Programs & Examples On #Collision

The intersection of one or more objects or concepts, such as communications packets or function names. For questions about collision detection (in computer graphics) use [tag:collision-detection] instead.

Likelihood of collision using most significant bits of a UUID in Java

According to the documentation, the static method UUID.randomUUID() generates a type 4 UUID.

This means that six bits are used for some type information and the remaining 122 bits are assigned randomly.

The six non-random bits are distributed with four in the most significant half of the UUID and two in the least significant half. So the most significant half of your UUID contains 60 bits of randomness, which means you on average need to generate 2^30 UUIDs to get a collision (compared to 2^61 for the full UUID).

So I would say that you are rather safe. Note, however that this is absolutely not true for other types of UUIDs, as Carl Seleborg mentions.

Incidentally, you would be slightly better off by using the least significant half of the UUID (or just generating a random long using SecureRandom).

Warning: "continue" targeting switch is equivalent to "break". Did you mean to use "continue 2"?

I've got the same problem when I run composer install
I solve it by doing in composer directory php composer.phar self-update and then in my project directory composer update

Check if returned value is not null and if so assign it, in one line, with one method call

Same principle as Loki's answer but shorter. Just keep in mind that shorter doesn't automatically mean better.

dinner = Optional.ofNullable(cage.getChicken())
  .orElse(getFreerangeChicken());

Note: This usage of Optional is explicitly discouraged by the architects of the JDK and the designers of the Optional feature. You are allocating a fresh object and immediately throwing it away every time. But on the other hand it can be quite readable.

VBA Excel 2-Dimensional Arrays

Here's A generic VBA Array To Range function that writes an array to the sheet in a single 'hit' to the sheet. This is much faster than writing the data into the sheet one cell at a time in loops for the rows and columns... However, there's some housekeeping to do, as you must specify the size of the target range correctly.

This 'housekeeping' looks like a lot of work and it's probably rather slow: but this is 'last mile' code to write to the sheet, and everything is faster than writing to the worksheet. Or at least, so much faster that it's effectively instantaneous, compared with a read or write to the worksheet, even in VBA, and you should do everything you possibly can in code before you hit the sheet.

A major component of this is error-trapping that I used to see turning up everywhere . I hate repetitive coding: I've coded it all here, and - hopefully - you'll never have to write it again.

A VBA 'Array to Range' function

Public Sub ArrayToRange(rngTarget As Excel.Range, InputArray As Variant)
' Write an array to an Excel range in a single 'hit' to the sheet
' InputArray must be a 2-Dimensional structure of the form Variant(Rows, Columns)

' The target range is resized automatically to the dimensions of the array, with
' the top left cell used as the start point.

' This subroutine saves repetitive coding for a common VBA and Excel task.

' If you think you won't need the code that works around common errors (long strings
' and objects in the array, etc) then feel free to comment them out.

On Error Resume Next

'
' Author: Nigel Heffernan
' HTTP://Excellerando.blogspot.com
'
' This code is in te public domain: take care to mark it clearly, and segregate
' it from proprietary code if you intend to assert intellectual property rights
' or impose commercial confidentiality restrictions on that proprietary code

Dim rngOutput As Excel.Range

Dim iRowCount   As Long
Dim iColCount   As Long
Dim iRow        As Long
Dim iCol        As Long
Dim arrTemp     As Variant
Dim iDimensions As Integer

Dim iRowOffset  As Long
Dim iColOffset  As Long
Dim iStart      As Long


Application.EnableEvents = False
If rngTarget.Cells.Count > 1 Then
    rngTarget.ClearContents
End If
Application.EnableEvents = True

If IsEmpty(InputArray) Then
    Exit Sub
End If


If TypeName(InputArray) = "Range" Then
    InputArray = InputArray.Value
End If

' Is it actually an array? IsArray is sadly broken so...
If Not InStr(TypeName(InputArray), "(") Then
    rngTarget.Cells(1, 1).Value2 = InputArray
    Exit Sub
End If


iDimensions = ArrayDimensions(InputArray)

If iDimensions < 1 Then

    rngTarget.Value = CStr(InputArray)

ElseIf iDimensions = 1 Then

    iRowCount = UBound(InputArray) - LBound(InputArray)
    iStart = LBound(InputArray)
    iColCount = 1

    If iRowCount > (655354 - rngTarget.Row) Then
        iRowCount = 655354 + iStart - rngTarget.Row
        ReDim Preserve InputArray(iStart To iRowCount)
    End If

    iRowCount = UBound(InputArray) - LBound(InputArray)
    iColCount = 1

    ' It's a vector. Yes, I asked for a 2-Dimensional array. But I'm feeling generous.
    ' By convention, a vector is presented in Excel as an arry of 1 to n rows and 1 column.
    ReDim arrTemp(LBound(InputArray, 1) To UBound(InputArray, 1), 1 To 1)
    For iRow = LBound(InputArray, 1) To UBound(InputArray, 1)
        arrTemp(iRow, 1) = InputArray(iRow)
    Next

    With rngTarget.Worksheet
        Set rngOutput = .Range(rngTarget.Cells(1, 1), rngTarget.Cells(iRowCount + 1, iColCount))
        rngOutput.Value2 = arrTemp
        Set rngTarget = rngOutput
    End With

    Erase arrTemp

ElseIf iDimensions = 2 Then

    iRowCount = UBound(InputArray, 1) - LBound(InputArray, 1)
    iColCount = UBound(InputArray, 2) - LBound(InputArray, 2)

    iStart = LBound(InputArray, 1)

    If iRowCount > (65534 - rngTarget.Row) Then
        iRowCount = 65534 - rngTarget.Row
        InputArray = ArrayTranspose(InputArray)
        ReDim Preserve InputArray(LBound(InputArray, 1) To UBound(InputArray, 1), iStart To iRowCount)
        InputArray = ArrayTranspose(InputArray)
    End If


    iStart = LBound(InputArray, 2)
    If iColCount > (254 - rngTarget.Column) Then
        ReDim Preserve InputArray(LBound(InputArray, 1) To UBound(InputArray, 1), iStart To iColCount)
    End If



    With rngTarget.Worksheet

        Set rngOutput = .Range(rngTarget.Cells(1, 1), rngTarget.Cells(iRowCount + 1, iColCount + 1))

        Err.Clear
        Application.EnableEvents = False
        rngOutput.Value2 = InputArray
        Application.EnableEvents = True

        If Err.Number <> 0 Then
            For iRow = LBound(InputArray, 1) To UBound(InputArray, 1)
                For iCol = LBound(InputArray, 2) To UBound(InputArray, 2)
                    If IsNumeric(InputArray(iRow, iCol)) Then
                        ' no action
                    Else
                        InputArray(iRow, iCol) = "" & InputArray(iRow, iCol)
                        InputArray(iRow, iCol) = Trim(InputArray(iRow, iCol))
                    End If
                Next iCol
            Next iRow
            Err.Clear
            rngOutput.Formula = InputArray
        End If 'err<>0

        If Err <> 0 Then
            For iRow = LBound(InputArray, 1) To UBound(InputArray, 1)
                For iCol = LBound(InputArray, 2) To UBound(InputArray, 2)
                    If IsNumeric(InputArray(iRow, iCol)) Then
                        ' no action
                    Else
                        If Left(InputArray(iRow, iCol), 1) = "=" Then
                            InputArray(iRow, iCol) = "'" & InputArray(iRow, iCol)
                        End If
                        If Left(InputArray(iRow, iCol), 1) = "+" Then
                            InputArray(iRow, iCol) = "'" & InputArray(iRow, iCol)
                        End If
                        If Left(InputArray(iRow, iCol), 1) = "*" Then
                            InputArray(iRow, iCol) = "'" & InputArray(iRow, iCol)
                        End If
                    End If
                Next iCol
            Next iRow
            Err.Clear
            rngOutput.Value2 = InputArray
        End If 'err<>0

        If Err <> 0 Then
            For iRow = LBound(InputArray, 1) To UBound(InputArray, 1)
                For iCol = LBound(InputArray, 2) To UBound(InputArray, 2)

                    If IsObject(InputArray(iRow, iCol)) Then
                        InputArray(iRow, iCol) = "[OBJECT] " & TypeName(InputArray(iRow, iCol))
                    ElseIf IsArray(InputArray(iRow, iCol)) Then
                        InputArray(iRow, iCol) = Split(InputArray(iRow, iCol), ",")
                    ElseIf IsNumeric(InputArray(iRow, iCol)) Then
                        ' no action
                    Else
                        InputArray(iRow, iCol) = "" & InputArray(iRow, iCol)
                        If Len(InputArray(iRow, iCol)) > 255 Then
                            ' Block-write operations fail on strings exceeding 255 chars. You *have*
                            ' to go back and check, and write this masterpiece one cell at a time...
                            InputArray(iRow, iCol) = Left(Trim(InputArray(iRow, iCol)), 255)
                        End If
                    End If
                Next iCol
            Next iRow
            Err.Clear
            rngOutput.Text = InputArray
        End If 'err<>0

        If Err <> 0 Then
            Application.ScreenUpdating = False
            Application.Calculation = xlCalculationManual
            iRowOffset = LBound(InputArray, 1) - 1
            iColOffset = LBound(InputArray, 2) - 1
            For iRow = 1 To iRowCount
                If iRow Mod 100 = 0 Then
                    Application.StatusBar = "Filling range... " & CInt(100# * iRow / iRowCount) & "%"
                End If
                For iCol = 1 To iColCount
                    rngOutput.Cells(iRow, iCol) = InputArray(iRow + iRowOffset, iCol + iColOffset)
                Next iCol
            Next iRow
            Application.StatusBar = False
            Application.ScreenUpdating = True


        End If 'err<>0


        Set rngTarget = rngOutput   ' resizes the range This is useful, *most* of the time

    End With

End If

End Sub

You will need the source for ArrayDimensions:

This API declaration is required in the module header:

Private Declare Sub CopyMemory Lib "kernel32" Alias "RtlMoveMemory" _
                   (Destination As Any, _
                    Source As Any, _
                    ByVal Length As Long)

...And here's the function itself:

