Programs & Examples On #First class

An entity in a programming language is called first-class if it can be constructed and manipulated at runtime.

Pair/tuple data type in Go

You could do something like this if you wanted

package main

import "fmt"

type Pair struct {
    a, b interface{}

func main() {
    p1 := Pair{"finished", 42}
    p2 := Pair{6.1, "hello"}
    fmt.Println("p1=", p1, "p2=", p2)
    fmt.Println("p1.b", p1.b)
    // But to use the values you'll need a type assertion
    s := p1.a.(string) + " now"
    fmt.Println("p1.a", s)

However I think what you have already is perfectly idiomatic and the struct describes your data perfectly which is a big advantage over using plain tuples.

Java multiline string

Stephen Colebourne has created a proposal for adding multi-line strings in Java 7.

Also, Groovy already has support for multi-line strings.

Does functional programming replace GoF design patterns?

You can't have this discussion without bringing up type systems.

The main features of functional programming include functions as first-class values, currying, immutable values, etc. It doesn't seem obvious to me that OO design patterns are approximating any of those features.

That's because these features don't address the same issues that OOP does... they are alternatives to imperative programming. The FP answer to OOP lies in the type systems of ML and Haskell... specifically sum types, abstract data types, ML modules, and Haskell typeclasses.

But of course there are still design patterns which are not solved by FP languages. What is the FP equivalent of a singleton? (Disregarding for a moment that singletons are generally a terrible pattern to use)

The first thing typeclasses do is eliminate the need for singletons.

You could go through the list of 23 and eliminate more, but I don't have time to right now.

How to get MAC address of client using PHP?


    $findme = "Physical";
    $pmac = strpos($mycom, $findme); 

    echo $mac;

This prints the mac address of client machine

How to copy marked text in notepad++

It would be a great feature to have in Notepad++. I use the following technique to extract all the matches out of a file:

select-string -Path input.txt -Pattern "[0-9a-zA-Z ]*" -AllMatches | % { $_.Matches } | select-object Value > output.txt

And if you'd like only the distinct matches in a sorted list:

select-string -Path input.txt -Pattern "[0-9a-zA-Z ]" -AllMatches | % { $_.Matches } | select-object Value -unique | sort-object Value > output.txt

How to write inside a DIV box with javascript


<div id="log"></div>


document.getElementById("log").innerHTML="WHATEVER YOU WANT...";

Apache Tomcat Connection refused

you can try to stop and start again with :

$ cd /path/apache-tomcat x.x.x/bin


$ sh

when succesfully done the last step you must turn on your tomcat and catalina with command

$ sh

I managed to resolve my problem with this way

setState() inside of componentDidUpdate()

You can use setStateinside componentDidUpdate. The problem is that somehow you are creating an infinite loop because there's no break condition.

Based on the fact that you need values that are provided by the browser once the component is rendered, I think your approach about using componentDidUpdate is correct, it just needs better handling of the condition that triggers the setState.

Calling a Sub and returning a value

Sub don't return values and functions don't have side effects.

Sometimes you want both side effect and return value.

This is easy to be done once you know that VBA passes arguments by default by reference so you can write your code in this way:

Sub getValue(retValue as Long)
    retValue = 42 
End SUb 

Sub Main()
    Dim retValue As Long
    getValue retValue 
End SUb

Remove part of string after "."

We can pretend they are filenames and remove extensions:

# [1] "NM_020506"    "NM_020519"    "NM_001030297" "NM_010281"    "NM_011419"    "NM_053155"

Git 'fatal: Unable to write new index file'

In my case, pausing dropbox sync solved the issue

Which comment style should I use in batch files?

A very detailed and analytic discussion on the topic is available on THIS page

It has the example codes and the pros/cons of different options.

How to set the size of button in HTML

If using the following HTML:

<button id="submit-button"></button>

Style can be applied through JS using the style object available on an HTMLElement.

To set height and width to 200px of the above example button, this would be the JS:

var myButton = document.getElementById('submit-button'); = '200px'; '200px';

I believe with this method, you are not directly writing CSS (inline or external), but using JavaScript to programmatically alter CSS Declarations.

Generating combinations in c++

A simple way using std::next_permutation:

#include <iostream>
#include <algorithm>
#include <vector>

int main() {
    int n, r;
    std::cin >> n;
    std::cin >> r;

    std::vector<bool> v(n);
    std::fill(v.end() - r, v.end(), true);

    do {
        for (int i = 0; i < n; ++i) {
            if (v[i]) {
                std::cout << (i + 1) << " ";
        std::cout << "\n";
    } while (std::next_permutation(v.begin(), v.end()));
    return 0;

or a slight variation that outputs the results in an easier to follow order:

#include <iostream>
#include <algorithm>
#include <vector>

int main() {
   int n, r;
   std::cin >> n;
   std::cin >> r;

   std::vector<bool> v(n);
   std::fill(v.begin(), v.begin() + r, true);

   do {
       for (int i = 0; i < n; ++i) {
           if (v[i]) {
               std::cout << (i + 1) << " ";
       std::cout << "\n";
   } while (std::prev_permutation(v.begin(), v.end()));
   return 0;

A bit of explanation:

It works by creating a "selection array" (v), where we place r selectors, then we create all permutations of these selectors, and print the corresponding set member if it is selected in in the current permutation of v.

You can implement it if you note that for each level r you select a number from 1 to n.

In C++, we need to 'manually' keep the state between calls that produces results (a combination): so, we build a class that on construction initialize the state, and has a member that on each call returns the combination while there are solutions: for instance

#include <iostream>
#include <iterator>
#include <vector>
#include <cstdlib>

using namespace std;

struct combinations
    typedef vector<int> combination_t;

    // initialize status
   combinations(int N, int R) :
       completed(N < 1 || R > N),
       N(N), R(R)
       for (int c = 1; c <= R; ++c)

   // true while there are more solutions
   bool completed;

   // count how many generated
   int generated;

   // get current and compute next combination
   combination_t next()
       combination_t ret = curr;

       // find what to increment
       completed = true;
       for (int i = R - 1; i >= 0; --i)
           if (curr[i] < N - R + i + 1)
               int j = curr[i] + 1;
               while (i <= R-1)
                   curr[i++] = j++;
               completed = false;

       return ret;


   int N, R;
   combination_t curr;

int main(int argc, char **argv)
    int N = argc >= 2 ? atoi(argv[1]) : 5;
    int R = argc >= 3 ? atoi(argv[2]) : 2;
    combinations cs(N, R);
    while (!cs.completed)
        combinations::combination_t c =;
        copy(c.begin(), c.end(), ostream_iterator<int>(cout, ","));
        cout << endl;
    return cs.generated;

test output:


Check if EditText is empty.

EditText txtUserID = (EditText) findViewById(;

String UserID = txtUserID.getText().toString();

if (UserID.equals("")) 


You will see the message in LogCat....

How do I assert an Iterable contains elements with a certain property?

Thank you @Razvan who pointed me in the right direction. I was able to get it in one line and I successfully hunted down the imports for Hamcrest 1.3.

the imports:

import static;
import static org.hamcrest.Matchers.contains;
import static org.hamcrest.MatcherAssert.assertThat;
import static org.hamcrest.beans.HasPropertyWithValue.hasProperty;

the code:

assertThat( myClass.getMyItems(), contains(
    hasProperty("name", is("foo")), 
    hasProperty("name", is("bar"))

How can a divider line be added in an Android RecyclerView?

In the October 2016 update, the support library v25.0.0 now has a default implementation of basic horizontal and vertical dividers available!

 recyclerView.addItemDecoration(new DividerItemDecoration(recyclerView.getContext(), DividerItemDecoration.VERTICAL));

Why shouldn't I use PyPy over CPython if PyPy is 6.3 times faster?

Supported Python Versions

To cite the Zen of Python:

Readability counts.

For example, Python 3.7 introduced dataclasses and Python 3.8 introduced fstring =.

There might be other features in Python 3.7 and Python 3.8 which are more important to you. The point is that PyPy does not support Python 3.7 or Python 3.8 at the moment.

Shameless self-advertisement: Killer Features by Python version - if you want to know more things you miss by using older Python versions

Java Scanner String input

When you read in the year month day hour minutes with something like nextInt() it leaves rest of the line in the parser/buffer (even if it is blank) so when you call nextLine() you are reading the rest of this first line.

I suggest you to use instead of scan.nextLine().

Oracle 11g SQL to get unique values in one column of a multi-column query

I'd use the RANK() function in a subselect and then just pull the row where rank = 1.

select person, language
    select person, language, rank() over(order by language) as rank
    from table A
    group by person, language
where rank = 1

Linq: GroupBy, Sum and Count

The following query works. It uses each group to do the select instead of SelectMany. SelectMany works on each element from each collection. For example, in your query you have a result of 2 collections. SelectMany gets all the results, a total of 3, instead of each collection. The following code works on each IGrouping in the select portion to get your aggregate operations working correctly.

var results = from line in Lines
              group line by line.ProductCode into g
              select new ResultLine {
                ProductName = g.First().Name,
                Price = g.Sum(pc => pc.Price).ToString(),
                Quantity = g.Count().ToString(),

Input type DateTime - Value format?

This article seems to show the valid types that are acceptable

 <!-- without @datetime content must be a valid date, time, or precise datetime -->
<time datetime="2009-11-13">13<sup>th</sup> November</time>
 <!-- when using @datetime the content can be anything relevant -->
<time datetime="20:00">starting at 8pm</time>
 <!-- time example -->
<time datetime="2009-11-13T20:00+00:00">8pm on my birthday</time>
 <!-- datetime with time-zone example -->
<time datetime="2009-11-13T20:00Z">8pm on my birthday</time>
 <!-- datetime with time-zone “Z” -->

This one covers using it in the <input> field:

<input type="date" name="d" min="2011-08-01" max="2011-08-15"> This example of the HTML5 input type "date" combine with the attributes min and max shows how we can restrict the dates a user can input. The attributes min and max are not dependent on each other and can be used independently.

<input type="time" name="t" value="12:00"> The HTML5 input type "time" allows users to choose a corresponding time that is displayed in a 24hour format. If we did not include the default value of "12:00" the time would set itself to the time of the users local machine.

<input type="week" name="w"> The HTML5 Input type week will display the numerical version of the week denoted by a "W" along with the corresponding year.

<input type="month" name="m"> The HTML5 input type month does exactly what you might expect it to do. It displays the month. To be precise it displays the numerical version of the month along with the year.

<input type="datetime" name="dt"> The HTML5 input type Datetime displays the UTC date and time code. User can change the the time steps forward or backward in one minute increments. If you wish to display the local date and time of the user you will need to use the next example datetime-local

<input type="datetime-local" name="dtl" step="7200"> Because datetime steps through one minute at a time, you may want to change the default increment by using the attribute "step". In the following example we will have it increment by two hours by setting the attribute step to 7200 (60seconds X 60 minutes X 2).

Image Processing: Algorithm Improvement for 'Coca-Cola Can' Recognition

You need a program that learns and improves classification accuracy organically from experience.

I'll suggest deep learning, with deep learning this becomes a trivial problem.

You can retrain the inception v3 model on Tensorflow:

How to Retrain Inception's Final Layer for New Categories.

In this case, you will be training a convolutional neural network to classify an object as either a coca-cola can or not.

Xcode - Warning: Implicit declaration of function is invalid in C99

The compiler wants to know the function before it can use it

just declare the function before you call it

#include <stdio.h>

int Fibonacci(int number); //now the compiler knows, what the signature looks like. this is all it needs for now

int main(int argc, const char * argv[])
    int input;
    printf("Please give me a number : ");
    scanf("%d", &input);
    printf("The fibonacci number of %d is : %d", input, Fibonacci(input)); //!!!

}/* main */

int Fibonacci(int number)

Number of rows affected by an UPDATE in PL/SQL

For those who want the results from a plain command, the solution could be:

  DBMS_OUTPUT.PUT_LINE(TO_Char(SQL%ROWCOUNT)||' rows affected.');

The basic problem is that SQL%ROWCOUNT is a PL/SQL variable (or function), and cannot be directly accessed from an SQL command. By using a noname PL/SQL block, this can be achieved.

... If anyone has a solution to use it in a SELECT Command, I would be interested.

How can we convert an integer to string in AngularJs

.toString() is available, or just add "" to the end of the int

var x = 3,
    toString = x.toString(),
    toConcat = x + "";

Angular is simply JavaScript at the core.

ASP.NET MVC - Set custom IIdentity or IPrincipal

I can't speak directly for ASP.NET MVC, but for ASP.NET Web Forms, the trick is to create a FormsAuthenticationTicket and encrypt it into a cookie once the user has been authenticated. This way, you only have to call the database once (or AD or whatever you are using to perform your authentication), and each subsequent request will authenticate based on the ticket stored in the cookie.

A good article on this: (broken link)


Since the link above is broken, I would recommend LukeP's solution in his answer above: - I would also suggest that the accepted answer be changed to that one.

Edit 2: An alternative for the broken link:

Get and set position with jQuery .offset()

It's doable but you have to know that using offset() sets the position of the element relative to the document:

$('.layer1').offset( $('.layer2').offset() );

How does numpy.histogram() work?

import numpy as np    
hist, bin_edges = np.histogram([1, 1, 2, 2, 2, 2, 3], bins = range(5))

Below, hist indicates that there are 0 items in bin #0, 2 in bin #1, 4 in bin #3, 1 in bin #4.

