Programs & Examples On #Objective c blocks

Blocks are Apple’s implementation of closures for C, which are also available for Objective-C and C++.

Store a closure as a variable in Swift

This works too:

var exeBlk = {
    () -> Void in
exeBlk = {
    //do something
//instead of nil:
exeBlk = {}

Waiting until two async blocks are executed before starting another block

The first answer is essentially correct, but if you want the very simplest way to accomplish the desired result, here's a stand-alone code example demonstrating how to do it with a semaphore (which is also how dispatch groups work behind the scenes, JFYI):

#include <dispatch/dispatch.h>
#include <stdio.h>

        dispatch_queue_t myQ = dispatch_queue_create("my.conQ", DISPATCH_QUEUE_CONCURRENT);
        dispatch_semaphore_t mySem = dispatch_semaphore_create(0);

        dispatch_async(myQ, ^{ printf("Hi I'm block one!\n"); sleep(2); dispatch_semaphore_signal(mySem);});
        dispatch_async(myQ, ^{ printf("Hi I'm block two!\n"); sleep(4); dispatch_semaphore_signal(mySem);});
        dispatch_async(myQ, ^{ dispatch_semaphore_wait(mySem, DISPATCH_TIME_FOREVER); printf("Hi, I'm the final block!\n"); });

Assign a variable inside a Block to a variable outside a Block

When I saw the same error, I tried to resolve it like:

   __block CGFloat docHeight = 0.0;

    [self evaluateJavaScript:@"document.height" completionHandler:^(id height, NSError *error) {
        docHeight = [height floatValue];

and its working fine

Just add "__block" before Variable.

What does the "__block" keyword mean?

@bbum covers blocks in depth in a blog post and touches on the __block storage type.

__block is a distinct storage type

Just like static, auto, and volatile, __block is a storage type. It tells the compiler that the variable’s storage is to be managed differently.


However, for __block variables, the block does not retain. It is up to you to retain and release, as needed.

As for use cases you will find __block is sometimes used to avoid retain cycles since it does not retain the argument. A common example is using self.

//Now using myself inside a block will not 
//retain the value therefore breaking a
//possible retain cycle.
__block id myself = self;

How do you trigger a block after a delay, like -performSelector:withObject:afterDelay:?

Xcode 10.2 and Swift 5 and above

DispatchQueue.main.asyncAfter(deadline: .now() + 2, execute: {
   // code to execute                 

Can I use Objective-C blocks as properties?

You can follow the format below and can use the testingObjectiveCBlock property in the class.

typedef void (^testingObjectiveCBlock)(NSString *errorMsg);

@interface MyClass : NSObject
@property (nonatomic, strong) testingObjectiveCBlock testingObjectiveCBlock;

For more info have a look here

How to hide axes and gridlines in Matplotlib (python)

# Hide grid lines

# Hide axes ticks

Note, you need matplotlib>=1.2 for set_zticks() to work.

Date difference in years using C#

If you're dealing with months and years you need something that knows how many days each month has and which years are leap years.

Enter the Gregorian Calendar (and other culture-specific Calendar implementations).

While Calendar doesn't provide methods to directly calculate the difference between two points in time, it does have methods such as

DateTime AddWeeks(DateTime time, int weeks)
DateTime AddMonths(DateTime time, int months)
DateTime AddYears(DateTime time, int years)

Get height of div with no height set in css

Can do this in jQuery. Try all options .height(), .innerHeight() or .outerHeight().

$('document').ready(function() {
    $('#right_div').css({'height': $('#left_div').innerHeight()});

Example Screenshot

enter image description here

Hope this helps. Thanks!!

Change default timeout for mocha

Adding this for completeness. If you (like me) use a script in your package.json file, just add the --timeout option to mocha:

"scripts": {
  "test": "mocha 'test/**/*.js' --timeout 10000",
  "test-debug": "mocha --debug 'test/**/*.js' --timeout 10000"

Then you can run npm run test to run your test suite with the timeout set to 10,000 milliseconds.

How to get the current taxonomy term ID (not the slug) in WordPress?

It's the term slug you want.Looks like you can get the id like this if that's what you need:

function get_term_link( $term, $taxonomy = '' ) {
    global $wp_rewrite;

    if ( !is_object($term) ) {
        if ( is_int( $term ) ) {
            $term = get_term( $term, $taxonomy );
        } else {
            $term = get_term_by( 'slug', $term, $taxonomy );

Add text to Existing PDF using Python

Leveraging David Dehghan's answer above, the following works in Python 2.7.13:

from PyPDF2 import PdfFileWriter, PdfFileReader, PdfFileMerger

import StringIO

from reportlab.pdfgen import canvas
from reportlab.lib.pagesizes import letter

packet = StringIO.StringIO()
# create a new PDF with Reportlab
can = canvas.Canvas(packet, pagesize=letter)
can.drawString(290, 720, "Hello world")

#move to the beginning of the StringIO buffer
new_pdf = PdfFileReader(packet)
# read your existing PDF
existing_pdf = PdfFileReader("original.pdf")
output = PdfFileWriter()
# add the "watermark" (which is the new pdf) on the existing page
page = existing_pdf.getPage(0)
# finally, write "output" to a real file
outputStream = open("destination.pdf", "wb")

JQuery .hasClass for multiple values in an if statement

This may be another solution:

if ($('html').attr('class').match(/m320|m768/)) {  
  // do stuff   

according to it's quite fast, too.

How to import local packages in go?

Well, I figured out the problem. Basically Go starting path for import is $HOME/go/src

So I just needed to add myapp in front of the package names, that is, the import should be:

import (

What is the difference between encode/decode?

There are a few encodings that can be used to de-/encode from str to str or from unicode to unicode. For example base64, hex or even rot13. They are listed in the codecs module.


The decode message on a unicode string can undo the corresponding encode operation:

In [1]: u'0a'.decode('hex')
Out[1]: '\n'

The returned type is str instead of unicode which is unfortunate in my opinion. But when you are not doing a proper en-/decode between str and unicode this looks like a mess anyway.

RESTful web service - how to authenticate requests from other services?

Any solution to this problem boils down to a shared secret. I also don't like the hard-coded user-name and password option but it does have the benefit of being quite simple. The client certificate is also good but is it really much different? There's a cert on the server and one on the client. It's main advantage is that it's harder to brute force. Hopefully you've got other protections in place to protect against that though.

I don't think your point A for the client certificate solution is difficult to resolve. You just use a branch. if (client side certificat) { check it } else { http basic auth } I'm no java expert and I've never worked with it to do client side certificates. However a quick Google leads us to this tutorial which looks right up your alley.

Despite all of this "what's best" discussion, let me just point out that there is another philosophy that says, "less code, less cleverness is better." (I personally hold this philosophy). The client certificate solution sounds like a lot of code.

I know you expressed questions about OAuth, but the OAuth2 proposal does include a solution to your problem called "bearer tokens" which must be used in conjunction with SSL. I think, for the sake of simplicity, I'd choose either the hard-coded user/pass (one per app so that they can be revoked individually) or the very similar bearer tokens.

Where do I find the Instagram media ID of a image

Here's a better way:

Render as json object and you can easily extract media id from it ---

For instance, in PHP

$api = file_get_contents("");      
$apiObj = json_decode($api,true);      
$media_id = $apiObj['media_id'];

For instance, in JS

    type: 'GET',     
    url: '',     
    cache: false,     
    dataType: 'jsonp',     
    success: function(data) {           
            var media_id = data[0].media_id;          

Adjusting the Xcode iPhone simulator scale and size

However iOS Simulator->HardWare->Device menu.

Pointtype command for gnuplot

You first have to tell Gnuplot to use a style that uses points, e.g. with points or with linespoints. Try for example:

plot sin(x) with points


Now try:

plot sin(x) with points pointtype 5


You may also want to look at the output from the test command which shows you the capabilities of the current terminal. Here are the capabilities for my pngairo terminal:

How do I resolve `The following packages have unmet dependencies`

The command to have Ubuntu fix unmet dependencies and broken packages is

sudo apt-get install -f

from the man page:

-f, --fix-broken Fix; attempt to correct a system with broken dependencies in place. This option, when used with install/remove, can omit any packages to permit APT to deduce a likely solution. If packages are specified, these have to completely correct the problem. The option is sometimes necessary when running APT for the first time; APT itself does not allow broken package dependencies to exist on a system. It is possible that a system's dependency structure can be so corrupt as to require manual intervention (which usually means using dselect(1) or dpkg --remove to eliminate some of the offending packages)

Ubuntu will try to fix itself when you run the command. When it completes, you can test if it worked by running the command again, and you should receive output similar to:

Reading package lists... Done Building dependency tree Reading state information... Done 0 upgraded, 0 newly installed, 0 to remove and 2 not upgraded.

Setting values of input fields with Angular 6

You should use the following:

       <td><input id="priceInput-{{}}" type="number" [(ngModel)]="orderLine.price"></td>

You will need to add the FormsModule to your app.module in the inputs section as follows:

import { FormsModule } from '@angular/forms';

  declarations: [
  imports: [

The use of the brackets around the ngModel are as follows:

  • The [] show that it is taking an input from your TS file. This input should be a public member variable. A one way binding from TS to HTML.

  • The () show that it is taking output from your HTML file to a variable in the TS file. A one way binding from HTML to TS.

  • The [()] are both (e.g. a two way binding)

See here for more information:

I would also suggest replacing id="priceInput-{{}}" with something like this [id]="getElementId(orderLine)" where getElementId(orderLine) returns the element Id in the TS file and can be used anywere you need to reference the element (to avoid simple bugs like calling it priceInput1 in one place and priceInput-1 in another. (if you still need to access the input by it's Id somewhere else)

Java Immutable Collections

Pure4J supports what you are after, in two ways.

First, it provides an @ImmutableValue annotation, so that you can annotate a class to say that it is immutable. There is a maven plugin to allow you to check that your code actually is immutable (use of final etc.).

Second, it provides the persistent collections from Clojure, (with added generics) and ensures that elements added to the collections are immutable. Performance of these is apparently pretty good. Collections are all immutable, but implement java collections interfaces (and generics) for inspection. Mutation returns new collections.

Disclaimer: I'm the developer of this

How can I specify my .keystore file with Spring Boot and Tomcat?

Starting with Spring Boot 1.2, you can configure SSL using or application.yml. Here's an example for

server.port = 8443
server.ssl.key-store = classpath:keystore.jks
server.ssl.key-store-password = secret
server.ssl.key-password = another-secret

Same thing with application.yml:

  port: 8443
    key-store: classpath:keystore.jks
    key-store-password: secret
    key-password: another-secret

Here's a link to the current reference documentation.

Change a HTML5 input's placeholder color with CSS

/* do not group these rules */_x000D_
*::-webkit-input-placeholder {_x000D_
    color: red;_x000D_
*:-moz-placeholder {_x000D_
    /* FF 4-18 */_x000D_
    color: red;_x000D_
    opacity: 1;_x000D_
*::-moz-placeholder {_x000D_
    /* FF 19+ */_x000D_
    color: red;_x000D_
    opacity: 1;_x000D_
*:-ms-input-placeholder {_x000D_
    /* IE 10+ */_x000D_
    color: red;_x000D_
*::-ms-input-placeholder {_x000D_
    /* Microsoft Edge */_x000D_
    color: red;_x000D_
*::placeholder {_x000D_
    /* modern browser */_x000D_
    color: red;_x000D_
<input placeholder="hello"/> <br />_x000D_
<textarea placeholder="hello"></textarea>

This will style all input and textarea placeholders.

Important Note: Do not group these rules. Instead, make a separate rule for every selector (one invalid selector in a group makes the whole group invalid).

How to Determine the Screen Height and Width in Flutter

MediaQuery.of(context).size.width and MediaQuery.of(context).size.height works great, but every time need to write expressions like width/20 to set specific height width.

I've created a new application on flutter, and I've had problems with the screen sizes when switching between different devices.

Yes, flutter_screenutil plugin available for adapting screen and font size. Let your UI display a reasonable layout on different screen sizes!


Add dependency:

Please check the latest version before installation.

    sdk: flutter
  # add flutter_ScreenUtil
  flutter_screenutil: ^0.4.2

Add the following imports to your Dart code:

import 'package:flutter_screenutil/flutter_screenutil.dart';

Initialize and set the fit size and font size to scale according to the system's "font size" accessibility option

//fill in the screen size of the device in the design

//default value : width : 1080px , height:1920px , allowFontScaling:false
ScreenUtil.instance = ScreenUtil()..init(context);

//If the design is based on the size of the iPhone6 ??(iPhone6 ??750*1334)
ScreenUtil.instance = ScreenUtil(width: 750, height: 1334)..init(context);

//If you wang to set the font size is scaled according to the system's "font size" assist option
ScreenUtil.instance = ScreenUtil(width: 750, height: 1334, allowFontScaling: true)..init(context);


//for example:
           width: ScreenUtil().setWidth(375),
           height: ScreenUtil().setHeight(200),

////If you want to display a square:
           width: ScreenUtil().setWidth(300),
           height: ScreenUtil().setWidth(300),

Please refer updated documentation for more details

Note: I tested and using this plugin, which really works great with all devices including iPad

Hope this will helps someone

How to call function that takes an argument in a Django template?

What you could do is, create the "function" as another template file and then include that file passing the parameters to it.