Private Function ArrayDimensions(arr As Variant) As Integer
  '-----------------------------------------------------------------
  ' will return:
  ' -1 if not an array
  ' 0  if an un-dimmed array
  ' 1  or more indicating the number of dimensions of a dimmed array
  '-----------------------------------------------------------------


  ' Retrieved from Chris Rae's VBA Code Archive - http://chrisrae.com/vba
  ' Code written by Chris Rae, 25/5/00

  ' Originally published by R. B. Smissaert.
  ' Additional credits to Bob Phillips, Rick Rothstein, and Thomas Eyde on VB2TheMax

  Dim ptr As Long
  Dim vType As Integer

  Const VT_BYREF = &H4000&

  'get the real VarType of the argument
  'this is similar to VarType(), but returns also the VT_BYREF bit
  CopyMemory vType, arr, 2

  'exit if not an array
  If (vType And vbArray) = 0 Then
    ArrayDimensions = -1
    Exit Function
  End If

  'get the address of the SAFEARRAY descriptor
  'this is stored in the second half of the
  'Variant parameter that has received the array
  CopyMemory ptr, ByVal VarPtr(arr) + 8, 4

  'see whether the routine was passed a Variant
  'that contains an array, rather than directly an array
  'in the former case ptr already points to the SA structure.
  'Thanks to Monte Hansen for this fix

  If (vType And VT_BYREF) Then
    ' ptr is a pointer to a pointer
    CopyMemory ptr, ByVal ptr, 4
  End If

  'get the address of the SAFEARRAY structure
  'this is stored in the descriptor

  'get the first word of the SAFEARRAY structure
  'which holds the number of dimensions
  '...but first check that saAddr is non-zero, otherwise
  'this routine bombs when the array is uninitialized

  If ptr Then
    CopyMemory ArrayDimensions, ByVal ptr, 2
  End If

End Function

Also: I would advise you to keep that declaration private. If you must make it a public Sub in another module, insert the Option Private Module statement in the module header. You really don't want your users calling any function with CopyMemoryoperations and pointer arithmetic.

Differences between utf8 and latin1

In latin1 each character is exactly one byte long. In utf8 a character can consist of more than one byte. Consequently utf8 has more characters than latin1 (and the characters they do have in common aren't necessarily represented by the same byte/bytesequence).

What is the effect of encoding an image in base64?

It will be approximately 37% larger:

Very roughly, the final size of Base64-encoded binary data is equal to 1.37 times the original data size

Source: http://en.wikipedia.org/wiki/Base64

How do you remove duplicates from a list whilst preserving order?

Eliminating the duplicate values in a sequence, but preserve the order of the remaining items. Use of general purpose generator function.

# for hashable sequence
def remove_duplicates(items):
    seen = set()
    for item in items:
        if item not in seen:
            yield item
            seen.add(item)

a = [1, 5, 2, 1, 9, 1, 5, 10]
list(remove_duplicates(a))
# [1, 5, 2, 9, 10]



# for unhashable sequence
def remove_duplicates(items, key=None):
    seen = set()
    for item in items:
        val = item if key is None else key(item)
        if val not in seen:
            yield item
            seen.add(val)

a = [ {'x': 1, 'y': 2}, {'x': 1, 'y': 3}, {'x': 1, 'y': 2}, {'x': 2, 'y': 4}]
list(remove_duplicates(a, key=lambda d: (d['x'],d['y'])))
# [{'x': 1, 'y': 2}, {'x': 1, 'y': 3}, {'x': 2, 'y': 4}]

PHP array() to javascript array()

To convert you PHP array to JS , you can do it like this :

var js_array = [<?php echo '"'.implode('","',  $disabledDaysRange ).'"' ?>];

or using JSON_ENCODE :

var js_array =<?php echo json_encode($disabledDaysRange );?>;

Example without JSON_ENCODE:

<script type='text/javascript'>
    <?php
    $php_array = array('abc','def','ghi');
    ?>
    var js_array = [<?php echo '"'.implode('","', $php_array).'"' ?>];
    alert(js_array[0]);
</script>

Example with JSON_ENCODE :

<script type='text/javascript'>
    <?php
    $php_array = array('abc','def','ghi');
    ?>
    var js_array =<?php echo json_encode($disabledDaysRange );?>;
    alert(js_array[0]);
</script>

Are there such things as variables within an Excel formula?

Now you can use the function LET to declare variables within Excel formulas. This function is available since Jun 2020 for Microsoft 365 users.

Given your example, the formula will be:

=LET(MyFunc,VLOOKUP(A1,B:B,1,0), IF(MyFunc > 10, MyFunc - 10, MyFunc ) )

The 1st argument is the variable name and the 2nd argument is the function or range. You can add more pairs of arguments variable, function/range.

After adding the variables, the last argument will be your formula of interest -- calling the variables you just created.

For more information, please access the Microsoft webpage here.

How to make a button redirect to another page using jQuery or just Javascript

In your html, you can add data attribute to your button:

<button type="submit" class="mybtn" data-target="/search.html">Search</button>

Then you can use jQuery to change the url:

$('.mybtn').on('click', function(event) {
    event.preventDefault(); 
    var url = $(this).data('target');
    location.replace(url);
});

Hope this helps

How to remove the hash from window.location (URL) with JavaScript without page refresh?

To remove the hash, you may try using this function

function remove_hash_from_url()
{
    var uri = window.location.toString();
    if (uri.indexOf("#") > 0) {
        var clean_uri = uri.substring(0, uri.indexOf("#"));
        window.history.replaceState({}, document.title, clean_uri);
    }
}

How to edit an Android app?

You would need to decompile the apk as Davis suggested, can use tools such as apkTool , then if you need to change the source code you would need other tools to do that.

You would then need to put the apk back together and sign it, if you don't have the original key used to sign the apk this means the new apk will have a different signature.

If the developer employed any obfuscation or other techniques to protect the app then it gets more complicated.

In short its a pretty complex and technical procedure, so if the developer is really just out of reach, its better to wait until he is in reach. And ask for the source code next time.

Calling a Variable from another Class

I would suggest to use a variable instead of a public field:

public class Variables
{
   private static string name = "";

   public static string Name
   { 
        get { return name; }
        set { name = value; }

   }
}

From another class, you call your variable like this:

public class Main
{
    public void DoSomething()
    {
         string var = Variables.Name;
    }
}

Accessing certain pixel RGB value in openCV

A piece of code is easier for people who have such problem. I share my code and you can use it directly. Please note that OpenCV store pixels as BGR.

cv::Mat vImage_; 

if(src_)
{
    cv::Vec3f vec_;

    for(int i = 0; i < vHeight_; i++)
        for(int j = 0; j < vWidth_; j++)
        {
            vec_ = cv::Vec3f((*src_)[0]/255.0, (*src_)[1]/255.0, (*src_)[2]/255.0);//Please note that OpenCV store pixels as BGR.

            vImage_.at<cv::Vec3f>(vHeight_-1-i, j) = vec_;

            ++src_;
        }
}

if(! vImage_.data ) // Check for invalid input
    printf("failed to read image by OpenCV.");
else
{
    cv::namedWindow( windowName_, CV_WINDOW_AUTOSIZE);
    cv::imshow( windowName_, vImage_); // Show the image.
}

ValueError: unsupported pickle protocol: 3, python2 pickle can not load the file dumped by python 3 pickle?

Pickle uses different protocols to convert your data to a binary stream.

You must specify in python 3 a protocol lower than 3 in order to be able to load the data in python 2. You can specify the protocol parameter when invoking pickle.dump.

How do I get whole and fractional parts from double in JSP/Java?

double value = 3.25;
double fractionalPart = value % 1;
double integralPart = value - fractionalPart;

Difference between size and length methods?

length variable:

In Java, array (not java.util.Array) is a predefined class in the language itself. To find the elements of an array, designers used length variable (length is a field member in the predefined class). They must have given length() itself to have uniformity in Java; but did not. The reason is by performance, executing length variable is speedier than calling the method length(). It is like comparing two strings with == and equals(). equals() is a method call which takes more time than executing == operator.

size() method:

It is used to find the number of elements present in collection classes. It is defined in java.util.Collection interface.

How can I specify working directory for popen

subprocess.Popen takes a cwd argument to set the Current Working Directory; you'll also want to escape your backslashes ('d:\\test\\local'), or use r'd:\test\local' so that the backslashes aren't interpreted as escape sequences by Python. The way you have it written, the \t part will be translated to a tab.

So, your new line should look like:

subprocess.Popen(r'c:\mytool\tool.exe', cwd=r'd:\test\local')

To use your Python script path as cwd, import os and define cwd using this:

os.path.dirname(os.path.realpath(__file__)) 

Regex - how to match everything except a particular pattern

If you want to match a word A in a string and not to match a word B. For example: If you have a text:

1. I have a two pets - dog and a cat
2. I have a pet - dog

If you want to search for lines of text that HAVE a dog for a pet and DOESN'T have cat you can use this regular expression:

^(?=.*?\bdog\b)((?!cat).)*$

It will find only second line:

2. I have a pet - dog

outline on only one border

The great thing about HTML/CSS is that there's usually more than one way to achieve the same effect. Here's another solution that does what you want:

<nav id="menu1">
    <ul>
        <li><a href="#">Menu Link 1</a></li>
        <li><a href="#">Menu Link 2</a></li>
    </ul>
</nav>

nav {
    background:#666;
    margin:1em;
    padding:.5em 0;
}
nav ul {
    border-top:1px dashed #fff;
    list-style:none;
    padding:.5em;
}
nav ul li {
    display:inline-block;
}
nav ul li a {
    color:#fff;
}

http://jsfiddle.net/10basetom/uCX3G/1/

How to change JAVA.HOME for Eclipse/ANT

If you are using Eclipse, try the following:

  • Right click on the ant build file, then choose "Properties".
  • Click on the "Run/Debug Settings", then click on the launch configuration file. You should be able to edit it then.
  • After you click "Edit", you should see a new window with a "Properties" tab which will show you a list of Ant build properties. There is a "java.home" property in the list. Make sure it refers to the correct path.