# array([0, 2, 4, 1])   

bin_edges indicates that bin #0 is the interval [0,1), bin #1 is [1,2), ..., bin #3 is [3,4).

print (bin_edges)
# array([0, 1, 2, 3, 4]))  

Play with the above code, change the input to np.histogram and see how it works.

But a picture is worth a thousand words:

import matplotlib.pyplot as plt[:-1], hist, width = 1)
plt.xlim(min(bin_edges), max(bin_edges))   

enter image description here

onchange event on input type=range is not triggering in firefox while dragging

For a good cross-browser behavior, and understandable code, best is to use the onchange attribute in combination of a form:

function showVal(){
  valBox.innerHTML = inVal.value;
<form onchange="showVal()">
  <input type="range" min="5" max="10" step="1" id="inVal">

<span id="valBox"></span>

The same using oninput, the value is changed directly.

function showVal(){
  valBox.innerHTML = inVal.value;
<form oninput="showVal()">
  <input type="range" min="5" max="10" step="1" id="inVal">

<span id="valBox"></span>

Two models in one view in ASP MVC 3

Another option which doesn't have the need to create a custom Model is to use a Tuple<>.

@model Tuple<Person,Order>

It's not as clean as creating a new class which contains both, as per Andi's answer, but it is viable.

Convert an image to grayscale

None of the examples above create 8-bit (8bpp) bitmap images. Some software, such as image processing, only supports 8bpp. Unfortunately the MS .NET libraries do not have a solution. The PixelFormat.Format8bppIndexed format looks promising but after a lot of attempts I couldn't get it working.

To create a true 8-bit bitmap file you need to create the proper headers. Ultimately I found the Grayscale library solution for creating 8-bit bitmap (BMP) files. The code is very simple:

Image image = Image.FromFile("c:/path/to/image.jpg");
GrayBMP_File.CreateGrayBitmapFile(image, "c:/path/to/8bpp/image.bmp");

The code for this project is far from pretty but it works, with one little simple-to-fix problem. The author hard-coded the image resolution to 10x10. Image processing programs do not like this. The fix is open GrayBMP_File.cs (yeah, funky file naming, I know) and replace lines 50 and 51 with the code below. The example sets the resolution to 200x200 but you should change it to the proper number.

int resX = 200;
int resY = 200;
// horizontal resolution
Copy_to_Index(DIB_header, BitConverter.GetBytes(resX * 100), 24);
// vertical resolution 
Copy_to_Index(DIB_header, BitConverter.GetBytes(resY * 100), 28);

What is the worst programming language you ever worked with?

Nobody said AS400????

I had that at university, and it was definitely the worst...

Execute method on startup in Spring

For Java 1.8 users that are getting a warning when trying to reference the @PostConstruct annotation, I ended up instead piggybacking off the @Scheduled annotation which you can do if you already have an @Scheduled job with fixedRate or fixedDelay.

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import org.springframework.scheduling.annotation.EnableScheduling;
import org.springframework.scheduling.annotation.Scheduled;
import org.springframework.stereotype.Component;

public class ScheduledTasks {

private static final Logger LOGGER = LoggerFactory.getLogger(ScheduledTasks.class);

private static boolean needToRunStartupMethod = true;

    @Scheduled(fixedRate = 3600000)
    public void keepAlive() {
        //log "alive" every hour for sanity checks
        if (needToRunStartupMethod) {
            needToRunStartupMethod = false;

    public void runOnceOnlyOnStartup() {
        LOGGER.debug("running startup job");


How do you reinstall an app's dependencies using npm?

Most of the time I use the following command to achieve a complete reinstall of all the node modules (be sure you are in the project folder).

rm -rf node_modules && npm install

You can also run npm cache clean after removing the node_modules folder to be sure there aren't any cached dependencies.

PopupWindow $BadTokenException: Unable to add window -- token null is not valid

try to show popup like this

new Handler().postDelayed(new Runnable(){

    public void run() {
       popupWindow.showAtLocation(context.getWindow().getDecorView(), Gravity.CENTER,0,0);

}, 200L);

Merging Cells in Excel using C#

Using the Interop you get a range of cells and call the .Merge() method on that range.

eWSheet.Range[eWSheet.Cells[1, 1], eWSheet.Cells[4, 1]].Merge();

How to store Configuration file and read it using React

In case you have a .properties file or a .ini file

Actually in case if you have any file that has key value pairs like this:


You can import that into webpack by a npm module called properties-reader

I found this really helpful since I'm integrating react with Java Spring framework where there is already an file. This helps me to keep all config together in one place.

  1. Import that from dependencies section in package.json

"properties-reader": "0.0.16"

  1. Import this module into webpack.config.js on top

const PropertiesReader = require('properties-reader');

  1. Read the properties file

const appProperties = PropertiesReader('Path/to/your/properties.file')._properties;

  1. Import this constant as config

externals: { 'Config': JSON.stringify(appProperties) }

  1. Use it as the same way as mentioned in the accepted answer

var Config = require('Config') fetchData(Config.serverUrl + '/Enterprises/...')

How to remove leading whitespace from each line in a file

For this specific problem, something like this would work:

$ sed 's/^ *//g' < input.txt > output.txt

It says to replace all spaces at the start of a line with nothing. If you also want to remove tabs, change it to this:

$ sed 's/^[ \t]+//g' < input.txt > output.txt

The leading "s" before the / means "substitute". The /'s are the delimiters for the patterns. The data between the first two /'s are the pattern to match, and the data between the second and third / is the data to replace it with. In this case you're replacing it with nothing. The "g" after the final slash means to do it "globally", ie: over the entire file rather than on only the first match it finds.

Finally, instead of < input.txt > output.txt you can use the -i option which means to edit the file "in place". Meaning, you don't need to create a second file to contain your result. If you use this option you will lose your original file.

ActiveRecord OR query

If you want to use an OR operator on one column's value, you can pass an array to .where and ActiveRecord will use IN(value,other_value):

Model.where(:column => ["value", "other_value"]


SELECT `table_name`.* FROM `table_name` WHERE `table_name`.`column` IN ('value', 'other_value')

This should achieve the equivalent of an OR on a single column

python: urllib2 how to send cookie with urlopen request

Use cookielib. The linked doc page provides examples at the end. You'll also find a tutorial here.

How can I find out a file's MIME type (Content-Type)?

file version < 5 : file -i -b /path/to/file
file version >=5 : file --mime-type -b /path/to/file

How do I get to IIS Manager?

To open IIS Manager, click Start, type inetmgr in the Search Programs and Files box, and then press ENTER.

if the IIS Manager doesn't open that means you need to install it.

So, Follow the instruction at this link:

Opposite of %in%: exclude rows with values specified in a vector

Here is a version using filter in dplyr that applies the same technique as the accepted answer by negating the logical with !:

D2 <- D1 %>% dplyr::filter(!V1 %in% c('B','N','T'))

Should I use SVN or Git?

I would set up a Subversion repository. By doing it this way, individual developers can choose whether to use Subversion clients or Git clients (with git-svn). Using git-svn doesn't give you all the benefits of a full Git solution, but it does give individual developers a great deal of control over their own workflow.

I believe it will be a relatively short time before Git works just as well on Windows as it does on Unix and Mac OS X (since you asked).

Subversion has excellent tools for Windows, such as TortoiseSVN for Explorer integration and AnkhSVN for Visual Studio integration.

Your password does not satisfy the current policy requirements

I had the same Problem and the Answer is just Right in front of you, remember when you ran the script while installing mysql like

sudo mysql_secure_installation

there somewhere you chose which password type would you like to chose

There are three levels of password validation policy:

LOW Length >= 8 MEDIUM Length >= 8, numeric, mixed case, and special characters STRONG Length >= 8, numeric, mixed case, special characters and dictionary file

Please enter 0 = LOW, 1 = MEDIUM and 2 = STRONG:

you have to give a password to same policy

here are some sample examples for your passwords:
for type 0: abcdabcd
for type 1: abcd1234
for type 2: ancd@1234

Check file uploaded is in csv format

So I ran into this today.

Was attempting to validate an uploaded CSV file's MIME type by looking at $_FILES['upload_file']['type'], but for certain users on various browsers (and not necessarily the same browsers between said users; for instance it worked fine for me in FF but for another user it didn't work on FF) the $_FILES['upload_file']['type'] was coming up as "application/" instead of the expected "text/csv" or "text/plain".

So I resorted to using the (IMHO) much more reliable finfo_* functions something like this:

$acceptable_mime_types = array('text/plain', 'text/csv', 'text/comma-separated-values');

if (!empty($_FILES) && array_key_exists('upload_file', $_FILES) && $_FILES['upload_file']['error'] == UPLOAD_ERR_OK) {
    $tmpf = $_FILES['upload_file']['tmp_name'];

    // Make sure $tmpf is kosher, then:

    $finfo = finfo_open(FILEINFO_MIME_TYPE);
    $mime_type = finfo_file($finfo, $tmpf);

    if (!in_array($mime_type, $acceptable_mime_types)) {
        // Unacceptable mime type.

.NET NewtonSoft JSON deserialize map to a different property name

I am using JsonProperty attributes when serializing but ignoring them when deserializing using this ContractResolver:

public class IgnoreJsonPropertyContractResolver: DefaultContractResolver
        protected override IList<JsonProperty> CreateProperties(Type type, MemberSerialization memberSerialization)
            var properties = base.CreateProperties(type, memberSerialization);
            foreach (var p in properties) { p.PropertyName = p.UnderlyingName; }
            return properties;

The ContractResolver just sets every property back to the class property name (simplified from Shimmy's solution). Usage:

var airplane= JsonConvert.DeserializeObject<Airplane>(json, 
    new JsonSerializerSettings { ContractResolver = new IgnoreJsonPropertyContractResolver() });

What does "Use of unassigned local variable" mean?

Because if none of the if statements evaluate to true then the local variable will be unassigned. Throw an else statement in there and assign some values to those variables in case the if statements don't evaluate to true. Post back here if that doesn't make the error go away.

Your other option is to initialize the variables to some default value when you declare them at the beginning of your code.

Get protocol, domain, and port from URL

Why not use:

let full = window.location.origin

Why use the params keyword?

Might sound stupid, But Params doesn't allow multidimensional array. Whereas you can pass a multidimensional array to a function.

Javascript change font color

Consider changing your markup to this:

<span id="someId">onlineff</span>

Then you can use this script:

var x = document.getElementById('someId'); = '#00FF00';

see it here:

Use of contains in Java ArrayList<String>

You are right that it should work; perhaps you forgot to instantiate something. Does your code look something like this?

String rssFeedURL = "";
this.rssFeedURLS = new ArrayList<String>();
if(this.rssFeedURLs.contains(rssFeedURL)) {
// this code will execute

For reference, note that the following conditional will also execute if you append this code to the above:

String copyURL = new String(rssFeedURL);
if(this.rssFeedURLs.contains(copyURL)) {
// code will still execute because contains() checks equals()

Even though (rssFeedURL == copyURL) is false, rssFeedURL.equals(copyURL) is true. The contains method cares about the equals method.

How to horizontally center an element

#inner {_x000D_
  display: table;_x000D_
  margin: 0 auto;_x000D_
<div id="outer" style="width:100%">_x000D_
  <div id="inner">Foo foo</div>_x000D_

AngularJS - Any way for $ to send request parameters instead of JSON?

Quick adjustment - for those of you having trouble with the global configuration of the transformRequest function, here's the snippet i'm using to get rid of the Cannot read property 'jquery' of undefined error:

$httpProvider.defaults.transformRequest = function(data) {
        return data != undefined ? $.param(data) : null;

Split string on whitespace in Python

Using split() will be the most Pythonic way of splitting on a string.

It's also useful to remember that if you use split() on a string that does not have a whitespace then that string will be returned to you in a list.


>>> "ark".split()

no suitable HttpMessageConverter found for response type

Or you can use

public void setSupportedMediaTypes(List supportedMediaTypes)

method which belongs to AbstractHttpMessageConverter<T>, to add some ContentTypes you like. This way can let the MappingJackson2HttpMessageConverter canRead() your response, and transform it to your desired Class, which on this case,is ProductList Class.

and I think this step should hooked up with the Spring Context initializing. for example, by using

implements ApplicationListener { ... }

Iterating over arrays in Python 3

The for loop iterates over the elements of the array, not its indexes. Suppose you have a list ar = [2, 4, 6]:

When you iterate over it with for i in ar: the values of i will be 2, 4 and 6. So, when you try to access ar[i] for the first value, it might work (as the last position of the list is 2, a[2] equals 6), but not for the latter values, as a[4] does not exist.

If you intend to use indexes anyhow, try using for index, value in enumerate(ar):, then theSum = theSum + ar[index] should work just fine.