Inside index.html

<h3> Latest Songs </h3>
{% include "song_player_list.html" with songs=latest_songs %}

Inside song_player_list.html

{%  for song in songs %}
<div id='songtile'>
<a href='/songs/download/{{}}/'><i class='fa fa-cloud-download'></i>&nbsp;Download</a>

{% endfor %}

How can I determine browser window size on server side C#

Here's an Ajax, asxh handler and session variables approach:


using System;
using System.Web;

public class windowSize : IHttpHandler , System.Web.SessionState.IRequiresSessionState  {

    public void ProcessRequest (HttpContext context) {
        context.Response.ContentType = "application/json";

        var json = new System.Web.Script.Serialization.JavaScriptSerializer();
        var output = json.Serialize(new { isFirst = context.Session["BrowserWidth"] == null });

        context.Session["BrowserWidth"] =  context.Request.QueryString["Width"]; 
        context.Session["BrowserHeight"] = context.Request.QueryString["Height"];

    public bool IsReusable
        get { throw new NotImplementedException(); }


window.onresize = function (event) {
function SetWidthHeight() {
    var height = $(window).height();
    var width = $(window).width();
        url: "windowSize.ashx",
        data: {
            'Height': height,
            'Width': width
        contentType: "application/json; charset=utf-8",
        dataType: "json"
    }).done(function (data) {     
        if (data.isFirst) {
    }).fail(function (xhr) {
        alert("Problem to retrieve browser size.");

$(function () {

On aspx file:

<script src="Scripts/jquery-1.9.1.min.js"></script>
<script src="Scripts/BrowserWindowSize.js"></script>
<asp:Label ID="lblDim" runat="server" Text=""></asp:Label>

Code behind:

protected void Page_Load(object sender, EventArgs e)
      if (Session["BrowserWidth"] != null)
          // Do all code here to avoid double execution first time
          // ....
          lblDim.Text = "Width: " + Session["BrowserWidth"] + " Height: " + Session["BrowserHeight"];


Is there a standard sign function (signum, sgn) in C/C++?

The accepted Answer with the overload below does indeed not trigger -Wtype-limits.

template <typename T> inline constexpr
  int signum(T x, std::false_type) {
  return T(0) < x;

template <typename T> inline constexpr
  int signum(T x, std::true_type) {
  return (T(0) < x) - (x < T(0));

template <typename T> inline constexpr
  int signum(T x) {
  return signum(x, std::is_signed<T>());

For C++11 an alternative could be.

template <typename T>
typename std::enable_if<std::is_unsigned<T>::value, int>::type
inline constexpr signum(T const x) {
    return T(0) < x;  

template <typename T>
typename std::enable_if<std::is_signed<T>::value, int>::type
inline constexpr signum(T const x) {
    return (T(0) < x) - (x < T(0));  

For me it does not trigger any warnings on GCC 5.3.1.

Error: [ng:areq] from angular controller

I've got that error when the controller name was not the same (case sensitivity!):

.controller('mainCOntroller', ...  // notice CO

and in view

<div class="container" ng-controller="mainController">  <!-- notice Co -->

Why is it faster to check if dictionary contains the key, rather than catch the exception in case it doesn't?

Dictionaries are specifically designed to do super fast key lookups. They are implemented as hashtables and the more entries the faster they are relative to other methods. Using the exception engine is only supposed to be done when your method has failed to do what you designed it to do because it is a large set of object that give you a lot of functionality for handling errors. I built an entire library class once with everything surrounded by try catch blocks once and was appalled to see the debug output which contained a seperate line for every single one of over 600 exceptions!

Is there a way to change the spacing between legend items in ggplot2?

Looks like the best approach (in 2018) is to use legend.key.size under the theme object. (e.g., see here).


    gp <- ggplot(data = mtcars, aes(mpg, cyl, colour = factor(cyl))) +

This is real easy if you are using theme_bw():

  gpbw <- gp + theme_bw()

#Change spacing size:

  g1bw <- gpbw + theme(legend.key.size = unit(0, 'lines'))
  g2bw <- gpbw + theme(legend.key.size = unit(1.5, 'lines'))
  g3bw <- gpbw + theme(legend.key.size = unit(3, 'lines'))


enter image description here

However, this doesn't work quite so well otherwise (e.g., if you need the grey background on your legend symbol):

  g1 <- gp + theme(legend.key.size = unit(0, 'lines'))
  g2 <- gp + theme(legend.key.size = unit(1.5, 'lines'))
  g3 <- gp + theme(legend.key.size = unit(3, 'lines'))


#Notice that the legend symbol squares get bigger (that's what legend.key.size does). 

#Let's [indirectly] "control" that, too:
  gp2 <- g3
  g4 <- gp2 + theme(legend.key = element_rect(size = 1))
  g5 <- gp2 + theme(legend.key = element_rect(size = 3))
  g6 <- gp2 + theme(legend.key = element_rect(size = 10))

  grid.arrange(g4,g5,g6,nrow=3)   #see picture below, left

Notice that white squares begin blocking legend title (and eventually the graph itself if we kept increasing the value).

  #This shows you why:
    gt <- gp2 + theme(legend.key = element_rect(size = 10,color = 'yellow' ))

enter image description here

I haven't quite found a work-around for fixing the above problem... Let me know in the comments if you have an idea, and I'll update accordingly!

  • I wonder if there is some way to re-layer things using $layers...

What is the difference between float and double?

I just ran into a error that took me forever to figure out and potentially can give you a good example of float precision.

#include <iostream>
#include <iomanip>

int main(){
  for(float t=0;t<1;t+=0.01){
     std::cout << std::fixed << std::setprecision(6) << t << std::endl;

The output is


As you can see after 0.83, the precision runs down significantly.

However, if I set up t as double, such an issue won't happen.

It took me five hours to realize this minor error, which ruined my program.

If REST applications are supposed to be stateless, how do you manage sessions?

I see that the basic issue here is mixing up Session with State. And while REST specifies that you should NOT store the State on the server, nothing prevents you from storing a user Session.

Managing the State on the server means that your server knows exactly what the client is doing (what page they're viewing in which section of the application). And this is what you shouldn't need to do.

I agree with the other people saying that you should keep the session storage to a minimum size; and while that's common sense, it's actually also dependent on the application. So, in short, you can still keep a session with cached data to handle the requests with less load on the server, and manage the authentication by providing a temporary authentication/access token for the client to use. Whenever the session/token is expired, generate a new one and ask the client to use it.

Someone might argue that the client should better generate the token. I say it works both ways, and it would depend on the application, and who's going to work with the API.

Also keeping some sensitive session data on the server should be the right way to do. You cannot trust the client to keep their shopping cart that (for example) contains a field named "isFreeGift". Such information should be kept on the server.

The video link provided by Santanu Dey in his answer is helpful. Watch it if you haven't.

Just a side note: It seems all the answers already given seem to disregard the fact that some operations could cause a heavy load on the server. That's relevant in terms of power consumption, hardware consumption, and cost (for servers rented by CPU cycle). A good developer shouldn't be lazy in optimizing their application, even if the operation can be done very quickly on a modern CPU on some rented server for which they don't pay its electricity and maintenance bill.

Althoght the question is a few years old, I hope that my answer would still be helpful.

HTML anchor link - href and onclick both?

Just return true instead?

The return value from the onClick code is what determines whether the link's inherent clicked action is processed or not - returning false means that it isn't processed, but if you return true then the browser will proceed to process it after your function returns and go to the proper anchor.

Using IF ELSE statement based on Count to execute different Insert statements

IF exists

IF exists (select * from table_1 where col1 = 'value')
    -- one or more
    insert into table_1 (col1) values ('valueB')
    -- zero
    insert into table_1 (col1) values ('value') 

Parse JSON file using GSON

One thing that to be remembered while solving such problems is that in JSON file, a { indicates a JSONObject and a [ indicates JSONArray. If one could manage them properly, it would be very easy to accomplish the task of parsing the JSON file. The above code was really very helpful for me and I hope this content adds some meaning to the above code.

The Gson JsonReader documentation explains how to handle parsing of JsonObjects and JsonArrays:

  • Within array handling methods, first call beginArray() to consume the array's opening bracket. Then create a while loop that accumulates values, terminating when hasNext() is false. Finally, read the array's closing bracket by calling endArray().
  • Within object handling methods, first call beginObject() to consume the object's opening brace. Then create a while loop that assigns values to local variables based on their name. This loop should terminate when hasNext() is false. Finally, read the object's closing brace by calling endObject().

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

This worked for me!!!!

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

<project xmlns=""




'tuple' object does not support item assignment

A tuple is immutable and thus you get the error you posted.

>>> pixels = [1, 2, 3]
>>> pixels[0] = 5
>>> pixels = (1, 2, 3)
>>> pixels[0] = 5
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
TypeError: 'tuple' object does not support item assignment

In your specific case, as correctly pointed out in other answers, you should write:

pixel = (pixel[0] + 20, pixel[1], pixel[2])

How to check all versions of python installed on osx and centos

compgen -c python | grep -P '^python\d'

This lists some other python things too, But hey, You can identify all python versions among them.

How to kill/stop a long SQL query immediately?

First execute the below command:


After that execute the below command with SPID, which you got from above command:

KILL {SPID value}

ffmpeg - Converting MOV files to MP4

The command to just stream it to a new container (mp4) needed by some applications like Adobe Premiere Pro without encoding (fast) is:

ffmpeg -i -qscale 0 output.mp4

Alternative as mentioned in the comments, which re-encodes with best quaility (-qscale 0):

ffmpeg -i -q:v 0 output.mp4

Reactjs convert html string to jsx

I recommend using Interweave created by milesj. Its a phenomenal library that makes use of a number if ingenious techniques to parse and safely insert HTML into the DOM.

Interweave is a react library to safely render HTML, filter attributes, autowrap text with matchers, render emoji characters, and much more.

  • Interweave is a robust React library that can:
    • Safely render HTML without using dangerouslySetInnerHTML.
    • Safely strip HTML tags.
    • Automatic XSS and injection protection.
    • Clean HTML attributes using filters.
    • Interpolate components using matchers.
    • Autolink URLs, IPs, emails, and hashtags.
    • Render Emoji and emoticon characters.
    • And much more!

Usage Example:

import React from 'react';
import { Markup } from 'interweave';

const articleContent = "<p><b>Lorem ipsum dolor laboriosam.</b> </p><p>Facere debitis impedit doloremque eveniet eligendi reiciendis <u>ratione obcaecati repellendus</u> culpa? Blanditiis enim cum tenetur non rem, atque, earum quis, reprehenderit accusantium iure quas beatae.</p><p>Lorem ipsum dolor sit amet <a href='#testLink'>this is a link, click me</a> Sunt ducimus corrupti? Eveniet velit numquam deleniti, delectus  <ol><li>reiciendis ratione obcaecati</li><li>repellendus culpa? Blanditiis enim</li><li>cum tenetur non rem, atque, earum quis,</li></ol>reprehenderit accusantium iure quas beatae.</p>"

<Markup content={articleContent} /> // this will take the articleContent string and convert it to HTML markup. See:

//to install package using npm, execute the command
npm install interweave

Count the number of occurrences of a string in a VARCHAR field?

A little bit simpler and more effective variation of @yannis solution:

    CHAR_LENGTH(description) - CHAR_LENGTH( REPLACE ( description, 'value', '1234') ) 
        AS `count`    
FROM <table> 

The difference is that I replace the "value" string with a 1-char shorter string ("1234" in this case). This way you don't need to divide and round to get an integer value.

Generalized version (works for every needle string):

SET @needle = 'value';
    CHAR_LENGTH(description) - CHAR_LENGTH(REPLACE(description, @needle, SPACE(LENGTH(@needle)-1))) 
        AS `count`    
FROM <table> 

How to reset all checkboxes using jQuery or pure JS?

In some cases the checkbox may be selected by default. If you want to restore default selection rather than set as unselected, compare the defaultChecked property.

        this.checked = item.defaultChecked; 

String replacement in batch file

You can use the following little trick:

set word=table
set str="jump over the chair"
call set str=%%str:chair=%word%%%
echo %str%

The call there causes another layer of variable expansion, making it necessary to quote the original % signs but it all works out in the end.

Seedable JavaScript random number generator

OK, here's the solution I settled on.

First you create a seed value using the "newseed()" function. Then you pass the seed value to the "srandom()" function. Lastly, the "srandom()" function returns a pseudo random value between 0 and 1.

The crucial bit is that the seed value is stored inside an array. If it were simply an integer or float, the value would get overwritten each time the function were called, since the values of integers, floats, strings and so forth are stored directly in the stack versus just the pointers as in the case of arrays and other objects. Thus, it's possible for the value of the seed to remain persistent.

Finally, it is possible to define the "srandom()" function such that it is a method of the "Math" object, but I'll leave that up to you to figure out. ;)

Good luck!


// Global variables used for the seeded random functions, below.
var seedobja = 1103515245
var seedobjc = 12345
var seedobjm = 4294967295 //0x100000000

// Creates a new seed for seeded functions such as srandom().
function newseed(seednum)
    return [seednum]

// Works like Math.random(), except you provide your own seed as the first argument.
function srandom(seedobj)
    seedobj[0] = (seedobj[0] * seedobja + seedobjc) % seedobjm
    return seedobj[0] / (seedobjm - 1)

// Store some test values in variables.
var my_seed_value = newseed(230951)
var my_random_value_1 = srandom(my_seed_value)
var my_random_value_2 = srandom(my_seed_value)
var my_random_value_3 = srandom(my_seed_value)

// Print the values to console. Replace "WScript.Echo()" with "alert()" if inside a Web browser.

Lua 4 (my personal target environment):

-- Global variables used for the seeded random functions, below.
seedobja = 1103515.245
seedobjc = 12345
seedobjm = 4294967.295 --0x100000000

-- Creates a new seed for seeded functions such as srandom().
function newseed(seednum)
    return {seednum}

-- Works like random(), except you provide your own seed as the first argument.
function srandom(seedobj)
    seedobj[1] = mod(seedobj[1] * seedobja + seedobjc, seedobjm)
    return seedobj[1] / (seedobjm - 1)

-- Store some test values in variables.
my_seed_value = newseed(230951)
my_random_value_1 = srandom(my_seed_value)
my_random_value_2 = srandom(my_seed_value)
my_random_value_3 = srandom(my_seed_value)

-- Print the values to console.