SQL Server "AFTER INSERT" trigger doesn't see the just-inserted row

You can reverse the logic. Instead of deleting an invalid row after it has been inserted, write an INSTEAD OF trigger to insert only if you verify the row is valid.

CREATE TRIGGER mytrigger ON sometable
INSTEAD OF INSERT
AS BEGIN
  DECLARE @isnum TINYINT;

  SELECT @isnum = ISNUMERIC(somefield) FROM inserted;

  IF (@isnum = 1)
    INSERT INTO sometable SELECT * FROM inserted;
  ELSE
    RAISERROR('somefield must be numeric', 16, 1)
      WITH SETERROR;
END

If your application doesn't want to handle errors (as Joel says is the case in his app), then don't RAISERROR. Just make the trigger silently not do an insert that isn't valid.

I ran this on SQL Server Express 2005 and it works. Note that INSTEAD OF triggers do not cause recursion if you insert into the same table for which the trigger is defined.

Convert char* to string C++

char *charPtr = "test string";
cout << charPtr << endl;

string str = charPtr;
cout << str << endl;

Get Insert Statement for existing row in MySQL

There is a quite easy and useful solution for creating an INSERT Statement for editing without the need to export SQL with just Copy & Paste (Clipboard):

  • Select the row in a query result window of MySQL Workbench, probably even several rows. I use this even if the row does contain different data than I want to insert in my script or when the goal is to create a prepared statement with ? placeholders.
  • Paste the copied row which is in your clipboard now into the same table (query results list is an editor in workbench) into the last free row.
  • Press "Apply" and a windows opens showing you the INSERT statement - DO NOT EXECUTE
  • Copy the SQL from the window to your clipboard
  • CANCEL the execution, thus not changing the database but keeping the SQL in your clipboard.
  • Paste the SQL wherever you want and edit it as you like, like e.g. inserting ? placeholders

How do I add a library project to Android Studio?

I have just found an easier way (rather than writing directly into the .gradle files).

This is for Android Studio 1.1.0.

  1. Menu File -> New Module...:

    Import Existing Project

    Click on "Import Existing Project".

  2. Select the desired library and the desired module.

  3. Click finish. Android Studio will import the library into your project. It will sync gradle files.

  4. Add the imported module to your project's dependencies.

    Right click on the app folder -> Open Module settings -> go to the dependencies tab -> Click on the '+' button -> click on Module Dependency.

    The library module will be then added to the project's dependencies.

    Add library module

  5. ???

  6. Profit

How to implement onBackPressed() in Fragments?

Ok guys I finally found out a good solution.

In your onCreate() in your activity housing your fragments add a backstack change listener like so:

    fragmentManager.addOnBackStackChangedListener(new FragmentManager.OnBackStackChangedListener() {
        @Override
        public void onBackStackChanged() {
            List<Fragment> f = fragmentManager.getFragments();
            //List<Fragment> f only returns one value
            Fragment frag = f.get(0);
            currentFragment = frag.getClass().getSimpleName();
        }
    });

(Also adding my fragmenManager is declared in the activities O Now every time you change fragment the current fragment String will become the name of the current fragment. Then in the activities onBackPressed() you can control the actions of your back button as so:

    @Override
    public void onBackPressed() {

    switch (currentFragment) {
        case "FragmentOne":
            // your code here
            return;
        case "FragmentTwo":
            // your code here
            return;
        default:
            fragmentManager.popBackStack();
            // default action for any other fragment (return to previous)
    }

}

I can confirm that this method works for me.

Change the Theme in Jupyter Notebook?

My complete solution:

1) Get Dark Reader on chrome which will not only get you a great Dark Theme for Jupyter but also for every single website you'd like (you can play with the different filters. I use Dynamic).

2) Paste those lines of code in your notebook so the legends and axes become visible:

from jupyterthemes import jtplot
jtplot.style(theme='monokai', context='notebook', ticks=True, grid=False)

You're all set for a disco coding night !

nginx- duplicate default server error

In my case junk files from editor caused the problem. I had a config as below:

#...
http {
 # ...
 include ../sites/*;
}

In the ../sites directory initially I had a default.config file. However, by mistake I saved duplicate files as default.config.save and default.config.save.1. Removing them resolved the issue.

How can I remove Nan from list Python/NumPy

import numpy as np

mylist = [3, 4, 5, np.nan]
l = [x for x in mylist if ~np.isnan(x)]

This should remove all NaN. Of course, I assume that it is not a string here but actual NaN (np.nan).

Create array of regex matches

Java makes regex too complicated and it does not follow the perl-style. Take a look at MentaRegex to see how you can accomplish that in a single line of Java code:

String[] matches = match("aa11bb22", "/(\\d+)/g" ); // => ["11", "22"]

Java Array, Finding Duplicates

public static ArrayList<Integer> duplicate(final int[] zipcodelist) {

    HashSet<Integer> hs = new HashSet<>();
    ArrayList<Integer> al = new ArrayList<>();
    for(int element: zipcodelist) {
        if(hs.add(element)==false) {
            al.add(element);
        }   
    }
    return al;
}

Laravel where on relationship object

The correct syntax to do this on your relations is:

Event::whereHas('participants', function ($query) {
    return $query->where('IDUser', '=', 1);
})->get();

Read more at https://laravel.com/docs/5.8/eloquent-relationships#eager-loading

Does Python have a package/module management system?

Poetry is what you're looking for. It takes care of dependency management, virtual environments, running.

Batch script to delete files

Lets say you saved your software onto your desktop.
if you want to remove an entire folder like an uninstaller program you could use this.

cd C:\Users\User\Detsktop\
rd /s /q SOFTWARE

this will delete the entire folder called software and all of its files and subfolders

Make Sure You Delete The Correct Folder Cause This Does Not Have A Yes / No Option

Converting HTML to PDF using PHP?

If you wish to create a pdf from php, pdflib will help you (as some others suggested).

Else, if you want to convert an HTML page to PDF via PHP, you'll find a little trouble outta here.. For 3 years I've been trying to do it as best as I can.

So, the options I know are:

DOMPDF : php class that wraps the html and builds the pdf. Works good, customizable (if you know php), based on pdflib, if I remember right it takes even some CSS. Bad news: slow when the html is big or complex.

HTML2PS: same as DOMPDF, but this one converts first to a .ps (ghostscript) file, then, to whatever format you need (pdf, jpg, png). For me is little better than dompdf, but has the same speed problem.. but, better compatibility with CSS.

Those two are php classes, but if you can install some software on the server, and access it throught passthru() or system(), give a look to these too:

wkhtmltopdf: based on webkit (safari's wrapper), is really fast and powerful.. seems like this is the best one (atm) for converting html pages to pdf on the fly; taking only 2 seconds for a 3 page xHTML document with CSS2. It is a recent project, anyway, the google.code page is often updated.

htmldoc : This one is a tank, it never really stops/crashes.. the project looks dead since 2007, but anyway if you don't need CSS compatibility this can be nice for you.

Open a URL in a new tab (and not a new window)

Whether to open the URL in a new tab or a new window, is actually controlled by the user's browser preferences. There is no way to override it in JavaScript.

window.open() behaves differently depending on how it is being used. If it is called as a direct result of a user action, let us say a button click, it should work fine and open a new tab (or window):

const button = document.querySelector('#openTab');

// add click event listener
button.addEventListener('click', () => {
    // open a new tab
    const tab = window.open('https://attacomsian.com', '_blank');
});

However, if you try to open a new tab from an AJAX request callback, the browser will block it as it was not a direct user action.

To bypass the popup blocker and open a new tab from a callback, here is a little hack:

const button = document.querySelector('#openTab');

// add click event listener
button.addEventListener('click', () => {

    // open an empty window
    const tab = window.open('about:blank');

    // make an API call
    fetch('/api/validate')
        .then(res => res.json())
        .then(json => {

            // TODO: do something with JSON response

            // update the actual URL
            tab.location = 'https://attacomsian.com';
            tab.focus();
        })
        .catch(err => {
            // close the empty window
            tab.close();
        });
});

Change Orientation of Bluestack : portrait/landscape mode

New version 4.100.x.xxxx

Try this:

More Apps > Android Settings > Accessibility > Auto-rotate screen = Enabled

enter image description here

How to delete duplicates on a MySQL table?

this removes duplicates in place, without making a new table

ALTER IGNORE TABLE `table_name` ADD UNIQUE (title, SID)

note: only works well if index fits in memory

How do I call a SQL Server stored procedure from PowerShell?

Here is a function I use to execute sql commands. You just have to change $sqlCommand.CommandText to the name of your sproc and $SqlCommand.CommandType to CommandType.StoredProcedure.

function execute-Sql{
    param($server, $db, $sql )
    $sqlConnection = new-object System.Data.SqlClient.SqlConnection
    $sqlConnection.ConnectionString = 'server=' + $server + ';integrated security=TRUE;database=' + $db 
    $sqlConnection.Open()
    $sqlCommand = new-object System.Data.SqlClient.SqlCommand
    $sqlCommand.CommandTimeout = 120
    $sqlCommand.Connection = $sqlConnection
    $sqlCommand.CommandText= $sql
    $text = $sql.Substring(0, 50)
    Write-Progress -Activity "Executing SQL" -Status "Executing SQL => $text..."
    Write-Host "Executing SQL => $text..."
    $result = $sqlCommand.ExecuteNonQuery()
    $sqlConnection.Close()
}

Node.js Port 3000 already in use but it actually isn't?

I've seen the same thing and tried all the suggestions above without success. Here are steps that resolve it for me: - turn off wifi - npm start (this should work) - turn on wifi

I'm not exactly sure what the root issue is but that resolved it for me.

BOOLEAN or TINYINT confusion

As of MySql 5.1 version reference

BIT(M) =  approximately (M+7)/8 bytes, 
BIT(1) =  (1+7)/8 = 1 bytes (8 bits)

=========================================================================

TINYINT(1) take 8 bits.

https://dev.mysql.com/doc/refman/5.7/en/storage-requirements.html#data-types-storage-reqs-numeric

When is JavaScript synchronous?

Is synchronous on all cases.