Inserting a text where cursor is using Javascript/jquery

Adding text to current cursor position involves two steps:

  1. Adding the text at the current cursor position
  2. Updating the current cursor position


Tested in Chrome 48, Firefox 45, IE 11 and Edge 25


function addTextAtCaret(textAreaId, text) {
    var textArea = document.getElementById(textAreaId);
    var cursorPosition = textArea.selectionStart;
    addTextAtCursorPosition(textArea, cursorPosition, text);
    updateCursorPosition(cursorPosition, text, textArea);
function addTextAtCursorPosition(textArea, cursorPosition, text) {
    var front = (textArea.value).substring(0, cursorPosition);
    var back = (textArea.value).substring(cursorPosition, textArea.value.length);
    textArea.value = front + text + back;
function updateCursorPosition(cursorPosition, text, textArea) {
    cursorPosition = cursorPosition + text.length;
    textArea.selectionStart = cursorPosition;
    textArea.selectionEnd = cursorPosition;


    <button type="button" onclick="addTextAtCaret('textArea','Apple')">Insert Apple!</button>
    <button type="button" onclick="addTextAtCaret('textArea','Mango')">Insert Mango!</button>
    <button type="button" onclick="addTextAtCaret('textArea','Orange')">Insert Orange!</button>
<textarea id="textArea" rows="20" cols="50"></textarea>

How would I extract a single file (or changes to a file) from a git stash?

Edit: See cambunctious's answer, which is basically what I now prefer because it only uses the changes in the stash, rather than comparing them to your current state. This makes the operation additive, with much less chance of undoing work done since the stash was created.

To do it interactively, you would first do

git diff stash^! -- path/to/relevant/file/in/stash.ext perhaps/another/file.ext > my.patch

...then open the patch file in a text editor, alter as required, then do

git apply < my.patch

cambunctious's answer bypasses the interactivity by piping one command directly to the other, which is fine if you know you want all changes from the stash. You can edit the stash^! to be any commit range that has the cumulative changes you want (but check over the output of the diff first).

If applying the patch/diff fails, you can change the last command to git apply --reject which makes all the changes it can, and leaves .rej files where there are conflicts it can;r resolve. The .rej files can then be applied using wiggle, like so:

wiggle --replace path/to/relevant/file/in/stash.ext path/to/relevant/file/in/stash.ext.rej

This will either resolve the conflict, or give you conflict markers that you'd get from a merge.

Previous solution: There is an easy way to get changes from any branch, including stashes:

$ git checkout --patch stash@{0} path/to/file

You may omit the file spec if you want to patch in many parts. Or omit patch (but not the path) to get all changes to a single file. Replace 0 with the stash number from git stash list, if you have more than one. Note that this is like diff, and offers to apply all differences between the branches. To get changes from only a single commit/stash, have a look at git cherry-pick --no-commit.

PostgreSQL Autoincrement

If you want to add sequence to id in the table which already exist you can use:

CREATE SEQUENCE user_id_seq;
ALTER TABLE user ALTER user_id SET DEFAULT NEXTVAL('user_id_seq');

How to get Database Name from Connection String using SqlConnectionStringBuilder

string connectString = "Data Source=(local);" + "Integrated Security=true";

SqlConnectionStringBuilder builder = new SqlConnectionStringBuilder(connectString);

Console.WriteLine("builder.InitialCatalog = " + builder.InitialCatalog);

Using module 'subprocess' with timeout

import subprocess, optparse, os, sys, re, datetime, threading, time, glob, shutil, xml.dom.minidom, traceback

class OutputManager:
    def __init__(self, filename, mode, console, logonly):
        self.con = console
        self.logtoconsole = True
        self.logtofile = False

        if filename:
                self.f = open(filename, mode)
                self.logtofile = True
                if logonly == True:
                    self.logtoconsole = False
            except IOError:
                print (sys.exc_value)
                print ("Switching to console only output...\n")
                self.logtofile = False
                self.logtoconsole = True

    def write(self, data):
        if self.logtoconsole == True:
        if self.logtofile == True:

def getTimeString():
        return time.strftime("%Y-%m-%d", time.gmtime())

def runCommand(command):
    Execute a command in new thread and return the
    stdout and stderr content of it.
        Output = subprocess.Popen(command, stdout=subprocess.PIPE, shell=True).communicate()[0]
    except Exception as e:
        print ("runCommand failed :%s" % (command))
        print (str(e))
        return None
    return Output

def GetOs():
    Os = ""
    if sys.platform.startswith('win32'):
        Os = "win"
    elif sys.platform.startswith('linux'):
        Os = "linux"
    elif sys.platform.startswith('darwin'):
        Os = "mac"
    return Os

def check_output(*popenargs, **kwargs):
        if 'stdout' in kwargs: 
            raise ValueError('stdout argument not allowed, it will be overridden.') 

        # Get start time.
        startTime =

        cmd = popenargs[0]

        if sys.platform.startswith('win32'):
            process = subprocess.Popen( cmd, stdout=subprocess.PIPE, shell=True) 
        elif sys.platform.startswith('linux'):
            process = subprocess.Popen( cmd , stdout=subprocess.PIPE, shell=True ) 
        elif sys.platform.startswith('darwin'):
            process = subprocess.Popen( cmd , stdout=subprocess.PIPE, shell=True ) 

        stdoutdata, stderrdata = process.communicate( timeout = timeoutValue )
        retcode = process.poll()

        # Catch crash error and log it.
        OutputHandle = None
            if retcode >= 1:
                OutputHandle = OutputManager( 'CrashJob_' + getTimeString() + '.txt', 'a+', sys.stdout, False)
                OutputHandle.write( cmd )
                print (stdoutdata)
                print (stderrdata)
        except Exception as e:
            print (str(e))

    except subprocess.TimeoutExpired:
            # Catch time out error and log it.
            Os = GetOs()
            if Os == 'win':
                killCmd = "taskkill /FI \"IMAGENAME eq {0}\" /T /F"
            elif Os == 'linux':
                killCmd = "pkill {0)"
            elif Os == 'mac':
                # Linux, Mac OS
                killCmd = "killall -KILL {0}"


            OutputHandle = None
                OutputHandle = OutputManager( 'KillJob_' + getTimeString() + '.txt', 'a+', sys.stdout, False)
                OutputHandle.write( cmd )
            except Exception as e:
                print (str(e))
    except Exception as e:
            for frame in traceback.extract_tb(sys.exc_info()[2]):
                        fname,lineno,fn,text = frame
                        print "Error in %s on line %d" % (fname, lineno)

How to use an output parameter in Java?

As a workaround a generic "ObjectHolder" can be used. See code example below.

The sample output is:

name: John Doe
name: Jim Miller

so the Person parameter has been modified since it's wrapped in the Holder which is passed by value - the generic param inside is a reference where the contents can be modified - so actually a different person is returned and the original stays as is.

 * show work around for missing call by reference in java
public class OutparamTest {

  * a test class to be used as parameter
 public static class Person {
   public String name;
     public String dob;
     public void show() {
      System.out.println("name: "+name+"\ndob:"+dob);

  * ObjectHolder (Generic ParameterWrapper)
 public static class ObjectHolder<T> {
    public ObjectHolder(T param) {
    public T param;

  * ObjectHolder is substitute for missing "out" parameter
 public static void setPersonData(ObjectHolder<Person> personHolder,String name,String dob) {
    // Holder needs to be dereferenced to get access to content
    personHolder.param=new Person();;

   * show how it works
  public static void main(String args[]) {
    Person jim=new Person();"Jim Miller";
    ObjectHolder<Person> testPersonHolder=new ObjectHolder(jim);
    // modify the testPersonHolder person content by actually creating and returning
    // a new Person in the "out parameter"
    setPersonData(testPersonHolder,"John Doe","1953-12-17");;;

How to pass values across the pages in without using Session

If it's just for passing values between pages and you only require it for the one request. Use Context.


The Context object holds data for a single user, for a single request, and it is only persisted for the duration of the request. The Context container can hold large amounts of data, but typically it is used to hold small pieces of data because it is often implemented for every request through a handler in the global.asax. The Context container (accessible from the Page object or using System.Web.HttpContext.Current) is provided to hold values that need to be passed between different HttpModules and HttpHandlers. It can also be used to hold information that is relevant for an entire request. For example, the IBuySpy portal stuffs some configuration information into this container during the Application_BeginRequest event handler in the global.asax. Note that this only applies during the current request; if you need something that will still be around for the next request, consider using ViewState. Setting and getting data from the Context collection uses syntax identical to what you have already seen with other collection objects, like the Application, Session, and Cache. Two simple examples are shown here:

// Add item to
Context Context.Items["myKey"] = myValue;

// Read an item from the
 Context Response.Write(Context["myKey"]);

Using the above. If you then do a Server.Transfer the data you've saved in the context will now be available to the next page. You don't have to concern yourself with removing/tidying up this data as it is only scoped to the current request.

Default keystore file does not exist?

Use This for MAC users

keytool -list -v -keystore ~/.android/debug.keystore -alias androiddebugkey -storepass android -keypass android

How can I change the size of a Bootstrap checkbox?

just use simple css

.big-checkbox {width: 1.5rem; height: 1.5rem;top:0.5rem}

Stratified Train/Test-split in scikit-learn

TL;DR : Use StratifiedShuffleSplit with test_size=0.25

Scikit-learn provides two modules for Stratified Splitting:

  1. StratifiedKFold : This module is useful as a direct k-fold cross-validation operator: as in it will set up n_folds training/testing sets such that classes are equally balanced in both.

Heres some code(directly from above documentation)

>>> skf = cross_validation.StratifiedKFold(y, n_folds=2) #2-fold cross validation
>>> len(skf)
>>> for train_index, test_index in skf:
...    print("TRAIN:", train_index, "TEST:", test_index)
...    X_train, X_test = X[train_index], X[test_index]
...    y_train, y_test = y[train_index], y[test_index]
...    #fit and predict with X_train/test. Use accuracy metrics to check validation performance
  1. StratifiedShuffleSplit : This module creates a single training/testing set having equally balanced(stratified) classes. Essentially this is what you want with the n_iter=1. You can mention the test-size here same as in train_test_split


>>> sss = StratifiedShuffleSplit(y, n_iter=1, test_size=0.5, random_state=0)
>>> len(sss)
>>> for train_index, test_index in sss:
...    print("TRAIN:", train_index, "TEST:", test_index)
...    X_train, X_test = X[train_index], X[test_index]
...    y_train, y_test = y[train_index], y[test_index]
>>> # fit and predict with your classifier using the above X/y train/test

LIKE operator in LINQ

In native LINQ you may use combination of Contains/StartsWith/EndsWith or RegExp.

In LINQ2SQL use method SqlMethods.Like()

    from i in db.myTable
    where SqlMethods.Like(i.field, "tra%ata")
    select i

add Assembly: System.Data.Linq (in System.Data.Linq.dll) to use this feature.

TSQL How do you output PRINT in a user defined function?

Tip: generate error.

declare @Day int, @Config_Node varchar(50)

    set @Config_Node = 'value to trace'

    set @Day = @Config_Node

You will get this message:

Conversion failed when converting the varchar value 'value to trace' to data type int.

Parsing boolean values with argparse

Here is another variation without extra row/s to set default values. The boolean value is always assigned, so that it can be used in logical statements without checking beforehand:

import argparse
parser = argparse.ArgumentParser(description="Parse bool")
parser.add_argument("--do-something", default=False, action="store_true",
                    help="Flag to do something")
args = parser.parse_args()

if args.do_something:
     print("Do something")
     print("Don't do something")

print(f"Check that args.do_something={args.do_something} is always a bool.")

GenyMotion Unable to start the Genymotion virtual device

The number of CPUs is insufficient. Select 1 CPU in Genymotion and restart the device.

Genymotion device configuration

How to access Session variables and set them in javascript?

I was looking for solution to this problem, until i found a very simple solution for accessing the session variables, assuming you use a .php file on server side. Hope it answers part of the question :

access session value

<script type="text/javascript">        
    var value = <?php echo $_SESSION['key']; ?>;

Edit : better example below, which you can try on, at the "codespace" tab

<!DOCTYPE html>
  <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
    $_SESSION['key'] = 10;
    $i = $_SESSION['key'];
  <p id="affichage">hello</p>

  <script type="text/javascript">
    var value =  <?php echo $i; ?>;


set session value

pass it a variable of whatever, you may want to. eg,

$you = 13;
$_SESSION['user_id'] = $you;

This should work, tho' not tested it.

Run multiple python scripts concurrently

You try the following ways to run the multiple python scripts:

  import os
  print "Starting script1"
  os.system("python arg1 arg2 arg3")
  print "script1 ended"
  print "Starting script2"
  os.system("python arg1 arg2 arg3")
  print "script2 ended"

Note: The execution of multiple scripts depends purely underlined operating system, and it won't be concurrent, I was new comer in Python when I answered it.

Update: I found a package: Above package can be used to run multiple scripts and function, please check this and maybe on weekend will provide some example too.


 import schedule
 import time
 import script1, script2

 def job():
     print("I'm working...")


 while True:

How to change default text file encoding in Eclipse?

I was having the same problem when I received a html to put inside my project and rename it to .jsp. To solve the problem, I needed to what people above already said, that is, to change text encoding in Eclipse Preferences. However, before renaming the files to .jsp, it was necessary to include the following line in the beginning of each .html file:

<%@ page language="java" contentType="text/html; charset=UTF-8"

I believe this forced Eclipse to understand that it was necessary to change file encoding when I tried to rename .html to .jsp.