How do I find the last column with data?

I know this is old, but I've tested this in many ways and it hasn't let me down yet, unless someone can tell me otherwise.

Row number

Row = ws.Cells.Find(What:="*", After:=[A1] , SearchOrder:=xlByRows, SearchDirection:=xlPrevious).Row

Column Letter

ColumnLetter = Split(ws.Cells.Find(What:="*", After:=[A1], SearchOrder:=xlByColumns, SearchDirection:=xlPrevious).Cells.Address(1, 0), "$")(0)

Column Number

ColumnNumber = ws.Cells.Find(What:="*", After:=[A1], SearchOrder:=xlByColumns, SearchDirection:=xlPrevious).Column

SQLite with encryption/password protection

You can use SQLite's function creation routines (PHP manual):

$db_obj->sqliteCreateFunction('Encrypt', 'MyEncryptFunction', 2);
$db_obj->sqliteCreateFunction('Decrypt', 'MyDecryptFunction', 2);

When inserting data, you can use the encryption function directly and INSERT the encrypted data or you can use the custom function and pass unencrypted data:

$insert_obj = $db_obj->prepare('INSERT INTO table (Clear, Encrypted) ' .
 'VALUES (:clear, Encrypt(:data, "' . $passwordhash_str . '"))');

When retrieving data, you can also use SQL search functionality:

$select_obj = $db_obj->prepare('SELECT Clear, ' .
 'Decrypt(Encrypted, "' . $passwordhash_str . '") AS PlainText FROM table ' .
 'WHERE PlainText LIKE :searchterm');

Google Chrome display JSON AJAX response as tree and not as a plain text

In order for it to display the JSON message properly it has to have the "application/json" mime type and to be correctly structured.

You can check the structure here

On postback, how can I check which control cause postback in Page_Init event

An addition to previous answers, to use Request.Params["__EVENTTARGET"] you have to set the option:

buttonName.UseSubmitBehavior = false;

Java Desktop application: SWT vs. Swing

Interesting question. I don't know SWT too well to brag about it (unlike Swing and AWT) but here's the comparison done on SWT/Swing/AWT.

And here's the site where you can get tutorial on basically anything on SWT (

Hope you make a right decision (if there are right decisions in coding)... :-)

JS search in object values

Although a bit late, but a more compact version may be the following:

* @param {string} quickCriteria Any string value to search for in the object properties.
* @param {any[]} objectArray The array of objects as the search domain
* @return {any[]} the search result
onQuickSearchChangeHandler(quickCriteria, objectArray){

   let quickResult = objectArray.filter(obj => Object.values(obj).some(val => val?val.toString().toLowerCase().includes(quickCriteria):false));

   return quickResult;

It can handle falsy values like false, undefined, null and all the data types that define .toString() method like number, boolean etc.

Check if a string matches a regex in Bash script

Where the usage of a regex can be helpful to determine if the character sequence of a date is correct, it cannot be used easily to determine if the date is valid. The following examples will pass the regular expression, but are all invalid dates: 20180231, 20190229, 20190431

So if you want to validate if your date string (let's call it datestr) is in the correct format, it is best to parse it with date and ask date to convert the string to the correct format. If both strings are identical, you have a valid format and valid date.

if [[ "$datestr" == $(date -d "$datestr" "+%Y%m%d" 2>/dev/null) ]]; then
     echo "Valid date"
     echo "Invalid date"

How to insert close button in popover for Bootstrap

You need to make the markup right

<button type="button" id="example" class="btn btn-primary">example</button>

Then, one way is to attach the close-handler inside the element itself, the following works :

$(document).ready(function() {
        placement: 'bottom',
        html: 'true',
        title : '<span class="text-info"><strong>title</strong></span>'+
                '<button type="button" id="close" class="close" onclick="$(&quot;#example&quot;).popover(&quot;hide&quot;);">&times;</button>',
        content : 'test'

Detect element content changes with jQuery

You can add a callback option to html (,or any) function:

$.fn.oldHtml = $.fn.html;
$.fn.html = function(html,fn){
  fn = fn || function(){};
  var result =  this.oldHtml(html);
  return result;

Demo here.

You do the change on some element, not the element is forced to change by something that you have to catch.

How to logout and redirect to login page using Laravel 5.4?

In your web.php (routes):


Route::get('logout', '\App\Http\Controllers\Auth\LoginController@logout');

In your LoginController.php


public function logout(Request $request) {
  return redirect('/login');

Also, in the top of LoginController.php, after namespace


use Auth;

Now, you are able to logout using URL or if you have created logout button, add href to /logout

How to convert a string to number in TypeScript?

As shown by other answers here, there are multiple ways to do the conversion:


I'd like to mention one more thing on parseInt though.

When using parseInt, it makes sense to always pass the radix parameter. For decimal conversion, that is 10. This is the default value for the parameter, which is why it can be omitted. For binary, it's a 2 and 16 for hexadecimal. Actually, any radix between and including 2 and 36 works.

parseInt('123')         // 123 (don't do this)
parseInt('123', 10)     // 123 (much better)

parseInt('1101', 2)     // 13
parseInt('0xfae3', 16)  // 64227

In some JS implementations, parseInt parses leading zeros as octal:

Although discouraged by ECMAScript 3 and forbidden by ECMAScript 5, many implementations interpret a numeric string beginning with a leading 0 as octal. The following may have an octal result, or it may have a decimal result. Always specify a radix to avoid this unreliable behavior.


The fact that code gets clearer is a nice side effect of specifying the radix parameter.

Since parseFloat only parses numeric expressions in radix 10, there's no need for a radix parameter here.

More on this:

The requested resource does not support HTTP method 'GET'

Resolved this issue by using http(s) when accessing the endpoint. The route I was accessing was not available over http. So I would say verify the protocols for which the route is available.

Convert Iterator to ArrayList

Better use a library like Guava:


Iterator<Element> myIterator = ... //some iterator
List<Element> myList = Lists.newArrayList(myIterator);

Another Guava example:


or Apache Commons Collections:

import org.apache.commons.collections.IteratorUtils;

Iterator<Element> myIterator = ...//some iterator

List<Element> myList = IteratorUtils.toList(myIterator);       

Get a json via Http Request in NodeJS

http sends/receives data as strings... this is just the way things are. You are looking to parse the string as json.

var jsonObject = JSON.parse(data);

How to parse JSON using Node.js?

Update or Insert (multiple rows and columns) from subquery in PostgreSQL

OMG Ponies's answer works perfectly, but just in case you need something more complex, here is an example of a slightly more advanced update query:

UPDATE table1 
SET col1 = subquery.col2,
    col2 = subquery.col3 
    SELECT as col1, as col2, t3.foobar as col3 
    FROM table2 t2 INNER JOIN table3 t3 ON = t3.t2_id
    WHERE t2.created_at > '2016-01-01'
) AS subquery
WHERE = subquery.col1;

Executing Javascript from Python

You can use js2py context to execute your js code and get output from document.write with mock document object:

import js2py

js = """
var output;
document = {
    write: function(value){
        output = value;
""" + your_script

context = js2py.EvalJs()

How do I get logs from all pods of a Kubernetes replication controller?

Worked for me:

kubectl logs -n namespace -l app=label -c container

Python String and Integer concatenation

string = 'string%d' % (i,)

No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin '...' is therefore not allowed access

You need to add this at start of your php page "login.php"

<?php header('Access-Control-Allow-Origin: *'); ?>

Bulk Insertion in Laravel using eloquent ORM

Maybe a more Laravel way to solve this problem is to use a collection and loop it inserting with the model taking advantage of the timestamps.


use App\Continent;
use Illuminate\Database\Seeder;

class InitialSeeder extends Seeder
     * Run the database seeds.
     * @return void
    public function run()
            ['name' => 'América'],
            ['name' => 'África'],
            ['name' => 'Europa'],
            ['name' => 'Asia'],
            ['name' => 'Oceanía'],
        ])->each(function ($item, $key) {


Sorry for my misunderstanding. For bulk inserting this could help and maybe with this you can make good seeders and optimize them a bit.


use App\Continent;
use Carbon\Carbon;
use Illuminate\Database\Seeder;

class InitialSeeder extends Seeder
     * Run the database seeds.
     * @return void
    public function run()
        $timestamp = Carbon::now();
        $password = bcrypt('secret');

        $continents = [
                'name' => 'América'
                'password' => $password,
                'created_at' => $timestamp,
                'updated_at' => $timestamp,
                'name' => 'África'
                'password' => $password,
                'created_at' => $timestamp,
                'updated_at' => $timestamp,
                'name' => 'Europa'
                'password' => $password,
                'created_at' => $timestamp,
                'updated_at' => $timestamp,
                'name' => 'Asia'
                'password' => $password,
                'created_at' => $timestamp,
                'updated_at' => $timestamp,
                'name' => 'Oceanía'
                'password' => $password,
                'created_at' => $timestamp,
                'updated_at' => $timestamp,


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';

Error: unable to verify the first certificate in nodejs

Another dirty hack, which will make all your requests insecure:


path.join vs path.resolve with __dirname

From the doc for path.resolve:

The resulting path is normalized and trailing slashes are removed unless the path is resolved to the root directory.

But path.join keeps trailing slashes


__dirname = '/';
path.resolve(__dirname, 'foo/'); // '/foo'
path.join(__dirname, 'foo/'); // '/foo/'

How to get a reference to an iframe's window object inside iframe's onload handler created from parent window

You're declaring everything in the parent page. So the references to window and document are to the parent page's. If you want to do stuff to the iframe's, use iframe || iframe.contentWindow to access its window, and iframe.contentDocument || iframe.contentWindow.document to access its document.

There's a word for what's happening, possibly "lexical scope": What is lexical scope?

The only context of a scope is this. And in your example, the owner of the method is doc, which is the iframe's document. Other than that, anything that's accessed in this function that uses known objects are the parent's (if not declared in the function). It would be a different story if the function were declared in a different place, but it's declared in the parent page.

This is how I would write it:

(function () {
  var dom, win, doc, where, iframe;

  iframe = document.createElement('iframe');
  iframe.src = "javascript:false";

  where = document.getElementsByTagName('script')[0];
  where.parentNode.insertBefore(iframe, where);

  win = iframe.contentWindow || iframe;
  doc = iframe.contentDocument || iframe.contentWindow.document;;
  doc._l = (function (w, d) {
    return function () {
      w.vanishing_global = new Date().getTime();

      var js = d.createElement("script");
      js.src = 'test-vanishing-global.js?' + w.vanishing_global; = "foobar";
      d.foobar = "foobar:" + Math.random();
      d.foobar = "barfoo:" + Math.random();
  })(win, doc);
  doc.write('<body onload="document._l();"></body>');

The aliasing of win and doc as w and d aren't necessary, it just might make it less confusing because of the misunderstanding of scopes. This way, they are parameters and you have to reference them to access the iframe's stuff. If you want to access the parent's, you still use window and document.

I'm not sure what the implications are of adding methods to a document (doc in this case), but it might make more sense to set the _l method on win. That way, things can be run without a prefix...such as <body onload="_l();"></body>

.NET HttpClient. How to POST string value?

There is an article about your question on's website. I hope it can help you.

How to call an api with asp net

Here is a small part from the POST section of the article

The following code sends a POST request that contains a Product instance in JSON format:

var gizmo = new Product() { Name = "Gizmo", Price = 100, Category = "Widget" };
response = await client.PostAsJsonAsync("api/products", gizmo);
if (response.IsSuccessStatusCode)
    // Get the URI of the created resource.
    Uri gizmoUrl = response.Headers.Location;

What is the difference between Set and List?

Like the answer as SET don't have duplicate value and List can. Of course, order is another one thing to different them apart.

How do Mockito matchers work?

Just a small addition to Jeff Bowman's excellent answer, as I found this question when searching for a solution to one of my own problems:

If a call to a method matches more than one mock's when trained calls, the order of the when calls is important, and should be from the most wider to the most specific. Starting from one of Jeff's examples:

when(foo.quux(anyInt(), anyInt())).thenReturn(true);
when(foo.quux(anyInt(), eq(5))).thenReturn(false);

is the order that ensures the (probably) desired result:

foo.quux(3 /*any int*/, 8 /*any other int than 5*/) //returns true
foo.quux(2 /*any int*/, 5) //returns false

If you inverse the when calls then the result would always be true.

Phonegap Cordova installation Windows

This answer was first posted here: cordova/phonegap does not make android directory

With the release of Cordova 3.3.0, it seems the PhoneGap team is trying to address the naming confusion. The documentations have been updated to recommend people using the cordova command instead. Do not use the phonegap command anymore.

Here is a fresh installation guide for a guaranteed trouble free set up:

  1. Install Cordova (forget the name PhoneGap from now on). For PC:

    C:> npm install -g cordova

  2. From command prompt, navigate to the folder you want to create your project using:

    cordova create hello com.example.hello HelloWorld
    cd hello

  3. Define the OS you want to suppport for example:

    cordova platform add wp8

  4. Install plugins (If needed). For example we want the following:

    cordova plugin add org.apache.cordova.device
    cordova plugin add
    cordova plugin add
    cordova plugin add

  5. Finally, generate the app using:
    cordova build wp8

Here is a link to the PhoneGapCordova 3.3.0 Documentation

How to insert values in table with foreign key using MySQL?