Example of blocking thread with Promises:

  const test = () => new Promise((result, reject) => {
    const time = new Date().getTime() + (3 * 1000);

    console.info('Test start...');

    while (new Date().getTime() < time) {
      // Waiting...
    }

    console.info('Test finish...');
  });

  test()
    .then(() => console.info('Then'))
    .finally(() => console.info('Finally'));

  console.info('Finish!');

The output will be:

Test start...
Test finish...
Finish!

What are the Ruby File.open modes and options?

In Ruby IO module documentation, I suppose.

Mode |  Meaning
-----+--------------------------------------------------------
"r"  |  Read-only, starts at beginning of file  (default mode).
-----+--------------------------------------------------------
"r+" |  Read-write, starts at beginning of file.
-----+--------------------------------------------------------
"w"  |  Write-only, truncates existing file
     |  to zero length or creates a new file for writing.
-----+--------------------------------------------------------
"w+" |  Read-write, truncates existing file to zero length
     |  or creates a new file for reading and writing.
-----+--------------------------------------------------------
"a"  |  Write-only, starts at end of file if file exists,
     |  otherwise creates a new file for writing.
-----+--------------------------------------------------------
"a+" |  Read-write, starts at end of file if file exists,
     |  otherwise creates a new file for reading and
     |  writing.
-----+--------------------------------------------------------
"b"  |  Binary file mode (may appear with
     |  any of the key letters listed above).
     |  Suppresses EOL <-> CRLF conversion on Windows. And
     |  sets external encoding to ASCII-8BIT unless explicitly
     |  specified.
-----+--------------------------------------------------------
"t"  |  Text file mode (may appear with
     |  any of the key letters listed above except "b").

Angular - How to apply [ngStyle] conditions

[ngStyle]="{'opacity': is_mail_sent ? '0.5' : '1' }"

How do I get the day of week given a date?

If you have dates as a string, it might be easier to do it using pandas' Timestamp

import pandas as pd
df = pd.Timestamp("2019-04-12")
print(df.dayofweek, df.weekday_name)

Output:

4 Friday

JQuery .hasClass for multiple values in an if statement

You just had some messed up parentheses in your 2nd attempt.

var $html = $("html");

if ($html.hasClass('m320') || $html.hasClass('m768')) {

  // do stuff 

}

CSS to stop text wrapping under image

Wrap a div around the image and the span and add the following to CSS like so:

HTML

        <li id="CN2787">
          <div><img class="fav_star" src="images/fav.png"></div>
          <div><span>Text, text and more text</span></div>
        </li>

CSS

            #CN2787 > div { 
                display: inline-block;
                vertical-align: top;
            }

            #CN2787 > div:first-of-type {
                width: 35%;
            }

            #CN2787 > div:last-of-type {
                width: 65%;
            }

LESS

        #CN2787 {
            > div { 
                display: inline-block;
                vertical-align: top;
            }

            > div:first-of-type {
                width: 35%;
            }
            > div:last-of-type {
                width: 65%;
            }
        }

Valid characters in a Java class name

Further to previous answers its worth noting that:

  1. Java allows any Unicode currency symbol in symbol names, so the following will all work:

$var1 £var2 €var3

I believe the usage of currency symbols originates in C/C++, where variables added to your code by the compiler conventionally started with '$'. An obvious example in Java is the names of '.class' files for inner classes, which by convention have the format 'Outer$Inner.class'

  1. Many C# and C++ programmers adopt the convention of placing 'I' in front of interfaces (aka pure virtual classes in C++). This is not required, and hence not done, in Java because the implements keyword makes it very clear when something is an interface.

Compare:

class Employee : public IPayable //C++

with

class Employee : IPayable //C#

and

class Employee implements Payable //Java

  1. Many projects use the convention of placing an underscore in front of field names, so that they can readily be distinguished from local variables and parameters e.g.

private double _salary;

A tiny minority place the underscore after the field name e.g.

private double salary_;

Select first 4 rows of a data.frame in R

For at DataFrame one can simply type

head(data, num=10L)

to get the first 10 for example.

For a data.frame one can simply type

head(data, 10)

to get the first 10.

Check if option is selected with jQuery, if not select a default

Look at the selectedIndex of the select element. BTW, that's a plain ol' DOM thing, not JQuery-specific.

mongo - couldn't connect to server 127.0.0.1:27017

@shakthydoss answer worked fine once, but after the second issue the .lock wasn't there, I just created a blank one, and it worked fine. So check if yours ain't there.

If you are using the command line:

cd /var/lib/mongodb

ls

"ls" will list all the files in the folder, if the mongod.lock isn't there, then:

sudo touch mongod.lock

Finally run command.

mongod –-repair

sudo service mongod start 

Mongo service should be working fine.

HQL ERROR: Path expected for join

select u from UserGroup ug inner join ug.user u 
where ug.group_id = :groupId 
order by u.lastname

As a named query:

@NamedQuery(
  name = "User.findByGroupId",
  query =
    "SELECT u FROM UserGroup ug " +
    "INNER JOIN ug.user u WHERE ug.group_id = :groupId ORDER BY u.lastname"
)

Use paths in the HQL statement, from one entity to the other. See the Hibernate documentation on HQL and joins for details.

Selecting distinct values from a JSON

I would use one Object and one Array, if you want to save some cycle:

var lookup = {};
var items = json.DATA;
var result = [];

for (var item, i = 0; item = items[i++];) {
  var name = item.name;

  if (!(name in lookup)) {
    lookup[name] = 1;
    result.push(name);
  }
}

In this way you're basically avoiding the indexOf / inArray call, and you will get an Array that can be iterate quicker than iterating object's properties – also because in the second case you need to check hasOwnProperty.

Of course if you're fine with just an Object you can avoid the check and the result.push at all, and in case get the array using Object.keys(lookup), but it won't be faster than that.

Load and execution sequence of a web page?

If you're asking this because you want to speed up your web site, check out Yahoo's page on Best Practices for Speeding Up Your Web Site. It has a lot of best practices for speeding up your web site.

ImportError: No module named pip

Run

curl https://bootstrap.pypa.io/get-pip.py -o get-pip.py

Then run the following command in the folder where you downloaded: get-pip.py

python get-pip.py

Java: how do I initialize an array size if it's unknown?

I agree that a data structure like a List is the best way to go:

List<Integer> values = new ArrayList<Integer>();
Scanner in = new Scanner(System.in);
int value;
int numValues = 0;
do {
    value = in.nextInt();
    values.add(value);
} while (value >= 1) && (value <= 100);

Or you can just allocate an array of a max size and load values into it:

int maxValues = 100;
int [] values = new int[maxValues];
Scanner in = new Scanner(System.in);
int value;
int numValues = 0;
do {
    value = in.nextInt();
    values[numValues++] = value;
} while (value >= 1) && (value <= 100) && (numValues < maxValues);

In Node.js, how do I "include" functions from my other files?

Udo G. said:

  • The eval() can't be used inside a function and must be called inside the global scope otherwise no functions or variables will be accessible (i.e. you can't create a include() utility function or something like that).

He's right, but there's a way to affect the global scope from a function. Improving his example:

function include(file_) {
    with (global) {
        eval(fs.readFileSync(file_) + '');
    };
};

include('somefile_with_some_declarations.js');

// the declarations are now accessible here.

Hope, that helps.

How to have PHP display errors? (I've added ini_set and error_reporting, but just gives 500 on errors)

To people using Codeigniter (i'm on C3):

The index.php file overwrite php.ini configuration, so on index.php file, line 68:

case 'development':
        error_reporting(-1);
        ini_set('display_errors', 1);
    break;

You can change this option to set what you need. Here's the complete list:

1   E_ERROR
2   E_WARNING
4   E_PARSE
8   E_NOTICE
16  E_CORE_ERROR
32  E_CORE_WARNING
64  E_COMPILE_ERROR
128 E_COMPILE_WARNING
256 E_USER_ERROR
512 E_USER_WARNING
1024    E_USER_NOTICE
6143    E_ALL
2048    E_STRICT
4096    E_RECOVERABLE_ERROR

Hope it helps.

C# Passing Function as Argument

public static T Runner<T>(Func<T> funcToRun)
{
    //Do stuff before running function as normal
    return funcToRun();
}

Usage:

var ReturnValue = Runner(() => GetUser(99));

Enabling/Disabling Microsoft Virtual WiFi Miniport

You go to your "device manager", find your "network adapters", then should find the virtual wifi adapter, then right click it and enable it. After that, you start your cmd with admin privileges, then try:

netsh wlan start hostednetwork

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

By design, Django templates cannot call into arbitrary Python code. This is a security and safety feature for environments where designers write templates, and it also prevents business logic migrating into templates.

If you want to do this, you can switch to using Jinja2 templates (http://jinja.pocoo.org/docs/), or any other templating system you like that supports this. No other part of django will be affected by the templates you use, because it is intentionally a one-way process. You could even use many different template systems in the same project if you wanted.

IntelliJ how to zoom in / out

Update: This answer is old. Intellij has since added actions to adjust font size. Check out Wilker's answer for assigning the new actions to keymaps.

Try Ctrl+Mouse Wheel which can be enabled under File > Settings... > Editor > General : Change font size (Zoom) with Ctrl+Mouse Wheel

How does Python's super() work with multiple inheritance?

class First(object):
  def __init__(self, a):
    print "first", a
    super(First, self).__init__(20)

class Second(object):
  def __init__(self, a):
    print "second", a
    super(Second, self).__init__()

class Third(First, Second):
  def __init__(self):
    super(Third, self).__init__(10)
    print "that's it"

t = Third()

Output is

first 10
second 20
that's it

Call to Third() locates the init defined in Third. And call to super in that routine invokes init defined in First. MRO=[First, Second]. Now call to super in init defined in First will continue searching MRO and find init defined in Second, and any call to super will hit the default object init. I hope this example clarifies the concept.

If you don't call super from First. The chain stops and you will get the following output.

first 10
that's it

Table with fixed header and fixed column on pure css

I've made some changes in in jsfiddle. This might be what you're trying to do.

http://jsfiddle.net/C8Dtf/81/

I have hardcoded the titles like so:

<table id="left_table" class="freeze_table">
    <tr class='tblTitle'>
         <th>Title 1</th>
         <th>Title 2</th>
    </tr>
</table>

And I added some styles as well.