How to cast/convert pointer to reference in C++

Call it like this:


Note that there is no casting going on here, as suggested in your question title. All we have done is de-referenced the pointer to the object which we then pass to the function.

SVN: Is there a way to mark a file as "do not commit"?

A solution that does not ignore changes in directory properties

I tried to use the solution based on changelist, but I have a couple of issues with it. First my repository has thousand of files, so the changelist to be committed is huge, and my svn status output became way too long and needed to be parsed to be useful. Most important is that I wanted to commit changes that came from a merge, which means they include property changes. When committing a changelist, the svn properties attached to the directory are not committed, so I had to do an extra commit:

svn ci --cl work -m "this commits files from the work changelist only"
svn up
svn ci --depth empty DIR . -m "record merge properties"

You may have to do that for several directories (here I record the properties of DIR and of the current dir .), basically those with a M in the second column when issuing the svn status command.


I used patches and svn patch. In pseudo-code:

svn diff $IGNORE_FILES > MYPATCH   # get the mods to ignore
svn patch --reverse-diff MYPATCH   # remove the mods
svn ci -m "message"                # check-in files and directory properties
svn patch MYPATCH                  # re-apply the mods

Like other posters, I end up using a script to maintain the list of files to ignore:

#! /usr/bin/env bash

finish() {
    svn patch MYPATCH               # re-apply the mods
trap finish EXIT

sources/platform/ecmwf-cca-intel-mpi.xml \
runtime/classic/platform/ecmwf-cca.job.tmpl \

svn diff $IGNORE_FILES > MYPATCH # get the mods to ignore
svn patch --reverse-diff MYPATCH # remove the mods

svn "$@"

I typically used it with ci and revert -R ..

two divs the same line, one dynamic width, one fixed

I think this is you want:

<style type="text/css">
border:1px solid red;
border:1px solid black;

border:1px solid black;
<div id="parent">
  <div class="left">Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat. Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt mollit anim id est laborum.</div>
  <div class="right">This is the right side content</div>

Here is the demo:

How to generate random number with the specific length in python

If you want it as a string (for example, a 10-digit phone number) you can use this:

n = 10
''.join(["{}".format(randint(0, 9)) for num in range(0, n)])

Converting a factor to numeric without losing information R (as.numeric() doesn't seem to work)

First, factor consists of indices and levels. This fact is very very important when you are struggling with factor.

For example,

> z <- factor(letters[c(3, 2, 3, 4)])

# human-friendly display, but internal structure is invisible
> z
[1] c b c d
Levels: b c d

# internal structure of factor
> unclass(z)
[1] 2 1 2 3
[1] "b" "c" "d"

here, z has 4 elements.
The index is 2, 1, 2, 3 in that order.
The level is associated with each index: 1 -> b, 2 -> c, 3 -> d.

Then, as.numeric converts simply the index part of factor into numeric.
as.character handles the index and levels, and generates character vector expressed by its level.

?as.numeric says that Factors are handled by the default method.

CardView not showing Shadow in Android L

move your "uses-sdk" attribute in top of the manifest like the below answer

Pytesseract : "TesseractNotFound Error: tesseract is not installed or it's not in your path", how do I fix this?

In windows, the command path must be redirected, for a default windows tesseract installation.

  1. In 32 bit system, add in this line after import commands.
pytesseract.pytesseract.tesseract_cmd = 'C:\Program Files (x86)\Tesseract-OCR\tesseract.exe' 
  1. In 64 bit system, add this line instead.
 pytesseract.pytesseract.tesseract_cmd = 'C:\Program Files\Tesseract-OCR\tesseract.exe'

Get Current date in epoch from Unix shell script

The Unix Date command will display in epoch time

the command is

date +"%s"

Edit: Some people have observed you asked for days, so it's the result of that command divided by 86,400

Convert a date format in epoch

Create Common Method to Convert String to Date format

public static void main(String[] args) throws Exception {
    long test = ConvertStringToDate("May 26 10:41:23", "MMM dd hh:mm:ss");
    long test2 = ConvertStringToDate("Tue, Jun 06 2017, 12:30 AM", "EEE, MMM dd yyyy, hh:mm a");
    long test3 = ConvertStringToDate("Jun 13 2003 23:11:52.454 UTC", "MMM dd yyyy HH:mm:ss.SSS zzz");

private static long ConvertStringToDate(String dateString, String format) {
    try {
        return new SimpleDateFormat(format).parse(dateString).getTime();
    } catch (ParseException e) {}
    return 0;

Pandas "Can only compare identically-labeled DataFrame objects" error

You can also try dropping the index column if it is not needed to compare:

print(df1.reset_index(drop=True) == df2.reset_index(drop=True))

I have used this same technique in a unit test like so:

from pandas.util.testing import assert_frame_equal

assert_frame_equal(actual.reset_index(drop=True), expected.reset_index(drop=True))

how to get curl to output only http response body (json) and no other headers etc

I was executing a get request an also want to see just the response and nothing else, seems like magic is done with -silent,-s option.

From the curl man page:

-s, --silent Silent or quiet mode. Don't show progress meter or error messages. Makes Curl mute. It will still output the data you ask for, potentially even to the terminal/stdout unless you redirect it.

Below the examples:

curl -s "http://host:8080/some/resource"
curl -silent "http://host:8080/some/resource"

Using custom headers

curl -s -H "Accept: application/json" "http://host:8080/some/resource")

Using POST method with a header

curl -s -X POST -H "Content-Type: application/json" "http://host:8080/some/resource") -d '{ "myBean": {"property": "value"}}'

You can also customize the output for specific values with -w, below the options I use to get just response codes of the curl:

curl -s -o /dev/null -w "%{http_code}" "http://host:8080/some/resource"

How can I see an the output of my C programs using Dev-C++?

Add a line getchar(); or system("pause"); before your return 0; in main function. It will work for you.

Change table header color using bootstrap

Try This:

table.table tr th{background-color:blue !important; font-color:white !important;}

hope this helps..

Passing arrays as url parameter

in the received page you can use:

parse_str($str, $array); var_dump($array);

Jmeter - Run .jmx file through command line and get the summary report in a excel

In Command line mode: I have planned on Linux OS.

  1. download the latest jmeter version. Apache JMeter 3.2 (Requires Java 8 or later) as of now.

  2. Extract in your desired directory. For example, extract to /tmp/

  3. Now, default output file format will be csv. No need to change anything or specify in the CLI command. for example: ./jmeter -n -t examples/test.jmx -l examples/output.csv

For changing the default format, change the following parameter in :

Now if you run the command : ./jmeter -n -t examples/test.jmx -l examples/output.jtl output get stored in xml format.

Now, make the request on multiple server(Additional info query): We can specify host and port as tags in

./jmeter -n -t examples/test.jmx -l examples/output.jtl -JHOST=<HOST> -JPORT=<PORT>

Microsoft.Jet.OLEDB.4.0' provider is not registered on the local machine

I ran into this issue with my desktop application ('Microsoft.Jet.OLEDB.4.0' provider is not registered on the local machine). I did not have the option to build as a 32 bit app. Hoping this would help others in the same situation.

I did the following and the issue went away:

  1. Installed the 64 bit version of Microsoft Access Database Engine 2010 Redistributable, as suggested by neo

  2. Changed my provider to Microsoft.ACE.OLEDB.12.0

How to paste text to end of every line? Sublime 2

Here's the workflow I use all the time, using the keyboard only

  1. Ctrl/Cmd + A Select All
  2. Ctrl/Cmd + Shift + L Split into Lines
  3. ' Surround every line with quotes

Note that this doesn't work if there are blank lines in the selection.

With jQuery, how do I capitalize the first letter of a text field while the user is still editing that field?

This will simply transform you first letter of text:


Does "git fetch --tags" include "git fetch"?

Note: starting with git 1.9/2.0 (Q1 2014), git fetch --tags fetches tags in addition to what are fetched by the same command line without the option.

See commit c5a84e9 by Michael Haggerty (mhagger):

Previously, fetch's "--tags" option was considered equivalent to specifying the refspec


on the command line; in particular, it caused the remote.<name>.refspec configuration to be ignored.

But it is not very useful to fetch tags without also fetching other references, whereas it is quite useful to be able to fetch tags in addition to other references.
So change the semantics of this option to do the latter.

If a user wants to fetch only tags, then it is still possible to specifying an explicit refspec:

git fetch <remote> 'refs/tags/*:refs/tags/*'

Please note that the documentation prior to was ambiguous about this aspect of "fetch --tags" behavior.
Commit f0cb2f1 (2012-12-14) fetch --tags made the documentation match the old behavior.
This commit changes the documentation to match the new behavior (see Documentation/fetch-options.txt).

Request that all tags be fetched from the remote in addition to whatever else is being fetched.

Since Git 2.5 (Q2 2015) git pull --tags is more robust:

See commit 19d122b by Paul Tan (pyokagan), 13 May 2015.
(Merged by Junio C Hamano -- gitster -- in commit cc77b99, 22 May 2015)

pull: remove --tags error in no merge candidates case

Since 441ed41 ("git pull --tags": error out with a better message., 2007-12-28, Git 1.5.4+), git pull --tags would print a different error message if git-fetch did not return any merge candidates:

It doesn't make sense to pull all tags; you probably meant:
       git fetch --tags

This is because at that time, git-fetch --tags would override any configured refspecs, and thus there would be no merge candidates. The error message was thus introduced to prevent confusion.

However, since c5a84e9 (fetch --tags: fetch tags in addition to other stuff, 2013-10-30, Git 1.9.0+), git fetch --tags would fetch tags in addition to any configured refspecs.
Hence, if any no merge candidates situation occurs, it is not because --tags was set. As such, this special error message is now irrelevant.

To prevent confusion, remove this error message.

With Git 2.11+ (Q4 2016) git fetch is quicker.

See commit 5827a03 (13 Oct 2016) by Jeff King (peff).
(Merged by Junio C Hamano -- gitster -- in commit 9fcd144, 26 Oct 2016)

fetch: use "quick" has_sha1_file for tag following

When fetching from a remote that has many tags that are irrelevant to branches we are following, we used to waste way too many cycles when checking if the object pointed at by a tag (that we are not going to fetch!) exists in our repository too carefully.

This patch teaches fetch to use HAS_SHA1_QUICK to sacrifice accuracy for speed, in cases where we might be racy with a simultaneous repack.

Here are results from the included perf script, which sets up a situation similar to the one described above:

Test            HEAD^               HEAD
5550.4: fetch   11.21(10.42+0.78)   0.08(0.04+0.02) -99.3%

That applies only for a situation where:

  1. You have a lot of packs on the client side to make reprepare_packed_git() expensive (the most expensive part is finding duplicates in an unsorted list, which is currently quadratic).
  2. You need a large number of tag refs on the server side that are candidates for auto-following (i.e., that the client doesn't have). Each one triggers a re-read of the pack directory.
  3. Under normal circumstances, the client would auto-follow those tags and after one large fetch, (2) would no longer be true.
    But if those tags point to history which is disconnected from what the client otherwise fetches, then it will never auto-follow, and those candidates will impact it on every fetch.

Git 2.21 (Feb. 2019) seems to have introduced a regression when the config remote.origin.fetch is not the default one ('+refs/heads/*:refs/remotes/origin/*')

fatal: multiple updates for ref 'refs/tags/v1.0.0' not allowed

Git 2.24 (Q4 2019) adds another optimization.

See commit b7e2d8b (15 Sep 2019) by Masaya Suzuki (draftcode).
(Merged by Junio C Hamano -- gitster -- in commit 1d8b0df, 07 Oct 2019)

fetch: use oidset to keep the want OIDs for faster lookup

During git fetch, the client checks if the advertised tags' OIDs are already in the fetch request's want OID set.
This check is done in a linear scan.
For a repository that has a lot of refs, repeating this scan takes 15+ minutes.

In order to speed this up, create a oid_set for other refs' OIDs.

Loop inside React JSX

Well, here you go.

    [1, 2, 3, 4, 5, 6].map((value, index) => {
        return <div key={index}>{value}</div>

All you have to do is just map your array and return whatever you want to render. And please don't forget to use key in the returned element.

Flutter: Trying to bottom-center an item in a Column, but it keeps left-aligning

1) You can use an Align widget, with FractionalOffset.bottomCenter.

2) You can also set left: 0.0 and right: 0.0 in the Positioned.

ASP.NET Core Web API Authentication

In this public Github repo you can see a simple example of a ASP.NET Core 2.2 web API with endpoints protected by Basic Authentication.

List Directories and get the name of the Directory

import os
for root, dirs, files in os.walk(top, topdown=False):
    for name in dirs:
        print os.path.join(root, name)

Walk is a good built-in for what you are doing

Oracle to_date, from mm/dd/yyyy to dd-mm-yyyy

You don't need to muck about with extracting parts of the date. Just cast it to a date using to_date and the format in which its stored, then cast that date to a char in the format you want. Like this:

select to_char(to_date('1/10/2011','mm/dd/yyyy'),'mm-dd-yyyy') from dual

How to parse a date?