Case 1: Insert Row and Query Foreign Key

Here is an alternate syntax I use:

INSERT INTO tab_student 
   SET name_student = 'Bobby Tables',
       id_teacher_fk = (
       SELECT id_teacher
         FROM tab_teacher
        WHERE name_teacher = 'Dr. Smith')

I'm doing this in Excel to import a pivot table to a dimension table and a fact table in SQL so you can import to both department and expenses tables from the following:

enter image description here

Case 2: Insert Row and Then Insert Dependant Row

Luckily, MySQL supports LAST_INSERT_ID() exactly for this purpose.

INSERT INTO tab_teacher
   SET name_teacher = 'Dr. Smith';
INSERT INTO tab_student 
   SET name_student = 'Bobby Tables',
       id_teacher_fk = LAST_INSERT_ID()

JavaScript: Alert.Show(message) From ASP.NET Code-behind

private void MessageBox(string msg)
    Label lbl = new Label();
    lbl.Text  = string.Format(@"<script type='text/javascript'>alert('{0}');</script>",msg);

Visual Studio C# IntelliSense not automatically displaying

I have found that at times even verifying the settings under Options --> Statement Completion (the answer above) doesn't work. In this case, saving and restarting Visual Studio will re-enable Intellisense.

Finally, this link has a list of other ways to troubleshoot Intellisense, broken down by language (for more specific errors).

How to perform grep operation on all files in a directory?

If you want to do multiple commands, you could use:

for I in `ls *.sql`
    grep "foo" $I >> foo.log
    grep "bar" $I >> bar.log

Uppercase first letter of variable

         str = str.replace(_x000D_
            function (a, w1, w2) {_x000D_
                            return w1 + w2.toLowerCase();_x000D_

nginx missing sites-available directory

I tried sudo apt install nginx-full. You will get all the required packages.

How to listen for changes to a MongoDB collection?

MongoDB has what is called capped collections and tailable cursors that allows MongoDB to push data to the listeners.

A capped collection is essentially a collection that is a fixed size and only allows insertions. Here's what it would look like to create one:

db.createCollection("messages", { capped: true, size: 100000000 })

MongoDB Tailable cursors (original post by Jonathan H. Wage)


coll = db.collection('my_collection')
cursor =, :tailable => true)
loop do
  if doc = cursor.next_document
    puts doc
    sleep 1


$mongo = new Mongo();
$db = $mongo->selectDB('my_db')
$coll = $db->selectCollection('my_collection');
$cursor = $coll->find()->tailable(true);
while (true) {
    if ($cursor->hasNext()) {
        $doc = $cursor->getNext();
    } else {

Python (by Robert Stewart)

from pymongo import Connection
import time

db = Connection().my_db
coll = db.my_collection
cursor = coll.find(tailable=True)
while cursor.alive:
        doc =
        print doc
    except StopIteration:

Perl (by Max)

use 5.010;

use strict;
use warnings;
use MongoDB;

my $db = MongoDB::Connection->new;
my $coll = $db->my_db->my_collection;
my $cursor = $coll->find->tailable(1);
for (;;)
    if (defined(my $doc = $cursor->next))
        say $doc;
        sleep 1;

Additional Resources:

Ruby/Node.js Tutorial which walks you through creating an application that listens to inserts in a MongoDB capped collection.

An article talking about tailable cursors in more detail.

PHP, Ruby, Python, and Perl examples of using tailable cursors.

Awaiting multiple Tasks with different results

Use Task.WhenAll and then await the results:

var tCat = FeedCat();
var tHouse = SellHouse();
var tCar = BuyCar();
await Task.WhenAll(tCat, tHouse, tCar);
Cat cat = await tCat;
House house = await tHouse;
Tesla car = await tCar; 
//as they have all definitely finished, you could also use Task.Value.

./ line 1: import: command not found

When you see "import: command not found" on the very first import, it is caused by the parser not using the character encoding matching your py file. Especially when you are not using ASCII encoding in your py file.

The way to get it right is to specify the correct encoding on top of your py file to match your file character encoding.

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
import os

Invalid attempt to read when no data is present

You have to call dr.Read() before attempting to read any data. That method will return false if there is nothing to read.

What is Turing Complete?

From wikipedia:

Turing completeness, named after Alan Turing, is significant in that every plausible design for a computing device so far advanced can be emulated by a universal Turing machine — an observation that has become known as the Church-Turing thesis. Thus, a machine that can act as a universal Turing machine can, in principle, perform any calculation that any other programmable computer is capable of. However, this has nothing to do with the effort required to write a program for the machine, the time it may take for the machine to perform the calculation, or any abilities the machine may possess that are unrelated to computation.

While truly Turing-complete machines are very likely physically impossible, as they require unlimited storage, Turing completeness is often loosely attributed to physical machines or programming languages that would be universal if they had unlimited storage. All modern computers are Turing-complete in this sense.

I don't know how you can be more non-technical than that except by saying "turing complete means 'able to answer computable problem given enough time and space'".

Difference between string object and string literal

String s = new String("FFFF") creates 2 objects: "FFFF" string and String object, which point to "FFFF" string, so it is like pointer to pointer (reference to reference, I am not keen with terminology).

It is said you should never use new String("FFFF")

Contain form within a bootstrap popover?

I work in WordPress a lot so use PHP.

My method is to contain my HTML in a PHP Variable, and then echo the variable in data-content.

$my-data-content = '<form><input type="text"/></form>';

along with

data-content='<?php echo $my-data-content; ?>' 

entity framework Unable to load the specified metadata resource

Craig Stuntz has written an extensive (in my opinion) blog post on troubleshooting this exact error message, I personally would start there.

The following res: (resource) references need to point to your model.

<add name="Entities" connectionString="metadata=

Make sure each one has the name of your .edmx file after the "*/", with the "edmx" changed to the extension for that res (.csdl, .ssdl, or .msl).

It also may help to specify the assembly rather than using "//*/".

Worst case, you can check everything (a bit slower but should always find the resource) by using

<add name="Entities" connectionString="metadata=
        res://*/;provider= <!-- ... -->

Custom Listview Adapter with filter Android

In your CustomAdapter class implement filterable.

listview with search search listview

 public class CustomAdapter extends BaseAdapter implements Filterable {

    private List<ItemsModel> itemsModelsl;
    private List<ItemsModel> itemsModelListFiltered;
    private Context context;

    public CustomAdapter(List<ItemsModel> itemsModelsl, Context context) {
        this.itemsModelsl = itemsModelsl;
        this.itemsModelListFiltered = itemsModelsl;
        this.context = context;

    public int getCount() {
        return itemsModelListFiltered.size();

    public Object getItem(int position) {
        return itemsModelListFiltered.get(position);

    public long getItemId(int position) {
        return position;

    public View getView(final int position, View convertView, ViewGroup parent) {
        View view = getLayoutInflater().inflate(R.layout.row_items,null);

        TextView names = view.findViewById(;
        TextView emails = view.findViewById(;
        ImageView imageView = view.findViewById(;


        view.setOnClickListener(new View.OnClickListener() {
            public void onClick(View v) {
                Log.e("main activity","item clicked");
                startActivity(new Intent(MainActivity.this,ItemsPreviewActivity.class).putExtra("items",itemsModelListFiltered.get(position)));


        return view;

    public Filter getFilter() {
        Filter filter = new Filter() {
            protected FilterResults performFiltering(CharSequence constraint) {

                FilterResults filterResults = new FilterResults();
                if(constraint == null || constraint.length() == 0){
                    filterResults.count = itemsModelsl.size();
                    filterResults.values = itemsModelsl;

                    List<ItemsModel> resultsModel = new ArrayList<>();
                    String searchStr = constraint.toString().toLowerCase();

                    for(ItemsModel itemsModel:itemsModelsl){
                        if(itemsModel.getName().contains(searchStr) || itemsModel.getEmail().contains(searchStr)){

                         filterResults.count = resultsModel.size();
                            filterResults.values = resultsModel;


                return filterResults;

            protected void publishResults(CharSequence constraint, FilterResults results) {

                itemsModelListFiltered = (List<ItemsModel>) results.values;

        return filter;


You can get the whole tutorial here: ListView With Search/Filter and OnItemClickListener

Github Source Code

Correct way to populate an Array with a Range in Ruby

Check this:

a = [*(1..10), :top, *10.downto( 1 )]

generating variable names on fly in python

Though I don't see much point, here it is:

for i in xrange(0, len(prices)):
    exec("price%d = %s" % (i + 1, repr(prices[i])));

Android emulator failed to allocate memory 8

This error fires if you set the AVD RAM to anything that is larger then the single largest block of continuous memory the emulator is able to allocate. Close anything RAM heavy, start your emulator, start everything else you need. In a previous answer I have limited this to x86 images with IntelHAXM, but this actually is the case for all types of emulator instances.

Load local javascript file in chrome for testing?

Running a simple local HTTP server

To test such examples, one needs a local webserver. One of the easiest ways to do this for our purposes is to use Python's SimpleHTTPServer (or http.server, depending on the version of Python installed.)

# Install Python & try one of the following depending on your python version. if the version is 3.X
python3 -m http.server
# On windows try "python" instead of "python3", or "py -3"
# If Python version is 2.X
python -m SimpleHTTPServer

What underlies this JavaScript idiom: var self = this?

Actually self is a reference to window (window.self) therefore when you say var self = 'something' you override a window reference to itself - because self exist in window object.

This is why most developers prefer var that = this over var self = this;

Anyway; var that = this; is not in line with the good practice ... presuming that your code will be revised / modified later by other developers you should use the most common programming standards in respect with developer community

Therefore you should use something like var oldThis / var oThis / etc - to be clear in your scope // not that much but will save few seconds and few brain cycles

Selecting the last value of a column

try this: =INDIRECT("B"&arrayformula(max((B3:B<>"")*row(B3:B))))

Suppose the column in which you are looking for the last value is B.

And yes, it works with blanks.

How is TeamViewer so fast?

A bit late answer, but I suggest you have a look at a not well known project on codeplex called ConferenceXP

ConferenceXP is an open source research platform that provides simple, flexible, and extensible conferencing and collaboration using high-bandwidth networks and the advanced multimedia capabilities of Microsoft Windows. ConferenceXP helps researchers and educators develop innovative applications and solutions that feature broadcast-quality audio and video in support of real-time distributed collaboration and distance learning environments.

Full source (it's huge!) is provided. It implements the RTP protocol.

How to use mouseover and mouseout in Angular 6

The Angular6 equivalent code should be:


<div (mouseover)="changeText=true" (mouseout)="changeText=false">
  <span *ngIf="!changeText">Hide</span>
  <span *ngIf="changeText">Show</span>


   selector: 'app-main',
   templateUrl: './app.component.html'
export class AppComponent {
    changeText: boolean;
    constructor() {
       this.changeText = false;

Notice that there is no such thing as $scope anymore as it existed in AngularJS. Its been replaced with member variables from the component class. Also, there is no scope resolution algorithm based on prototypical inheritance either - it either resolves to a component class member, or it doesn't.

Detecting iOS / Android Operating system

You can test the user agent string:

 * Determine the mobile operating system.
 * This function returns one of 'iOS', 'Android', 'Windows Phone', or 'unknown'.
 * @returns {String}
function getMobileOperatingSystem() {
  var userAgent = navigator.userAgent || navigator.vendor || window.opera;

      // Windows Phone must come first because its UA also contains "Android"
    if (/windows phone/i.test(userAgent)) {
        return "Windows Phone";

    if (/android/i.test(userAgent)) {
        return "Android";

    // iOS detection from:
    if (/iPad|iPhone|iPod/.test(userAgent) && !window.MSStream) {
        return "iOS";

    return "unknown";

How do I create a constant in Python?

Edit: Added sample code for Python 3

Note: this other answer looks like it provides a much more complete implementation similar to the following (with more features).

First, make a metaclass:

class MetaConst(type):
    def __getattr__(cls, key):
        return cls[key]

    def __setattr__(cls, key, value):
        raise TypeError

This prevents statics properties from being changed. Then make another class that uses that metaclass:

class Const(object):
    __metaclass__ = MetaConst

    def __getattr__(self, name):
        return self[name]

    def __setattr__(self, name, value):
        raise TypeError

Or, if you're using Python 3:

class Const(object, metaclass=MetaConst):
    def __getattr__(self, name):
        return self[name]

    def __setattr__(self, name, value):
        raise TypeError

This should prevent instance props from being changed. To use it, inherit:

class MyConst(Const):
    A = 1
    B = 2

Now the props, accessed directly or via an instance, should be constant:

# 1
my_const = MyConst()
# 1

MyConst.A = 'changed'
# TypeError
my_const.A = 'changed'
# TypeError

Here's an example of above in action. Here's another example for Python 3.

Batch Files - Error Handling

I guess this feature was added since the OP but for future reference errors that would output in the command window can be redirected to a file independent of the standard output

command 1> file - Write the standard output of command to file

command 2> file - Write the standard error of command to file

PHP DOMDocument loadHTML not encoding UTF-8 correctly

You must feed the DOMDocument a version of your HTML with a header that make sense. Just like HTML5.

$profile ='<?xml version="1.0" encoding="'.$_encoding.'"?>'. $html;

maybe is a good idea to keep your html as valid as you can, so you don't get into issues when you'll start query... around :-) and stay away from htmlentities!!!! That's an an necessary back and forth wasting resources. keep your code insane!!!!