.tblTitle{
   position:absolute;
    top:0px;
    margin-bottom:30px;
    background:lightblue;
}
td, th{
    padding:5px;
    height:40px;
    width:40px;
    font-size:14px;
}

Hope this is what you want :)

Check whether a value exists in JSON object

This example puts your JSON into proper format and does an existence check. I use jquery for convenience.

http://jsfiddle.net/nXFxC/

<!-- HTML -->
<span id="test">Hello</span><br>
<span id="test2">Hello</span>

//Javascript

$(document).ready(function(){
    var JSON = {"animals":[{"name":"cat"}, {"name":"dog"}]};

if(JSON.animals[1].name){      
$("#test").html("It exists");
}
if(!JSON.animals[2]){       
$("#test2").html("It doesn't exist");
}
});

PostgreSQL 'NOT IN' and subquery

When using NOT IN you should ensure that none of the values are NULL:

SELECT mac, creation_date 
FROM logs 
WHERE logs_type_id=11
AND mac NOT IN (
    SELECT mac
    FROM consols
    WHERE mac IS NOT NULL -- add this
)

DateTime's representation in milliseconds?

SELECT CAST(DATEDIFF(S, '1970-01-01', SYSDATETIME()) AS BIGINT) * 1000

This does not give you full precision, but DATEDIFF(MS... causes overflow. If seconds are good enough, this should do it.

Set a request header in JavaScript

W3C Spec on setrequestheader.

The brief points:

If the request header had already been set, then the new value MUST be concatenated to the existing value using a U+002C COMMA followed by a U+0020 SPACE for separation.

UAs MAY give the User-Agent header an initial value, but MUST allow authors to append values to it.

However - After searching through the framework XHR in jQuery they don't allow you to change the User-Agent or Referer headers. The closest thing:

// Set header so the called script knows that it's an XMLHttpRequest
xhr.setRequestHeader("X-Requested-With", "XMLHttpRequest");

I'm leaning towards the opinion that what you want to do is being denied by a security policy in FF - if you want to pass some custom Referer type header you could always do:

xhr.setRequestHeader('X-Alt-Referer', 'http://www.google.com');

How to sort a list of strings numerically?

You could pass a function to the key parameter to the .sort method. With this, the system will sort by key(x) instead of x.

list1.sort(key=int)

BTW, to convert the list to integers permanently, use the map function

list1 = list(map(int, list1))   # you don't need to call list() in Python 2.x

or list comprehension

list1 = [int(x) for x in list1]

CSS Printing: Avoiding cut-in-half DIVs between pages?

@media print{
    /* use your css selector */    
    div{ 
        page-break-inside: avoid;
    }
}

For all new browser this solution works. See caniuse.com/#search=page-break-inside

Is <div style="width: ;height: ;background: "> CSS?

Yes, it is called Inline CSS, Here you styling the div using some height, width, and background.

Here the example:

<div style="width:50px;height:50px;background color:red">

You can achieve same using Internal or External CSS

2.Internal CSS:

  <head>
    <style>
    div {
    height:50px;
    width:50px;
    background-color:red;
    foreground-color:white;
    }
    </style>
  </head>
  <body>
    <div></div>
  </body>

3.External CSS:

<head>
<link rel="stylesheet" type="text/css" href="style.css">
</head>
<body>
<div></div>
</body>

style.css /external css file/

 div {
        height:50px;
        width:50px;
        background-color:red;
    }

Download all stock symbol list of a market

There does not seem to be a straight-forward way provided by Google or Yahoo finance portals to download the full list of tickers. One possible 'brute force' way to get it is to query their APIs for every possible combinations of letters and save only those that return valid results. As silly as it may seem there are people who actually do it (ie. check this: http://investexcel.net/all-yahoo-finance-stock-tickers/).

You can download lists of symbols from exchanges directly or 3rd party websites as suggested by @Eugene S and @Capn Sparrow, however if you intend to use it to fetch data from Google or Yahoo, you have to sometimes use prefixes or suffixes to make sure that you're getting the correct data. This is because some symbols may repeat between exchanges, so Google and Yahoo prepend or append exchange codes to the tickers in order to distinguish between them. Here's an example:

Company:  Vodafone
------------------
LSE symbol:    VOD
 in Google:    LON:VOD
 in Yahoo:     VOD.L
NASDAQ symbol: VOD
 in Google:    NASDAQ:VOD
 in Yahoo:     VOD

How do I serialize a Python dictionary into a string, and then back to a dictionary?

It depends on what you're wanting to use it for. If you're just trying to save it, you should use pickle (or, if you’re using CPython 2.x, cPickle, which is faster).

>>> import pickle
>>> pickle.dumps({'foo': 'bar'})
b'\x80\x03}q\x00X\x03\x00\x00\x00fooq\x01X\x03\x00\x00\x00barq\x02s.'
>>> pickle.loads(_)
{'foo': 'bar'}

If you want it to be readable, you could use json:

>>> import json
>>> json.dumps({'foo': 'bar'})
'{"foo": "bar"}'
>>> json.loads(_)
{'foo': 'bar'}

json is, however, very limited in what it will support, while pickle can be used for arbitrary objects (if it doesn't work automatically, the class can define __getstate__ to specify precisely how it should be pickled).

>>> pickle.dumps(object())
b'\x80\x03cbuiltins\nobject\nq\x00)\x81q\x01.'
>>> json.dumps(object())
Traceback (most recent call last):
  ...
TypeError: <object object at 0x7fa0348230c0> is not JSON serializable

Get distance between two points in canvas

To find the distance between 2 points, you need to find the length of the hypotenuse in a right angle triangle with a width and height equal to the vertical and horizontal distance:

Math.hypot(endX - startX, endY - startY)

How to activate "Share" button in android app?

Create a button with an id share and add the following code snippet.

share.setOnClickListener(new View.OnClickListener() {             
    @Override
    public void onClick(View v) {

        Intent sharingIntent = new Intent(android.content.Intent.ACTION_SEND);
        sharingIntent.setType("text/plain");
        String shareBody = "Your body here";
        String shareSub = "Your subject here";
        sharingIntent.putExtra(android.content.Intent.EXTRA_SUBJECT, shareSub);
        sharingIntent.putExtra(android.content.Intent.EXTRA_TEXT, shareBody);
        startActivity(Intent.createChooser(sharingIntent, "Share using"));
    }
});

The above code snippet will open the share chooser on share button click action. However, note...The share code snippet might not output very good results using emulator. For actual results, run the code snippet on android device to get the real results.

Xampp localhost/dashboard

If you want to display directory than edit htdocs/index.php file

Below code is display all directory in table

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<title>Welcome to Nims Server</title>
<meta http-equiv="Content-Type" content="text/html; charset=UTF-8" />
<link href="server/style.css" rel="stylesheet" type="text/css" />
</head>
<body>
<!-- START PAGE SOURCE -->
<div id="wrap">
  <div id="top">
    <h1 id="sitename">Nims <em>Server</em> Directory list</h1>
    <div id="searchbar">
      <form action="#">
        <div id="searchfield">
          <input type="text" name="keyword" class="keyword" />
          <input class="searchbutton" type="image" src="server/images/searchgo.gif"  alt="search" />
        </div>
      </form>
    </div>
  </div>

<div class="background">
<div class="transbox">
<table width="100%" border="0" cellspacing="3" cellpadding="5" style="border:0px solid #333333;background: #F9F9F9;"> 
<tr>
<?php
//echo md5("saketbook007");

//File functuion DIR is used here.
$d = dir($_SERVER['DOCUMENT_ROOT']); 
$i=-1;
//Loop start with read function
while ($entry = $d->read()) {
if($entry == "." || $entry ==".."){
}else{
?>
<td  class="site" width="33%"><a href="<?php echo $entry;?>" ><?php echo ucfirst($entry); ?></a></td>  
<?php 
}
if($i%3 == 0){
echo "</tr><tr>";
}
$i++;
}?>
</tr> 
</table>

<?php $d->close();
?> 

</div>
</div>
</div>
   </div></div></body>
</html>

Style:

@import url("fontface.css");
* {
    padding:0;
    margin:0;
}
.clear {
    clear:both;
}

body {
    background:url(images/bg.jpg) repeat;
    font-family:"Palatino Linotype", "Book Antiqua", Palatino, serif;
    color:#212713;
}
#wrap {
    width:1300px;
    margin:auto;
}

#sitename {
    font: normal 46px chunk;
    color:#1b2502;
    text-shadow:#5d7a17 1px 1px 1px;
    display:block;
    padding:45px 0 0 0;
    width:60%;
    float:left;
}
#searchbar {
    width:39%;
    float:right;
}
#sitename em {
    font-family:"Palatino Linotype", "Book Antiqua", Palatino, serif;
}
#top {
    height:145px;
}
img {

    width:90%;
    height:250px;
    padding:10px;
    border:1px solid #000;
    margin:0 0 0 50px;
}


.post h2 a {
    color:#656f42;
    text-decoration:none;
}
#searchbar {
    padding:55px 0 0 0;
}
#searchfield {
    background:url(images/searchbar.gif) no-repeat;
    width:239px;
    height:35px;
    float:right;
}
#searchfield .keyword {
    width:170px;
    background:transparent;
    border:none;
    padding:8px 0 0 10px;
    color:#fff;
    display:block;
    float:left;
}
#searchfield .searchbutton {
    display:block;
    float:left;
    margin:7px 0 0 5px;
}

div.background
{
  background:url(h.jpg) repeat-x;
  border: 2px solid black;

  width:99%;
}
div.transbox
{
  margin: 15px;
  background-color: #ffffff;

  border: 1px solid black;
  opacity:0.8;
  filter:alpha(opacity=60); /* For IE8 and earlier */
  height:500px;
}

.site{

border:1px solid #CCC; 
}

.site a{text-decoration:none;font-weight:bold; color:#000; line-height:2}
.site:hover{background:#000; border:1px solid #03C;}
.site:hover a{color:#FFF}

Output : enter image description here

Datagridview full row selection but get single cell value

If you want to get the contents of selected cell; you need the index of row and cell.

int rowindex = dataGridView1.CurrentCell.RowIndex;
int columnindex = dataGridView1.CurrentCell.ColumnIndex; 

dataGridView1.Rows[rowindex].Cells[columnindex].Value.ToString();

displaying a string on the textview when clicking a button in android

Check this:

hello.setOnClickListener(new OnClickListener() {
    @Override
    public void onClick(View paramView) {
        text.setText("hello");
    }
});

Change DataGrid cell colour based on values

To do this in the Code Behind (VB.NET)

Dim txtCol As New DataGridTextColumn

Dim style As New Style(GetType(TextBlock))
Dim tri As New Trigger With {.Property = TextBlock.TextProperty, .Value = "John"}
tri.Setters.Add(New Setter With {.Property = TextBlock.BackgroundProperty, .Value = Brushes.Green})
style.Triggers.Add(tri)

xtCol.ElementStyle = style

How to share data between different threads In C# using AOP?

