usrclg"].value;
  if (b == "") {
    alert("College must be filled out");
    return false;
  var letters = /^[A-Za-z]+$/;
  if (b.test(letters)) {
    //Your logice will be here.
  } else {
    alert("Please enter only alphabets");
    return false;

  row.cells[1].innerHTML = x;
  row.cells[2].innerHTML = y;
  row.cells[3].innerHTML = z;
  row.cells[4].innerHTML = a;
  row.cells[5].innerHTML = b;


  <form name="myform">
      <center> Admission form </center>
        <td>Name :</td>
        <td><input type="text" name="usrname" PlaceHolder="Enter Your First Name" required></td>

        <td> Email ID :</td>
        <td><input type="text" name="usremail" PlaceHolder="Enter Your email address" pattern="[^@]+@[a-zA-Z]+\.[a-zA-Z]{2,6}" required></td>

        <td>Age :</td>
        <td><input type="number" name="usrage" PlaceHolder="Enter Your Age" required></td>

        <td>Dept :</td>
        <td><input type="text" name="usrdpt" PlaceHolder="Enter Dept"></td>

        <td>College :</td>
        <td><input type="text" name="usrclg" PlaceHolder="Enter college"></td>

          <Button type="button" onclick="validateform()" id="Add">Add</button>
          <Button type="button" onclick="onUpdatefunction()" style="display:none;" id="update">update</button>
        <td><button type="reset">Reset</button></td>
      <table id="mytable" border="1">
          <th>Email ID</th>



For MySQL, you can do it like this:

CREATE TABLE New_Users   SELECT * FROM Old_Users group by ID;

Programmatically stop execution of python script?

You could raise SystemExit(0) instead of going to all the trouble to import sys; sys.exit(0).

How to generate List<String> from SQL query?

I think this is what you're looking for.

List<String> columnData = new List<String>();

using(SqlConnection connection = new SqlConnection("conn_string"))
    string query = "SELECT Column1 FROM Table1";
    using(SqlCommand command = new SqlCommand(query, connection))
        using (SqlDataReader reader = command.ExecuteReader())
            while (reader.Read())

Not tested, but this should work fine.

Adding an .env file to React Project

  1. Install dotenv as devDependencies:
npm i --save-dev dotenv
  1. Create a .env file in the root directory:
|- node-modules/
|- public/
|- src/
|- .env
|- .gitignore
|- package.json
|- package.lock.json.
  1. Update the .env file like below & REACT_APP_ is the compulsory prefix for the variable name.
  1. [ Optional but Good Practice ] Now you can create a configuration file to store the variables and export the variable so can use it from others file.

For example, I've create a file named base.js and update it like below:

export const BASE_URL = process.env.REACT_APP_BASE_URL;
export const API_KEY = process.env.REACT_APP_API_KEY;
  1. Or you can simply just call the environment variable in your JS file in the following way:

Stylesheet not updating

First, try to Force reload or Clear cache and Empty chase and hard reload. You can do it by pressing F12 and then by right-clicking on it.

2nd Solution: Check your HTML base tag. You can learn more about it from here.

ToList()-- does it create a new list?

In the case where the source object is a true IEnumerable (i.e. not just a collection packaged an as enumerable), ToList() may NOT return the same object references as in the original IEnumerable. It will return a new List of objects, but those objects may not be the same or even Equal to the objects yielded by the IEnumerable when it is enumerated again

Bootstrap carousel resizing image

Give class img-fluid to your div carousel-item.Finally it will be:

<div class="carousel-item active img-fluid">
      <img class="d-block w-100" src="path to image" alt="First slide">

How to skip to next iteration in jQuery.each() util?

jQuery.noop() can help

$(".row").each( function() {
    if (skipIteration) {

Babel 6 regeneratorRuntime is not defined

Just install:

npm install --save-dev @babel/plugin-transform-runtime

and add it to the plugins array of Babel.

"Cross origin requests are only supported for HTTP." error when loading a local file

For all y'all on MacOS... setup a simple LaunchAgent to enable these glamorous capabilities in your own copy of Chrome...

Save a plist, named whatever (, for example) in ~/Library/LaunchAgents with similar content to...

<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "">
<plist version="1.0">
        <string>/Applications/Google Chrome</string>

It should launch at startup.. but you can force it to do so at any time with the terminal command

launchctl load -w ~/Library/LaunchAgents/


Group a list of objects by an attribute

You can sort like this:

    Collections.sort(studlist, new Comparator<Student>() {

        public int compare(Student o1, Student o2) {
            return o1.getStud_location().compareTo(o2.getStud_location());

Assuming you also have the getter for location on your Student class.

New xampp security concept: Access Forbidden Error 403 - Windows 7 - phpMyAdmin

Comment out the line Require local in httpd-xampp.conf.
Restart Apache.
Worked for me connecting my mobile phone to my test web-site on my PC. No idea of the security implications.

How to configure WAMP (localhost) to send email using Gmail?

It's quite simple. (Adapt syntax for your convenience)

public $smtp = array(
    'transport' => 'Smtp',
    'from' => '[email protected]',
    'host' => 'ssl://',
    'port' => 465,
    'timeout' => 30,
    'username' => '[email protected]',
    'password' => '*****'

Adding attributes to an XML node

If you serialize the object that you have, you can do something like this by using "System.Xml.Serialization.XmlAttributeAttribute" on every property that you want to be specified as an attribute in your model, which in my opinion is a lot easier:

[System.Xml.Serialization.XmlTypeAttribute(AnonymousType = true)]
public class UserNode
    public string userName { get; set; }

    public string passWord { get; set; }

    public int Age { get; set; }
    public string Name { get; set; }         

 public class LoginNode 
    public UserNode id { get; set; }

Then you just serialize to XML an instance of LoginNode called "Login", and that's it!

Here you have a few examples to serialize and object to XML, but I would suggest to create an extension method in order to be reusable for other objects.

How does bitshifting work in Java?

byte x = 51; //00101011
byte y = (byte) (x >> 2); //00001010 aka Base(10) 10

cannot make a static reference to the non-static field

You are trying to access non static field directly from static method which is not legal in java. balance is a non static field, so either access it using object reference or make it static.

AJAX Mailchimp signup form integration

Based on gbinflames' answer, I kept the POST and URL, so that the form would continue to work for those with JS off.

<form class="myform" action="" method="POST">
  <input type="hidden" name="u" value="XXXXXXXXXXXXXXXX">
  <input type="hidden" name="id" value="XXXXXXXXX">
  <input class="input" type="text" value="" name="MERGE1" placeholder="First Name" required>
  <input type="submit" value="Send" name="submit" id="mc-embedded-subscribe">

Then, using jQuery's .submit() changed the type, and URL to handle JSON repsonses.

$('.myform').submit(function(e) {
  var $this = $(this);
      type: "GET", // GET & url for json slightly different
      url: "",
      data: $this.serialize(),
      dataType    : 'json',
      contentType: "application/json; charset=utf-8",
      error       : function(err) { alert("Could not connect to the registration server."); },
      success     : function(data) {
          if (data.result != "success") {
              // Something went wrong, parse data.msg string and display message
          } else {
              // It worked, so hide form and display thank-you message.
  return false;

C# Clear Session

The other big difference is Abandon does not remove items immediately, but when it does then cleanup it does a loop over session items to check for STA COM objects it needs to handle specially. And this can be a problem.

Under high load it's possible for two (or more) requests to make it to the server for the same session (that is two requests with the same session cookie). Their execution will be serialized, but since Abandon doesn't clear out the items synchronously but rather sets a flag it's possible for both requests to run, and both requests to schedule a work item to clear out session "later". Both these work items can then run at the same time, and both are checking the session objects, and both are clearing out the array of objects, and what happens when you have two things iterating over a list and changing it?? Boom! And since this happens in a queueuserworkitem callback and is NOT done in a try/catch (thanks MS), it will bring down your entire app domain. Been there.

Writing .csv files from C++

You must ";" separator, CSV => Comma Separator Value

 ofstream Morison_File ("linear_wave_loading.csv");         //Opening file to print info to
    Morison_File << "'Time'; 'Force(N/m)' " << endl;          //Headings for file
    for (t = 0; t <= 20; t++) {
      u = sin(omega * t);
      du = cos(omega * t); 
      F = (0.5 * rho * C_d * D * u * fabs(u)) + rho * Area * C_m * du; 

      cout << "t = " << t << "\t\tF = " << F << endl;
      Morison_File << t << ";" << F;



How to add reference to a method parameter in javadoc?

I guess you could write your own doclet or taglet to support this behaviour.

Taglet Overview

Doclet Overview

How do I pull my project from github?

Since you have wiped out your computer and want to checkout your project again, you could start by doing the below initial settings:

git config --global "Your Name"
git config --global [email protected]

Login to your github account, go to the repository you want to clone, and copy the URL under "Clone with HTTPS".

You can clone the remote repository by using HTTPS, even if you had setup SSH the last time:

git clone


If you had setup SSH for your remote repository previously, you will have to add that key to the known hosts ssh file on your PC; if you don't and try to do git clone [email protected]:username/repo-name.git, you will see an error similar to the one below:

Cloning into 'repo-name'...
The authenticity of host ' (' can't be established.
RSA key fingerprint is SHA256:nThbg6kXDoJWGl7E1IGOCspZomTxdCARLviMw6E5SY8.
Are you sure you want to continue connecting (yes/no/[fingerprint])? yes
Warning: Permanently added ',' (RSA) to the list of known hosts.
[email protected]: Permission denied (publickey).
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.

Using HTTPS is a easier than SSH in this case.

How to pass a parameter to routerLink that is somewhere inside the URL?

In your particular example you'd do the following routerLink:

[routerLink]="['user',, 'details']"

To do so in a controller, you can inject Router and use:

router.navigate(['user',, 'details']);

More info in the Angular docs Link Parameters Array section of Routing & Navigation

Deleting rows with Python in a CSV file

You should have if row[2] != "0". Otherwise it's not checking to see if the string value is equal to 0.

what is Promotional and Feature graphic in Android Market/Play Store?

I found this nice write-up that clears it up pretty nicely:

The different graphic assets we request are used to highlight and promote your application in Android Market, and possibly other Google-owned properties. If you’d like to restrict the marketing of your app to just Android Market, you have the option of opting-out of marketing by selecting the "Marketing Opt-Out" in the Developer Console.

Screenshots (Required):
We require 2 screenshots.
Use: Displayed on the details page for your application in Android Market.
You may upload up to 8 screenshots.
Specs: 320w x 480h, 480w x 800h, or 480w x 854h; 24 bit PNG or JPEG (no alpha) Full bleed, no border in art.
Landscape thumbnails are cropped, but we preserve the image’s full size and aspect ratio if the user opens it up on market client.
High Resolution Application Icon (Required):
Use: In various locations in Android Market.
Does not replace your launcher icon.
Specs: 512x512, 32-bit PNG with alpha; Max size of 1024KB.
This does not replace your launcher icon, but should be a higher-fidelity, higher-resolution version of your application icon.
Same safe-frame as current launcher guidelines, just scaled up:
Full Asset: 512 x 512 px.
Circle or non-square icons: 426 x 426 px, centered within the PNG.
Square Icons: 398 x 398 px.
Drop shadow: black, 75% opaque, 90 degrees down, distance of 14px, size of 36px.
Tweak as necessary to fit icon style (e.g., Google Maps icon has a drop shadow of varying height).
Promotional Graphic (Optional):
Use: In various locations in Android Market.
Specs: 180w x 120h, 24 bit PNG or JPEG (no alpha), Full bleed, no border in art.
Feature Graphic (Optional):
Use: The featured section in Android Market. Will be downsized to mini or micro.
Specs: 1024w x 500h, 24 bit PNG or JPEG (no alpha) with no transparency
Use a safe frame of 924x400 (50 pixel of safe padding on each side). All the important content of the graphic should be within this safe frame. Pixels outside of this safe frame may be cropped for stylistic purposes.
If incorporating text, use large font sizes, and keep the graphic simple, as this graphic may be scaled down from its original size.
This graphic may be displayed alone without the app icon.
Video Link (Optional):
Specs: Enter the URL to a YouTube video showcasing your app.
Short videos (30 seconds - 2 minutes) highlighting the top features of your app work best.

Deny access to one specific folder in .htaccess

You can create a .htaccess file for the folder, wich should have denied access with

Deny from  all

or you can redirect to a custom 404 page

Redirect /includes/ 404.html

How can I find non-ASCII characters in MySQL?