C++ vector of char array

Use std::string instead of char-arrays

std::string k ="abcde";
std::vector<std::string> v;

How to make an HTTP request + basic auth in Swift

You provide credentials in a URLRequest instance, like this in Swift 3:

let username = "user"
let password = "pass"
let loginString = String(format: "%@:%@", username, password)
let loginData = String.Encoding.utf8)!
let base64LoginString = loginData.base64EncodedString()

// create the request
let url = URL(string: "")!
var request = URLRequest(url: url)
request.httpMethod = "POST"
request.setValue("Basic \(base64LoginString)", forHTTPHeaderField: "Authorization")

// fire off the request
// make sure your class conforms to NSURLConnectionDelegate
let urlConnection = NSURLConnection(request: request, delegate: self)

Or in an NSMutableURLRequest in Swift 2:

// set up the base64-encoded credentials
let username = "user"
let password = "pass"
let loginString = NSString(format: "%@:%@", username, password)
let loginData: NSData = loginString.dataUsingEncoding(NSUTF8StringEncoding)!
let base64LoginString = loginData.base64EncodedStringWithOptions([])

// create the request
let url = NSURL(string: "")
let request = NSMutableURLRequest(URL: url)
request.HTTPMethod = "POST"
request.setValue("Basic \(base64LoginString)", forHTTPHeaderField: "Authorization")

// fire off the request
// make sure your class conforms to NSURLConnectionDelegate
let urlConnection = NSURLConnection(request: request, delegate: self)

XMLHttpRequest blocked by CORS Policy

I believe sideshowbarker 's answer here has all the info you need to fix this. If your problem is just No 'Access-Control-Allow-Origin' header is present on the response you're getting, you can set up a CORS proxy to get around this. Way more info on it in the linked answer

In Javascript, how to conditionally add a member to an object?

var a = {
    ...(condition ? {b: 1} : '') // if condition is true 'b' will be added.

I hope this is the much efficient way to add an entry based on the condition. For more info on how to conditionally add entries inside an object literals.

Java Date vs Calendar

A little bit late at party, but Java has a new Date Time API in JDK 8. You may want to upgrade your JDK version and embrace the standard. No more messy date/calendar, no more 3rd party jars.

The OutputPath property is not set for this project

This happened to me because I had moved the following line close to the beginning of the .csproj file:

  <Import Project="$(MSBuildToolsPath)\Microsoft.CSharp.targets"/>

It needs to be placed after the PropertyGroups that define your Configuration|Platform.

Searching multiple files for multiple words

If you are using Notepad++ editor (like the tag of the question suggests), you can use the great "Find in Files" functionality.

Go to Search > Find in Files (Ctrl+Shift+F for the keyboard addicted) and enter:

  • Find What = (test1|test2)
  • Filters = *.txt
  • Directory = enter the path of the directory you want to search in. You can check Follow current doc. to have the path of the current file to be filled.
  • Search mode = Regular Expression

How to show loading spinner in jQuery?

Use the loading plugin:


unix sort descending order

If you only want to sort only on the 5th field then use -k5,5.

Also, use the -t command line switch to specify the delimiter to tab. Try this:

sort  -k5,5 -r -n -t \t filename

or if the above doesn't work (with the tab) this:

sort  -k5,5 -r -n -t $'\t' filename

The man page for sort states:

-t, --field-separator=SEP use SEP instead of non-blank to blank transition

Finally, this SO question Unix Sort with Tab Delimiter might be helpful.

Explanation of <script type = "text/template"> ... </script>

It's a way of adding text to HTML without it being rendered or normalized.

It's no different than adding it like:

 <textarea style="display:none"><span>{{name}}</span></textarea>

What is the standard Python docstring format?

Docstring conventions are in PEP-257 with much more detail than PEP-8.

However, docstrings seem to be far more personal than other areas of code. Different projects will have their own standard.

I tend to always include docstrings, because they tend to demonstrate how to use the function and what it does very quickly.

I prefer to keep things consistent, regardless of the length of the string. I like how to code looks when indentation and spacing are consistent. That means, I use:

def sq(n):
    Return the square of n. 
    return n * n


def sq(n):
    """Returns the square of n."""
    return n * n

And tend to leave off commenting on the first line in longer docstrings:

def sq(n):
    Return the square of n, accepting all numeric types:

    >>> sq(10)

    >>> sq(10.434)

    Raises a TypeError when input is invalid:

    >>> sq(4*'435')
    Traceback (most recent call last):
    TypeError: can't multiply sequence by non-int of type 'str'

    return n*n

Meaning I find docstrings that start like this to be messy.

def sq(n):
    """Return the squared result. 

WMI "installed" query different from add/remove programs list?

Not the best, but whether it is practical method:

Use HijackThis.

Run hijack this, click the "Open the Misc Tools section" button

HijackThis Main Menu

click "Open Uninstall Manager"

HijackThis Configuration

click save list (*.txt), yes to the prompts, notepad will open with your add/remove programs list.

HijackThis Add/Remove Programs Manager


Windows batch script launch program and exit console

start "" ExeToExecute

method does not work for me in the case of Xilinx xsdk, because as pointed out by @jeb in the comments below it is actaully a bat file.

so what does not work de-facto is

start "" BatToExecute

I am trying to open xsdk like that and it opens a separate cmd that needs to be closed and xsdk can run on its own

Before launching xsdk I run (source) the Env / Paths (with settings64.bat) so that xsdk.bat command gets recognized (simply as xsdk, withoitu the .bat)

what works with .bat

call BatToExecute

Best way to check if object exists in Entity Framework?

Why not do it?

var result= ctx.table.Where(x => x.UserName == "Value").FirstOrDefault();

if(result?.field == value)
  // Match!

What does 'git blame' do?

The git blame command annotates lines with information from the revision which last modified the line, and... with Git 2.22 (Q2 2019), will do so faster, because of a performance fix around "git blame", especially in a linear history (which is the norm we should optimize for).

See commit f892014 (02 Apr 2019) by David Kastrup (fedelibre). (Merged by Junio C Hamano -- gitster -- in commit 4d8c4da, 25 Apr 2019)

blame.c: don't drop origin blobs as eagerly

When a parent blob already has chunks queued up for blaming, dropping the blob at the end of one blame step will cause it to get reloaded right away, doubling the amount of I/O and unpacking when processing a linear history.

Keeping such parent blobs in memory seems like a reasonable optimization that should incur additional memory pressure mostly when processing the merges from old branches.

How to find which version of TensorFlow is installed in my system?

To get more information about tensorflow and its options you can use below command:

>> import tensorflow as tf
>> help(tf)

Putting HTML inside Html.ActionLink(), plus No Link Text?

Here is an uber expansion of @tvanfosson's answer. I was inspired by it and decide to make it more generic.

    public static MvcHtmlString NestedActionLink(this HtmlHelper htmlHelper, string linkText, string actionName,
        string controllerName, object routeValues = null, object htmlAttributes = null,
        RouteValueDictionary childElements = null)
        var htmlAttributesDictionary = HtmlHelper.AnonymousObjectToHtmlAttributes(htmlAttributes);

        if (childElements != null)
            var urlHelper = new UrlHelper(htmlHelper.ViewContext.RequestContext);

            var anchorTag = new TagBuilder("a");
                routeValues == null
                    ? urlHelper.Action(actionName, controllerName)
                    : urlHelper.Action(actionName, controllerName, routeValues));
            TagBuilder childTag = null;

            if (childElements != null)
                foreach (var childElement in childElements)
                    childTag = new TagBuilder(childElement.Key.Split('|')[0]);
                    object elementAttributes;
                    childElements.TryGetValue(childElement.Key, out elementAttributes);

                    var attributes = HtmlHelper.AnonymousObjectToHtmlAttributes(elementAttributes);

                    foreach (var attribute in attributes)
                        switch (attribute.Key)
                            case "@class":
                            case "InnerText":
                                childTag.MergeAttribute(attribute.Key, attribute.Value.ToString());
                    if (childTag != null) anchorTag.InnerHtml += childTag.ToString();
            return MvcHtmlString.Create(anchorTag.ToString(TagRenderMode.Normal));
            return htmlHelper.ActionLink(linkText, actionName, controllerName, routeValues, htmlAttributesDictionary);

Why call git branch --unset-upstream to fixup?

For me, .git/refs/origin/master had got corrupt.

I did the following, which fixed the problem for me.

rm .git/refs/remotes/origin/master
git fetch
git branch --set-upstream-to=origin/master

Handling optional parameters in javascript

I know this is a pretty old question, but I dealt with this recently. Let me know what you think of this solution.

I created a utility that lets me strongly type arguments and let them be optional. You basically wrap your function in a proxy. If you skip an argument, it's undefined. It may get quirky if you have multiple optional arguments with the same type right next to each other. (There are options to pass functions instead of types to do custom argument checks, as well as specifying default values for each parameter.)

This is what the implementation looks like:

function displayOverlay(/*message, timeout, callback*/) {
  return arrangeArgs(arguments, String, Number, Function, 
    function(message, timeout, callback) {
      /* ... your code ... */

For clarity, here is what is going on:

function displayOverlay(/*message, timeout, callback*/) {
  //arrangeArgs is the proxy
  return arrangeArgs(
           //first pass in the original arguments
           //then pass in the type for each argument
           String,  Number,  Function, 
           //lastly, pass in your function and the proxy will do the rest!
           function(message, timeout, callback) {

             //debug output of each argument to verify it's working
             console.log("message", message, "timeout", timeout, "callback", callback);

             /* ... your code ... */


You can view the arrangeArgs proxy code in my GitHub repository here:

Here is the utility function with some comments copied from the repository:

 ****** Overview ******
 * Strongly type a function's arguments to allow for any arguments to be optional.
 * Other resources:
 ****** Example implementation ******
 * //all args are optional... will display overlay with default settings
 * var displayOverlay = function() {
 *   return Sysmo.optionalArgs(arguments, 
 *            String, [Number, false, 0], Function, 
 *            function(message, timeout, callback) {
 *              var overlay = new Overlay(message);
 *              overlay.timeout = timeout;
 *              overlay.display({onDisplayed: callback});
 *            });
 * }
 ****** Example function call ******
 * //the window.alert() function is the callback, message and timeout are not defined.
 * displayOverlay(alert);
 * //displays the overlay after 500 miliseconds, then alerts... message is not defined.
 * displayOverlay(500, alert);
 ****** Setup ******
 * arguments = the original arguments to the function defined in your javascript API.
 * config = describe the argument type
 *  - Class - specify the type (e.g. String, Number, Function, Array) 
 *  - [Class/function, boolean, default] - pass an array where the first value is a class or a function...
 *                                         The "boolean" indicates if the first value should be treated as a function.
 *                                         The "default" is an optional default value to use instead of undefined.
arrangeArgs: function (/* arguments, config1 [, config2] , callback */) {
  //config format: [String, false, ''], [Number, false, 0], [Function, false, function(){}]
  //config doesn't need a default value.
  //config can also be classes instead of an array if not required and no default value.

  var configs = Sysmo.makeArray(arguments),
      values = Sysmo.makeArray(configs.shift()),
      callback = configs.pop(),
      args = [],
      done = function() {
        //add the proper number of arguments before adding remaining values
        if (!args.length) {
          args = Array(configs.length);
        //fire callback with args and remaining values concatenated
        return callback.apply(null, args.concat(values));

  //if there are not values to process, just fire callback
  if (!values.length) {
    return done();

  //loop through configs to create more easily readable objects
  for (var i = 0; i < configs.length; i++) {

    var config = configs[i];

    //make sure there's a value
    if (values.length) {

      //type or validator function
      var fn = config[0] || config,
          //if config[1] is true, use fn as validator, 
          //otherwise create a validator from a closure to preserve fn for later use
          validate = (config[1]) ? fn : function(value) {
            return value.constructor === fn;

      //see if arg value matches config
      if (validate(values[0])) {

    //add a default value if there is no value in the original args
    //or if the type didn't match

  return done();

Char array to hex string C++

Code snippet above provides incorrect byte order in string, so I fixed it a bit.

char const hex[16] = { '0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A',   'B','C','D','E','F'};

std::string byte_2_str(char* bytes, int size) {
  std::string str;
  for (int i = 0; i < size; ++i) {
    const char ch = bytes[i];
    str.append(&hex[(ch  & 0xF0) >> 4], 1);
    str.append(&hex[ch & 0xF], 1);
  return str;

javascript: get a function's variable's value within another function

the OOP way to do this in ES5 is to make that variable into a property using the this keyword.

function first(){

function second() {
    y=new first();

How to truncate float values?

Most answers are way too complicated in my opinion, how about this?

digits = 2  # Specify how many digits you want

fnum = '122.485221'
truncated_float = float(fnum[:fnum.find('.') + digits + 1])

>>> 122.48

Simply scanning for the index of '.' and truncate as desired (no rounding). Convert string to float as final step.

Or in your case if you get a float as input and want a string as output:

fnum = str(122.485221)  # convert float to string first
truncated_float = fnum[:fnum.find('.') + digits + 1]  # string output

What does the C++ standard state the size of int, long type to be?

As others have answered, the "standards" all leave most of the details as "implementation defined" and only state that type "char" is at leat "char_bis" wide, and that "char <= short <= int <= long <= long long" (float and double are pretty much consistent with the IEEE floating point standards, and long double is typically same as double--but may be larger on more current implementations).

Part of the reasons for not having very specific and exact values is because languages like C/C++ were designed to be portable to a large number of hardware platforms--Including computer systems in which the "char" word-size may be 4-bits or 7-bits, or even some value other than the "8-/16-/32-/64-bit" computers the average home computer user is exposed to. (Word-size here meaning how many bits wide the system normally operates on--Again, it's not always 8-bits as home computer users may expect.)