When you start a thread you are executing a method of some chosen class. All attributes of that class are visible.

  Worker myWorker = new Worker( /* arguments */ );

  Thread myThread = new Thread(new ThreadStart(myWorker.doWork));

  myThread.Start();

Your thread is now in the doWork() method and can see any atrributes of myWorker, which may themselves be other objects. Now you just need to be careful to deal with the cases of having several threads all hitting those attributes at the same time.

Why is a "GRANT USAGE" created the first time I grant a user privileges?

In addition mysql passwords when not using the IDENTIFIED BY clause, may be blank values, if non-blank, they may be encrypted. But yes USAGE is used to modify an account by granting simple resource limiters such as MAX_QUERIES_PER_HOUR, again this can be specified by also using the WITH clause, in conjuction with GRANT USAGE(no privileges added) or GRANT ALL, you can also specify GRANT USAGE at the global level, database level, table level,etc....

Android and setting alpha for (image) view alpha

I am not sure about the XML but you can do it by code in the following way.

ImageView myImageView = new ImageView(this);
myImageView.setAlpha(xxx);

In pre-API 11:

  • range is from 0 to 255 (inclusive), 0 being transparent and 255 being opaque.

In API 11+:

  • range is from 0f to 1f (inclusive), 0f being transparent and 1f being opaque.

How do I do a simple 'Find and Replace" in MsSQL?

The following will find and replace a string in every database (excluding system databases) on every table on the instance you are connected to:

Simply change 'Search String' to whatever you seek and 'Replace String' with whatever you want to replace it with.

--Getting all the databases and making a cursor
DECLARE db_cursor CURSOR FOR  
SELECT name 
FROM master.dbo.sysdatabases 
WHERE name NOT IN ('master','model','msdb','tempdb')  -- exclude these databases

DECLARE @databaseName nvarchar(1000)
--opening the cursor to move over the databases in this instance
OPEN db_cursor
FETCH NEXT FROM db_cursor INTO @databaseName   

WHILE @@FETCH_STATUS = 0   
BEGIN
    PRINT @databaseName
    --Setting up temp table for the results of our search
    DECLARE @Results TABLE(TableName nvarchar(370), RealColumnName nvarchar(370), ColumnName nvarchar(370), ColumnValue nvarchar(3630))

    SET NOCOUNT ON

    DECLARE @SearchStr nvarchar(100), @ReplaceStr nvarchar(100), @SearchStr2 nvarchar(110)
    SET @SearchStr = 'Search String'
    SET @ReplaceStr = 'Replace String'
    SET @SearchStr2 = QUOTENAME('%' + @SearchStr + '%','''')

    DECLARE @TableName nvarchar(256), @ColumnName nvarchar(128)
    SET  @TableName = ''

    --Looping over all the tables in the database
    WHILE @TableName IS NOT NULL
    BEGIN
        DECLARE @SQL nvarchar(2000)
        SET @ColumnName = ''
        DECLARE @result NVARCHAR(256)
        SET @SQL = 'USE ' + @databaseName + '
            SELECT @result = MIN(QUOTENAME(TABLE_SCHEMA) + ''.'' + QUOTENAME(TABLE_NAME))
            FROM    [' + @databaseName + '].INFORMATION_SCHEMA.TABLES
            WHERE       TABLE_TYPE = ''BASE TABLE'' AND TABLE_CATALOG = ''' + @databaseName + '''
                AND QUOTENAME(TABLE_SCHEMA) + ''.'' + QUOTENAME(TABLE_NAME) > ''' + @TableName + '''
                AND OBJECTPROPERTY(
                        OBJECT_ID(
                            QUOTENAME(TABLE_SCHEMA) + ''.'' + QUOTENAME(TABLE_NAME)
                                ), ''IsMSShipped''
                                ) = 0'
        EXEC master..sp_executesql @SQL, N'@result nvarchar(256) out', @result out

        SET @TableName = @result
        PRINT @TableName

        WHILE (@TableName IS NOT NULL) AND (@ColumnName IS NOT NULL)
        BEGIN
            DECLARE @ColumnResult NVARCHAR(256)
            SET @SQL = '
                SELECT @ColumnResult = MIN(QUOTENAME(COLUMN_NAME))
                FROM    [' + @databaseName + '].INFORMATION_SCHEMA.COLUMNS
                WHERE       TABLE_SCHEMA    = PARSENAME(''[' + @databaseName + '].' + @TableName + ''', 2)
                    AND TABLE_NAME  = PARSENAME(''[' + @databaseName + '].' + @TableName + ''', 1)
                    AND DATA_TYPE IN (''char'', ''varchar'', ''nchar'', ''nvarchar'')
                    AND TABLE_CATALOG = ''' + @databaseName + '''
                    AND QUOTENAME(COLUMN_NAME) > ''' + @ColumnName + ''''
            PRINT @SQL
            EXEC master..sp_executesql @SQL, N'@ColumnResult nvarchar(256) out', @ColumnResult out
            SET @ColumnName = @ColumnResult 

            PRINT @ColumnName

            IF @ColumnName IS NOT NULL
            BEGIN
                INSERT INTO @Results
                EXEC
                (
                    'USE ' + @databaseName + '
                    SELECT ''' + @TableName + ''',''' + @ColumnName + ''',''' + @TableName + '.' + @ColumnName + ''', LEFT(' + @ColumnName + ', 3630) 
                    FROM ' + @TableName + ' (NOLOCK) ' +
                    ' WHERE ' + @ColumnName + ' LIKE ' + @SearchStr2
                )
            END
        END
    END

    --Declaring another temporary table
    DECLARE @time_to_update TABLE(TableName nvarchar(370), RealColumnName nvarchar(370))

    INSERT INTO @time_to_update
    SELECT TableName, RealColumnName FROM @Results GROUP BY TableName, RealColumnName

    DECLARE @MyCursor CURSOR;
    BEGIN
        DECLARE @t nvarchar(370)
        DECLARE @c nvarchar(370)
        --Looping over the search results   
        SET @MyCursor = CURSOR FOR
        SELECT TableName, RealColumnName FROM @time_to_update GROUP BY TableName, RealColumnName

        --Getting my variables from the first item
        OPEN @MyCursor 
        FETCH NEXT FROM @MyCursor 
        INTO @t, @c

        WHILE @@FETCH_STATUS = 0
        BEGIN
            -- Updating the old values with the new value
            DECLARE @sqlCommand varchar(1000)
            SET @sqlCommand = '
                USE ' + @databaseName + '
                UPDATE [' + @databaseName + '].' + @t + ' SET ' + @c + ' = REPLACE(' + @c + ', ''' + @SearchStr + ''', ''' + @ReplaceStr + ''') 
                WHERE ' + @c + ' LIKE ''' + @SearchStr2 + ''''
            PRINT @sqlCommand
            BEGIN TRY
                EXEC (@sqlCommand)
            END TRY
            BEGIN CATCH
                PRINT ERROR_MESSAGE()
            END CATCH

            --Getting next row values
            FETCH NEXT FROM @MyCursor 
            INTO @t, @c 
        END;

        CLOSE @MyCursor ;
        DEALLOCATE @MyCursor;
    END;

    DELETE FROM @time_to_update
    DELETE FROM @Results

    FETCH NEXT FROM db_cursor INTO @databaseName
END   

CLOSE db_cursor   
DEALLOCATE db_cursor

Note: this isn't ideal, nor is it optimized

Add common prefix to all cells in Excel

  1. Enter the function of = CONCATENATE("X",A1) in one cell other than A say D
  2. Click the Cell D1, and drag the fill handle across the range that you want to fill.All the cells should have been added the specific prefix text.

You can see the changes made to the repective cells.

How do I limit the number of returned items?

models.Post.find({published: true}, {sort: {'date': -1}, limit: 20}, function(err, posts) {
 // `posts` with sorted length of 20
});

Random state (Pseudo-random number) in Scikit learn

sklearn.model_selection.train_test_split(*arrays, **options)[source]

Split arrays or matrices into random train and test subsets

Parameters: ... 
    random_state : int, RandomState instance or None, optional (default=None)

If int, random_state is the seed used by the random number generator; If RandomState instance, random_state is the random number generator; If None, the random number generator is the RandomState instance used by np.random. source: http://scikit-learn.org/stable/modules/generated/sklearn.model_selection.train_test_split.html

'''Regarding the random state, it is used in many randomized algorithms in sklearn to determine the random seed passed to the pseudo-random number generator. Therefore, it does not govern any aspect of the algorithm's behavior. As a consequence, random state values which performed well in the validation set do not correspond to those which would perform well in a new, unseen test set. Indeed, depending on the algorithm, you might see completely different results by just changing the ordering of training samples.''' source: https://stats.stackexchange.com/questions/263999/is-random-state-a-parameter-to-tune

Adding values to Arraylist

in the first you don't define the type that will be held and linked within your arraylist construct

this is the preferred method to do so, you define the type of list and the ide will handle the rest

in the third one you will better just define List for shorter code

How do you use MySQL's source command to import large files in windows

C:\xampp\mysql\bin\mysql -u root -p testdatabase < C:\Users\Juan\Desktop\databasebackup.sql

That worked for me to import 400MB file into my database.