It depends exactly what you're defining as "ASCII", but I would suggest trying a variant of a query like this:

SELECT * FROM tableName WHERE columnToCheck NOT REGEXP '[A-Za-z0-9]';

That query will return all rows where columnToCheck contains any non-alphanumeric characters. If you have other characters that are acceptable, add them to the character class in the regular expression. For example, if periods, commas, and hyphens are OK, change the query to:

SELECT * FROM tableName WHERE columnToCheck NOT REGEXP '[A-Za-z0-9.,-]';

The most relevant page of the MySQL documentation is probably 12.5.2 Regular Expressions.

Why does adb return offline after the device string?

Check that the ADB version that you are running is newer than the version of the OS on the connected devices. For me, updating the ADB helped to get the device online.

How do I fetch lines before/after the grep result in bash?

You can use the -B and -A to print lines before and after the match.

grep -i -B 10 'error' data

Will print the 10 lines before the match, including the matching line itself.

Escaping backslash in string - javascript

I think this is closer to the answer you're looking for:

<input type="file">

$file = $(file);
var filename = fileElement[0].files[0].name;

Assert an object is a specific type

Solution for JUnit 5

The documentation says:

However, JUnit Jupiter’s org.junit.jupiter.Assertions class does not provide an assertThat() method like the one found in JUnit 4’s org.junit.Assert class which accepts a Hamcrest Matcher. Instead, developers are encouraged to use the built-in support for matchers provided by third-party assertion libraries.

Example for Hamcrest:

import static org.hamcrest.CoreMatchers.instanceOf;
import static org.hamcrest.MatcherAssert.assertThat;

import org.junit.jupiter.api.Test;

class HamcrestAssertionDemo {

    void assertWithHamcrestMatcher() {
        SubClass subClass = new SubClass();
        assertThat(subClass, instanceOf(BaseClass.class));


Example for AssertJ:

import static org.assertj.core.api.Assertions.assertThat;

import org.junit.jupiter.api.Test;

class AssertJDemo {

    void assertWithAssertJ() {
        SubClass subClass = new SubClass();


Note that this assumes you want to test behaviors similar to instanceof (which accepts subclasses). If you want exact equal type, I don’t see a better way than asserting the two class to be equal like you mentioned in the question.

Rename file with Git

Note that, from March 15th, 2013, you can move or rename a file directly from GitHub:

(you don't even need to clone that repo, git mv xx and git push back to GitHub!)


You can also move files to entirely new locations using just the filename field.
To navigate down into a folder, just type the name of the folder you want to move the file into followed by /.
The folder can be one that’s already part of your repository, or it can even be a brand-new folder that doesn’t exist yet!


WPF: Grid with column/row margin/padding?

You could use something like this:

<Style TargetType="{x:Type DataGridCell}">
  <Setter Property="Padding" Value="4" />
  <Setter Property="Template">
      <ControlTemplate TargetType="{x:Type DataGridCell}">
        <Border Padding="{TemplateBinding Padding}" BorderBrush="{TemplateBinding BorderBrush}" BorderThickness="{TemplateBinding BorderThickness}" Background="{TemplateBinding Background}" SnapsToDevicePixels="True">
          <ContentPresenter SnapsToDevicePixels="{TemplateBinding SnapsToDevicePixels}"/>

Or if you don't need the TemplateBindings:

<Style TargetType="{x:Type DataGridCell}">
   <Setter Property="Template">
          <ControlTemplate TargetType="{x:Type DataGridCell}">
              <Border Padding="4">
                  <ContentPresenter />

What's the best way to detect a 'touch screen' device using JavaScript?

This seems to be working fine for me so far:

//Checks if a touch screen
is_touch_screen = 'ontouchstart' in document.documentElement;

if (is_touch_screen) {
  // Do something if a touch screen
else {
  // Not a touch screen (i.e. desktop)

Non-static method requires a target

I've found this issue to be prevalent in Entity Framework when we instantiate an Entity manually rather than through DBContext which will resolve all the Navigation Properties. If there are Foreign Key references (Navigation Properties) between tables and you use those references in your lambda (e.g. ProductDetail.Products.ID) then that "Products" context remains null if you manually created the Entity.

Laravel Carbon subtract days from current date

From Laravel 5.6 you can use whereDate:

$users = Users::where('status_id', 'active')
       ->whereDate( 'created_at', '>', now()->subDays(30))

You also have whereMonth / whereDay / whereYear / whereTime

Unable to set variables in bash script

folder = "ABC" tries to run a command named folder with arguments = and "ABC". The format of command in bash is:

command arguments separated with space

while assignment is done with:


  • In [ -f $newfoldername/Primetime.eyetv], [ is a command (test) and -f and $newfoldername/Primetime.eyetv] are two arguments. It expects a third argument (]) which it can't find (arguments must be separated with space) and thus will show error.
  • [-f $newfoldername/Primetime.eyetv] tries to run a command [-f with argument $newfoldername/Primetime.eyetv]

Generally for cases like this, paste your code in shellcheck and see the feedback.

Comparing HTTP and FTP for transferring files

I just benchmarked a file transfer over both FTP and HTTP :

  • over two very good server connections
  • using the same 1GB .zip file
  • under the same network conditions (tested one after the other)

The result:

  • using FTP: 6 minutes
  • using HTTP: 4 minutes
  • using a concurrent http downloader software (fdm): 1 minute

So, basically under a "real life" situation:

1) HTTP is faster than FTP when downloading one big file.

2) HTTP can use parallel chunk download which makes it 6x times faster than FTP depending on the network conditions.

How do I generate a random int number?

The Random class is used to create random numbers. (Pseudo-random that is of course.).


Random rnd = new Random();
int month  = rnd.Next(1, 13);  // creates a number between 1 and 12
int dice   = rnd.Next(1, 7);   // creates a number between 1 and 6
int card   = rnd.Next(52);     // creates a number between 0 and 51

If you are going to create more than one random number, you should keep the Random instance and reuse it. If you create new instances too close in time, they will produce the same series of random numbers as the random generator is seeded from the system clock.

Javascript replace all "%20" with a space

The percentage % sign followed by two hexadecimal numbers (UTF-8 character representation) typically denotes a string which has been encoded to be part of a URI. This ensures that characters that would otherwise have special meaning don't interfere. In your case %20 is immediately recognisable as a whitespace character - while not really having any meaning in a URI it is encoded in order to avoid breaking the string into multiple "parts".

Don't get me wrong, regex is the bomb! However any web technology worth caring about will already have tools available in it's library to handle standards like this for you. Why re-invent the wheel...?

var str = 'xPasswords%20do%20not%20match';
console.log( decodeURI(str) ); // "xPasswords do not match"

Javascript has both decodeURI and decodeURIComponent which differ slightly in respect to their encodeURI and encodeURIComponent counterparts - you should familiarise yourself with the documentation.

How to extract the nth word and count word occurrences in a MySQL string?

The following is a proposed solution for the OP's specific problem (extracting the 2nd word of a string), but it should be noted that, as mc0e's answer states, actually extracting regex matches is not supported out-of-the-box in MySQL. If you really need this, then your choices are basically to 1) do it in post-processing on the client, or 2) install a MySQL extension to support it.

BenWells has it very almost correct. Working from his code, here's a slightly adjusted version:

  LOCATE(' ', sentence) + CHAR_LENGTH(' '),
  LOCATE(' ', sentence,
  ( LOCATE(' ', sentence) + 1 ) - ( LOCATE(' ', sentence) + CHAR_LENGTH(' ') )

As a working example, I used:

  LOCATE(' ', sentence) + CHAR_LENGTH(' '),
  LOCATE(' ', sentence,
  ( LOCATE(' ', sentence) + 1 ) - ( LOCATE(' ', sentence) + CHAR_LENGTH(' ') )
) as string
FROM (SELECT 'THIS IS A TEST' AS sentence) temp

This successfully extracts the word IS

How to make parent wait for all child processes to finish?

pid_t child_pid, wpid;
int status = 0;

//Father code (before child processes start)

for (int id=0; id<n; id++) {
    if ((child_pid = fork()) == 0) {
        //child code

while ((wpid = wait(&status)) > 0); // this way, the father waits for all the child processes 

//Father code (After all child processes end)

wait waits for a child process to terminate, and returns that child process's pid. On error (eg when there are no child processes), -1 is returned. So, basically, the code keeps waiting for child processes to finish, until the waiting errors out, and then you know they are all finished.

Append an empty row in dataframe using pandas

Assuming your df.index is sorted you can use:

df.loc[df.index.max() + 1] = None

It handles well different indexes and column types.

[EDIT] it works with pd.DatetimeIndex if there is a constant frequency, otherwise we must specify the new index exactly e.g:

df.loc[df.index.max() + pd.Timedelta(milliseconds=1)] = None

long example:

df = pd.DataFrame([[pd.Timestamp(12432423), 23, 'text_field']], 
                    columns=["timestamp", "speed", "text"],
                    index=pd.DatetimeIndex(start='2111-11-11',freq='ms', periods=1))

<class 'pandas.core.frame.DataFrame'> DatetimeIndex: 1 entries, 2111-11-11 to 2111-11-11 Freq: L Data columns (total 3 columns): timestamp 1 non-null datetime64[ns] speed 1 non-null int64 text 1 non-null object dtypes: datetime64[ns](1), int64(1), object(1) memory usage: 32.0+ bytes

df.loc[df.index.max() + 1] = None

<class 'pandas.core.frame.DataFrame'> DatetimeIndex: 2 entries, 2111-11-11 00:00:00 to 2111-11-11 00:00:00.001000 Data columns (total 3 columns): timestamp 1 non-null datetime64[ns] speed 1 non-null float64 text 1 non-null object dtypes: datetime64[ns](1), float64(1), object(1) memory usage: 64.0+ bytes


                            timestamp                   speed      text
2111-11-11 00:00:00.000 1970-01-01 00:00:00.012432423   23.0    text_field
2111-11-11 00:00:00.001 NaT NaN NaN

Java: set timeout on a certain block of code?

If you want a CompletableFuture way you could have a method like

public MyResponseObject retrieveDataFromEndpoint() {

   CompletableFuture<MyResponseObject> endpointCall 
       = CompletableFuture.supplyAsync(() ->
             yourRestService.callEnpoint(withArg1, withArg2));

   try {
       return endpointCall.get(10, TimeUnit.MINUTES);
   } catch (TimeoutException 
               | InterruptedException 
               | ExecutionException e) {
       throw new RuntimeException("Unable to fetch data", e);

If you're using spring, you could annotate the method with a @Retryable so that it retries the method three times if an exception is thrown.

Capitalize the first letter of both words in a two word string

From the help page for ?toupper:

.simpleCap <- function(x) {
    s <- strsplit(x, " ")[[1]]
    paste(toupper(substring(s, 1,1)), substring(s, 2),
          sep="", collapse=" ")

> sapply(name, .simpleCap)

zip code         state   final count 
"Zip Code"       "State" "Final Count"

CSS root directory

In the CSS all you have to do is put url(logical path to the image file)

In Flask, What is request.args and how is it used?

@martinho as a newbie using Flask and Python myself, I think the previous answers here took for granted that you had a good understanding of the fundamentals. In case you or other viewers don't know the fundamentals, I'll give more context to understand the answer...

... the request.args is bringing a "dictionary" object for you. The "dictionary" object is similar to other collection-type of objects in Python, in that it can store many elements in one single object. Therefore the answer to your question

And how many parameters request.args.get() takes.

It will take only one object, a "dictionary" type of object (as stated in the previous answers). This "dictionary" object, however, can have as many elements as needed... (dictionaries have paired elements called Key, Value).

Other collection-type of objects besides "dictionaries", would be "tuple", and "list"... you can run a google search on those and "data structures" in order to learn other Python fundamentals. This answer is based Python; I don't have an idea if the same applies to other programming languages.

ld cannot find an existing library

The problem is the linker is looking for but you only have

A quick hack is to symlink to

Authentication plugin 'caching_sha2_password' cannot be loaded

Actually MySql allows two type of authentication at the time of installation.

  1. Password Encryption
  2. Legacy Encryption

enter image description here

Read Here

So by checking legacy authentication the issue was resolved.

C#: Printing all properties of an object

Don't think so. I've always had to write them or use someone else's work to get that info. Has to be reflection as far as i'm aware.