If you really need a object (in the sense of a series of bits representing an integral value) of a specific number of bits, most compilers have some method of specifying that; But it's generally not portable, even between compilers made by the ame company but for different platforms. Some standards and practices (especially limits.h and the like) are common enough that most compilers will have support for determining at the best-fit type for a specific range of values, but not the number of bits used. (That is, if you know you need to hold values between 0 and 127, you can determine that your compiler supports an "int8" type of 8-bits which will be large enought to hold the full range desired, but not something like an "int7" type which would be an exact match for 7-bits.)

Note: Many Un*x source packages used "./configure" script which will probe the compiler/system's capabilities and output a suitable Makefile and config.h. You might examine some of these scripts to see how they work and how they probe the comiler/system capabilities, and follow their lead.

How do I create the small icon next to the website tab for my site?

This is for the icon in the browser (most of the sites omit the type):

<link rel="icon" type="image/"
     href="" />


<link rel="icon" type="image/png"
     href="" />


<link rel="apple-touch-icon"

for the shortcut icon:

<link rel="shortcut icon"
     href="" />

Place them in the <head></head> section.

Edit may 2019 some additional examples from MDN

Creating a zero-filled pandas data frame

Similar to @Shravan, but without the use of numpy:

  height = 10
  width = 20
  df_0 = pd.DataFrame(0, index=range(height), columns=range(width))

Then you can do whatever you want with it:

post_instantiation_fcn = lambda x: str(x)
df_ready_for_whatever = df_0.applymap(post_instantiation_fcn)

What is the difference between const and readonly in C#?

A constant will be compiled into the consumer as a literal value while the static string will serve as a reference to the value defined.

As an exercise, try creating an external library and consume it in a console application, then alter the values in the library and recompile it (without recompiling the consumer program), drop the DLL into the directory and run the EXE manually, you should find that the constant string does not change.

How do I remove the title bar from my app?

Go to styles.xml and change .DarkActionBar for .NoActionBar

<style name="AppTheme" parent="Theme.AppCompat.Light.DarkActionBar">
        <item name="colorPrimary">@color/colorPrimary</item>
        <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
        <item name="colorAccent">@color/colorAccent</item>


<style name="AppTheme" parent="Theme.AppCompat.Light.NoActionBar">
        <item name="colorPrimary">@color/colorPrimary</item>
        <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
        <item name="colorAccent">@color/colorAccent</item>

if colors are irrelevant to your app, you can actually go for

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

Initializing array of structures

There are only two syntaxes at play here.

  1. Plain old array initialisation:

    int x[] = {0, 0}; // x[0] = 0, x[1] = 0
  2. A designated initialiser. See the accepted answer to this question: How to initialize a struct in accordance with C programming language standards

    The syntax is pretty self-explanatory though. You can initialise like this:

    struct X {
        int a;
        int b;
    struct X foo = { 0, 1 }; // a = 0, b = 1

    or to use any ordering,

    struct X foo = { .b = 0, .a = 1 }; // a = 1, b = 0

C++ equivalent of java's instanceof

dynamic_cast is known to be inefficient. It traverses up the inheritance hierarchy, and it is the only solution if you have multiple levels of inheritance, and need to check if an object is an instance of any one of the types in its type hierarchy.

But if a more limited form of instanceof that only checks if an object is exactly the type you specify, suffices for your needs, the function below would be a lot more efficient:

template<typename T, typename K>
inline bool isType(const K &k) {
    return typeid(T).hash_code() == typeid(k).hash_code();

Here's an example of how you'd invoke the function above:

DerivedA k;
Base *p = &k;

cout << boolalpha << isType<DerivedA>(*p) << endl;  // true
cout << boolalpha << isType<DerivedB>(*p) << endl;  // false

You'd specify template type A (as the type you're checking for), and pass in the object you want to test as the argument (from which template type K would be inferred).

Playing a MP3 file in a WinForm application

  1. first go to the properties of your project
  2. click on add references
  3. add the library under COM object for window media player then type your code where you want


        WMPLib.WindowsMediaPlayer wplayer = new WMPLib.WindowsMediaPlayer();
        wplayer.URL = @"C:\Users\Adil M\Documents\Visual Studio 2012\adil.mp3";;

Insert/Update Many to Many Entity Framework . How do I do it?

In entity framework, when object is added to context, its state changes to Added. EF also changes state of each object to added in object tree and hence you are either getting primary key violation error or duplicate records are added in table.

How to find the UpgradeCode and ProductCode of an installed application in Windows 7

If you have msi installer open it with Orca (tool from Microsoft), table Property (rows UpgradeCode, ProductCode, Product version etc) or table Upgrade column Upgrade Code.

Try to find instller via registry: HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall find required subkey and watch value InstallSource. Maybe along the way you'll be able to find the MSI file.

How to Call a Function inside a Render in React/Jsx

The fix was at the accepted answer. Yet if someone wants to know why it worked and why the implementation in the SO question didn't work,

First, functions are first class objects in JavaScript. That means they are treated like any other variable. Function can be passed as an argument to other functions, can be returned by another function and can be assigned as a value to a variable. Read more here.

So we use that variable to invoke the function by adding parentheses () at the end.

One thing, If you have a function that returns a funtion and you just need to call that returned function, you can just have double paranthesis when you call the outer function ()().

EditText, clear focus on touch outside

I really think it's a more robust way to use getLocationOnScreen than getGlobalVisibleRect. Because I meet a problem. There is a Listview which contain some Edittext and and set ajustpan in the activity. I find getGlobalVisibleRect return a value that looks like including the scrollY in it, but the event.getRawY is always by the screen. The below code works well.

public boolean dispatchTouchEvent(MotionEvent event) {
    if (event.getAction() == MotionEvent.ACTION_DOWN) {
        View v = getCurrentFocus();
        if ( v instanceof EditText) {
            if (!isPointInsideView(event.getRawX(), event.getRawY(), v)) {
                Log.i(TAG, "!isPointInsideView");

                Log.i(TAG, "dispatchTouchEvent clearFocus");
                InputMethodManager imm = (InputMethodManager) getSystemService(Context.INPUT_METHOD_SERVICE);
                imm.hideSoftInputFromWindow(v.getWindowToken(), 0);
    return super.dispatchTouchEvent( event );

 * Determines if given points are inside view
 * @param x - x coordinate of point
 * @param y - y coordinate of point
 * @param view - view object to compare
 * @return true if the points are within view bounds, false otherwise
private boolean isPointInsideView(float x, float y, View view) {
    int location[] = new int[2];
    int viewX = location[0];
    int viewY = location[1];

    Log.i(TAG, "location x: " + location[0] + ", y: " + location[1]);

    Log.i(TAG, "location xWidth: " + (viewX + view.getWidth()) + ", yHeight: " + (viewY + view.getHeight()));

    // point is inside view bounds
    return ((x > viewX && x < (viewX + view.getWidth())) &&
            (y > viewY && y < (viewY + view.getHeight())));

Using 'make' on OS X

@Daniel's suggestion worked perfectly for me. To install

, open Xcode, go to Preferences -> Downloads -> Components -> Command Line Tools.You can then test with
gcc -v

How can I make the browser wait to display the page until it's fully loaded?

Don't use display:none. If you do, you will see images resize/reposition when you do the show(). Use visibility:hidden instead and it will lay everything out correctly, but it just won't be visible until you tell it to.

Difference between DataFrame, Dataset, and RDD in Spark

A DataFrame is equivalent to a table in RDBMS and can also be manipulated in similar ways to the "native" distributed collections in RDDs. Unlike RDDs, Dataframes keep track of the schema and support various relational operations that lead to more optimized execution. Each DataFrame object represents a logical plan but because of their "lazy" nature no execution occurs until the user calls a specific "output operation".

How to configure Spring Security to allow Swagger URL to be accessed without authentication

I updated with /configuration/** and /swagger-resources/** and it worked for me.

public void configure(WebSecurity web) throws Exception {
    web.ignoring().antMatchers("/v2/api-docs", "/configuration/ui", "/swagger-resources/**", "/configuration/**", "/swagger-ui.html", "/webjars/**");


What does API level mean?

API level is basically the Android version. Instead of using the Android version name (eg 2.0, 2.3, 3.0, etc) an integer number is used. This number is increased with each version. Android 1.6 is API Level 4, Android 2.0 is API Level 5, Android 2.0.1 is API Level 6, and so on.

Count number of occurrences of a pattern in a file (even on same line)

A belated post:
Use the search regex pattern as a Record Separator (RS) in awk
This allows your regex to span \n-delimited lines (if you need it).

printf 'X \n moo X\n XX\n' | 
   awk -vRS='X[^X]*X' 'END{print (NR<2?0:NR-1)}'

Double free or corruption after queue::push

You need to define a copy constructor, assignment, operator.

class Test {
   Test(const Test &that); //Copy constructor
   Test& operator= (const Test &rhs); //assignment operator

Your copy that is pushed on the queue is pointing to the same memory your original is. When the first is destructed, it deletes the memory. The second destructs and tries to delete the same memory.

Subdomain on different host

sub domain is part of the domain, it's like subletting a room of an apartment. A records has to be setup on the dns for the domain e.g has IP 123.456.789.999 and hosted with Godaddy. Now to get the sub domain

of which the site is actually on another server then

login to Godaddy and add an A record dnsimple and point the IP to the other server

And that's it.

Binding ItemsSource of a ComboBoxColumn in WPF DataGrid

Pls, check if DataGridComboBoxColumn xaml below would work for you:

    SelectedValueBinding="{Binding CompanyID}" 

        <Style TargetType="{x:Type ComboBox}">
            <Setter Property="ItemsSource" Value="{Binding Path=DataContext.CompanyItems, RelativeSource={RelativeSource AncestorType={x:Type Window}}}" />
        <Style TargetType="{x:Type ComboBox}">
            <Setter Property="ItemsSource" Value="{Binding Path=DataContext.CompanyItems, RelativeSource={RelativeSource AncestorType={x:Type Window}}}" />

Here you can find another solution for the problem you're facing: Using combo boxes with the WPF DataGrid

Inserting line breaks into PDF

Or just try this after each text passage for a new line.

$pdf->Write(0, ' ', '*', 0, 'C', TRUE, 0, false, false, 0) ;

How to normalize a vector in MATLAB efficiently? Any related built-in function?

I don't know any MATLAB and I've never used it, but it seems to me you are dividing. Why? Something like this will be much faster:

d = 1/norm(V)
V1 = V * d

Change color of Button when Mouse is over

<Button Background="#FF4148" BorderThickness="0" BorderBrush="Transparent">
     <Border HorizontalAlignment="Right" BorderBrush="#FF6A6A" BorderThickness="0>
         <Style TargetType="Border">
                 <Trigger Property="IsMouseOver" Value="True">
                     <Setter Property="Background" Value="#FF6A6A" />
      <StackPanel Orientation="Horizontal">
           <Image  RenderOptions.BitmapScalingMode="HighQuality"   Source="//ImageName.png"   />

Select Last Row in the Table

If you are looking for the actual row that you just inserted with Laravel 3 and 4 when you perform a save or create action on a new model like:



$user = User::create(array('email' => '[email protected]'));

then the inserted model instance will be returned and can be used for further action such as redirecting to the profile page of the user just created.

Looking for the last inserted record works on low volume system will work almost all of the time but if you ever have to inserts go in at the same time you can end up querying to find the wrong record. This can really become a problem in a transactional system where multiple tables need updated.

Multiple Updates in MySQL

You may also be interested in using joins on updates, which is possible as well.

Update someTable Set someValue = 4 From someTable s Inner Join anotherTable a on = Where = 4
-- Only updates someValue in someTable who has a foreign key on anotherTable with a value of 4.

Edit: If the values you are updating aren't coming from somewhere else in the database, you'll need to issue multiple update queries.

Why does PEP-8 specify a maximum line length of 79 characters?

Much of the value of PEP-8 is to stop people arguing about inconsequential formatting rules, and get on with writing good, consistently formatted code. Sure, no one really thinks that 79 is optimal, but there's no obvious gain in changing it to 99 or 119 or whatever your preferred line length is. I think the choices are these: follow the rule and find a worthwhile cause to battle for, or provide some data that demonstrates how readability and productivity vary with line length. The latter would be extremely interesting, and would have a good chance of changing people's minds I think.

How to insert array of data into mysql using php

    foreach($EMailArr as $key => $value){

    $R_ID = (int) $value['R_ID'];
    $email = mysql_real_escape_string( $value['email'] );
    $name = mysql_real_escape_string( $value['name'] );

    $sql = "INSERT INTO email_list (R_ID, EMAIL, NAME) values ('$R_ID', '$email', '$name')";
    mysql_query($sql) or exit(mysql_error()); 

A better example solution with PDO:

 $q = $sql->prepare("INSERT INTO `email_list` 
                     SET `R_ID` = ?, `EMAIL` = ?, `NAME` = ?");

 foreach($EMailArr as $value){
   $q ->execute( array( $value['R_ID'], $value['email'], $value['name'] ));

What event handler to use for ComboBox Item Selected (Selected Item not necessarily changed)

For me ComboBox.DropDownClosed Event did it.

private void cbValueType_DropDownClosed(object sender, EventArgs e)
        if (cbValueType.SelectedIndex == someIntValue) //sel ind already updated
            // change sel Index of other Combo for example
            cbDataType.SelectedIndex = someotherIntValue;

Convert boolean result into number/integer

+!! allows you to apply this on a variable even when it's undefined:

+!!undefined    // 0
+!!false        // 0
+!!true         // 1

+!!(<boolean expression>)  // 1 if it evaluates to true, 0 otherwise

Differences between Html.TextboxFor and Html.EditorFor in MVC and Razor

There is also a slight difference in the html output for a string data type.

<input id="Contact_FirstName" class="text-box single-line" type="text" value="Greg" name="Contact.FirstName">

<input id="Contact_FirstName" type="text" value="Greg" name="Contact.FirstName">

Splitting templated C++ classes into .hpp/.cpp files--is it possible?