$apply already in progress error

We can use setTimeout function in such cases.

console.log('primary task');

setTimeout(function() {
  
  console.log('secondary task');

}, 0);

This will make sure that secondary task will be executed when execution of primary task is finished.

How to set up a cron job to run an executable every hour?

Did you mean the executable fails to run , if invoked from any other directory? This is rather a bug on the executable. One potential reason could be the executable requires some shared libraires from the installed folder. You may check environment variable LD_LIBRARY_PATH

Scanning Java annotations at runtime

The Classloader API doesn't have an "enumerate" method, because class loading is an "on-demand" activity -- you usually have thousands of classes in your classpath, only a fraction of which will ever be needed (the rt.jar alone is 48MB nowadays!).

So, even if you could enumerate all classes, this would be very time- and memory-consuming.

The simple approach is to list the concerned classes in a setup file (xml or whatever suits your fancy); if you want to do this automatically, restrict yourself to one JAR or one class directory.

"You tried to execute a query that does not include the specified aggregate function"

GROUP BY can be selected from Total row in query design view in MS Access.
If Total row not shown in design view (as in my case). You can go to SQL View and add GROUP By fname etc. Then Total row will automatically show in design view.
You have to select as Expression in this row for calculated fields.

Why does Boolean.ToString output "True" and not "true"

How is it not compatible with C#? Boolean.Parse and Boolean.TryParse is case insensitive and the parsing is done by comparing the value to Boolean.TrueString or Boolean.FalseString which are "True" and "False".

EDIT: When looking at the Boolean.ToString method in reflector it turns out that the strings are hard coded so the ToString method is as follows:

public override string ToString()
{
    if (!this)
    {
        return "False";
    }
    return "True";
}

What does <> mean in excel?

It means "not equal to" (as in, the values in cells E37-N37 are not equal to "", or in other words, they are not empty.)

Test if a vector contains a given element

You can use the %in% operator:

vec <- c(1, 2, 3, 4, 5)
1 %in% vec # true
10 %in% vec # false

java.lang.IllegalStateException: Error processing condition on org.springframework.boot.autoconfigure.jdbc.JndiDataSourceAutoConfiguration

In my case I had created a SB app from the SB Initializer and had included a fair number of deps in it to other things. I went in and commented out the refs to them in the build.gradle file and so was left with:

implementation 'org.springframework.boot:spring-boot-starter-hateoas'
compileOnly 'org.projectlombok:lombok'
developmentOnly 'org.springframework.boot:spring-boot-devtools'
runtimeOnly 'org.hsqldb:hsqldb'
runtimeOnly 'org.postgresql:postgresql'
annotationProcessor 'org.springframework.boot:spring-boot-configuration-processor'
annotationProcessor 'org.projectlombok:lombok'
testImplementation 'org.springframework.boot:spring-boot-starter-test'
testImplementation 'org.springframework.restdocs:spring-restdocs-mockmvc'

as deps. Then my bare-bones SB app was able to build and get running successfully. As I go to try to do things that may need those commented-out libs I will add them back and see what breaks.

The most accurate way to check JS object's type?

Accepted answer is correct, but I like to define this little utility in most projects I build.

var types = {
   'get': function(prop) {
      return Object.prototype.toString.call(prop);
   },
   'null': '[object Null]',
   'object': '[object Object]',
   'array': '[object Array]',
   'string': '[object String]',
   'boolean': '[object Boolean]',
   'number': '[object Number]',
   'date': '[object Date]',
}

Used like this:

if(types.get(prop) == types.number) {

}

If you're using angular you can even have it cleanly injected:

angular.constant('types', types);

Vim: insert the same characters across multiple lines

:%s/^/vendor_/

or am I missing something?

Show Current Location and Nearby Places and Route between two places using Google Maps API in Android

Lots of answers so far, which are all excellent pointers to API's and tutorials. One thing I'd like to add is that I work out how far the markers are from my location using something like:

float distance = (float) loc.distanceTo(loc2);

Hope this helps refine the detail for your problem. It returns a rough estimate of distance (in m) between points, and is useful for getting rid of POI that might be too far away - good to declutter your map?

How to remove element from array in forEach loop?

Although Xotic750's answer provides several good points and possible solutions, sometimes simple is better.

You know the array being iterated on is being mutated in the iteration itself (i.e. removing an item => index changes), thus the simplest logic is to go backwards in an old fashioned for (à la C language):

_x000D_
_x000D_
let arr = ['a', 'a', 'b', 'c', 'b', 'a', 'a'];_x000D_
_x000D_
for (let i = arr.length - 1; i >= 0; i--) {_x000D_
  if (arr[i] === 'a') {_x000D_
    arr.splice(i, 1);_x000D_
  }_x000D_
}_x000D_
_x000D_
document.body.append(arr.join());
_x000D_
_x000D_
_x000D_

If you really think about it, a forEach is just syntactic sugar for a for loop... So if it's not helping you, just please stop breaking your head against it.

pip connection failure: cannot fetch index base URL http://pypi.python.org/simple/

I had a similar problem, but in my case I was getting the error:

Downloading/unpacking bencode
  Cannot fetch index base URL http://c.pypi.python.org/simple/
  Could not find any downloads that satisfy the requirement bencode
No distributions at all found for bencode
Storing complete log in /home/andrew/.pip/pip.log

In my case I was able to fix the error by editing ~/.pip/pip.conf and changing http://c.pypi.python.org/simple/ to http://pypi.python.org/simple and then pip worked fine again.

Passing an array by reference in C?

also be aware that if you are creating a array within a method, you cannot return it. If you return a pointer to it, it would have been removed from the stack when the function returns. you must allocate memory onto the heap and return a pointer to that. eg.

//this is bad
char* getname()
{
  char name[100];
  return name;
}

//this is better
char* getname()
{
  char *name = malloc(100);
  return name;
  //remember to free(name)
}

builder for HashMap

A simple map builder is trivial to write:

public class Maps {

    public static <Q,W> MapWrapper<Q,W> map(Q q, W w) {
        return new MapWrapper<Q, W>(q, w);
    }

    public static final class MapWrapper<Q,W> {
        private final HashMap<Q,W> map;
        public MapWrapper(Q q, W w) {
            map = new HashMap<Q, W>();
            map.put(q, w);
        }
        public MapWrapper<Q,W> map(Q q, W w) {
            map.put(q, w);
            return this;
        }
        public Map<Q,W> getMap() {
            return map;
        }
    }

    public static void main(String[] args) {
        Map<String, Integer> map = Maps.map("one", 1).map("two", 2).map("three", 3).getMap();
        for (Map.Entry<String, Integer> entry : map.entrySet()) {
            System.out.println(entry.getKey() + " = " + entry.getValue());
        }
    }
}

How to view the list of compile errors in IntelliJ?

I think this comes closest to what you wish:

(From IntelliJ IDEA Q&A for Eclipse Users):

enter image description here

The above can be combined with a recently introduced option in Compiler settings to get a view very similar to that of Eclipse.

Things to do:

  1. Switch to 'Problems' view in the Project pane:

    enter image description here

  2. Enable the setting to compile the project automatically :

    enter image description here

  3. Finally, look at the Problems view:

    enter image description here

Here is a comparison of what the same project (with a compilation error) looks like in Intellij IDEA 13.xx and Eclipse Kepler:

enter image description here

enter image description here

Relevant Links: The maven project shown above : https://github.com/ajorpheus/CompileTimeErrors
FAQ For 'Eclipse Mode' / 'Automatically Compile' a project : http://devnet.jetbrains.com/docs/DOC-1122

How to monitor the memory usage of Node.js?

The built-in process module has a method memoryUsage that offers insight in the memory usage of the current Node.js process. Here is an example from in Node v0.12.2 on a 64-bit system:

$ node --expose-gc
> process.memoryUsage();  // Initial usage
{ rss: 19853312, heapTotal: 9751808, heapUsed: 4535648 }
> gc();                   // Force a GC for the baseline.
undefined
> process.memoryUsage();  // Baseline memory usage.
{ rss: 22269952, heapTotal: 11803648, heapUsed: 4530208 }
> var a = new Array(1e7); // Allocate memory for 10m items in an array
undefined
> process.memoryUsage();  // Memory after allocating so many items
{ rss: 102535168, heapTotal: 91823104, heapUsed: 85246576 }
> a = null;               // Allow the array to be garbage-collected
null
> gc();                   // Force GC (requires node --expose-gc)
undefined
> process.memoryUsage();  // Memory usage after GC
{ rss: 23293952, heapTotal: 11803648, heapUsed: 4528072 }
> process.memoryUsage();  // Memory usage after idling
{ rss: 23293952, heapTotal: 11803648, heapUsed: 4753376 }

In this simple example, you can see that allocating an array of 10M elements consumers approximately 80MB (take a look at heapUsed).
If you look at V8's source code (Array::New, Heap::AllocateRawFixedArray, FixedArray::SizeFor), then you'll see that the memory used by an array is a fixed value plus the length multiplied by the size of a pointer. The latter is 8 bytes on a 64-bit system, which confirms that observed memory difference of 8 x 10 = 80MB makes sense.

JSON Parse File Path

This solution uses an Asynchronous call. It will likely work better than a synchronous solution.

var request = new XMLHttpRequest();
request.open("GET", "../../data/file.json", false);
request.send(null);
request.onreadystatechange = function() {
  if ( request.readyState === 4 && request.status === 200 ) {
    var my_JSON_object = JSON.parse(request.responseText);
    console.log(my_JSON_object);
  }
}

Allow User to input HTML in ASP.NET MVC - ValidateInput or AllowHtml

In my case, the AllowHtml attribute was not working when combined with the OutputCache action filter. This answer solved the problem for me. Hope this helps someone.

Create File If File Does Not Exist

or:

using FileStream fileStream = File.Open(path, FileMode.Append);
using StreamWriter file = new StreamWriter(fileStream);
// ...

jQuery select option elements by value

function select_option(index)
{
    var optwewant;
    for (opts in $('#span_id').children('select'))
    {
        if (opts.value() = index)
        {
            optwewant = opts;
            break;
        }
    }
    alert (optwewant);
}

Format a Go string without printing?