Check this out. I was investigating some debugging on long object graphs and noticed this when i Add Watches, VS throws in this class: Mscorlib_CollectionDebugView<>. It's an internal type for displaying collections nicely for viewing in the watch windows/code debug modes. Now coz it's internal you can reference it, but u can use Reflector to copy (from mscorlib) the code and have your own (the link above has a copy/paste example). Looks really useful.

Proper use of mutexes in Python

You have to unlock your Mutex at sometime...

How to find prime numbers between 0 - 100?

First, change your inner code for another loop (for and while) so you can repeat the same code for different values.

More specific for your problem, if you want to know if a given n is prime, you need to divide it for all values between 2 and sqrt(n). If any of the modules is 0, it is not prime.

If you want to find all primes, you can speed it and check n only by dividing by the previously found primes. Another way of speeding the process is the fact that, apart from 2 and 3, all the primes are 6*k plus or less 1.

rbind error: "names do not match previous names"

The names of the first dataframe do not match the names of the second one. Just as the error message says.

> identical(names(xd.small[[1]]), names(xd.small[[2]]) )

If you do not care about the names of the 3rd or 4th columns of the second df, you can coerce them to be the same:

> names(xd.small[[1]]) <- names(xd.small[[2]]) 
> identical(names(xd.small[[1]]), names(xd.small[[2]]) )
[1] TRUE

Then things should proceed happily.

Adding 'serial' to existing column in Postgres


Here's a version where you don't need a human to read a value and type it out themselves.

SELECT setval('foo_a_seq', coalesce(max(a), 0) + 1, false) FROM foo;
ALTER TABLE foo ALTER COLUMN a SET DEFAULT nextval('foo_a_seq'); 

Another option would be to employ the reusable Function shared at the end of this answer.

A non-interactive solution

Just adding to the other two answers, for those of us who need to have these Sequences created by a non-interactive script, while patching a live-ish DB for instance.

That is, when you don't wanna SELECT the value manually and type it yourself into a subsequent CREATE statement.

In short, you can not do:

    START WITH ( SELECT max(a) + 1 FROM foo );

... since the START [WITH] clause in CREATE SEQUENCE expects a value, not a subquery.

Note: As a rule of thumb, that applies to all non-CRUD (i.e.: anything other than INSERT, SELECT, UPDATE, DELETE) statements in pgSQL AFAIK.

However, setval() does! Thus, the following is absolutely fine:

SELECT setval('foo_a_seq', max(a)) FROM foo;

If there's no data and you don't (want to) know about it, use coalesce() to set the default value:

SELECT setval('foo_a_seq', coalesce(max(a), 0)) FROM foo;
--                         ^      ^         ^
--                       defaults to:       0

However, having the current sequence value set to 0 is clumsy, if not illegal.
Using the three-parameter form of setval would be more appropriate:

--                                             vvv
SELECT setval('foo_a_seq', coalesce(max(a), 0) + 1, false) FROM foo;
--                                                  ^   ^
--                                                is_called

Setting the optional third parameter of setval to false will prevent the next nextval from advancing the sequence before returning a value, and thus:

the next nextval will return exactly the specified value, and sequence advancement commences with the following nextval.

— from this entry in the documentation

On an unrelated note, you also can specify the column owning the Sequence directly with CREATE, you don't have to alter it later:


In summary:

SELECT setval('foo_a_seq', coalesce(max(a), 0) + 1, false) FROM foo;
ALTER TABLE foo ALTER COLUMN a SET DEFAULT nextval('foo_a_seq'); 

Using a Function

Alternatively, if you're planning on doing this for multiple columns, you could opt for using an actual Function.

CREATE OR REPLACE FUNCTION make_into_serial(table_name TEXT, column_name TEXT) RETURNS INTEGER AS $$
    start_with INTEGER;
    sequence_name TEXT;
    sequence_name := table_name || '_' || column_name || '_seq';
    EXECUTE 'SELECT coalesce(max(' || column_name || '), 0) + 1 FROM ' || table_name
            INTO start_with;
    EXECUTE 'CREATE SEQUENCE ' || sequence_name ||
            ' START WITH ' || start_with ||
            ' OWNED BY ' || table_name || '.' || column_name;
    EXECUTE 'ALTER TABLE ' || table_name || ' ALTER COLUMN ' || column_name ||
            ' SET DEFAULT nextVal(''' || sequence_name || ''')';
    RETURN start_with;

Use it like so:

INSERT INTO foo (data) VALUES ('asdf');
-- ERROR: null value in column "a" violates not-null constraint

SELECT make_into_serial('foo', 'a');
INSERT INTO foo (data) VALUES ('asdf');
-- OK: 1 row(s) affected

How to reverse an std::string?

I'm not sure what you mean by a string that contains binary numbers. But for reversing a string (or any STL-compatible container), you can use std::reverse(). std::reverse() operates in place, so you may want to make a copy of the string first:

#include <algorithm>
#include <iostream>
#include <string>

int main()
    std::string foo("foo");
    std::string copy(foo);
    std::cout << foo << '\n' << copy << '\n';

    std::reverse(copy.begin(), copy.end());
    std::cout << foo << '\n' << copy << '\n';

How to configure socket connect timeout

There should be a ReceiveTimeout property in the Socket class.

Socket.ReceiveTimeout Property

Saving numpy array to txt file row wise

import numpy as np

a = [1,2,3]    
b = np.array(a).reshape((1,3))    

Get the length of a String

You can add this function to your extention

extension NSString { 
    func charLength() -> Int {
        return count(self as String)

How to add an Access-Control-Allow-Origin header

For Java based Application add this to your web.xml file:





Saving an Excel sheet in a current directory with VBA

Taking this one step further, to save a file to a relative directory, you can use the replace function. Say you have your workbook saved in: c:\property\california\sacramento\workbook.xlsx, use this to move the property to berkley:

workBookPath = Replace(ActiveWorkBook.path, "sacramento", "berkley")
myWorkbook.SaveAs(workBookPath & "\" & "newFileName.xlsx"

Only works if your file structure contains one instance of the text used to replace. YMMV.

What does "connection reset by peer" mean?

This means that a TCP RST was received and the connection is now closed. This occurs when a packet is sent from your end of the connection but the other end does not recognize the connection; it will send back a packet with the RST bit set in order to forcibly close the connection.

This can happen if the other side crashes and then comes back up or if it calls close() on the socket while there is data from you in transit, and is an indication to you that some of the data that you previously sent may not have been received.

It is up to you whether that is an error; if the information you were sending was only for the benefit of the remote client then it may not matter that any final data may have been lost. However you should close the socket and free up any other resources associated with the connection.

The import org.junit cannot be resolved

If you are using Java 9 or above you may need to require the junit dependency in your

module myModule {
    requires junit;

How to change port number in vue-cli project

In my vue project in visual studio code, I had to set this in /config/index.js. Change it in the:

module.exports = {
    dev: {
          // Paths
          assetsSubDirectory: 'static',
          assetsPublicPath: '/',
          proxyTable: {},

          host: 'localhost', // can be overwritten by process.env.HOST
          port: 8090, // can be overwritten by process.env.PORT, if port is in use, a free one will be determined
          autoOpenBrowser: false,
          errorOverlay: true,
          notifyOnErrors: true,
          poll: false    

AttributeError: 'str' object has no attribute 'strftime'

you should change cr_date(str) to datetime object then you 'll change the date to the specific format:

cr_date = '2013-10-31 18:23:29.000227'
cr_date = datetime.datetime.strptime(cr_date, '%Y-%m-%d %H:%M:%S.%f')
cr_date = cr_date.strftime("%m/%d/%Y")

Error:java: invalid source release: 8 in Intellij. What does it mean?

You need to click to the project Open Module Settings and change the path of your JDK, if in the file POM you use jdk 1.8, configure jdk 1.8 with correct path.

How to get cookie expiration date / creation date from javascript?

If you are using Chrome you can goto the "Resources" tab and find the item "Cookies" in the left sidebar. From there select the domain you are checking the set cookie for and it will give you a list of cookies associated with that domain, along with their expiration date.

What parameters should I use in a Google Maps URL to go to a lat-lon?

This is current accepted way to link to a specific lat lon (rather than search for the nearest object).
  • z is the zoom level (1-20)
  • t is the map type ("m" map, "k" satellite, "h" hybrid, "p" terrain, "e" GoogleEarth)
  • q is the search query, if it is prefixed by loc: then google assumes it is a lat lon separated by a +

Scatter plot with error bars

Another (easier - at least for me) way to do this is below.


data(movies, package="ggplot2movies")
Plot average Length vs Rating
rating_by_len = tapply(movies$length,

plot(names(rating_by_len), rating_by_len, ylim=c(0, 200)
     ,xlab = "Rating", ylab = "Length", main="Average Rating by Movie Length", pch=21)
Add error bars to the plot: mean - sd, mean + sd
sds = tapply(movies$length, movies$rating, sd)
upper = rating_by_len + sds
lower = rating_by_len - sds

Hope that helps.

Greater than and less than in one statement

This is one ugly way to do this. I would just use a local variable.

EDIT: If size() > 0 as well.

if (orderBean.getFiles().size() + Integer.MIN_VALUE-1 < Integer.MIN_VALUE + 5-1)

java get file size efficiently

The benchmark given by GHad measures lots of other stuff (such as reflection, instantiating objects, etc.) besides getting the length. If we try to get rid of these things then for one call I get the following times in microseconds:

   file sum___19.0, per Iteration___19.0
    raf sum___16.0, per Iteration___16.0
channel sum__273.0, per Iteration__273.0

For 100 runs and 10000 iterations I get:

   file sum__1767629.0, per Iteration__1.7676290000000001
    raf sum___881284.0, per Iteration__0.8812840000000001
channel sum___414286.0, per Iteration__0.414286

I did run the following modified code giving as an argument the name of a 100MB file.

import java.nio.channels.*;
import java.util.*;

public class FileSizeBench {

  private static File file;
  private static FileChannel channel;
  private static RandomAccessFile raf;

  public static void main(String[] args) throws Exception {
    int runs = 1;
    int iterations = 1;

    file = new File(args[0]);
    channel = new FileInputStream(args[0]).getChannel();
    raf = new RandomAccessFile(args[0], "r");

    HashMap<String, Double> times = new HashMap<String, Double>();
    times.put("file", 0.0);
    times.put("channel", 0.0);
    times.put("raf", 0.0);

    long start;
    for (int i = 0; i < runs; ++i) {
      long l = file.length();

      start = System.nanoTime();
      for (int j = 0; j < iterations; ++j)
        if (l != file.length()) throw new Exception();
      times.put("file", times.get("file") + System.nanoTime() - start);

      start = System.nanoTime();
      for (int j = 0; j < iterations; ++j)
        if (l != channel.size()) throw new Exception();
      times.put("channel", times.get("channel") + System.nanoTime() - start);

      start = System.nanoTime();
      for (int j = 0; j < iterations; ++j)
        if (l != raf.length()) throw new Exception();
      times.put("raf", times.get("raf") + System.nanoTime() - start);
    for (Map.Entry<String, Double> entry : times.entrySet()) {
            entry.getKey() + " sum: " + 1e-3 * entry.getValue() +
            ", per Iteration: " + (1e-3 * entry.getValue() / runs / iterations));

How to enable mod_rewrite for Apache 2.2

Use below command

sudo a2enmod rewrite

And the restart apache through below command

sudo service apache2 restart

error code 1292 incorrect date value mysql

I happened to be working in localhost , in windows 10, using WAMP, as it turns out, Wamp has a really accessible configuration interface to change the MySQL configuration. You just need to go to the Wamp panel, then to MySQL, then to settings and change the mode to sql-mode: none.(essentially disabling the strict mode) The following picture illustrates this.

enter image description here

Simplest JQuery validation rules example

rules: {
    cname: {
        required: true,
        minlength: 2
messages: {
    cname: {
        required: "<li>Please enter a name.</li>",
        minlength: "<li>Your name is not long enough.</li>"

Align inline-block DIVs to top of container element

<style type="text/css">
        div {
  text-align: center;

            width: 150px;
            height: 150px;
            border-radius: 50%;

            display: block;

<script src=""></script>
  <input type='password' class='secondInput mt-4 mr-1' placeholder="Password">
  <span class='dif'></span>

<script type="text/javascript">

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


how to cancel/abort ajax request in axios

Axios does not support canceling requests at the moment. Please see this issue for details.