1) Remember the main reason to separate .h and .cpp files is to hide the class implementation as a separately-compiled Obj code that can be linked to the user’s code that included a .h of the class.

2) Non-template classes have all variables concretely and specifically defined in .h and .cpp files. So the compiler will have the need information about all data types used in the class before compiling/translating ? generating the object/machine code Template classes have no information about the specific data type before the user of the class instantiate an object passing the required data type:

        TClass<int> myObj;

3) Only after this instantiation, the complier generate the specific version of the template class to match the passed data type(s).

4) Therefore, .cpp Can NOT be compiled separately without knowing the users specific data type. So it has to stay as source code within “.h” until the user specify the required data type then, it can be generated to a specific data type then compiled

How to copy directories with spaces in the name

After some trial and error and observing the results (in other words, I hacked it), I got it to work.

Quotes ARE required to use a path name with spaces. The trick is there MUST be a space after the path names before the closing this...

robocopy "C:\Source Path " "C:\Destination Path " /option1 /option2...

This almost seems like a bug and certainly not very intuitive.

Todd K.

How to get query string parameter from MVC Razor markup?

If you are using .net core 2.0 this would be:


Sample usage:

<a href="@Url.Action("Query",new {parm1=Context.Request.Query["queryparm1"]})">GO</a>

Joining pairs of elements of a list

Without building temporary lists:

>>> import itertools
>>> s = 'abcdefgh'
>>> si = iter(s)
>>> [''.join(each) for each in itertools.izip(si, si)]
['ab', 'cd', 'ef', 'gh']


>>> import itertools
>>> s = 'abcdefgh'
>>> si = iter(s)
>>> map(''.join, itertools.izip(si, si))
['ab', 'cd', 'ef', 'gh']

Is there any use for unique_ptr with array?

In a nutshell: it's by far the most memory-efficient.

A std::string comes with a pointer, a length, and a "short-string-optimization" buffer. But my situation is I need to store a string that is almost always empty, in a structure that I have hundreds of thousands of. In C, I would just use char *, and it would be null most of the time. Which works for C++, too, except that a char * has no destructor, and doesn't know to delete itself. By contrast, a std::unique_ptr<char[]> will delete itself when it goes out of scope. An empty std::string takes up 32 bytes, but an empty std::unique_ptr<char[]> takes up 8 bytes, that is, exactly the size of its pointer.

The biggest downside is, every time I want to know the length of the string, I have to call strlen on it.

Is there a command to refresh environment variables from the command prompt in Windows?

Environment variables are kept in HKEY_LOCAL_MACHINE\SYSTEM\ControlSet\Control\Session Manager\Environment.

Many of the useful env vars, such as Path, are stored as REG_SZ. There are several ways to access the registry including REGEDIT:

REGEDIT /E &lt;filename&gt; "HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Session Manager\Environment"

The output starts with magic numbers. So to search it with the find command it needs to be typed and redirected: type <filename> | findstr -c:\"Path\"

So, if you just want to refresh the path variable in your current command session with what's in system properties the following batch script works fine:


    @echo off

    REM This solution requests elevation in order to read from the registry.

    if exist %temp%\env.reg del %temp%\env.reg /q /f

    REGEDIT /E %temp%\env.reg "HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Session Manager\Environment"

    if not exist %temp%\env.reg (
       echo "Unable to write registry to temp location"
       exit 1

    SETLOCAL EnableDelayedExpansion

    for /f "tokens=1,2* delims==" %%i in ('type %temp%\env.reg ^| findstr -c:\"Path\"=') do (
       set upath=%%~j
       echo !upath:\\=\! >%temp%\newpath


     for /f "tokens=*" %%i in (%temp%\newpath) do set path=%%i

How to list all methods for an object in Ruby?

What about one of these?


How to make Scrollable Table with fixed headers using CSS

I can think of a cheeky way to do it, I don't think this will be the best option but it will work.

Create the header as a separate table then place the other in a div and set a max size, then allow the scroll to come in by using overflow.

table {_x000D_
  width: 500px;_x000D_
.scroll {_x000D_
  max-height: 60px;_x000D_
  overflow: auto;_x000D_
<table border="1">_x000D_
<div class="scroll">_x000D_
    <tr><td>Text Text</td><td>Text Text</td><td>Text Text</td><td>Text Text</td></tr>_x000D_
    <tr><td>Text Text</td><td>Text Text</td><td>Text Text</td><td>Text Text</td></tr>_x000D_
    <tr><td>Text Text</td><td>Text Text</td><td>Text Text</td><td>Text Text</td></tr>_x000D_
    <tr><td>Text Text</td><td>Text Text</td><td>Text Text</td><td>Text Text</td></tr>_x000D_
    <tr><td>Text Text</td><td>Text Text</td><td>Text Text</td><td>Text Text</td></tr>_x000D_
    <tr><td>Text Text</td><td>Text Text</td><td>Text Text</td><td>Text Text</td></tr>_x000D_
    <tr><td>More Text</td><td>More Text</td><td>More Text</td><td>More Text</td></tr>_x000D_
    <tr><td>Text Text</td><td>Text Text</td><td>Text Text</td><td>Text Text</td></tr>_x000D_
    <tr><td>Even More Text Text</td><td>Even More Text Text</td><td>Even More Text Text</td><td>Even More Text Text</td></tr>_x000D_

html <input type="text" /> onchange event not working

onchange only occurs when the change to the input element is committed by the user, most of the time this is when the element loses focus.

if you want your function to fire everytime the element value changes you should use the oninput event - this is better than the key up/down events as the value can be changed with the user's mouse ie pasted in, or auto-fill etc

Read more about the change event here

Read more about the input event here

Is this the right way to clean-up Fragment back stack when leaving a deeply nested stack?

Thanks to Joachim answer, I use the code to clear all back stack entry finally.

// In your FragmentActivity use getSupprotFragmentManager() to get the FragmentManager.

// Clear all back stack.
int backStackCount = getSupportFragmentManager().getBackStackEntryCount();
for (int i = 0; i < backStackCount; i++) {

    // Get the back stack fragment id.
    int backStackId = getSupportFragmentManager().getBackStackEntryAt(i).getId();


} /* end of for */

PHP Parse error: syntax error, unexpected '?' in helpers.php 233

I had approximately the same problem with Laravel 5.5 on ubuntu, finally i've found a solution here to switch between the versions of php used by apache :

  1. sudo a2dismod php5
  2. sudo a2enmod php7.1
  3. sudo service apache2 restart

and it works

Server certificate verification failed: issuer is not trusted

can you try to run svn checkout once manually to your URL https://yoururl/trunk C:\ant-1.8.1\Test_Checkout using command line and accept certificate.

Or as @AndrewSpear says below

Rather than checking out manually run svn list https://your.repository.url from Terminal (Mac) / Command Line (Win) to get the option to accept the certificate permanently

svn will ask you for confirmation. accept it permanently.

After that this should work for subsequent requests from ant script.

compare differences between two tables in mysql

I found another solution in this link

SELECT MIN (tbl_name) AS tbl_name, PK, column_list
  SELECT ' source_table ' as tbl_name, S.PK, S.column_list
  FROM source_table AS S
  SELECT 'destination_table' as tbl_name, D.PK, D.column_list
  FROM destination_table AS D 
)  AS alias_table
GROUP BY PK, column_list

Incorrect syntax near ''

The error for me was that I read the SQL statement from a text file, and the text file was saved in the UTF-8 with BOM (byte order mark) format.

To solve this, I opened the file in Notepad++ and under Encoding, chose UTF-8. Alternatively you can remove the first three bytes of the file with a hex editor.

C++ Redefinition Header Files (winsock2.h)

In my project (I use VS 2008 SP1) works next solution:

Header file:

#pragma once
#define _WINSOCKAPI_
#include <windows.h>

Cpp class:

#include "Util.h"
#include "winsock2class.h"
#pragma comment(lib, "Ws2_32.lib")

where #include "winsock2class.h" mean class which implemented winsock2.h :

#include <winsock2.h>
#include <windows.h>
#pragma comment(lib, "Ws2_32.lib")

Deleting an element from an array in PHP

$arrayName = array( '1' => 'somevalue',
                    '2' => 'somevalue1',
                    '3' => 'somevalue3',

// somevalue


What is the proper way to display the full InnerException?

To pretty print just the Messages part of deep exceptions, you could do something like this:

public static string ToFormattedString(this Exception exception)
    IEnumerable<string> messages = exception
        .Where(e => !String.IsNullOrWhiteSpace(e.Message))
        .Select(e => e.Message.Trim());
    string flattened = String.Join(Environment.NewLine, messages); // <-- the separator here
    return flattened;

public static IEnumerable<Exception> GetAllExceptions(this Exception exception)
    yield return exception;

    if (exception is AggregateException aggrEx)
        foreach (Exception innerEx in aggrEx.InnerExceptions.SelectMany(e => e.GetAllExceptions()))
            yield return innerEx;
    else if (exception.InnerException != null)
        foreach (Exception innerEx in exception.InnerException.GetAllExceptions())
            yield return innerEx;

This recursively goes through all inner exceptions (including the case of AggregateExceptions) to print all Message property contained in them, delimited by line break.


var outerAggrEx = new AggregateException(
    "Outer aggr ex occurred.",
    new AggregateException("Inner aggr ex.", new FormatException("Number isn't in correct format.")),
    new IOException("Unauthorized file access.", new SecurityException("Not administrator.")));

Outer aggr ex occurred.
Inner aggr ex.
Number isn't in correct format.
Unauthorized file access.
Not administrator.

You will need to listen to other Exception properties for more details. For e.g. Data will have some information. You could do:

foreach (DictionaryEntry kvp in exception.Data)

To get all derived properties (not on base Exception class), you could do:

    .Where(p => p.CanRead)
    .Where(p => p.GetMethod.GetBaseDefinition().DeclaringType != typeof(Exception));

Is either GET or POST more secure than the other?

My usual methodology for choosing is something like:

  • GET for items that will be retrieved later by URL
    • E.g. Search should be GET so you can do search.php?s=XXX later on
  • POST for items that will be sent
    • This is relatively invisible comapred to GET and harder to send, but data can still be sent via cURL.

How to enable mbstring from php.ini?

All XAMPP packages come with Multibyte String (php_mbstring.dll) extension installed.

If you have accidentally removed DLL file from php/ext folder, just add it back (get the copy from XAMPP zip archive - its downloadable).

If you have deleted the accompanying INI configuration line from php.ini file, add it back as well:


Also, ensure to restart your webserver (Apache) using XAMPP control panel.

Additional Info on Enabling PHP Extensions

  • install extension (e.g. put php_mbstring.dll into /XAMPP/php/ext directory)
  • in php.ini, ensure extension directory specified (e.g. extension_dir = "ext")
  • ensure correct build of DLL file (e.g. 32bit thread-safe VC9 only works with DLL files built using exact same tools and configuration: 32bit thread-safe VC9)
  • ensure PHP API versions match (If not, once you restart the webserver you will receive related error.)

Does Java SE 8 have Pairs or Tuples?


Map.Entry can be used as a Pair.

Unfortunately it does not help with Java 8 streams as the problem is that even though lambdas can take multiple arguments, the Java language only allows for returning a single value (object or primitive type). This implies that whenever you have a stream you end up with being passed a single object from the previous operation. This is a lack in the Java language, because if multiple return values was supported AND streams supported them we could have much nicer non-trivial tasks done by streams.

Until then, there is only little use.

EDIT 2018-02-12: While working on a project I wrote a helper class which helps handling the special case of having an identifier earlier in the stream you need at a later time but the stream part in between does not know about it. Until I get around to release it on its own it is available at with a unit test at

How to run regasm.exe from command line other than Visual Studio command prompt?

By dragging and dropping the dll onto 'regasm' you can register it. You can open two 'Window Explorer' windows. One will contain the dll you wish to register. The 2nd window will be the location of the 'regasm' application. Scroll down in both windows so that you have a view of both the dll and 'regasm'. It helps to reduce the size of the two windows so they are side-by-side. Be sure to drag the dll over the 'regasm' that is labeled 'application'. There are several 'regasm' files but you only want the application.

"undefined" function declared in another file?

If your source folder is structured /go/src/blog (assuming the name of your source folder is blog).

  1. cd /go/src/blog ... (cd inside the folder that has your package)
  2. go install
  3. blog

That should run all of your files at the same time, instead of you having to list the files manually or "bashing" a method on the command line.

What is the difference between children and childNodes in JavaScript?

Understand that .children is a property of an Element. 1 Only Elements have .children, and these children are all of type Element. 2

However, .childNodes is a property of Node. .childNodes can contain any node. 3

A concrete example would be:

let el = document.createElement("div");
el.textContent = "foo";

el.childNodes.length === 1; // Contains a Text node child.
el.children.length === 0;   // No Element children.

Most of the time, you want to use .children because generally you don't want to loop over Text or Comment nodes in your DOM manipulation.

If you do want to manipulate Text nodes, you probably want .textContent instead. 4

1. Technically, it is an attribute of ParentNode, a mixin included by Element.
2. They are all elements because .children is a HTMLCollection, which can only contain elements.
3. Similarly, .childNodes can hold any node because it is a NodeList.
4. Or .innerText. See the differences here or here.

Ruby: Can I write multi-line string with no concatenation?

If you do mind extra spaces and newlines, you can use

conn.exec %w{select attr1, attr2, attr3, attr4, attr5, attr6, attr7
  from table1, table2, table3, etc, etc, etc, etc, etc,
  where etc etc etc etc etc etc etc etc etc etc etc etc etc} * ' '

(use %W for interpolated strings)

How do I alter the precision of a decimal column in Sql Server?