How about getSelectedDate? Anyway, specifically on your code question, the problem is with this line:

new SimpleDateFormat("yyyy-MM-dd");

The string that goes in the constructor has to match the format of the date. The documentation for how to do that is here. Looks like you need something close to "EEE MMM d HH:mm:ss zzz yyyy"

Why have header files and .cpp files?

Because C, where the concept originated, is 30 years old, and back then, it was the only viable way to link together code from multiple files.

Today, it's an awful hack which totally destroys compilation time in C++, causes countless needless dependencies (because class definitions in a header file expose too much information about the implementation), and so on.

CSS/Javascript to force html table row on a single line

If you don't want the text to wrap and you don't want the size of the column to get bigger then set a width and height on the column and set "overflow: hidden" in your stylesheet.

To do this on only one column you will want to add a class to that column on each row. Otherwise you can set it on all columns, that is up to you.


<table width="300px">
    <td>Column 1</td><td>Column 2</td>
   <td class="column-1">this is the text in column one which wraps</td>
   <td>this is the column two test</td>


  overflow: hidden;
  width: 150px;
  height: 1.2ex; 

An ex unit is the relative font size for height, if you are using pixels to set the font size you may wish to use that instead.

How do you run a script on login in *nix?

Place it in your bash profile:


using setTimeout on promise chain

.then(() => new Promise((resolve) => setTimeout(resolve, 15000)))


when I need sleep in async function I throw in

await new Promise(resolve => setTimeout(resolve, 1000))

Can you do greater than comparison on a date in a Rails 3 search?

If you hit problems where column names are ambiguous, you can do:

date_field = Note.arel_table[:date]
Note.where(user_id:, notetype: p[:note_type]).
     order(date_field.asc(), Note.arel_table[:created_at].asc())

React - Component Full Screen (with height 100%)

#app {
  height: 100%;
  min-height: 100vh;

Always full height of view min

Cannot find or open the PDB file in Visual Studio C++ 2010

If you have more as one Project in your Project Map use THE SAME hard coded PathFile PDB Name in all your Sub-Projects:

Use e.g.

D:\Visual Studio Projects\my_app\MyFile.pdb

Dont use e.g.


in all the Sub-Projects !!!

= Compiler Param /Fd

How to get the return value from a thread in python?

Most answers I've found are long and require being familiar with other modules or advanced python features, and will be rather confusing to someone unless they're already familiar with everything the answer talks about.

Working code for a simplified approach:

import threading, time, random

class ThreadWithResult(threading.Thread):
    def __init__(self, group=None, target=None, name=None, args=(), kwargs={}, *, daemon=None):
        def function():
            self.result = target(*args, **kwargs)
        super().__init__(group=group, target=function, name=name, daemon=daemon)

def function_to_thread(n):
    count = 0
    while count < 3:
            print(f'still running thread {n}')
            count +=1
    result = random.random()
    print(f'Return value of thread {n} should be: {result}')
    return result

def main():
    thread1 = ThreadWithResult(target=function_to_thread, args=(1,))
    thread2 = ThreadWithResult(target=function_to_thread, args=(2,))


Explanation: I wanted to simplify things significantly, so I created a ThreadWithResult class and had it inherit from threading.Thread. The nested function function in __init__ calls the threaded function we want to save the value of, and saves the result of that as the instance attribute self.result after the thread finishes executing.

Creating an instance of this is identical to creating an instance of threading.Thread. Pass in the function you want to run on a new thread to the target argument and any arguments that your function might need to the args argument and any keyword arguments to the kwargs argument.


my_thread = ThreadWithResult(target=my_function, args=(arg1, arg2, arg3))

I think this is significantly easier to understand than the vast majority of answers, and this approach requires no extra imports! I included the time and random module to simulate the behavior of a thread, but they're not required to achieve the functionality asked in the original question.

I know I'm answering this looong after the question was asked, but I hope this can help more people in the future!

EDIT: I created the save-thread-result PyPI package to allow you to access the same code above and reuse it across projects (GitHub code is here). The PyPI package fully extends the threading.Thread class, so you can set any attributes you would set on threading.thread on the ThreadWithResult class as well!

The original answer above goes over the main idea behind this subclass, but for more information, see the more detailed explanation (from the module docstring) here.

Quick usage example:

pip3 install -U save-thread-result     # MacOS/Linux
pip  install -U save-thread-result     # Windows

python3     # MacOS/Linux
python      # Windows
from save_thread_result import ThreadWithResult

# As of Release 0.0.3, you can also specify values for
#`group`, `name`, and `daemon` if you want to set those
# values manually.
thread = ThreadWithResult(
    target = my_function,
    args   = (my_function_arg1, my_function_arg2, ...)
    kwargs = (my_function_kwarg1=kwarg1_value, my_function_kwarg2=kwarg2_value, ...)

if getattr(thread, 'result', None):
    # thread.result attribute not set - something caused
    # the thread to terminate BEFORE the thread finished
    # executing the function passed in through the
    # `target` argument
    print('ERROR! Something went wrong while executing this thread, and the function you passed in did NOT complete!!')

# seeing help about the class and information about the threading.Thread super class methods and attributes available:

Firebug-like debugger for Google Chrome

jQuerify is the perfect extension to embed jQuery into Chrome Console and is as simple as you can imagine. This extension also indicates if jQuery has been already embedded into a page.

This extension is used to embed jQuery into any page you want. It allows to use jQuery in the console shell (You can invoke Chrome console by Ctrl + Shift + j".).

To embed jQuery into the selected tab click on extension button.

How to get post slug from post in WordPress?

this simple code worked for me:

$postId = get_the_ID();
$slug = basename(get_permalink($postId));
echo $slug;

What is the difference between rb and r+b modes in file objects

On Windows, 'b' appended to the mode opens the file in binary mode, so there are also modes like 'rb', 'wb', and 'r+b'. Python on Windows makes a distinction between text and binary files; the end-of-line characters in text files are automatically altered slightly when data is read or written. This behind-the-scenes modification to file data is fine for ASCII text files, but it’ll corrupt binary data like that in JPEG or EXE files. Be very careful to use binary mode when reading and writing such files. On Unix, it doesn’t hurt to append a 'b' to the mode, so you can use it platform-independently for all binary files.

Source: Reading and Writing Files

Creating an index on a table variable

If Table variable has large data, then instead of table variable(@table) create temp table (#table).table variable doesn't allow to create index after insert.

 CREATE TABLE #Table(C1 int,       
  C2 NVarchar(100) , C3 varchar(100)
  1. Create table with unique clustered index

  2. Insert data into Temp "#Table" table

  3. Create non clustered indexes.


oracle varchar to number

Since the column is of type VARCHAR, you should convert the input parameter to a string rather than converting the column value to a number:

select * from exception where exception_value = to_char(105);

Exclude subpackages from Spring autowiring?

You can also use @SpringBootApplication, which according to Spring documentation does the same functionality as the following three annotations: @Configuration, @EnableAutoConfiguration @ComponentScan in one annotation.

@SpringBootApplication(exclude= {Foo.class})
public class MySpringConfiguration {}

How to Set AllowOverride all

On Linux, in order to relax access to the document root, you should edit the following file:


And depending on what directory level you want to relax access to, you have to change the directive

AllowOverride None


AllowOverride All

So, assuming you want to allow access to files on the /var/www/html directory, you should change the following lines from:

<Directory "/var/www/html">
 AllowOverride None


<Directory "/var/www/html">
 AllowOverride All

How to get current html page title with javascript

Like this :

jQuery(document).ready(function () {
    var title = jQuery(this).attr('title');

works for IE, Firefox and Chrome.

Using any() and all() to check if a list contains one set of values or another

Generally speaking:

all and any are functions that take some iterable and return True, if

  • in the case of all(), no values in the iterable are falsy;
  • in the case of any(), at least one value is truthy.

A value x is falsy iff bool(x) == False. A value x is truthy iff bool(x) == True.

Any non-booleans in the iterable will be fine — bool(x) will coerce any x according to these rules: 0, 0.0, None, [], (), [], set(), and other empty collections will yield False, anything else True. The docstring for bool uses the terms 'true'/'false' for 'truthy'/'falsy', and True/False for the concrete boolean values.

In your specific code samples:

You misunderstood a little bit how these functions work. Hence, the following does something completely not what you thought:

if any(foobars) == big_foobar:

...because any(foobars) would first be evaluated to either True or False, and then that boolean value would be compared to big_foobar, which generally always gives you False (unless big_foobar coincidentally happened to be the same boolean value).

Note: the iterable can be a list, but it can also be a generator/generator expression (˜ lazily evaluated/generated list) or any other iterator.

What you want instead is:

if any(x == big_foobar for x in foobars):

which basically first constructs an iterable that yields a sequence of booleans—for each item in foobars, it compares the item to big_foobar and emits the resulting boolean into the resulting sequence:

tmp = (x == big_foobar for x in foobars)

then any walks over all items in tmp and returns True as soon as it finds the first truthy element. It's as if you did the following:

In [1]: foobars = ['big', 'small', 'medium', 'nice', 'ugly']                                        

In [2]: big_foobar = 'big'                                                                          

In [3]: any(['big' == big_foobar, 'small' == big_foobar, 'medium' == big_foobar, 'nice' == big_foobar, 'ugly' == big_foobar])        
Out[3]: True

Note: As DSM pointed out, any(x == y for x in xs) is equivalent to y in xs but the latter is more readable, quicker to write and runs faster.

Some examples:

In [1]: any(x > 5 for x in range(4))
Out[1]: False

In [2]: all(isinstance(x, int) for x in range(10))
Out[2]: True

In [3]: any(x == 'Erik' for x in ['Erik', 'John', 'Jane', 'Jim'])
Out[3]: True

In [4]: all([True, True, True, False, True])
Out[4]: False

See also:

Error handling in getJSON calls

$.getJSON() is a kind of abstraction of a regular AJAX call where you would have to tell that you want a JSON encoded response.

  url: url,
  dataType: 'json',
  data: data,
  success: callback

You can handle errors in two ways: generically (by configuring your AJAX calls before actually calling them) or specifically (with method chain).

'generic' would be something like:

      "error":function() { alert("error");  }

And the 'specific' way:

$.getJSON("example.json", function() {
.done(function() { alert("second success"); })
.fail(function() { alert("error"); })
.always(function() { alert("complete"); });

Trim last character from a string

string helloOriginal = "Hello! World!";
string newString = helloOriginal.Substring(0,helloOriginal.LastIndexOf('!'));

How to prevent http file caching in Apache httpd (MAMP)

Based on the example here:

The following will probably work in .htaccess

 <IfModule mod_expires.c>
   # Enable expirations.
   ExpiresActive On

   # Cache all files for 2 weeks after access (A).
   ExpiresDefault A1209600

  <FilesMatch (\.js|\.html)$>
     ExpiresActive Off

OpenCV TypeError: Expected cv::UMat for argument 'src' - What is this?

Just add this at start: image = cv2.imread(image)

PHP check whether property exists in object or class

Just putting my 2 cents here.

Given the following class:

class Foo
  private $data;

  public function __construct(array $data)
    $this->data = $data;

  public function __get($name)
    return $data[$name];

  public function __isset($name)
    return array_key_exists($name, $this->data);

the following will happen:

$foo = new Foo(['key' => 'value', 'bar' => null]);

var_dump(property_exists($foo, 'key'));  // false
var_dump(isset($foo->key));  // true
var_dump(property_exists($foo, 'bar'));  // false
var_dump(isset($foo->bar));  // true, although $data['bar'] == null

Hope this will help anyone

Python equivalent of D3.js

I've got a good example of automatically generating D3.js network diagrams using Python here:

The cool thing is that you end up with auto-generated HTML and JS and can embed the interactive D3 chart in a notebook with an IFrame

how to reset <input type = "file">


The following code worked for me with jQuery. It works in every browser and allows to preserve events and custom properties.

var $el = $('#uploadCaptureInputFile');


See this jsFiddle for code and demonstration.


See How to reset file input with JavaScript for more information.

Output first 100 characters in a string

Slicing of arrays is done with [first:last+1].

One trick I tend to use a lot of is to indicate extra information with ellipses. So, if your field is one hundred characters, I would use:

if len(s) <= 100:
    print s
    print "%s..."%(s[:97])

And yes, I know () is superfluous in this case for the % formatting operator, it's just my style.

Checking the form field values before submitting that page

While you have a return value in checkform, it isn't being used anywhere - try using onclick="return checkform()" instead.

You may want to considering replacing this method with onsubmit="return checkform()" in the form tag instead, though both will work for clicking the button.

Python's "in" set operator

Strings, though they are not set types, have a valuable in property during validation in scripts:

yn = input("Are you sure you want to do this? ")
if yn in "yes":
    #accepts 'y' OR 'e' OR 's' OR 'ye' OR 'es' OR 'yes'
    return True
return False

I hope this helps you better understand the use of in with this example.

Unable to find the wrapper "https" - did you forget to enable it when you configured PHP?

For those using Winginx (nginx based instead of Apache based), I fixed it with these 4 steps:

  1. On the Tools menu hit the Winginx PHP5 Config (never mind the 5 in the name...):

    Winginx PHP5 Config

  2. Select the PHP version you want the php.ini to change:

    PHP version selection

  3. On the PHP Extensions tab select the php_openssl extension and hit the Save button:

    php_openssl selection

  4. restart the appropriate PHP service through the taskbar (Stop and Start):

    Restart PHP service

How to generate components in a specific folder with Angular CLI?