UPDATE: Cancellation support was added in axios v0.15.

EDIT: The axios cancel token API is based on the withdrawn cancelable promises proposal.


const cancelTokenSource = axios.CancelToken.source();

axios.get('/user/12345', {
  cancelToken: cancelTokenSource.token

// Cancel request

Replace image src location using CSS

You could do this but it is hacky

.application-title {
   /* set these dims according to your image size */

.application-title img {

Here is a working example:

Replace values in list using Python

Build a new list with a list comprehension:

new_items = [x if x % 2 else None for x in items]

You can modify the original list in-place if you want, but it doesn't actually save time:

items = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
for index, item in enumerate(items):
    if not (item % 2):
        items[index] = None

Here are (Python 3.6.3) timings demonstrating the non-timesave:

In [1]: %%timeit
   ...: items = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
   ...: for index, item in enumerate(items):
   ...:     if not (item % 2):
   ...:         items[index] = None
1.06 µs ± 33.7 ns per loop (mean ± std. dev. of 7 runs, 1000000 loops each)

In [2]: %%timeit
   ...: items = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
   ...: new_items = [x if x % 2 else None for x in items]
891 ns ± 13.6 ns per loop (mean ± std. dev. of 7 runs, 1000000 loops each)

And Python 2.7.6 timings:

In [1]: %%timeit
   ...: items = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
   ...: for index, item in enumerate(items):
   ...:     if not (item % 2):
   ...:         items[index] = None
1000000 loops, best of 3: 1.27 µs per loop
In [2]: %%timeit
   ...: items = [0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
   ...: new_items = [x if x % 2 else None for x in items]
1000000 loops, best of 3: 1.14 µs per loop

json Uncaught SyntaxError: Unexpected token :

You've told jQuery to expect a JSONP response, which is why jQuery has added the callback=jQuery16406345664265099913_1319854793396&_=1319854793399 part to the URL (you can see this in your dump of the request).

What you're returning is JSON, not JSONP. Your response looks like

{"red" : "#f00"}

and jQuery is expecting something like this:

jQuery16406345664265099913_1319854793396({"red" : "#f00"})

If you actually need to use JSONP to get around the same origin policy, then the server serving colors.json needs to be able to actually return a JSONP response.

If the same origin policy isn't an issue for your application, then you just need to fix the dataType in your jQuery.ajax call to be json instead of jsonp.

byte array to pdf

Usually this happens if something is wrong with the byte array.

File.WriteAllBytes("filename.PDF", Byte[]);

This creates a new file, writes the specified byte array to the file, and then closes the file. If the target file already exists, it is overwritten.

Asynchronous implementation of this is also available.

public static System.Threading.Tasks.Task WriteAllBytesAsync 
(string path, byte[] bytes, System.Threading.CancellationToken cancellationToken = null);

if else in a list comprehension

The other solutions are great for a single if / else construct. However, ternary statements within list comprehensions are arguably difficult to read.

Using a function aids readability, but such a solution is difficult to extend or adapt in a workflow where the mapping is an input. A dictionary can alleviate these concerns:

row = [None, 'This', 'is', 'a', 'filler', 'test', 'string', None]

d = {None: '', 'filler': 'manipulated'}

res = [d.get(x, x) for x in row]


['', 'This', 'is', 'a', 'manipulated', 'test', 'string', '']

Are there any worse sorting algorithms than Bogosort (a.k.a Monkey Sort)?

A worst case performance of O(8) might not even make it an algorithm according to some.

An algorithm is just a series of steps and you can always do worse by tweaking it a little bit to get the desired output in more steps than it was previously taking. One could purposely put the knowledge of the number of steps taken into the algorithm and make it terminate and produce the correct output only after X number of steps have been done. That X could very well be of the order of O(n2) or O(nn!) or whatever the algorithm desired to do. That would effectively increase its best-case as well as average case bounds.

But your worst-case scenario cannot be topped :)

How to import large sql file in phpmyadmin

In MAMP, You could load huge files by :

  1. creating a new folder in this directory /MAMP/bin/phpMyAdmin/"folderName"

  2. and then edit "/MAMP/bin/phpMyAdmin/" line 531 :

       $cfg['UploadDir']= 'folderName';   
  3. Copy your .sql or .csv Files into this folder.

  4. Now you will have another option in "PhpMyAdmin" : Select from the web server upload directory newFolder/: You could select your file and import it.

    You could load any file now !!

How to plot an array in python?

if you give a 2D array to the plot function of matplotlib it will assume the columns to be lines:

If x and/or y is 2-dimensional, then the corresponding columns will be plotted.

In your case your shape is not accepted (100, 1, 1, 8000). As so you can using numpy squeeze to solve the problem quickly:

np.squeez doc: Remove single-dimensional entries from the shape of an array.

import numpy as np
import matplotlib.pyplot as plt

data = np.random.randint(3, 7, (10, 1, 1, 80))
newdata = np.squeeze(data) # Shape is now: (10, 80)
plt.plot(newdata) # plotting by columns

But notice that 100 sets of 80 000 points is a lot of data for matplotlib. I would recommend that you look for an alternative. The result of the code example (run in Jupyter) is:

Jupyter matplotlib plot

How to stretch a table over multiple pages

You should \usepackage{longtable}.

In PHP with PDO, how to check the final SQL parametrized query?

What I did to print that actual query is a bit complicated but it works :)

In method that assigns variables to my statement I have another variable that looks a bit like this:

$this->fullStmt = str_replace($column, '\'' . str_replace('\'', '\\\'', $param) . '\'', $this->fullStmt);

$column is my token
$param is the actual value being assigned to token
$this->fullStmt is my print only statement with replaced tokens

What it does is a simply replace tokens with values when the real PDO assignment happens.

I hope I did not confuse you and at least pointed you in right direction.

HTML Form: Select-Option vs Datalist-Option

Datalist includes autocomplete and suggestions natively, it can also allow a user to enter a value that is not defined in the suggestions.

Select only gives you pre-defined options the user has to select from

Multiline TextView in Android?

for me non of the solutions did not work. I know it is not a complete answer for this question, but sometimes it can help.

I put 4 textviews in a vertical linearlayout.



This solution is good for cases that the text view text is constant, like labels.

What does "collect2: error: ld returned 1 exit status" mean?

Try running task manager to determine if your program is still running.

If it is running then stop it and run it again. the [Error] ld returned 1 exit status will not come back

Using an index to get an item, Python

You can use pop():


output is 4

Inline Form nested within Horizontal Form in Bootstrap 3

Another option is to put all of the fields that you want on a single line within a single form-group.

See demo here

<form class="form-horizontal">
    <div class="form-group">
        <label for="name" class="col-xs-2 control-label">Name</label>
        <div class="col-xs-10">
            <input type="text" class="form-control col-sm-10" name="name" placeholder="name"/>

    <div class="form-group">
        <label for="birthday" class="col-xs-3 col-sm-2 control-label">Birthday</label>
        <div class="col-xs-3">
            <input type="text" class="form-control" placeholder="year"/>
        <div class="col-xs-3">
            <input type="text" class="form-control" placeholder="month"/>
        <div class="col-xs-3">
            <input type="text" class="form-control" placeholder="day"/>

How to get response from S3 getObject in Node.js?

Based on the answer by @peteb, but using Promises and Async/Await:

const AWS = require('aws-sdk');

const s3 = new AWS.S3();

async function getObject (bucket, objectKey) {
  try {
    const params = {
      Bucket: bucket,
      Key: objectKey 

    const data = await s3.getObject(params).promise();

    return data.Body.toString('utf-8');
  } catch (e) {
    throw new Error(`Could not retrieve file from S3: ${e.message}`)

// To retrieve you need to use `await getObject()` or `getObject().then()`
getObject('my-bucket', 'path/to/the/object.txt').then(...);

Best practice for instantiating a new Android Fragment

There is also another way:

Fragment.instantiate(context, MyFragment.class.getName(), myBundle)

Why Local Users and Groups is missing in Computer Management on Windows 10 Home?

Windows 10 Home Edition does not have Local Users and Groups option so that is the reason you aren't able to see that in Computer Management.

You can use User Accounts by pressing Window+R, typing netplwiz and pressing OK as described here.

Angular 2 Date Input not binding to date value

In Typescript - app.component.ts file

export class AppComponent implements OnInit {
    currentDate = new Date();

In HTML Input field

<input id="form21_1" type="text" tabindex="28" title="DATE" [ngModel]="currentDate | date:'MM/dd/yyyy'" />

It will display the current date inside the input field.

mysql.h file can't be found

I think you can try this gcc -I/usr/include/mysql *.c -L/usr/lib/mysql -lmysqlclient -o *

How to automate browsing using python?

selenium will do exactly what you want and it handles javascript

Node: log in a file instead of the console

For simple cases, we could redirect the Standard Out (STDOUT) and Standard Error (STDERR) streams directly to a file(say, test.log) using '>' and '2>&1'


// test.js
(function() {
    // Below outputs are sent to Standard Out (STDOUT) stream
    console.log("Hello Log");"Hello Info");
    // Below outputs are sent to Standard Error (STDERR) stream
    console.error("Hello Error");
    console.warn("Hello Warning");

node test.js > test.log 2>&1

As per the POSIX standard, 'input', 'output' and 'error' streams are identified by the positive integer file descriptors (0, 1, 2). i.e., stdin is 0, stdout is 1, and stderr is 2.

Step 1: '2>&1' will redirect from 2 (stderr) to 1 (stdout)

Step 2: '>' will redirect from 1 (stdout) to file (test.log)

Using Html.ActionLink to call action on different controller

this code worked for me in partial view:

<a href="/Content/[email protected]">@item.Title</a>

Changing button color programmatically

If you assign it to a class it should work:

  function changeClass(){
    document.getElementById('myButton').className = 'formatForButton';

  .formatForButton {

  <input id='myButton' type=button class=none value='Change Color to pink' onclick='changeClass()'>

HTML 5 input type="number" element for floating point numbers on Chrome

Try <input type="number" step="any" />

It won't have validation problems and the arrows will have step of "1"

Constraint validation: When the element has an allowed value step, and the result of applying the algorithm to convert a string to a number to the string given by the element's value is a number, and that number subtracted from the step base is not an integral multiple of the allowed value step, the element is suffering from a step mismatch.

The following range control only accepts values in the range 0..1, and allows 256 steps in that range:

<input name=opacity type=range min=0 max=1 step=0.00392156863>

The following control allows any time in the day to be selected, with any accuracy (e.g. thousandth-of-a-second accuracy or more):

<input name=favtime type=time step=any>

Normally, time controls are limited to an accuracy of one minute.

How to set a timer in android

I am using a handler and runnable to create a timer. I wrapper this in an abstract class. Just derive/implement it and you are good to go:

 public static abstract class SimpleTimer {
    abstract void onTimer();

    private Runnable runnableCode = null;
    private Handler handler = new Handler();

    void startDelayed(final int intervalMS, int delayMS) {
        runnableCode = new Runnable() {
            public void run() {
                handler.postDelayed(runnableCode, intervalMS);
        handler.postDelayed(runnableCode, delayMS);

    void start(final int intervalMS) {
        startDelayed(intervalMS, 0);

    void stop() {

Note that the handler.postDelayed is called before the code to be executed - this will make the timer more closed timed as "expected". However in cases were the timer runs to frequently and the task (onTimer()) is long - there might be overlaps. If you want to start counting intervalMS after the task is done, move the onTimer() call a line above.

Android WebView progress bar

wait until the process is over ...

while(webview.getProgress()< 100){}

Matrix Transpose in Python

If your rows are not equal you can also use map:

>>> uneven = [['a','b','c'],['d','e'],['g','h','i']]
>>> map(None,*uneven)
[('a', 'd', 'g'), ('b', 'e', 'h'), ('c', None, 'i')]

Edit: In Python 3 the functionality of map changed, itertools.zip_longest can be used instead:
Source: What’s New In Python 3.0

>>> import itertools
>>> uneven = [['a','b','c'],['d','e'],['g','h','i']]
>>> list(itertools.zip_longest(*uneven))
[('a', 'd', 'g'), ('b', 'e', 'h'), ('c', None, 'i')]

Toggle display:none style with JavaScript

Give your ul an id,

<ul id='yourUlId' class="subforums" style="display: none; overflow-x: visible; overflow-y: visible; ">

then do

var yourUl = document.getElementById("yourUlId"); = === 'none' ? '' : 'none';

IF you're using jQuery, this becomes:

var $yourUl = $("#yourUlId"); 
$yourUl.css("display", $yourUl.css("display") === 'none' ? '' : 'none');

Finally, you specifically said that you wanted to manipulate this css property, and not simply show or hide the underlying element. Nonetheless I'll mention that with jQuery


will alternate between showing or hiding this element.