Go to enterprise manager, design table, click on your field.

Make a decimal column

In the properties at the bottom there is a precision property

How to send a HTTP OPTIONS request from the command line?

The curl installed by default in Debian supports HTTPS since a great while back. (a long time ago there were two separate packages, one with and one without SSL but that's not the case anymore)


You can send an OPTIONS request with curl like this:

curl -i -X OPTIONS

You may also use -v instead of -i to see more output.


To send a plain * (instead of the path, see RFC 7231) with the OPTIONS method, you need curl 7.55.0 or later as then you can run a command line like:

curl -i --request-target "*" -X OPTIONS

Programmatically scroll a UIScrollView

scrollView.setContentOffset(CGPoint(x: y, y: x), animated: true)

Disable webkit's spin buttons on input type="number"?

It seems impossible to prevent spinners from appearing in Opera. As a temporary workaround, you can make room for the spinners. As far as I can tell, the following CSS adds just enough padding, only in Opera:

input[type=number] {
    padding-right: 1.2em;

How to make a dropdown readonly using jquery?

Setting an element with disabled will not submit the data, however select elements don't have readonly.

You can simulate a readonly on select using CSS for styling and JS to prevent change with tab:

select[readonly] {
  background: #eee;
  pointer-events: none;
  touch-action: none;

Then use it like:

var readonly_select = $('select');
$(readonly_select).attr('readonly', true).attr('data-original-value', $(readonly_select).val()).on('change', function(i) {


  // Updated 08/2018 to prevent changing value with tab_x000D_
$('a').on('click', function() {_x000D_
var readonly_select = $('select');_x000D_
$(readonly_select).attr('readonly', true).attr('data-original-value', $(readonly_select).val()).on('change', function(i) {_x000D_
select[readonly] {_x000D_
  background: #eee;_x000D_
  pointer-events: none;_x000D_
  touch-action: none;_x000D_
<script src=""></script>_x000D_
<a href="#">Click here to enable readonly</a>_x000D_
<option>Example 1</option>_x000D_
<option selected>Example 2</option>_x000D_
<option>Example 3</option>_x000D_

Difference of two date time in sql server

SELECT  DATEDIFF(day, '2010-01-22 15:29:55.090', '2010-01-22 15:30:09.153')

Replace day with other units you want to get the difference in, like second, minute etc.

MySQL Multiple Joins in one query?

Just add another join:

SELECT dashboard_data.headline,
FROM dashboard_data 
    INNER JOIN dashboard_messages
            ON dashboard_message_id = 
    INNER JOIN images
            ON dashboard_messages.image_id = images.image_id

Run reg command in cmd (bat file)?

In command line it's better to use REG tool rather than REGEDIT:

REG IMPORT yourfile.reg

REG is designed for console mode, while REGEDIT is for graphical mode. This is why running regedit.exe /S yourfile.reg is a bad idea, since you will not be notified if the there's an error, whereas REG Tool will prompt:

>  REG IMPORT missing_file.reg

ERROR: Error opening the file. There may be a disk or file system error.

>  %windir%\System32\reg.exe /?

REG Operation [Parameter List]

  Operation  [ QUERY   | ADD    | DELETE  | COPY    |
               SAVE    | LOAD   | UNLOAD  | RESTORE |
               COMPARE | EXPORT | IMPORT  | FLAGS ]

Return Code: (Except for REG COMPARE)

  0 - Successful
  1 - Failed

For help on a specific operation type:

  REG Operation /?


  REG ADD /?

Read environment variables in Node.js

If you want to see all the Enviroment Variables on execution time just write in some nodejs file like server.js:



HAVING is used to filter on aggregations in your GROUP BY.

For example, to check for duplicate names:

SELECT Name FROM Usernames

how to convert binary string to decimal?

        var num = 10;

        alert("Binary " + num.toString(2));   //1010
        alert("Octal " + num.toString(8));    //12
        alert("Hex " + num.toString(16));     //a

        alert("Binary to Decimal "+ parseInt("1010", 2));  //10
        alert("Octal to Decimal " + parseInt("12", 8));    //10
        alert("Hex to Decimal " + parseInt("a", 16));      //10

How to check type of object in Python?

What type() means:

I think your question is a bit more general than I originally thought. type() with one argument returns the type or class of the object. So if you have a = 'abc' and use type(a) this returns str because the variable a is a string. If b = 10, type(b) returns int.

See also python documentation on type().

For comparisons:

If you want a comparison you could use: if type(v) == h5py.h5r.Reference (to check if it is a h5py.h5r.Reference instance).

But it is recommended that one uses if isinstance(v, h5py.h5r.Reference) but then also subclasses will evaluate to True.

If you want to print the class use print v.__class__.__name__.

More generally: You can compare if two instances have the same class by using type(v) is type(other_v) or isinstance(v, other_v.__class__).

How to use Redirect in the new react-router-dom of Reactjs

To navigate to another component you can use this.props.history.push('/main');

import React, { Component, Fragment } from 'react'

class Example extends Component {

  redirect() {

  render() {
    return (

 export default Example

remove first element from array and return the array minus the first element

This should remove the first element, and then you can return the remaining:

var myarray = ["item 1", "item 2", "item 3", "item 4"];_x000D_

As others have suggested, you could also use slice(1);

var myarray = ["item 1", "item 2", "item 3", "item 4"];_x000D_

How to get file path from OpenFileDialog and FolderBrowserDialog?

I am sorry if i am late to reply here but i just thought i should throw in a much simpler solution for the OpenDialog.

OpenDialog ofd = new OpenDialog();
var fullPathIncludingFileName = ofd.Filename; //returns the full path including the filename
var fullPathExcludingFileName = ofd.Filename.Replace(ofd.SafeFileName, "");//will remove the filename from the full path

I have not yet used a FolderBrowserDialog before so i will trust my fellow coders's take on this. I hope this helps.

How to use JavaScript regex over multiple lines?

[.\n] doesn't work, because dot in [] (by regex definition; not javascript only) means the dot-character. You can use (.|\n) (or (.|[\n\r])) instead.

How to add a browser tab icon (favicon) for a website?

  1. Use a tool to convert your png to a ico file. You can search "favicon generator" and you can find many online tools.
  2. Place the ico address in the head with a link-tag:

    <link rel="shortcut icon" href="">

When is it appropriate to use UDP instead of TCP?

The key question was related to "what kind of situations would UDP be the better choice [over tcp]"

There are many great answers above but what is lacking is any formal, objective assessment of the impact of transport uncertainty upon TCP performance.

With the massive growth of mobile applications, and the "occasionally connected" or "occasionally disconnected" paradigms that go with them, there are certainly situations where the overhead of TCP's attempts to maintain a connection when connections are hard to come by leads to a strong case for UDP and its "message oriented" nature.

Now I don't have the math/research/numbers on this, but I have produced apps that have worked more reliably using and ACK/NAK and message numbering over UDP than could be achieved with TCP when connectivity was generally poor and poor old TCP just spent it's time and my client's money just trying to connect. You get this in regional and rural areas of many western countries....

How to slice an array in Bash

See the Parameter Expansion section in the Bash man page. A[@] returns the contents of the array, :1:2 takes a slice of length 2, starting at index 1.

A=( foo bar "a  b c" 42 )
C=("${A[@]:1}")       # slice to the end of the array
echo "${B[@]}"        # bar a  b c
echo "${B[1]}"        # a  b c
echo "${C[@]}"        # bar a  b c 42
echo "${C[@]: -2:2}"  # a  b c 42 # The space before the - is necesssary

Note that the fact that "a b c" is one array element (and that it contains an extra space) is preserved.

Cannot get Kerberos service ticket: KrbException: Server not found in Kerberos database (7)

sqlcmd works, System.Data.SqlClient not working - Server not found in Kerberos database. You should add RestrictedKrbHost SPN

5.1.2 SPNs with Serviceclass Equal to "RestrictedKrbHost"

Supporting the "RestrictedKrbHost" service class allows client applications to use Kerberos authentication when they do not have the identity of the service but have the server name. This does not provide client-to-service mutual authentication, but rather client-to-server computer authentication. Services of different privilege levels have the same session key and could decrypt each other's data if the underlying service does not ensure that data cannot be accessed by higher services.

How to run a cron job inside a docker container?

Unfortunately, none of the above answers worked for me, although all answers lead to the solution and eventually to my solution, here is the snippet if it helps someone. Thanks

This can be solved with the bash file, due to the layered architecture of the Docker, cron service doesn't get initiated with RUN/CMD/ENTRYPOINT commands.

Simply add a bash file which will initiate the cron and other services (if required)


FROM gradle:6.5.1-jdk11 AS build
# apt
RUN apt-get update
RUN apt-get -y install cron
# Setup cron to run every minute to print (you can add/update your cron here)
RUN touch /var/log/cron-1.log
RUN (crontab -l ; echo "* * * * * echo testing cron.... >> /var/log/cron-1.log 2>&1") | crontab
RUN chmod +x
CMD ["bash",""]

service cron start & tail -f /var/log/cron-2.log

If any other service is also required to run along with cron then add that service with & in the same command, for example: /opt/wildfly/bin/ & service cron start & tail -f /var/log/cron-2.log

Once you will get into the docker container there you can see that testing cron.... will be getting printed every minute in file: /var/log/cron-1.log

How do I run all Python unit tests in a directory?

This BASH script will execute the python unittest test directory from ANYWHERE in the file system, no matter what working directory you are in: its working directory always be where that test directory is located.

ALL TESTS, independent $PWD

unittest Python module is sensitive to your current directory, unless you tell it where (using discover -s option).

This is useful when staying in the ./src or ./example working directory and you need a quick overall unit test:

dirname="`dirname $this_program`"
readlink="`readlink -e $dirname`"

python -m unittest discover -s "$readlink"/test -v

SELECTED TESTS, independent $PWD

I name this utility file: and use it like this: <test-python-filename-minus-dot-py-fileextension>
dirname="`dirname $this_program`"
readlink="`readlink -e $dirname`"

(cd "$dirname"/test; python -m unittest $1)

No need for a test/ file to burden your package/memory-overhead during production.

How to verify static void method has been called with power mockito

Thou the above answer is widely accepted and well documented, I found some of the reason to post my answer here :-

    doNothing().when(InternalUtils.class); //This is the preferred way
                                           //to mock static void methods.
    InternalUtils.sendEmail(anyString(), anyString(), anyString(), anyString());

Here, I dont understand why we are calling InternalUtils.sendEmail ourself. I will explain in my code why we don't need to do that.


So, we have mocked the class which is fine. Now, lets have a look how we need to verify the sendEmail(/..../) method.

public class InternalServiceTest {

    private InternalService.Order order;

    private InternalService internalService;

    public void setup() {
        internalService = new InternalService();

    public void processOrder() throws Exception {



        InternalService.InternalUtils.sendEmail(anyString(), any(String[].class), anyString(), anyString());


These two lines is where the magic is, First line tells the PowerMockito framework that it needs to verify the class it statically mocked. But which method it need to verify ?? Second line tells which method it needs to verify.

InternalService.InternalUtils.sendEmail(anyString(), any(String[].class), anyString(), anyString());

This is code of my class, sendEmail api twice.

public class InternalService {

    public void processOrder(Order order) {
        if (order.isSuccessful()) {
            InternalUtils.sendEmail("", new String[1], "", "");
            InternalUtils.sendEmail("", new String[1], "", "");

    public static class InternalUtils{

        public static void sendEmail(String from, String[]  to, String msg, String body){



    public class Order{

        public boolean isSuccessful(){
            return true;



As it is calling twice you just need to change the verify(times(2))... that's all.

Compiled vs. Interpreted Languages

The extreme and simple cases:

  • A compiler will produce a binary executable in the target machine's native executable format. This binary file contains all required resources except for system libraries; it's ready to run with no further preparation and processing and it runs like lightning because the code is the native code for the CPU on the target machine.

  • An interpreter will present the user with a prompt in a loop where he can enter statements or code, and upon hitting RUN or the equivalent the interpreter will examine, scan, parse and interpretatively execute each line until the program runs to a stopping point or an error. Because each line is treated on its own and the interpreter doesn't "learn" anything from having seen the line before, the effort of converting human-readable language to machine instructions is incurred every time for every line, so it's dog slow. On the bright side, the user can inspect and otherwise interact with his program in all kinds of ways: Changing variables, changing code, running in trace or debug modes... whatever.

With those out of the way, let me explain that life ain't so simple any more. For instance,

  • Many interpreters will pre-compile the code they're given so the translation step doesn't have to be repeated again and again.
  • Some compilers compile not to CPU-specific machine instructions but to bytecode, a kind of artificial machine code for a ficticious machine. This makes the compiled program a bit more portable, but requires a bytecode interpreter on every target system.
  • The bytecode interpreters (I'm looking at Java here) recently tend to re-compile the bytecode they get for the CPU of the target section just before execution (called JIT). To save time, this is often only done for code that runs often (hotspots).
  • Some systems that look and act like interpreters (Clojure, for instance) compile any code they get, immediately, but allow interactive access to the program's environment. That's basically the convenience of interpreters with the speed of binary compilation.
  • Some compilers don't really compile, they just pre-digest and compress code. I heard a while back that's how Perl works. So sometimes the compiler is just doing a bit of the work and most of it is still interpretation.

In the end, these days, interpreting vs. compiling is a trade-off, with time spent (once) compiling often being rewarded by better runtime performance, but an interpretative environment giving more opportunities for interaction. Compiling vs. interpreting is mostly a matter of how the work of "understanding" the program is divided up between different processes, and the line is a bit blurry these days as languages and products try to offer the best of both worlds.