If you use VSCode, consider using the Angular Console

It provides an interface for the Angular CLI. You will see an option to specify the path.

The Angular CLI is immensely powerful and extensible. In fact, there are so many capabilities that it is helpful for developers to have all of the different configuration options for every command available to them.

With Angular Console, you’ll get recommendations and be able to pull up even the most easily forgotten or rarely used features!

Angular Console is, first and foremost, a more productive way to work with what the Angular CLI provides.

How do you resize a form to fit its content automatically?

I used this code and it works just fine

const int margin = 5;
        Rectangle rect = new Rectangle(
            Screen.PrimaryScreen.WorkingArea.X + margin,
            Screen.PrimaryScreen.WorkingArea.Y + margin,
            Screen.PrimaryScreen.WorkingArea.Width - 2 * margin,
            Screen.PrimaryScreen.WorkingArea.Height - 2 * (margin - 7));
        this.Bounds = rect;

How to implement onBackPressed() in Fragments?

Try this one, if you really want to enable onBackPressed() in Fragment. After wasting an hour of time, I made this solution which exactly fits over the needs, from my prior experiences.

You just need to focus on the value of private int STATUS_FRAGMENT=0; which suffices the need of addToBackStack() in fragments.

import android.view.MenuItem;
import android.view.View;

import androidx.annotation.NonNull;

import com.example.growfast.NavigationItemsFolder.CoreFragments.Cart;
import com.example.growfast.NavigationItemsFolder.CoreFragments.HelpDesk;
import com.example.growfast.NavigationItemsFolder.CoreFragments.Home;
import com.example.growfast.NavigationItemsFolder.CoreFragments.ProfileDetails;
import com.example.growfast.R;

public class BusinessManagement extends AppCompatActivity {

    public BottomNavigationView bottomNavigationView;
    private int STATUS_FRAGMENT=0;

    protected void onCreate(Bundle savedInstanceState) {


    private void setBottomNavigationMenu() {
        bottomNavigationView = findViewById(;

        bottomNavigationView.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {

            Fragment fragment = null;

            public boolean onNavigationItemSelected(@NonNull MenuItem item) {

                switch (item.getItemId()) {

                        fragment = new Home();

                        fragment = new ProfileDetails();
                        fragment = new Cart();
                        fragment = new HelpDesk();

                return loadFromFragment(fragment);


    private boolean loadFromFragment(Fragment fragment) {
        if (fragment != null) {
            getSupportFragmentManager().beginTransaction().replace(, fragment)
            return true;
        return false;

    public void onBackPressed() {
        if (STATUS_FRAGMENT==1) {


pandas: best way to select all columns whose names start with X

Another option for the selection of the desired entries is to use map:

df.loc[(df == 1).any(axis=1), x: x.startswith('foo'))]

which gives you all the columns for rows that contain a 1:

   foo.aa  foo.bars  foo.fighters foo.manchu
0     1.0         0             0        2         NA
1     2.1         0             1        4          0
2     NaN         0           NaN        1          0
5     6.8         1             0        5          0

The row selection is done by

(df == 1).any(axis=1)

as in @ajcr's answer which gives you:

0     True
1     True
2     True
3    False
4    False
5     True
dtype: bool

meaning that row 3 and 4 do not contain a 1 and won't be selected.

The selection of the columns is done using Boolean indexing like this: x: x.startswith('foo'))

In the example above this returns

array([False,  True,  True,  True,  True,  True, False], dtype=bool)

So, if a column does not start with foo, False is returned and the column is therefore not selected.

If you just want to return all rows that contain a 1 - as your desired output suggests - you can simply do

df.loc[(df == 1).any(axis=1)]

which returns

   bar.baz  foo.aa  foo.bars  foo.fighters foo.manchu
0      5.0     1.0         0             0        2         NA      NA
1      5.0     2.1         0             1        4          0       0
2      6.0     NaN         0           NaN        1          0       1
5      6.8     6.8         1             0        5          0       0

Table 'performance_schema.session_variables' doesn't exist

I was able to log on to the mysql server after running the command @robregonm suggested:

mysql_upgrade -u root -p --force

A MySQL server restart is required.

JQuery Find #ID, RemoveClass and AddClass


jQuery addClass API reference

What does 'corrupted double-linked list' mean

I have found the answer to my question myself:)

So what I didn't understand was how the glibc could differentiate between a Segfault and a corrupted double-linked list, because according to my understanding, from perspective of glibc they should look like the same thing. Because if I implement a double-linked list inside my program, how could the glibc possibly know that this is a double-linked list, instead of any other struct? It probably can't, so thats why i was confused.

Now I've looked at malloc/malloc.c inside the glibc's code, and I see the following:

1543 /* Take a chunk off a bin list */
1544 #define unlink(P, BK, FD) {                                            \
1545   FD = P->fd;                                                          \
1546   BK = P->bk;                                                          \
1547   if (__builtin_expect (FD->bk != P || BK->fd != P, 0))                \
1548     malloc_printerr (check_action, "corrupted double-linked list", P); \
1549   else {                                                               \
1550     FD->bk = BK;                                                       \
1551     BK->fd = FD;                                                       \

So now this suddenly makes sense. The reason why glibc can know that this is a double-linked list is because the list is part of glibc itself. I've been confused because I thought glibc can somehow detect that some programming is building a double-linked list, which I wouldn't understand how that works. But if this double-linked list that it is talking about, is part of glibc itself, of course it can know it's a double-linked list.

I still don't know what has triggered this error. But at least I understand the difference between corrupted double-linked list and a Segfault, and how the glibc can know this struct is supposed to be a double-linked list:)

How to stop BackgroundWorker correctly

The problem is caused by the fact that cmbDataSourceExtractor.CancelAsync() is an asynchronous method, the Cancel operation has not yet completed when cmdDataSourceExtractor.RunWorkerAsync(...) exitst. You should wait for cmdDataSourceExtractor to complete before calling RunWorkerAsync again. How to do this is explained in this SO question.

Operation is not valid due to the current state of the object, when I select a dropdown list


Issue happens because Microsoft Security Update MS11-100 limits number of keys in Forms collection during HTTP POST request. To alleviate this problem you need to increase that number.

This can be done in your application Web.Config in the <appSettings> section (create the section directly under <configuration> if it doesn’t exist). Add 2 lines similar to the lines below to the section:

<add key="aspnet:MaxHttpCollectionKeys" value="2000" />
<add key="aspnet:MaxJsonDeserializerMembers" value="2000" />

The above example set the limit to 2000 keys. This will lift the limitation and the error should go away.

How to detect when a UIScrollView has finished scrolling

For all scrolls related to dragging interactions, this will be sufficient:

- (void)scrollViewDidEndDecelerating:(UIScrollView *)scrollView {
    _isScrolling = NO;

- (void)scrollViewDidEndDragging:(UIScrollView *)scrollView willDecelerate:(BOOL)decelerate {
    if (!decelerate) {
        _isScrolling = NO;

Now, if your scroll is due to a programmatic setContentOffset/scrollRectVisible (with animated = YES or you obviously know when scroll is ended):

 - (void)scrollViewDidEndScrollingAnimation {
     _isScrolling = NO;

If your scroll is due to something else (like keyboard opening or keyboard closing), it seems like you'll have to detect the event with a hack because scrollViewDidEndScrollingAnimation is not useful either.

The case of a PAGINATED scroll view:

Because, I guess, Apple apply an acceleration curve, scrollViewDidEndDecelerating get called for every drag so there's no need to use scrollViewDidEndDragging in this case.

What is HTTP "Host" header?

I would always recommend going to the authoritative source when trying to understand the meaning and purpose of HTTP headers.

The "Host" header field in a request provides the host and port
information from the target URI, enabling the origin server to
distinguish among resources while servicing requests for multiple
host names on a single IP address.

Can I have an onclick effect in CSS?

If you give the element a tabindex then you can use the :focus pseudo class to simulate a click.


<img id="btnLeft" tabindex="0" src="" />



PHP/MySQL Insert null values

I think you need quotes around your {$row['null_field']}, so '{$row['null_field']}'

If you don't have the quotes, you'll occasionally end up with an insert statement that looks like this: insert into table2 (f1, f2) values ('val1',) which is a syntax error.

If that is a numeric field, you will have to do some testing above it, and if there is no value in null_field, explicitly set it to null..

Expand/collapse section in UITableView in iOS

I got a nice solution inspired by Apple's Table View Animations and Gestures. I deleted unnecessary parts from Apple's sample and translated it into swift.

I know the answer is quite long, but all the code is necessary. Fortunately, you can just copy and paste most of the code and just need to do a bit modification on step 1 and 3

1.create SectionHeaderView.swift and SectionHeaderView.xib

import UIKit

protocol SectionHeaderViewDelegate {
    func sectionHeaderView(sectionHeaderView: SectionHeaderView, sectionOpened: Int)
    func sectionHeaderView(sectionHeaderView: SectionHeaderView, sectionClosed: Int)

class SectionHeaderView: UITableViewHeaderFooterView {
    var section: Int?
    @IBOutlet weak var titleLabel: UILabel!
    @IBOutlet weak var disclosureButton: UIButton!
    @IBAction func toggleOpen() {
    var delegate: SectionHeaderViewDelegate?
    func toggleOpenWithUserAction(userAction: Bool) {
        self.disclosureButton.selected = !self.disclosureButton.selected
        if userAction {
            if self.disclosureButton.selected {
                self.delegate?.sectionHeaderView(self, sectionClosed: self.section!)
            } else {
                self.delegate?.sectionHeaderView(self, sectionOpened: self.section!)
    override func awakeFromNib() {
        var tapGesture: UITapGestureRecognizer = UITapGestureRecognizer(target: self, action: "toggleOpen")
        // change the button image here, you can also set image via IB.
        self.disclosureButton.setImage(UIImage(named: "arrow_up"), forState: UIControlState.Selected)
        self.disclosureButton.setImage(UIImage(named: "arrow_down"), forState: UIControlState.Normal)

the SectionHeaderView.xib(the view with gray background) should look something like this in a tableview(you can customize it according to your needs, of course): enter image description here


a) the toggleOpen action should be linked to disclosureButton

b) the disclosureButton and toggleOpen action are not necessary. You can delete these 2 things if you don't need the button.

2.create SectionInfo.swift

import UIKit

class SectionInfo: NSObject {
    var open: Bool = true
    var itemsInSection: NSMutableArray = []
    var sectionTitle: String?
    init(itemsInSection: NSMutableArray, sectionTitle: String) {
        self.itemsInSection = itemsInSection
        self.sectionTitle = sectionTitle
} your tableview

import UIKit

class TableViewController: UITableViewController, SectionHeaderViewDelegate  {
    let SectionHeaderViewIdentifier = "SectionHeaderViewIdentifier"
    var sectionInfoArray: NSMutableArray = []
    override func viewDidLoad() {
        let sectionHeaderNib: UINib = UINib(nibName: "SectionHeaderView", bundle: nil)
        self.tableView.registerNib(sectionHeaderNib, forHeaderFooterViewReuseIdentifier: SectionHeaderViewIdentifier)
        // you can change section height based on your needs
        self.tableView.sectionHeaderHeight = 30
        // You should set up your SectionInfo here
        var firstSection: SectionInfo = SectionInfo(itemsInSection: ["1"], sectionTitle: "firstSection")
        var secondSection: SectionInfo = SectionInfo(itemsInSection: ["2"], sectionTitle: "secondSection"))
        sectionInfoArray.addObjectsFromArray([firstSection, secondSection])
    // MARK: - Table view data source
    override func numberOfSectionsInTableView(tableView: UITableView) -> Int {
        return sectionInfoArray.count
    override func tableView(tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        if self.sectionInfoArray.count > 0 {
            var sectionInfo: SectionInfo = sectionInfoArray[section] as! SectionInfo
            if {
                return ? sectionInfo.itemsInSection.count : 0
        return 0
    override func tableView(tableView: UITableView, viewForHeaderInSection section: Int) -> UIView? {
        let sectionHeaderView: SectionHeaderView! = self.tableView.dequeueReusableHeaderFooterViewWithIdentifier(SectionHeaderViewIdentifier) as! SectionHeaderView
        var sectionInfo: SectionInfo = sectionInfoArray[section] as! SectionInfo
        sectionHeaderView.titleLabel.text = sectionInfo.sectionTitle
        sectionHeaderView.section = section
        sectionHeaderView.delegate = self
        let backGroundView = UIView()
        // you can customize the background color of the header here
        backGroundView.backgroundColor = UIColor(red:0.89, green:0.89, blue:0.89, alpha:1)
        sectionHeaderView.backgroundView = backGroundView
        return sectionHeaderView
    func sectionHeaderView(sectionHeaderView: SectionHeaderView, sectionOpened: Int) {
        var sectionInfo: SectionInfo = sectionInfoArray[sectionOpened] as! SectionInfo
        var countOfRowsToInsert = sectionInfo.itemsInSection.count = true
        var indexPathToInsert: NSMutableArray = NSMutableArray()
        for i in 0..<countOfRowsToInsert {
            indexPathToInsert.addObject(NSIndexPath(forRow: i, inSection: sectionOpened))
        self.tableView.insertRowsAtIndexPaths(indexPathToInsert as [AnyObject], withRowAnimation: .Top)
    func sectionHeaderView(sectionHeaderView: SectionHeaderView, sectionClosed: Int) {
        var sectionInfo: SectionInfo = sectionInfoArray[sectionClosed] as! SectionInfo
        var countOfRowsToDelete = sectionInfo.itemsInSection.count = false
        if countOfRowsToDelete > 0 {
            var indexPathToDelete: NSMutableArray = NSMutableArray()
            for i in 0..<countOfRowsToDelete {
                indexPathToDelete.addObject(NSIndexPath(forRow: i, inSection: sectionClosed))
            self.tableView.deleteRowsAtIndexPaths(indexPathToDelete as [AnyObject], withRowAnimation: .Top)

Upload failed You need to use a different version code for your APK because you already have one with version code 2

I received the same error while uploading a flutter app to playstore simply change the version code in pubspec.yaml worked for me. may be try changing the version code e.g from +1 to +2 and then rebuild the apk using

flutter build apk --split-per-abi 

and upload all the apk's to the playstore for your users. Next time when you want to push an update make sure to update the version code to +3 and so on.