How can you print multiple variables inside a string using printf?

printf("\nmaximum of %d and %d is = %d",a,b,c);

Is there a goto statement in Java?

Of course it is keyword, but it is not used on level of source code.

But if you use jasmin or other lower level language, which is transformed to bytecode, then "goto" is there

Python virtualenv questions

After creating virtual environment copy the activate.bat file from Script folder of python and paste to it your environment and open cmd from your virtual environment and run activate.bat file.enter image description here

Python JSON serialize a Decimal object

For anybody that wants a quick solution here is how I removed Decimal from my queries in Django

total_development_cost_var = process_assumption_objects.values('total_development_cost').aggregate(sum_dev = Sum('total_development_cost', output_field=FloatField()))
total_development_cost_var = list(total_development_cost_var.values())
  • Step 1: use , output_field=FloatField() in you r query
  • Step 2: use list eg list(total_development_cost_var.values())

Hope it helps

Postgresql Select rows where column = array

FROM    table
WHERE   some_id = ANY(ARRAY[1, 2])

or ANSI-compatible:

FROM    table
WHERE   some_id IN (1, 2)

The ANY syntax is preferred because the array as a whole can be passed in a bound variable:

FROM    table
WHERE   some_id = ANY(?::INT[])

You would need to pass a string representation of the array: {1,2}

Update Top 1 record in table sql server

It also works well ...

Update t
Set t.TIMESTAMP2 = '2013-12-12 15:40:31.593'
    Select Top 1 TIMESTAMP2
    From TX_Master_PCBA
    Where SERIAL_NO IN ('0500030309')
) t

Java error - "invalid method declaration; return type required"

Every method (other than a constructor) must have a return type.

public double diameter(){...

MaxJsonLength exception in ASP.NET MVC during JavaScriptSerializer

Alternative ASP.NET MVC 5 Fix:

In my case the error was occurring during the request. Best approach in my scenario is modifying the actual JsonValueProviderFactory which applies the fix to the global project and can be done by editing the global.cs file as such.


add a web.config entry:

<add key="aspnet:MaxJsonLength" value="20971520" />

and then create the two following classes

public class JsonValueProviderConfig
    public static void Config(ValueProviderFactoryCollection factories)
        var jsonProviderFactory = factories.OfType<JsonValueProviderFactory>().Single();
        factories.Add(new CustomJsonValueProviderFactory());

This is basically an exact copy of the default implementation found in System.Web.Mvc but with the addition of a configurable web.config appsetting value aspnet:MaxJsonLength.

public class CustomJsonValueProviderFactory : ValueProviderFactory

    /// <summary>Returns a JSON value-provider object for the specified controller context.</summary>
    /// <returns>A JSON value-provider object for the specified controller context.</returns>
    /// <param name="controllerContext">The controller context.</param>
    public override IValueProvider GetValueProvider(ControllerContext controllerContext)
        if (controllerContext == null)
            throw new ArgumentNullException("controllerContext");

        object deserializedObject = CustomJsonValueProviderFactory.GetDeserializedObject(controllerContext);
        if (deserializedObject == null)
            return null;

        Dictionary<string, object> strs = new Dictionary<string, object>(StringComparer.OrdinalIgnoreCase);
        CustomJsonValueProviderFactory.AddToBackingStore(new CustomJsonValueProviderFactory.EntryLimitedDictionary(strs), string.Empty, deserializedObject);

        return new DictionaryValueProvider<object>(strs, CultureInfo.CurrentCulture);

    private static object GetDeserializedObject(ControllerContext controllerContext)
        if (!controllerContext.HttpContext.Request.ContentType.StartsWith("application/json", StringComparison.OrdinalIgnoreCase))
            return null;

        string fullStreamString = (new StreamReader(controllerContext.HttpContext.Request.InputStream)).ReadToEnd();
        if (string.IsNullOrEmpty(fullStreamString))
            return null;

        var serializer = new JavaScriptSerializer()
            MaxJsonLength = CustomJsonValueProviderFactory.GetMaxJsonLength()
        return serializer.DeserializeObject(fullStreamString);

    private static void AddToBackingStore(EntryLimitedDictionary backingStore, string prefix, object value)
        IDictionary<string, object> strs = value as IDictionary<string, object>;
        if (strs != null)
            foreach (KeyValuePair<string, object> keyValuePair in strs)
                CustomJsonValueProviderFactory.AddToBackingStore(backingStore, CustomJsonValueProviderFactory.MakePropertyKey(prefix, keyValuePair.Key), keyValuePair.Value);


        IList lists = value as IList;
        if (lists == null)
            backingStore.Add(prefix, value);

        for (int i = 0; i < lists.Count; i++)
            CustomJsonValueProviderFactory.AddToBackingStore(backingStore, CustomJsonValueProviderFactory.MakeArrayKey(prefix, i), lists[i]);

    private class EntryLimitedDictionary
        private static int _maximumDepth;

        private readonly IDictionary<string, object> _innerDictionary;

        private int _itemCount;

        static EntryLimitedDictionary()
            _maximumDepth = CustomJsonValueProviderFactory.GetMaximumDepth();

        public EntryLimitedDictionary(IDictionary<string, object> innerDictionary)
            this._innerDictionary = innerDictionary;

        public void Add(string key, object value)
            int num = this._itemCount + 1;
            this._itemCount = num;
            if (num > _maximumDepth)
                throw new InvalidOperationException("The length of the string exceeds the value set on the maxJsonLength property.");
            this._innerDictionary.Add(key, value);

    private static string MakeArrayKey(string prefix, int index)
        return string.Concat(prefix, "[", index.ToString(CultureInfo.InvariantCulture), "]");

    private static string MakePropertyKey(string prefix, string propertyName)
        if (string.IsNullOrEmpty(prefix))
            return propertyName;
        return string.Concat(prefix, ".", propertyName);

    private static int GetMaximumDepth()
        int num;
        NameValueCollection appSettings = ConfigurationManager.AppSettings;
        if (appSettings != null)
            string[] values = appSettings.GetValues("aspnet:MaxJsonDeserializerMembers");
            if (values != null && values.Length != 0 && int.TryParse(values[0], out num))
                return num;
        return 1000;

    private static int GetMaxJsonLength()
        int num;
        NameValueCollection appSettings = ConfigurationManager.AppSettings;
        if (appSettings != null)
            string[] values = appSettings.GetValues("aspnet:MaxJsonLength");
            if (values != null && values.Length != 0 && int.TryParse(values[0], out num))
                return num;
        return 1000;

Eclipse count lines of code

ProjectCodeMeter counts LLOC (logical lines of code) exactly as you described (only effective lines). it integrates into eclipse as external code metrics tool, it's not real-time though, it generates a report.actually it counts many source code metrics such as complexity, arithmetic intricacy, hard coded strings, numeric constants.. even estimates development time in hours.

Using Position Relative/Absolute within a TD?

This trick also suitable, but in this case align properties (middle, bottom etc.) won't be working.

<td style="display: block; position: relative;">

python: [Errno 10054] An existing connection was forcibly closed by the remote host

I know this is a very old question but it may be that you need to set the request headers. This solved it for me.

For example 'user-agent', 'accept' etc. here is an example with user-agent:

url = 'your-url-here'
headers = {'user-agent': 'Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/86.0.4240.75 Safari/537.36'}
r = requests.get(url, headers=headers)

How to sort a list of objects based on an attribute of the objects?

from operator import attrgetter
ut.sort(key = attrgetter('count'), reverse = True)

How do I align spans or divs horizontally?

You can use divs with the float: left; attribute which will make them appear horizontally next to each other, but then you may need to use clearing on the following elements to make sure they don't overlap.

Compiling Java 7 code via Maven

I had this problem when working with eclipse, I had to change the project's build path so that it refers to jre 7

How can I make a weak protocol reference in 'pure' Swift (without @objc)

Supplemental Answer

I was always confused about whether delegates should be weak or not. Recently I've learned more about delegates and when to use weak references, so let me add some supplemental points here for the sake of future viewers.

  • The purpose of using the weak keyword is to avoid strong reference cycles (retain cycles). Strong reference cycles happen when two class instances have strong references to each other. Their reference counts never go to zero so they never get deallocated.

  • You only need to use weak if the delegate is a class. Swift structs and enums are value types (their values are copied when a new instance is made), not reference types, so they don't make strong reference cycles.

  • weak references are always optional (otherwise you would used unowned) and always use var (not let) so that the optional can be set to nil when it is deallocated.

  • A parent class should naturally have a strong reference to its child classes and thus not use the weak keyword. When a child wants a reference to its parent, though, it should make it a weak reference by using the weak keyword.

  • weak should be used when you want a reference to a class that you don't own, not just for a child referencing its parent. When two non-hierarchical classes need to reference each other, choose one to be weak. The one you choose depends on the situation. See the answers to this question for more on this.

  • As a general rule, delegates should be marked as weak because most delegates are referencing classes that they do not own. This is definitely true when a child is using a delegate to communicate with a parent. Using a weak reference for the delegate is what the documentation recommends. (But see this, too.)

  • Protocols can be used for both reference types (classes) and value types (structs, enums). So in the likely case that you need to make a delegate weak, you have to make it an object-only protocol. The way to do that is to add AnyObject to the protocol's inheritance list. (In the past you did this using the class keyword, but AnyObject is preferred now.)

    protocol MyClassDelegate: AnyObject {
        // ...
    class SomeClass {
        weak var delegate: MyClassDelegate?

Further Study

Reading the following articles is what helped me to understand this much better. They also discuss related issues like the unowned keyword and the strong reference cycles that happen with closures.


typeof operator in C

It is a C extension from the GCC compiler , see

Apply function to each element of a list

Or, alternatively, you can take a list comprehension approach:

>>> mylis = ['this is test', 'another test']
>>> [item.upper() for item in mylis]

What is the most efficient/quickest way to loop through rows in VBA (excel)?

For Each is much faster than for I=1 to X, for some reason. Just try to go through the same dictionary,

once with for each Dkey in dDict,

and once with for Dkey = lbound(dDict.keys) to ubound(dDict.keys)

=>You will notice a huge difference, even though you are going through the same construct.

My Routes are Returning a 404, How can I Fix Them?

I was getting the same problem using EasyPHP. Found that I had to specify AllowOverride All in my <Directory> block in httpd.conf. Without this, Apache sometimes ignores your .htaccess.

Mine ended up looking like this...

<Directory "D:/Dev">
    Options FollowSymLinks Indexes
    AllowOverride All                  
    Order deny,allow
    Allow from
    Deny from all
    Require all granted     

Show DataFrame as table in iPython Notebook

To display dataframes contained in a list:


Case insensitive searching in Oracle

Since 10gR2, Oracle allows to fine-tune the behaviour of string comparisons by setting the NLS_COMP and NLS_SORT session parameters:







Session altered.


Session altered.






You can also create case insensitive indexes:

create index

This information was taken from Oracle case insensitive searches. The article mentions REGEXP_LIKE but it seems to work with good old = as well.

In versions older than 10gR2 it can't really be done and the usual approach, if you don't need accent-insensitive search, is to just UPPER() both the column and the search expression.

Visual Studio error "Object reference not set to an instance of an object" after install of ASP.NET and Web Tools 2015

Restarting Visual Studio did it for me. On the next run, it displayed a "Scanning new and updated MEF components ..." and then it executed normally.

It seems to be related to Windows update somehow, although I don't have proof.

How can I mimic the bottom sheet from the Maps app?

I released a library based on my answer below.

It mimics the Shortcuts application overlay. See this article for details.

The main component of the library is the OverlayContainerViewController. It defines an area where a view controller can be dragged up and down, hiding or revealing the content underneath it.

let contentController = MapsViewController()
let overlayController = SearchViewController()

let containerController = OverlayContainerViewController()
containerController.delegate = self
containerController.viewControllers = [

window?.rootViewController = containerController

Implement OverlayContainerViewControllerDelegate to specify the number of notches wished:

enum OverlayNotch: Int, CaseIterable {
    case minimum, medium, maximum

func numberOfNotches(in containerViewController: OverlayContainerViewController) -> Int {
    return OverlayNotch.allCases.count

func overlayContainerViewController(_ containerViewController: OverlayContainerViewController,
                                    heightForNotchAt index: Int,
                                    availableSpace: CGFloat) -> CGFloat {
    switch OverlayNotch.allCases[index] {
        case .maximum:
            return availableSpace * 3 / 4
        case .medium:
            return availableSpace / 2
        case .minimum:
            return availableSpace * 1 / 4

SwiftUI (12/29/20)

A SwiftUI version of the library is now available.

Previous answer

I think there is a significant point that is not treated in the suggested solutions: the transition between the scroll and the translation.

Maps transition between the scroll and the translation

In Maps, as you may have noticed, when the tableView reaches contentOffset.y == 0, the bottom sheet either slides up or goes down.

The point is tricky because we can not simply enable/disable the scroll when our pan gesture begins the translation. It would stop the scroll until a new touch begins. This is the case in most of the proposed solutions here.

Here is my try to implement this motion.

Starting point: Maps App

To start our investigation, let's visualize the view hierarchy of Maps (start Maps on a simulator and select Debug > Attach to process by PID or Name > Maps in Xcode 9).

Maps debug view hierarchy

It doesn't tell how the motion works, but it helped me to understand the logic of it. You can play with the lldb and the view hierarchy debugger.

Our view controller stacks

Let's create a basic version of the Maps ViewController architecture.

We start with a BackgroundViewController (our map view):

class BackgroundViewController: UIViewController {
    override func loadView() {
        view = MKMapView()

We put the tableView in a dedicated UIViewController:

class OverlayViewController: UIViewController, UITableViewDataSource, UITableViewDelegate {

    lazy var tableView = UITableView()

    override func loadView() {
        view = tableView
        tableView.dataSource = self
        tableView.delegate = self


Now, we need a VC to embed the overlay and manage its translation. To simplify the problem, we consider that it can translate the overlay from one static point OverlayPosition.maximum to another OverlayPosition.minimum.

For now it only has one public method to animate the position change and it has a transparent view:

enum OverlayPosition {
    case maximum, minimum

class OverlayContainerViewController: UIViewController {

    let overlayViewController: OverlayViewController
    var translatedViewHeightContraint = ...

    override func loadView() {
        view = UIView()

    func moveOverlay(to position: OverlayPosition) {

Finally we need a ViewController to embed the all:

class StackViewController: UIViewController {

    private var viewControllers: [UIViewController]

    override func viewDidLoad() {
        viewControllers.forEach { gz_addChild($0, in: view) }

In our AppDelegate, our startup sequence looks like:

let overlay = OverlayViewController()
let containerViewController = OverlayContainerViewController(overlayViewController: overlay)
let backgroundViewController = BackgroundViewController()
window?.rootViewController = StackViewController(viewControllers: [backgroundViewController, containerViewController])

The difficulty behind the overlay translation

Now, how to translate our overlay?

Most of the proposed solutions use a dedicated pan gesture recognizer, but we actually already have one : the pan gesture of the table view. Moreover, we need to keep the scroll and the translation synchronised and the UIScrollViewDelegate has all the events we need!

A naive implementation would use a second pan Gesture and try to reset the contentOffset of the table view when the translation occurs:

func panGestureAction(_ recognizer: UIPanGestureRecognizer) {
    if isTranslating {
        tableView.contentOffset = .zero

But it does not work. The tableView updates its contentOffset when its own pan gesture recognizer action triggers or when its displayLink callback is called. There is no chance that our recognizer triggers right after those to successfully override the contentOffset. Our only chance is either to take part of the layout phase (by overriding layoutSubviews of the scroll view calls at each frame of the scroll view) or to respond to the didScroll method of the delegate called each time the contentOffset is modified. Let's try this one.

The translation Implementation

We add a delegate to our OverlayVC to dispatch the scrollview's events to our translation handler, the OverlayContainerViewController :

protocol OverlayViewControllerDelegate: class {
    func scrollViewDidScroll(_ scrollView: UIScrollView)
    func scrollViewDidStopScrolling(_ scrollView: UIScrollView)

class OverlayViewController: UIViewController {


    func scrollViewDidScroll(_ scrollView: UIScrollView) {

    func scrollViewDidEndDragging(_ scrollView: UIScrollView, willDecelerate decelerate: Bool) {

In our container, we keep track of the translation using a enum:

enum OverlayInFlightPosition {
    case minimum
    case maximum
    case progressing

The current position calculation looks like :

private var overlayInFlightPosition: OverlayInFlightPosition {
    let height = translatedViewHeightContraint.constant
    if height == maximumHeight {
        return .maximum
    } else if height == minimumHeight {
        return .minimum
    } else {
        return .progressing

We need 3 methods to handle the translation:

The first one tells us if we need to start the translation.

private func shouldTranslateView(following scrollView: UIScrollView) -> Bool {
    guard scrollView.isTracking else { return false }
    let offset = scrollView.contentOffset.y
    switch overlayInFlightPosition {
    case .maximum:
        return offset < 0
    case .minimum:
        return offset > 0
    case .progressing:
        return true

The second one performs the translation. It uses the translation(in:) method of the scrollView's pan gesture.

private func translateView(following scrollView: UIScrollView) {
    scrollView.contentOffset = .zero
    let translation = translatedViewTargetHeight - scrollView.panGestureRecognizer.translation(in: view).y
    translatedViewHeightContraint.constant = max(
        min(translation, Constant.maximumHeight)

The third one animates the end of the translation when the user releases its finger. We calculate the position using the velocity & the current position of the view.

private func animateTranslationEnd() {
    let position: OverlayPosition =  // ... calculation based on the current overlay position & velocity
    moveOverlay(to: position)

Our overlay's delegate implementation simply looks like :

class OverlayContainerViewController: UIViewController {

    func scrollViewDidScroll(_ scrollView: UIScrollView) {
        guard shouldTranslateView(following: scrollView) else { return }
        translateView(following: scrollView)

    func scrollViewDidStopScrolling(_ scrollView: UIScrollView) {
        // prevent scroll animation when the translation animation ends
        scrollView.isEnabled = false
        scrollView.isEnabled = true

Final problem: dispatching the overlay container's touches

The translation is now pretty efficient. But there is still a final problem: the touches are not delivered to our background view. They are all intercepted by the overlay container's view. We can not set isUserInteractionEnabled to false because it would also disable the interaction in our table view. The solution is the one used massively in the Maps app, PassThroughView:

class PassThroughView: UIView {
    override func hitTest(_ point: CGPoint, with event: UIEvent?) -> UIView? {
        let view = super.hitTest(point, with: event)
        if view == self {
            return nil
        return view

It removes itself from the responder chain.

In OverlayContainerViewController:

override func loadView() {
    view = PassThroughView()


Here is the result:


You can find the code here.

Please if you see any bugs, let me know ! Note that your implementation can of course use a second pan gesture, specially if you add a header in your overlay.

Update 23/08/18

We can replace scrollViewDidEndDragging with willEndScrollingWithVelocity rather than enabling/disabling the scroll when the user ends dragging:

func scrollView(_ scrollView: UIScrollView,
                willEndScrollingWithVelocity velocity: CGPoint,
                targetContentOffset: UnsafeMutablePointer<CGPoint>) {
    switch overlayInFlightPosition {
    case .maximum:
    case .minimum, .progressing:
        targetContentOffset.pointee = .zero
    animateTranslationEnd(following: scrollView)

We can use a spring animation and allow user interaction while animating to make the motion flow better:

func moveOverlay(to position: OverlayPosition,
                 duration: TimeInterval,
                 velocity: CGPoint) {
    overlayPosition = position
    translatedViewHeightContraint.constant = translatedViewTargetHeight
        withDuration: duration,
        delay: 0,
        usingSpringWithDamping: velocity.y == 0 ? 1 : 0.6,
        initialSpringVelocity: abs(velocity.y),
        options: [.allowUserInteraction],
        animations: {
    }, completion: nil)

What is a 'multi-part identifier' and why can't it be bound?

When you type the FROM table those errors will disappear. Type FROM below what your typing then Intellisense will work and multi-part identifier will work.

Checking length of dictionary object

var c = {'a':'A', 'b':'B', 'c':'C'};
var count = 0;
for (var i in c) {
   if (c.hasOwnProperty(i)) count++;


How to kill a while loop with a keystroke?

the following code works for me. It requires openCV (import cv2).

The code is composed of an infinite loop that is continuously looking for a key pressed. In this case, when the 'q' key is pressed, the program ends. Other keys can be pressed (in this example 'b' or 'k') to perform different actions such as change a variable value or execute a function.

import cv2

while True:
    k = cv2.waitKey(1) & 0xFF
    # press 'q' to exit
    if k == ord('q'):
    elif k == ord('b'):
        # change a variable / do something ...
    elif k == ord('k'):
        # change a variable / do something ...

Spring Boot java.lang.NoClassDefFoundError: javax/servlet/Filter

For Jar

Add pom.xml


Error using eclipse for Android - No resource found that matches the given name

I renamed the file in res/values "strings.xml" to "string.xml" (no 's' on the end), cleaned and rebuilt without error.

Get file size before uploading

You can use PHP filesize function. During upload using ajax, please check the filesize first by making a request an ajax request to php script that checks the filesize and return the value.

Printing pointers in C

It's not a pointer to character char* but a pointer to array of 4 characters: char* [4]. With g++ it doesn't compile:

main.cpp: In function ‘int main(int, char**)’: main.cpp:126: error: cannot convert ‘char (*)[4]’ to ‘char**’ in initialization

Moreover, the linux man pages says:


The void * pointer argument is printed in hexadecimal (as if by %#x or %#lx). It shoud be pointer to void.

You can change your code to:

char* s = "asd";
char** p = &s;

printf("The value of s is: %p\n", s);
printf("The address of s is: %p\n", &s);

printf("The value of p is: %p\n", p);
printf("The address of p is: %p\n", &p);

printf("The address of s[0] is: %p\n", &s[0]);
printf("The address of s[1] is: %p\n", &s[1]);
printf("The address of s[2] is: %p\n", &s[2]);


The value of s is: 0x403f00

The address of s is: 0x7fff2df9d588

The value of p is: 0x7fff2df9d588

The address of p is: 0x7fff2df9d580

The address of s[0] is: 0x403f00

The address of s[1] is: 0x403f01

The address of s[2] is: 0x403f02

Laravel Password & Password_Confirmation Validation

Try this:

'password' => 'required|min:6|confirmed',
'password_confirmation' => 'required|min:6'

How to avoid .pyc files?

Solution for ipython 6.2.1 using python 3.5.2 (Tested on Ubuntu 16.04 and Windows 10):

Ipython doesn’t respect %env PYTHONDONTWRITEBYTECODE =1 if set in the ipython interpretor or during startup in ~/.ipython/profile-default/startup/00-startup.ipy. Instead using the following in your ~.ipython/profile-default/startup/

import sys

Remove rows with all or some NAs (missing values) in data.frame

One approach that's both general and yields fairly-readable code is to use the filter() function and the across() helper functions from the {dplyr} package.


vars_to_check <- c("rnor", "cfam")

# Filter a specific list of columns to keep only non-missing entries

df %>% 
                ~ !

# Filter all the columns to exclude NA
df %>% 
                ~ !

# Filter only numeric columns
df %>%
                ~ !

Similarly, there are also the variant functions in the dplyr package (filter_all, filter_at, filter_if) which accomplish the same thing:


vars_to_check <- c("rnor", "cfam")

# Filter a specific list of columns to keep only non-missing entries
df %>% 
  filter_at(.vars = vars(one_of(vars_to_check)),
            ~ !