Note: that the version code and version name are different you can see that in android/ file. e.g version: 1.0.0+2

version is 1.0.0 and verison code is +2

Is it possible to style html5 audio tag?

some color tunings

audio {
    filter: sepia(20%) saturate(70%) grayscale(1) contrast(99%) invert(12%);
    width: 200px;
    height: 25px;

NPM vs. Bower vs. Browserify vs. Gulp vs. Grunt vs. Webpack

Webpack is a bundler. Like Browserfy it looks in the codebase for module requests (require or import) and resolves them recursively. What is more, you can configure Webpack to resolve not just JavaScript-like modules, but CSS, images, HTML, literally everything. What especially makes me excited about Webpack, you can combine both compiled and dynamically loaded modules in the same app. Thus one get a real performance boost, especially over HTTP/1.x. How exactly you you do it I described with examples here As an alternative for bundler one can think of Rollup.js (, which optimizes the code during compilation, but stripping all the found unused chunks.

For AMD, instead of RequireJS one can go with native ES2016 module system, but loaded with System.js (

Besides, I would point that npm is often used as an automating tool like grunt or gulp. Check out I personally go now with npm scripts only avoiding other automation tools, though in past I was very much into grunt. With other tools you have to rely on countless plugins for packages, that often are not good written and not being actively maintained. npm knows its packages, so you call to any of locally installed packages by name like:

  "scripts": {
    "start": "npm http-server"
  "devDependencies": {
    "http-server": "^0.10.0"

Actually you as a rule do not need any plugin if the package supports CLI.

if else statement in AngularJS templates

A possibility for Angular: I had to include an if - statement in the html part, I had to check if all variables of an URL that I produce are defined. I did it the following way and it seems to be a flexible approach. I hope it will be helpful for somebody.

The html part in the template:

    <div  *ngFor="let p of poemsInGrid; let i = index" >
        <a [routerLink]="produceFassungsLink(p[0],p[3])" routerLinkActive="active">

And the typescript part:

  produceFassungsLink(titel: string, iri: string) {
      if(titel !== undefined && iri !== undefined) {
         return titel.split('/')[0] + '---' + iri.split('raeber/')[1];
      } else {
         return 'Linkinformation has not arrived yet';

Thanks and best regards,


How do you test a public/private DSA keypair?

I always compare an MD5 hash of the modulus using these commands:

Certificate: openssl x509 -noout -modulus -in server.crt | openssl md5
Private Key: openssl rsa -noout -modulus -in server.key | openssl md5
CSR: openssl req -noout -modulus -in server.csr | openssl md5

If the hashes match, then those two files go together.

Laravel: getting a a single value from a MySQL query

[EDIT] The expected output of the pluck function has changed from Laravel 5.1 to 5.2. Hence why it is marked as deprecated in 5.1

In Laravel 5.1, pluck gets a single column's value from the first result of a query.

In Laravel 5.2, pluck gets an array with the values of a given column. So it's no longer deprecated, but it no longer do what it used to.

So short answer is use the value function if you want one column from the first row and you are using Laravel 5.1 or above.

Thanks to Tomas Buteler for pointing this out in the comments.

[ORIGINAL] For anyone coming across this question who is using Laravel 5.1, pluck() has been deprecated and will be removed completely in Laravel 5.2.

Consider future proofing your code by using value() instead.

return DB::table('users')->where('username', $username)->value('groupName');

AngularJs: How to check for changes in file input fields?

Angular elements (such as the root element of a directive) are jQuery [Lite] objects. This means we can register the event listener like so:

link($scope, $el) {
    const fileInputSelector = '.my-file-input'

    function setFile() {
        // access file via $el.find(fileInputSelector).get(0).files[0]

    $el.on('change', fileInputSelector, setFile)

This is jQuery event delegation. Here, the listener is attached to the root element of the directive. When the event is triggered, it will bubble up to the registered element and jQuery will determine if the event originated on an inner element matching the defined selector. If it does, the handler will fire.

Benefits of this method are:

  • the handler is bound to the $element which will be automatically cleaned up when the directive scope is destroyed.
  • no code in the template
  • will work even if the target delegate (input) has not yet been rendered when you register the event handler (such as when using ng-if or ng-switch)

HTML5 required attribute seems not working

Try putting it inside a form tag and closing the input tag:

  <input type = "text" class = "txtPost" placeholder = "Post a question?" required />
  <button class = "btnPost btnBlue">Post</button>

Remove all special characters from a string

Here, check out this function:

function seo_friendly_url($string){
    $string = str_replace(array('[\', \']'), '', $string);
    $string = preg_replace('/\[.*\]/U', '', $string);
    $string = preg_replace('/&(amp;)?#?[a-z0-9]+;/i', '-', $string);
    $string = htmlentities($string, ENT_COMPAT, 'utf-8');
    $string = preg_replace('/&([a-z])(acute|uml|circ|grave|ring|cedil|slash|tilde|caron|lig|quot|rsquo);/i', '\\1', $string );
    $string = preg_replace(array('/[^a-z0-9]/i', '/[-]+/') , '-', $string);
    return strtolower(trim($string, '-'));

Makefiles with source files in different directories

If you have code in one subdirectory dependent on code in another subdirectory, you are probably better off with a single makefile at top-level.

See Recursive Make Considered Harmful for the full rationale, but basically you want make to have the full information it needs to decide whether or not a file needs to be rebuilt, and it won't have that if you only tell it about a third of your project.

The link above seems to be not reachable. The same document is reachable here:

Usage of @see in JavaDoc?

The @see tag is a bit different than the @link tag,
limited in some ways and more flexible in others:

different JavaDoc link types Different JavaDoc link types

  1. Displays the member name for better learning, and is refactorable; the name will update when renaming by refactor
  2. Refactorable and customizable; your text is displayed instead of the member name
  3. Displays name, refactorable
  4. Refactorable, customizable
  5. A rather mediocre combination that is:
  • Refactorable, customizable, and stays in the See Also section
  • Displays nicely in the Eclipse hover
  • Displays the link tag and its formatting when generated
  • When using multiple @see items, commas in the description make the output confusing
  1. Completely illegal; causes unexpected content and illegal character errors in the generator

See the results below:

JavaDoc generation results with different link types JavaDoc generation results with different link types

Best regards.

Initializing default values in a struct

You don't even need to define a constructor

struct foo {
    bool a = true;
    bool b = true;
    bool c;
 } bar;

To clarify: these are called brace-or-equal-initializers (because you may also use brace initialization instead of equal sign). This is not only for aggregates: you can use this in normal class definitions. This was added in C++11.

“Origin null is not allowed by Access-Control-Allow-Origin” error for request made by application running from a file:// URL

In my case, same code worked fine on Firefox, but not on Google Chrome. Google Chrome's JavaScript console said:

XMLHttpRequest cannot load 
Origin is not allowed by Access-Control-Allow-Origin.
Refused to get unsafe header "X-JSON"

I had to drop the www part of the Ajax URL for it to match correctly with the origin URL and it worked fine then.

Detect if range is empty

Another possible solution. Count empty cells and subtract that value from the total number of cells

Sub Emptys()

Dim r As range
Dim totalCells As Integer

'My range To check'
Set r = ActiveSheet.range("A1:B5")

'Check for filled cells'
totalCells = r.Count- WorksheetFunction.CountBlank(r)

If totalCells = 0 Then
    MsgBox "Range is empty"
    MsgBox "Range is not empty"
End If

End Sub

How can I format a list to print each element on a separate line in python?

Embrace the future! Just to be complete, you can also do this the Python 3k way by using the print function:

from __future__ import print_function  # Py 2.6+; In Py 3k not needed

mylist = ['10', 12, '14']    # Note that 12 is an int




Eventually, print as Python statement will go away... Might as well start to get used to it.

Java: How to check if object is null?


The above line calls the "equals(...)" method on the drawable object.

So, when drawable is not null and it is a real object, then all goes well as calling the "equals(null)" method will return "false"

But when "drawable" is null, then it means calling the "equals(...)" method on null object, means calling a method on an object that doesn't exist so it throws "NullPointerException"

To check whether an object exists and it is not null, use the following

if(drawable == null) {

In above condition, we are checking that the reference variable "drawable" is null or contains some value (reference to its object) so it won't throw exception in case drawable is null as checking

null == null

is valid.

Getting a File's MD5 Checksum in Java

There's an example at Real's Java-How-to using the MessageDigest class.

Check that page for examples using CRC32 and SHA-1 as well.


public class MD5Checksum {

   public static byte[] createChecksum(String filename) throws Exception {
       InputStream fis =  new FileInputStream(filename);

       byte[] buffer = new byte[1024];
       MessageDigest complete = MessageDigest.getInstance("MD5");
       int numRead;

       do {
           numRead =;
           if (numRead > 0) {
               complete.update(buffer, 0, numRead);
       } while (numRead != -1);

       return complete.digest();

   // see this How-to for a faster way to convert
   // a byte array to a HEX string
   public static String getMD5Checksum(String filename) throws Exception {
       byte[] b = createChecksum(filename);
       String result = "";

       for (int i=0; i < b.length; i++) {
           result += Integer.toString( ( b[i] & 0xff ) + 0x100, 16).substring( 1 );
       return result;

   public static void main(String args[]) {
       try {
           // output :
           //  0bb2827c5eacf570b6064e24e0e6653b
           // ref :
           //          tomcat/tomcat-5/v5.5.17/bin
           //              /apache-tomcat-5.5.17.exe.MD5
           //  0bb2827c5eacf570b6064e24e0e6653b *apache-tomcat-5.5.17.exe
       catch (Exception e) {

How to save select query results within temporary table?

select *
into #TempTable
from SomeTale

select *
from #TempTable

CRON command to run URL address every 5 minutes

I try GET '' Important use ' add >/dev/null 2>&1 for not send email when this activate Sorry for my English

Concatenate a NumPy array to another NumPy array

Actually one can always create an ordinary list of numpy arrays and convert it later.

In [1]: import numpy as np

In [2]: a = np.array([[1,2],[3,4]])

In [3]: b = np.array([[1,2],[3,4]])

In [4]: l = [a]

In [5]: l.append(b)

In [6]: l = np.array(l)

In [7]: l.shape
Out[7]: (2, 2, 2)

In [8]: l
array([[[1, 2],
        [3, 4]],

       [[1, 2],
        [3, 4]]])

How to solve SQL Server Error 1222 i.e Unlock a SQL Server table

I had these SQL behavior settings enabled on options query execution: ANSI SET IMPLICIT_TRANSACTIONS checked. On execution of your query e.g create, alter table or stored procedure, you have to COMMIT it.

Just type COMMIT and execute it F5

Using "margin: 0 auto;" in Internet Explorer 8

One more time: we all hate IE!

<div style="width:100%;background-color:blue;">
    <div style="margin:0 auto;width:300px;background-color:red;">
        Not Working

<div style="width:100%;background-color:green;text-align:center;">
    <div style="margin:0 auto;width:300px;background-color:orange;text-align:left;">
        Working, but dumb that you have to use text-align

How to change letter spacing in a Textview?

I built a custom class that extends TextView and solves this problem... Check out my answer here =)

Test if string is URL encoded in PHP

You'll never know for sure if a string is URL-encoded or if it was supposed to have the sequence %2B in it. Instead, it probably depends on where the string came from, i.e. if it was hand-crafted or from some application.

Is it better to search the string for characters which would be encoded, which aren't, and if any exist then its not encoded.

I think this is a better approach, since it would take care of things that have been done programmatically (assuming the application would not have left a non-encoded character behind).

One thing that will be confusing here... Technically, the % "should be" encoded if it will be present in the final value, since it is a special character. You might have to combine your approaches to look for should-be-encoded characters as well as validating that the string decodes successfully if none are found.

OR is not supported with CASE Statement in SQL Server

select id,phno,case gender
when 'G' then 'M'
when 'L' then 'F'
'No gender'
as gender 
from contacts

What's the difference between align-content and align-items?