# Filter all the columns to exclude NA
df %>% 
  filter_all(~ !

# Filter only numeric columns
df %>%
            ~ !

Android ADB commands to get the device properties

You should use adb shell getprop command and grep specific info about your current device, For additional information you can read documentation: Android Debug Bridge documentation

I added some examples below:

  1. language - adb shell getprop | grep language

    [persist.sys.language]: [en]

    [ro.product.locale.language]: [en]

  2. boot complete ( device ready after reset) - adb shell getprop | grep boot_completed

    [sys.boot_completed]: [1]

  3. device model - adb shell getprop | grep model

    [ro.product.model]: [Nexus 4]

  4. sdk version - adb shell getprop | grep sdk

    []: [22]

  5. time zone - adb shell getprop | grep timezone

    [persist.sys.timezone]: [Asia/China]

  6. serial number - adb shell getprop | grep serialno

    [ro.boot.serialno]: [1234567]

JS jQuery - check if value is in array

The Array.prototype property represents the prototype for the Array constructor and allows you to add new properties and methods to all Array objects. we can create a prototype for this purpose

Array.prototype.has_element = function(element) {
    return $.inArray( element, this) !== -1;

And then use it like this

var numbers= [1, 2, 3, 4];
numbers.has_element(3) => true
numbers.has_element(10) => false

See the Demo below

Array.prototype.has_element = function(element) {_x000D_
  return $.inArray(element, this) !== -1;_x000D_
var numbers = [1, 2, 3, 4];_x000D_
<script src=""></script>

Transfer git repositories from GitLab to GitHub - can we, how to and pitfalls (if any)?

This is very easy by import repository feature Login to,

Side of profile picture you will find + button click on that then there will be option to import repository. you will find page like this. enter image description here Your old repository’s clone URL is required which is gitlab repo url in your case. then select Owner and then type name for this repo and click to begin import button.

Command line to remove an environment variable from the OS level configuration

The command in DougWare's answer did not work, but this did:

reg delete "HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Environment" /v FOOBAR /f

The shortcut HKLM can be used for HKEY_LOCAL_MACHINE.

How to split elements of a list?

Something like:

>>> l = ['element1\t0238.94', 'element2\t2.3904', 'element3\t0139847']
>>> [i.split('\t', 1)[0] for i in l]
['element1', 'element2', 'element3']

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

You also follow this code:

var response = new HttpResponseMessage(HttpStatusCode.NotFound)
      Content = new StringContent("Users doesn't exist", System.Text.Encoding.UTF8, "text/plain"),
      StatusCode = HttpStatusCode.NotFound
 throw new HttpResponseException(response);

how to destroy bootstrap modal window completely?

It works for Bootstrap v3.3.6

.on('', function () {
    // Some Code
}).on('', function () {
    // Some Code
}).on('', function () {

IntelliJ, can't start simple web application: Unable to ping server at localhost:1099

To fix this you need add your machine name in the /etc/hosts file to point to localhost(

You can find your machine name by running the following command:

$ hostname

From the output above you know your hostname is "macbook-pro". Edit "/etc/hosts" file and add that name at the end of line that lists localhost macbook-pro

Save the file.

Now you IntelliJ should be able to start your server.

Unable to cast object of type 'System.DBNull' to type 'System.String`

I use an extension to eliminate this problem for me, which may or may not be what you are after.

It goes like this:

public static class Extensions

    public String TrimString(this object item)
        return String.Format("{0}", item).Trim();



This extension does not return null values! If the item is null or DBNull.Value, it will return an empty String.


public string GetCustomerNumber(Guid id)
    var obj = 
            new SqlParameter("@id", id)
    return obj.TrimString();

Add Custom Headers using HttpWebRequest

A simple method of creating the service, adding headers and reading the JSON response,

private static void WebRequest()
    const string WEBSERVICE_URL = "<<Web Service URL>>";
        var webRequest = System.Net.WebRequest.Create(WEBSERVICE_URL);
        if (webRequest != null)
            webRequest.Method = "GET";
            webRequest.Timeout = 20000;
            webRequest.ContentType = "application/json";
            webRequest.Headers.Add("Authorization", "Basic dcmGV25hZFzc3VudDM6cGzdCdvQ=");
            using (System.IO.Stream s = webRequest.GetResponse().GetResponseStream())
                using (System.IO.StreamReader sr = new System.IO.StreamReader(s))
                    var jsonResponse = sr.ReadToEnd();
                    Console.WriteLine(String.Format("Response: {0}", jsonResponse));
    catch (Exception ex)

Java OCR implementation

If you are looking for a very extensible option or have a specific problem domain you could consider rolling your own using the Java Object Oriented Neural Engine. Another JOONE reference.

I used it successfully in a personal project to identify the letter from an image such as this, you can find all the source for the OCR component of my application on github, here.

Is "delete this" allowed in C++?

Well, in Component Object Model (COM) delete this construction can be a part of Release method that is called whenever you want to release aquisited object:

void IMyInterface::Release()
    if(instanceCount == 0)
        delete this;

Make EditText ReadOnly

This works for me:


Android Activity without ActionBar

Please find the default theme in styles.xml

<!-- Base application theme. -->
    <style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
        <!-- Customize your theme here. -->
        <item name="colorPrimary">@color/colorPrimary</item>
        <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
        <item name="colorAccent">@color/colorAccent</item>

And change parent this way

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

Convert a string to datetime in PowerShell

Chris Dents' answer has already covered the OPs' question but seeing as this was the top search on google for PowerShell format string as date I thought I'd give a different string example.

If like me, you get the time string like this 20190720170000.000000+000

An important thing to note is you need to use ToUniversalTime() when using [System.Management.ManagementDateTimeConverter] otherwise you get offset times against your input.

PS Code

Write-Host "This example is for the 24hr clock with HH"
Write-Host "ToUniversalTime() must be used when using [System.Management.ManagementDateTimeConverter]"
$my_date_24hr_time   = "20190720170000.000000+000"
$date_format         = "yyyy-MM-dd HH:mm"
Write-Host "-----------------------------"
Write-Host "This example is for the am pm clock with hh"
Write-Host "Again, ToUniversalTime() must be used when using [System.Management.ManagementDateTimeConverter]"
$my_date_ampm_time   = "20190720110000.000000+000"


This example is for the 24hr clock with HH
ToUniversalTime() must be used when using [System.Management.ManagementDateTimeConverter]

20 July 2019 17:00:00
2019-07-20 17:00
2019-07-20 17:00


This example is for the am pm clock with hh
Again, ToUniversalTime() must be used when using [System.Management.ManagementDateTimeConverter]

20 July 2019 11:00:00
2019-07-20 11:00
2019-07-20 11:00

MS doc on [Management.ManagementDateTimeConverter]:

ImportError: No Module named simplejson

@noskio is correct... it just means that simplejson isn't found on your system and you need to install it for Python older than 2.6. one way is to use the setuptools easy_install tool. with it, you can install it as easily as: easy_install simplejson

UPDATE (Feb 2014): this is probably old news to many of you, but pip is a more modern tool that works in a similar way (i.e., pip install simplejson), only it can also uninstall apps.

error NG6002: Appears in the NgModule.imports of AppModule, but could not be resolved to an NgModule class

For me I was working under Ubuntu

The error disappeared if I use sudo with ng

sudo ng build
sudo ng serve

How does Subquery in select statement work in oracle

In the Oracle RDBMS, it is possible to use a multi-row subquery in the select clause as long as the (sub-)output is encapsulated as a collection. In particular, a multi-row select clause subquery can output each of its rows as an xmlelement that is encapsulated in an xmlforest.

How to flush route table in windows?

In Microsoft Windows, you can go through by route -f command to delete your current Gateway, check route / ? for more advance option, like add / delete etc and also can write a batch to add route on specific time as well but if you need to delete IP cache, then you have the option to use arp command.

Push commits to another branch

git init _x000D_
#git remote remove origin_x000D_
git remote add origin  <http://...git>_x000D_
echo "This is for demo" >> _x000D_
git add README.md_x000D_
git commit -m "Initail Commit" _x000D_
git checkout -b branch1 _x000D_
git branch --list_x000D_
****add files***_x000D_
git add -A_x000D_
git status_x000D_
git commit -m "Initial - branch1"_x000D_
git push --set-upstream origin branch1_x000D_
#git push origin --delete  branch1_x000D_
#git branch --unset-upstream  

Split list into smaller lists (split in half)


How to initialize/instantiate a custom UIView class with a XIB file in Swift

override func draw(_ rect: CGRect) 
    AlertView.layer.cornerRadius = 4
    AlertView.clipsToBounds = true

    btnOk.layer.cornerRadius = 4
    btnOk.clipsToBounds = true   

class func instanceFromNib() -> LAAlertView {
    return UINib(nibName: "LAAlertView", bundle: nil).instantiate(withOwner: nil, options: nil)[0] as! LAAlertView

@IBAction func okBtnDidClicked(_ sender: Any) {


    UIView.animate(withDuration: 0.4, delay: 0.0, options: .allowAnimatedContent, animations: {() -> Void in
        self.AlertView.transform = CGAffineTransform(scaleX: 0.1, y: 0.1)

    }, completion: {(finished: Bool) -> Void in
        self.AlertView.transform = CGAffineTransform.identity
        self.AlertView.transform = CGAffineTransform(scaleX: 0.0, y: 0.0)
        self.AlertView.isHidden = true
        self.AlertView.alpha = 0.0

        self.alpha = 0.5

func removeAlertViewFromWindow()
    for subview  in (appDel.window?.subviews)! {
        if subview.tag == 500500{

public func openAlertView(title:String , string : String ){

    lblTital.text  = title
    txtView.text  = string

    self.frame = CGRect(x: 0, y: 0, width: screenWidth, height: screenHeight)

    AlertView.alpha = 1.0
    AlertView.isHidden = false

    UIView.animate(withDuration: 0.2, animations: {() -> Void in
        self.alpha = 1.0
    AlertView.transform = CGAffineTransform(scaleX: 0.0, y: 0.0)

    UIView.animate(withDuration: 0.3, delay: 0.2, options: .allowAnimatedContent, animations: {() -> Void in
        self.AlertView.transform = CGAffineTransform(scaleX: 1.1, y: 1.1)

    }, completion: {(finished: Bool) -> Void in
        UIView.animate(withDuration: 0.2, animations: {() -> Void in
            self.AlertView.transform = CGAffineTransform(scaleX: 1.0, y: 1.0)



Stop absolutely positioned div from overlapping text

Could you add z-index style to the two sections so that the one you want appears on top?

how to get the one entry from hashmap without iterating

Get values, convert it to an array, get array's first element:



How to add parameters to a HTTP GET request in Android?

List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("param1","value1");

String query = URLEncodedUtils.format(params, "utf-8");

URI url = URIUtils.createURI(scheme, userInfo, authority, port, path, query, fragment); //can be null
HttpGet httpGet = new HttpGet(url);

URI javadoc

Note: url = new URI(...) is buggy

How to display list items on console window in C#

While the answers with List<T>.ForEach are very good.

I found String.Join<T>(string separator, IEnumerable<T> values) method more useful.

Example :

List<string> numbersStrLst = new List<string>
            { "One", "Two", "Three","Four","Five"};

Console.WriteLine(String.Join(", ", numbersStrLst));//Output:"One, Two, Three, Four, Five"

int[] numbersIntAry = new int[] {1, 2, 3, 4, 5};
Console.WriteLine(String.Join("; ", numbersIntAry));//Output:"1; 2; 3; 4; 5"

Remarks :

If separator is null, an empty string (String.Empty) is used instead. If any member of values is null, an empty string is used instead.

Join(String, IEnumerable<String>) is a convenience method that lets you concatenate each element in an IEnumerable(Of String) collection without first converting the elements to a string array. It is particularly useful with Language-Integrated Query (LINQ) query expressions.

This should work just fine for the problem, whereas for others, having array values. Use other overloads of this same method, String.Join Method (String, Object[])


How to return a file (FileContentResult) in ASP.NET WebAPI

I am not exactly sure which part to blame, but here's why MemoryStream doesn't work for you:

As you write to MemoryStream, it increments it's Position property. The constructor of StreamContent takes into account the stream's current Position. So if you write to the stream, then pass it to StreamContent, the response will start from the nothingness at the end of the stream.

There's two ways to properly fix this:

1) construct content, write to stream

public HttpResponseMessage Test()
    var stream = new MemoryStream();
    var response = Request.CreateResponse(HttpStatusCode.OK);
    response.Content = new StreamContent(stream);
    // ...
    // stream.Write(...);
    // ...
    return response;

2) write to stream, reset position, construct content

public HttpResponseMessage Test()
    var stream = new MemoryStream();
    // ...
    // stream.Write(...);
    // ...
    stream.Position = 0;

    var response = Request.CreateResponse(HttpStatusCode.OK);
    response.Content = new StreamContent(stream);
    return response;

2) looks a little better if you have a fresh Stream, 1) is simpler if your stream does not start at 0

Monitor network activity in Android Phones

The DDMS tool included in the Android SDK includes a tool for monitoring network traffic. It does not provide the kind of detail you get from tcpdump and similar low level tools, but it is still very useful.

Oficial documentation:

What is the default value for Guid?

You can use Guid.Empty. It is a read-only instance of the Guid structure with the value of 00000000-0000-0000-0000-000000000000

you can also use these instead

var g = new Guid();
var g = default(Guid);

beware not to use Guid.NewGuid() because it will generate a new Guid.

use one of the options above which you and your team think it is more readable and stick to it. Do not mix different options across the code. I think the Guid.Empty is the best one since new Guid() might make us think it is generating a new guid and some may not know what is the value of default(Guid).

What languages are Windows, Mac OS X and Linux written in?

Wow!!! 9 years of question but I've just come across a series of internal article on Windows Command Line history and I think some part of it might be relevant Windows side of the question:

For those who care about such things: Many have asked whether Windows is written in C or C++. The answer is that - despite NT's Object-Based design - like most OS', Windows is almost entirely written in 'C'. Why? C++ introduces a cost in terms of memory footprint, and code execution overhead. Even today, the hidden costs of code written in C++ can be surprising, but back in the late 1990's, when memory cost ~$60/MB (yes … $60 per MEGABYTE!), the hidden memory cost of vtables etc. was significant. In addition, the cost of virtual-method call indirection and object-dereferencing could result in very significant performance & scale penalties for C++ code at that time. While one still needs to be careful, the performance overhead of modern C++ on modern computers is much less of a concern, and is often an acceptable trade-off considering its security, readability, and maintainability benefits ... which is why we're steadily upgrading the Console’s code to modern C++.

How to connect a Windows Mobile PDA to Windows 10

Here is the answer: Download the "Windows Mobile Device Center" for your machine type, likely 64bit.

Before you run the install, change the compatibility settings to 'Windows 7'. Then install it... Then run it: You'll find it under 'WMDC'.. Your device should now recognize, when plugged in, mine did!

In Mongoose, how do I sort by date? (node.js)

The correct answer is:

Blah.find({}).sort({date: -1}).execFind(function(err,docs){


git add remote branch

Here is the complete process to create a local repo and push the changes to new remote branch

  1. Creating local repository:-

    Initially user may have created the local git repository.

    $ git init :- This will make the local folder as Git repository,

  2. Link the remote branch:-

    Now challenge is associate the local git repository with remote master branch.

    $ git remote add RepoName RepoURL

    usage: git remote add []

  3. Test the Remote

    $ git remote show --->Display the remote name

    $ git remote -v --->Display the remote branches

  4. Now Push to remote

    $git add . ----> Add all the files and folder as git staged'

    $git commit -m "Your Commit Message" - - - >Commit the message

    $git push - - - - >Push the changes to the upstream

malloc for struct and pointer in C

Few points

struct Vector y = (struct Vector*)malloc(sizeof(struct Vector)); is wrong

it should be struct Vector *y = (struct Vector*)malloc(sizeof(struct Vector)); since y holds pointer to struct Vector.

1st malloc() only allocates memory enough to hold Vector structure (which is pointer to double + int)

2nd malloc() actually allocate memory to hold 10 double.

mvn clean install vs. deploy vs. release

  • mvn install will put your packaged maven project into the local repository, for local application using your project as a dependency.
  • mvn release will basically put your current code in a tag on your SCM, change your version in your projects.
  • mvn deploy will put your packaged maven project into a remote repository for sharing with other developers.

Resources :

How can I one hot encode in Python?

Here is a solution using DictVectorizer and the Pandas DataFrame.to_dict('records') method.

>>> import pandas as pd
>>> X = pd.DataFrame({'income': [100000,110000,90000,30000,14000,50000],
                      'country':['US', 'CAN', 'US', 'CAN', 'MEX', 'US'],
                      'race':['White', 'Black', 'Latino', 'White', 'White', 'Black']

>>> from sklearn.feature_extraction import DictVectorizer
>>> v = DictVectorizer()
>>> qualitative_features = ['country','race']
>>> X_qual = v.fit_transform(X[qualitative_features].to_dict('records'))
>>> v.vocabulary_
{'country=CAN': 0,
 'country=MEX': 1,
 'country=US': 2,
 'race=Black': 3,
 'race=Latino': 4,
 'race=White': 5}

>>> X_qual.toarray()
array([[ 0.,  0.,  1.,  0.,  0.,  1.],
       [ 1.,  0.,  0.,  1.,  0.,  0.],
       [ 0.,  0.,  1.,  0.,  1.,  0.],
       [ 1.,  0.,  0.,  0.,  0.,  1.],
       [ 0.,  1.,  0.,  0.,  0.,  1.],
       [ 0.,  0.,  1.,  1.,  0.,  0.]])

In Visual Studio Code How do I merge between two local branches?

Update June 2017 (from VSCode 1.14)

The ability to merge local branches has been added through PR 25731 and commit 89cd05f: accessible through the "Git: merge branch" command.
And PR 27405 added handling the diff3-style merge correctly.

Vahid's answer mention 1.17, but that September release actually added nothing regarding merge.
Only the 1.18 October one added Git conflict markers

From 1.18, with the combination of merge command (1.14) and merge markers (1.18), you truly can do local merges between branches.

Original answer 2016:

The Version Control doc does not mention merge commands, only merge status and conflict support.

Even the latest 1.3 June release does not bring anything new to the VCS front.

This is supported by issue 5770 which confirms you cannot use VS Code as a git mergetool, because:

Is this feature being included in the next iteration, by any chance?

Probably not, this is a big endeavour, since a merge UI needs to be implemented.

That leaves the actual merge to be initiated from command line only.

How to unzip a file using the command line?

Originally ZIP files were created with MS-DOS command line software from PKWare, the two programs were PKZIP.EXE and PKUNZIP.EXE. I think you can still download PKUNZIP at the PKWare site here:

The actual command line could look something like this:

C:\>pkunzip c:\ c:\extracttothisfolder\

TypeError: tuple indices must be integers, not str

I think you should do

for index, row in result: 

If you wanna access by name.

Playing .mp3 and .wav in Java?

Using MP3 Decoder/player/converter Maven Dependency.

import javazoom.jl.decoder.JavaLayerException;
import javazoom.jl.player.Player;


public class PlayAudio{

public static void main(String[] args) throws FileNotFoundException {

    try {
        FileInputStream fileInputStream = new FileInputStream("mp.mp3");
        Player player = new Player((fileInputStream));;
        System.out.println("Song is playing");
    }catch (Exception e){



Iterating through list of list in Python

So wait, this is just a list-within-a-list?

The easiest way is probably just to use nested for loops:

>>> a = [[1, 3, 4], [2, 4, 4], [3, 4, 5]]
>>> a
[[1, 3, 4], [2, 4, 4], [3, 4, 5]]
>>> for list in a:
...     for number in list:
...         print number

Or is it something more complicated than that? Arbitrary nesting or something? Let us know if there's something else as well.

Also, for performance reasons, you might want to look at using list comprehensions to do this:

How can I iterate through a string and also know the index (current position)?

I would use it-str.begin() In this particular case std::distance and operator- are the same. But if container will change to something without random access, std::distance will increment first argument until it reach second, giving thus linear time and operator- will not compile. Personally I prefer the second behaviour - it's better to be notified when you algorithm from O(n) became O(n^2)...

Basic calculator in Java

CompareStrings with equals(..) not with ==

if (operation.equals("+")
    System.out.println("your answer is" + (num1 + num2));
if (operation.equals("-"))
    System.out.println("your answer is" + (num1 - num2));
if (operation.equals("/"))
    System.out.println("your answer is" + (num1 / num2));
if (operation .equals( "*"))
    System.out.println("your answer is" + (num1 * num2));

And the ; after the conditions was an empty statement so the conditon had no effect at all.

If you use java 7 you can also replace the if statements with a switch.
In java <7 you can test, if operation has length 1 and than make a switch for the char [switch (operation.charAt(0))]

How can I open a URL in Android's web browser from my application?

Try this..Worked for me!

    public void webLaunch(View view) {
            WebView myWebView = (WebView) findViewById(;
            View view1=findViewById(;
            myWebView.loadUrl("<your link>");


xml code :-

 <WebView  xmlns:android=""

--------- OR------------------

String url = "";
Intent i = new Intent(Intent.ACTION_VIEW);

How to set selected value of jquery select2?

var $option = $("<option selected></option>").val('1').text("Pick me");


Try this append then select. Doesn't duplicate the option upon AJAX call.

use of entityManager.createNativeQuery(query,foo.class)

JPA was designed to provide an automatic mapping between Objects and a relational database. Since Integer is not a persistant entity, why do you need to use JPA ? A simple JDBC request will work fine.

Delegates in swift?

The solutions above seemed a little coupled and at the same time avoid reuse the same protocol in other controllers, that's why I've come with the solution that is more strong typed using generic type-erasure.

@noreturn public func notImplemented(){
    fatalError("not implemented yet")

public protocol DataChangedProtocol: class{
    typealias DataType

    func onChange(t:DataType)

class AbstractDataChangedWrapper<DataType> : DataChangedProtocol{

    func onChange(t: DataType) {

class AnyDataChangedWrapper<T: DataChangedProtocol> : AbstractDataChangedWrapper<T.DataType>{

    var base: T

    init(_ base: T ){
        self.base = base

    override func onChange(t: T.DataType) {

class AnyDataChangedProtocol<DataType> : DataChangedProtocol{

    var base: AbstractDataChangedWrapper<DataType>

    init<S: DataChangedProtocol where S.DataType == DataType>(_ s: S){
        self.base = AnyDataChangedWrapper(s)

    func onChange(t: DataType) {

class Source : DataChangedProtocol {
    func onChange(data: String) {
        print( "got new value \(data)" )

class Target {
    var delegate: AnyDataChangedProtocol<String>?

    func reportChange(data:String ){

var source = Source()
var target = Target()

target.delegate = AnyDataChangedProtocol(source)

output: got new value newValue

Ruby Arrays: select(), collect(), and map()

It looks like details is an array of hashes. So item inside of your block will be the whole hash. Therefore, to check the :qty key, you'd do something like the following:{ |item| item[:qty] != "" }

That will give you all items where the :qty key isn't an empty string.

official select documentation

How to add trendline in python matplotlib dot (scatter) graphs?

as explained here

With help from numpy one can calculate for example a linear fitting.

# plot the data itself

# calc the trendline
z = numpy.polyfit(x, y, 1)
p = numpy.poly1d(z)
# the line equation:
print "y=%.6fx+(%.6f)"%(z[0],z[1])

Get host domain from URL?

Try like this;

Uri.GetLeftPart( UriPartial.Authority )

Defines the parts of a URI for the Uri.GetLeftPart method. --> -->

nntp://[email protected] --> nntp://

file://server/filename.ext --> file://server

Uri uriAddress = new Uri("");
Console.WriteLine("The path of this Uri is {0}", uriAddress.GetLeftPart(UriPartial.Authority));


Database Structure for Tree Data Structure

If anyone using MS SQL Server 2008 and higher lands on this question: SQL Server 2008 and higher has a new "hierarchyId" feature designed specifically for this task.

More info at

Psexec "run as (remote) admin"

Simply add a -h after adding your credentials using a -u -p, and it will run with elevated privileges.

How to change MenuItem icon in ActionBar programmatically

I resolved this problem this way:

In onCreateOptionsMenu: = menu;"calendar");
ImageView imageView = new ImageView(getActivity());
MenuItem item =;

in onOptionsItemSelected:

if (item.getOrder() == 0) {
    return true;

How do I set hostname in docker-compose?

This seems to work correctly. If I put your config into a file:

$ cat > compose.yml <<EOF
  image: phensley/docker-dns
  hostname: affy
    - /var/run/docker.sock:/docker.sock

And then bring things up:

$ docker-compose -f compose.yml up
Creating tmp_dns_1...
Attaching to tmp_dns_1
dns_1 | 2015-04-28T17:47:45.423387 [dockerdns] table.add tmp_dns_1.docker ->

And then check the hostname inside the container, everything seems to be fine:

$ docker exec -it stack_dns_1 hostname

AngularJS: How do I manually set input to $valid in controller?

The answers above didn't help me solve my problem. After a long search I bumped into this partial solution.

I've finally solved my problem with this code to set the input field manually to ng-invalid (to set to ng-valid set it to 'true'):

$scope.myForm.inputName.$setValidity('required', false);