From the example at

align-content determines the spacing between lines

align-items determines how the items as a whole are aligned within the container.

When there is only one line, align-content has no effect

Android, ListView IllegalStateException: "The content of the adapter has changed but ListView did not receive a notification"

i haved same problem when add new data in lazy image loader i just put



       protected void onPostExecute(Void args) {
        // Close the progressdialog

hope it helps you

What is the best way to detect a mobile device?

This seems to be a comprehensive, modern solution:

It detects several platforms, smartphone vs. tablets, and orientation. It also adds classes to the BODY tag so detection takes place only once and you can read what device you're on with a simple series of jQuery hasClass functions.

Check it out...

[DISCLAIMER: I've got nothing to do with the person who wrote it.]

top -c command in linux to filter processes listed based on processname

Using pgrep to get pid's of matching command lines:

top -c -p $(pgrep -d',' -f string_to_match_in_cmd_line)

top -p expects a comma separated list of pids so we use -d',' in pgrep. The -f flag in pgrep makes it match the command line instead of program name.

Which data structures and algorithms book should I buy?

Introduction to Algorithms by Cormen et. al. is a standard introductory algorithms book, and is used by many universities, including my own. It has pretty good coverage and is very approachable.

And anything by Robert Sedgewick is good too.

What is the difference between Python and IPython?

Compared to Python, IPython (created by Fernando Perez in 2001) can do every thing what python can do. Ipython provides even extra features like tab-completion, testing, debugging, system calls and many other features. You can think IPython as a powerful interface to the Python language.

You can install Ipython using pip - pip install ipython

You can run Ipython by typing ipython in your terminal window.

Reverse Y-Axis in PyPlot

Alternatively, you can use the matplotlib.pyplot.axis() function, which allows you inverting any of the plot axis

ax = matplotlib.pyplot.axis()

Or if you prefer to only reverse the X-axis, then


Indeed, you can invert both axis:


Import JavaScript file and call functions using webpack, ES6, ReactJS

Named exports:

Let's say you create a file called utils.js, with utility functions that you want to make available for other modules (e.g. a React component). Then you would make each function a named export:

export function add(x, y) {
  return x + y

export function mutiply(x, y) {
  return x * y

Assuming that utils.js is located in the same directory as your React component, you can use its exports like this:

import { add, multiply } from './utils.js';
add(2, 3) // Can be called wherever in your component, and would return 5.

Or if you prefer, place the entire module's contents under a common namespace:

import * as utils from './utils.js'; 

Default exports:

If you on the other hand have a module that only does one thing (could be a React class, a normal function, a constant, or anything else) and want to make that thing available to others, you can use a default export. Let's say we have a file log.js, with only one function that logs out whatever argument it's called with:

export default function log(message) {

This can now be used like this:

import log from './log.js';
log('test') // Would print 'test' in the console.

You don't have to call it log when you import it, you could actually call it whatever you want:

import logToConsole from './log.js';
logToConsole('test') // Would also print 'test' in the console.


A module can have both a default export (max 1), and named exports (imported either one by one, or using * with an alias). React actually has this, consider:

import React, { Component, PropTypes } from 'react';

Absolute positioning ignoring padding of parent

I would set the child's width this way:

.child {position: absolute; width: calc(100% - padding);}

Padding, in the formula, is the sum of the left and right parent's padding. I admit it is probably not very elegant, but in my case, a div with the function of an overlay, it worked.

How to I say Is Not Null in VBA

you can do like follows. Remember, IsNull is a function which returns TRUE if the parameter passed to it is null, and false otherwise.

Not IsNull(Fields!W_O_Count.Value)

Redirect to external URI from ASP.NET MVC controller

Maybe the solution someone is looking for is this:


This work when used in the View as well.

Setting a backgroundImage With React Inline Styles

You Can try usimg

backgroundImage: url(process.env.PUBLIC_URL + "/      assets/image_location")

How to prevent long words from breaking my div?

p {
    overflow-wrap: break-word;

@-moz-document url-prefix() { 
    p {
        white-space: -moz-pre-wrap;
        word-wrap: break-word;

How to handle AccessViolationException

Compiled from above answers, worked for me, did following steps to catch it.

Step #1 - Add following snippet to config file

      <legacyCorruptedStateExceptionsPolicy enabled="true" />

Step #2

Add -



on the top of function you are tying catch the exception


Cookie blocked/not saved in IFRAME in Internet Explorer

I've implemented a full P3P policy before but didn't want go through the hassle again for a new project I was working on. I found this link useful for a simple solution to the problem, only having to specify a minimal compact P3P policy of "CAO PSA OUR":

The article quotes a (now broken) link to a Microsoft kb article. The policy did the trick for me!

Java File - Open A File And Write To It

To expand upon Mr. Eels comment, you can do it like this:

    File file = new File("C:\\A.txt");
    FileWriter writer;
    try {
        writer = new FileWriter(file, true);
        PrintWriter printer = new PrintWriter(writer);
    } catch (IOException e) {
        // TODO Auto-generated catch block

Don't say we ain't good to ya!

Download a file with Android, and showing the progress in a ProgressDialog

My personal advice is to use Progress Dialog and build up before execution , or initiate at OnPreExecute() , publish progress often if you use horizontal style of progress bar of the progress dialog. The remaining part is to optimize the algorithm of doInBackground.

How do I set headers using python's urllib?

For both Python 3 and Python 2, this works:

    from urllib.request import Request, urlopen  # Python 3
except ImportError:
    from urllib2 import Request, urlopen  # Python 2

req = Request('')
req.add_header('apikey', 'xxx')
content = urlopen(req).read()


How to get the path of src/test/resources directory in JUnit?

I have a Maven3 project using JUnit 4.12 and Java8. In order to get the path of a file called myxml.xml under src/test/resources, I do this from within the test case:

public void testApp()
    File inputXmlFile = new File(this.getClass().getResource("/myxml.xml").getFile());

Tested on Ubuntu 14.04 with IntelliJ IDE. Reference here.

mysql.h file can't be found

For those who are using Eclipse IDE.

After installing the full MySQL together with mysql client and mysql server and any mysql dev libraries,

You will need to tell Eclipse IDE about the following

  • Where to find mysql.h
  • Where to find libmysqlclient library
  • The path to search for libmysqlclient library

Here is how you go about it.

To Add mysql.h

1. GCC C Compiler -> Includes -> Include paths(-l) then click + and add path to your mysql.h In my case it was /usr/include/mysql

enter image description here

To add mysqlclient library and search path to where mysqlclient library see steps 3 and 4.

2. GCC C Linker -> Libraries -> Libraries(-l) then click + and add mysqlcient

enter image description here

3. GCC C Linker -> Libraries -> Library search path (-L) then click + and add search path to mysqlcient. In my case it was /usr/lib64/mysql because I am using a 64 bit Linux OS and a 64 bit MySQL Database.

Otherwise, if you are using a 32 bit Linux OS, you may find that it is found at /usr/lib/mysql

enter image description here

How do you beta test an iphone app?

In 2014 along with iOS 8 and XCode 6 apple introduced Beta Testing of iOS App using iTunes Connect.

You can upload your build to iTunes connect and invite testers using their mail id's. You can invite up to 2000 external testers using just their email address. And they can install the beta app through TestFlight

Why can't C# interfaces contain fields?

Beginning with C# 8.0, an interface may define a default implementation for members, including properties. Defining a default implementation for a property in an interface is rare because interfaces may not define instance data fields.

interface IEmployee
    string Name

    int Counter

public class Employee : IEmployee
    public static int numberOfEmployees;

    private string _name;
    public string Name  // read-write instance property
        get => _name;
        set => _name = value;

    private int _counter;
    public int Counter  // read-only instance property
        get => _counter;

    // constructor
    public Employee() => _counter = ++numberOfEmployees;

How to pick element inside iframe using document.getElementById

(this is to add to the chosen answer)

Make sure the iframe is loaded before you


Otherwise, your getElementById will be null.

PS: Can't comment, still low reputation to comment, but this is a follow-up on the chosen answer as I've spent some good debugging time trying to figure out I should force the iframe load before selecting the inner-iframe element.

Play sound file in a web-page in the background

<audio src="/music/good_enough.mp3" autoplay>
<p>If you are reading this, it is because your browser does not support the audio element.     </p>
<embed src="/music/good_enough.mp3" width="180" height="90" hidden="true" />

Works for me just fine.

How to run SQL in shell script

Maybe it's too late for answering but, there's a working code:

sqlplus -s "/ as sysdba" << EOF
    select (select instance_name from v\$instance) as DB_NAME,
      from dba_data_files
     order by 2;

How do I divide so I get a decimal value?

Check this out:,5.0/docs/api/java/math/BigDecimal.html#divideAndRemainder%28java.math.BigDecimal%29

You just need to wrap your int or long variable in a BigDecimal object, then invoke the divideAndRemainder method on it. The returned array will contain the quotient and the remainder (in that order).

Could not complete the operation due to error 80020101. IE

Switch off compatibility view if you use IE9.

How to include a font .ttf using CSS?

Did you try format?

@font-face {
  font-family: 'The name of the Font Family Here';
  src: URL('font.ttf') format('truetype');

Read this article:

Also, might depend on browser as well.

Input text dialog Android

How about this EXAMPLE? It seems straightforward.

final EditText txtUrl = new EditText(this);

// Set the default text to a link of the Queen

new AlertDialog.Builder(this)
  .setTitle("Moustachify Link")
  .setMessage("Paste in the link of an image to moustachify!")
  .setPositiveButton("Moustachify", new DialogInterface.OnClickListener() {
    public void onClick(DialogInterface dialog, int whichButton) {
      String url = txtUrl.getText().toString();
      moustachify(null, url);
  .setNegativeButton("Cancel", new DialogInterface.OnClickListener() {
    public void onClick(DialogInterface dialog, int whichButton) {

Programmatically set image to UIImageView with Xcode 6.1/Swift

You just need to drag and drop an ImageView, create the outlet action, link it, and provide an image (Xcode is going to look in your assets folder for the name you provided (here: "toronto"))

In yourProject/ViewController.swift

import UIKit

class ViewController: UIViewController {

    @IBOutlet weak var imgView: UIImageView!

    override func viewDidLoad() {

        imgView.image = UIImage(named: "toronto")

Push eclipse project to GitHub with EGit

The key lies in when you create the project in eclipse.

First step, you create the Java project in eclipse. Right click on the project and choose Team > Share>Git.

In the Configure Git Repository dialog, ensure that you select the option to create the Repository in the parent folder of the project.. enter image description here Then you can push to github.

N.B: Eclipse will give you a warning about putting git repositories in your workspace. So when you create your project, set your project directory outside the default workspace.

How to change the blue highlight color of a UITableViewCell?

Zonble has already provided an excellent answer. I thought it may be useful to include a short code snippet for adding a UIView to the tableview cell that will present as the selected background view.

cell = [[[UITableViewCell alloc] initWithFrame:CGRectZero reuseIdentifier:CellIdentifier] autorelease];

    UIView *selectionColor = [[UIView alloc] init];
    selectionColor.backgroundColor = [UIColor colorWithRed:(245/255.0) green:(245/255.0) blue:(245/255.0) alpha:1];
    cell.selectedBackgroundView = selectionColor;
  • cell is my UITableViewCell
  • I created a UIView and set its background color using RGB colours (light gray)
  • I then set the cell selectedBackgroundView to be the UIView that I created with my chosen background colour

This worked well for me. Thanks for the tip Zonble.

Python constructors and __init__

There is no notion of method overloading in Python. But you can achieve a similar effect by specifying optional and keyword arguments

Is there a way to make text unselectable on an HTML page?

Images can be selected too.

There are limits to using JavaScript to deselect text, as it might happen even in places where you want to select. To ensure a rich and successful career, steer clear of all requirements that need ability to influence or manage the browser beyond the ordinary... unless, of course, they are paying you extremely well.

How to reload current page in ReactJS?

Since React eventually boils down to plain old JavaScript, you can really place it anywhere! For instance, you could place it on a componentDidMount() in a React class.

For you edit, you may want to try something like this:

class Component extends React.Component {
  constructor(props) {
    this.onAddBucket = this.onAddBucket.bind(this);
  componentWillMount() {
      buckets: {},
  componentDidMount() {
  onAddBucket() {
    let self = this;
    let getToken = localStorage.getItem('myToken');
    var apiBaseUrl = "...";
    let input = {
      "name" :  this.state.fields["bucket_name"]
    axios.defaults.headers.common['Authorization'] = getToken;'...',input)
    .then(function (response) {
      if ( == 200) {
          buckets: this.state.buckets.concat(,
      } else {
    .catch(function (error) {
  render() {
    return (

How do you decrease navbar height in Bootstrap 3?

Minder Saini's example above almost works, but the .navbar-brand needs to be reduced as well.

A working example (using it on my own site) with Bootstrap 3.3.4:

.navbar-nav > li > a, .navbar-brand {
    padding-top:5px !important; padding-bottom:0 !important;
    height: 30px;
.navbar {min-height:30px !important;}

Edit for Mobile... To make this example work on mobile as well, you have to change the styling of the navbar toggle like so

.navbar-toggle {
     padding: 0 0;
     margin-top: 7px;
     margin-bottom: 0;