We can custom A new String type via define new Type with Format support.

package main

import (
    "fmt"
    "text/template"
    "strings"
)

type String string
func (s String) Format(data map[string]interface{}) (out string, err error) {
    t := template.Must(template.New("").Parse(string(s)))
    builder := &strings.Builder{}
    if err = t.Execute(builder, data); err != nil {
        return
    }
    out = builder.String()
    return
}


func main() {
    const tmpl = `Hi {{.Name}}!  {{range $i, $r := .Roles}}{{if $i}}, {{end}}{{.}}{{end}}`
    data := map[string]interface{}{
        "Name":     "Bob",
        "Roles":    []string{"dbteam", "uiteam", "tester"},
    }

    s ,_:= String(tmpl).Format(data)
    fmt.Println(s)
}

How do I make an image smaller with CSS?

Here's what I've done:

.resize {
    width: 400px;
    height: auto;
}

.resize {
    width: 300px;
    height: auto;
}

<img class="resize" src="example.jpg"/>

This will keep the image aspect ratio the same.

How to create a vector of user defined size but with no predefined values?

With the constructor:

// create a vector with 20 integer elements
std::vector<int> arr(20);

for(int x = 0; x < 20; ++x)
   arr[x] = x;

Nested select statement in SQL Server

You need to alias the subquery.

SELECT name FROM (SELECT name FROM agentinformation) a  

or to be more explicit

SELECT a.name FROM (SELECT name FROM agentinformation) a  

Using an array as needles in strpos

The below code not only shows how to do it, but also puts it in an easy to use function moving forward. It was written by "jesda". (I found it online)

PHP Code:

<?php
/* strpos that takes an array of values to match against a string
 * note the stupid argument order (to match strpos)
 */
function strpos_arr($haystack, $needle) {
    if(!is_array($needle)) $needle = array($needle);
    foreach($needle as $what) {
        if(($pos = strpos($haystack, $what))!==false) return $pos;
    }
    return false;
}
?>

Usage:

$needle = array('something','nothing');
$haystack = "This is something";
echo strpos_arr($haystack, $needle); // Will echo True

$haystack = "This isn't anything";
echo strpos_arr($haystack, $needle); // Will echo False 

Uncaught SoapFault exception: [HTTP] Error Fetching http headers

Try to set :

default_socket_timeout = 120

in your php.ini file.

java: run a function after a specific number of seconds

Example of using javax.swing.Timer

Timer timer = new Timer(3000, new ActionListener() {
  @Override
  public void actionPerformed(ActionEvent arg0) {
    // Code to be executed
  }
});
timer.setRepeats(false); // Only execute once
timer.start(); // Go go go!

This code will only be executed once, and the execution happens in 3000 ms (3 seconds).

As camickr mentions, you should lookup "How to Use Swing Timers" for a short introduction.

get an element's id

Yes. You can get an element by its ID by calling document.getElementById. It will return an element node if found, and null otherwise:

var x = document.getElementById("elementid");   // Get the element with id="elementid"
x.style.color = "green";                        // Change the color of the element

Redis: Show database size/size for keys

I usually prefer the key sampling method to troubleshoot such scenarios.

redis-cli -p 6379 -n db_number --bigkeys

Eg:-

redis-cli -p 6370 -n 0 --bigkeys

Clean out Eclipse workspace metadata

There is no easy way to remove the "outdated" stuff from an existing workspace. Using the "clean" parameter will not really help, as many of the files you refer to are "free form data", only known to the plugins that are no longer available.

Your best bet is to optimize the re-import, where I would like to point out the following:

  • When creating a new workspace, you can already choose to have some settings being copied from the current to the new workspace.
  • You can export the preferences of the current workspace (using the Export menu) and re-import them in the new workspace.
  • There are lots of recommendations on the Internet to just copy the ${old_workspace}/.metadata/.plugins/org.eclipse.core.runtime/.settings folder from the old to the new workspace. This is surely the fastest way, but it may lead to weird behaviour, because some of your plugins may depend on these settings and on some of the mentioned "free form data" stored elsewhere. (There are even people symlinking these folders over multiple workspaces, but this really requires to use the same plugins on all workspaces.)
  • You may want to consider using more project specific settings than workspace preferences in the future. So for instance all the Java compiler settings can either be set on the workspace level or on the project level. If set on the project level, you can put them under version control and are independent of the workspace.

WPF ListView - detect when selected item is clicked

These are all great suggestions, but if I were you, I would do this in your view model. Within your view model, you can create a relay command that you can then bind to the click event in your item template. To determine if the same item was selected, you can store a reference to your selected item in your view model. I like to use MVVM Light to handle the binding. This makes your project much easier to modify in the future, and allows you to set the binding in Blend.

When all is said and done, your XAML will look like what Sergey suggested. I would avoid using the code behind in your view. I'm going to avoid writing code in this answer, because there is a ton of examples out there.

Here is one: How to use RelayCommand with the MVVM Light framework

If you require an example, please comment, and I will add one.

~Cheers

I said I wasn't going to do an example, but I am. Here you go.

1) In your project, add MVVM Light Libraries Only.

2) Create a class for your view. Generally speaking, you have a view model for each view (view: MainWindow.xaml && viewModel: MainWindowViewModel.cs)

3) Here is the code for the very, very, very basic view model:

All included namespace (if they show up here, I am assuming you already added the reference to them. MVVM Light is in Nuget)

using GalaSoft.MvvmLight;
using GalaSoft.MvvmLight.CommandWpf;
using System;
using System.Collections.Generic;
using System.Collections.ObjectModel;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

Now add a basic public class:

/// <summary>
/// Very basic model for example
/// </summary>
public class BasicModel 
{
    public string Id { get; set; }
    public string Text { get; set; }

    /// <summary>
    /// Constructor
    /// </summary>
    /// <param name="text"></param>
    public BasicModel(string text)
    {
        this.Id = Guid.NewGuid().ToString();
        this.Text = text;
    }
}

Now create your viewmodel:

public class MainWindowViewModel : ViewModelBase
{
    public MainWindowViewModel()
    {
        ModelsCollection = new ObservableCollection<BasicModel>(new List<BasicModel>() {
            new BasicModel("Model one")
            , new BasicModel("Model two")
            , new BasicModel("Model three")
        });
    }

    private BasicModel _selectedBasicModel;

    /// <summary>
    /// Stores the selected mode.
    /// </summary>
    /// <remarks>This is just an example, may be different.</remarks>
    public BasicModel SelectedBasicModel 
    {
        get { return _selectedBasicModel; }
        set { Set(() => SelectedBasicModel, ref _selectedBasicModel, value); }
    }

    private ObservableCollection<BasicModel> _modelsCollection;

    /// <summary>
    /// List to bind to
    /// </summary>
    public ObservableCollection<BasicModel> ModelsCollection
    {
        get { return _modelsCollection; }
        set { Set(() => ModelsCollection, ref _modelsCollection, value); }
    }        
}

In your viewmodel, add a relaycommand. Please note, I made this async and had it pass a parameter.

    private RelayCommand<string> _selectItemRelayCommand;
    /// <summary>
    /// Relay command associated with the selection of an item in the observablecollection
    /// </summary>
    public RelayCommand<string> SelectItemRelayCommand
    {
        get
        {
            if (_selectItemRelayCommand == null)
            {
                _selectItemRelayCommand = new RelayCommand<string>(async (id) =>
                {
                    await selectItem(id);
                });
            }

            return _selectItemRelayCommand;
        }
        set { _selectItemRelayCommand = value; }
    }

    /// <summary>
    /// I went with async in case you sub is a long task, and you don't want to lock you UI
    /// </summary>
    /// <returns></returns>
    private async Task<int> selectItem(string id)
    {
        this.SelectedBasicModel = ModelsCollection.FirstOrDefault(x => x.Id == id);
        Console.WriteLine(String.Concat("You just clicked:", SelectedBasicModel.Text));
        //Do async work

        return await Task.FromResult(1);
    }

In the code behind for you view, create a property for you viewmodel and set the datacontext for your view to the viewmodel (please note, there are other ways to do this, but I am trying to make this a simple example.)

public partial class MainWindow : Window
{
    public MainWindowViewModel MyViewModel { get; set; }
    public MainWindow()
    {
        InitializeComponent();

        MyViewModel = new MainWindowViewModel();
        this.DataContext = MyViewModel;
    }
}

In your XAML, you need to add some namespaces to the top of your code

<Window x:Class="Basic_Binding.MainWindow"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:i="http://schemas.microsoft.com/expression/2010/interactivity"
    xmlns:Custom="clr-namespace:GalaSoft.MvvmLight;assembly=GalaSoft.MvvmLight"
    Title="MainWindow" Height="350" Width="525">

I added "i" and "Custom."

Here is the ListView:

<ListView 
        Grid.Row="0" 
        Grid.Column="0" 
        HorizontalContentAlignment="Stretch"
        ItemsSource="{Binding ModelsCollection}"
        ItemTemplate="{DynamicResource BasicModelDataTemplate}">
    </ListView>

Here is the ItemTemplate for the ListView:

<DataTemplate x:Key="BasicModelDataTemplate">
        <Grid>
            <TextBlock Text="{Binding Text}">
                <i:Interaction.Triggers>
                    <i:EventTrigger EventName="MouseLeftButtonUp">
                        <i:InvokeCommandAction 
                            Command="{Binding DataContext.SelectItemRelayCommand, 
                                RelativeSource={RelativeSource FindAncestor, 
                                        AncestorType={x:Type ItemsControl}}}"
                            CommandParameter="{Binding Id}">                                
                        </i:InvokeCommandAction>
                    </i:EventTrigger>
                </i:Interaction.Triggers>
            </TextBlock>
        </Grid>
    </DataTemplate>

Run your application, and check out the output window. You can use a converter to handle the styling of the selected item.

This may seem really complicated, but it makes life a lot easier down the road when you need to separate your view from your ViewModel (e.g. develop a ViewModel for multiple platforms.) Additionally, it makes working in Blend 10x easier. Once you develop your ViewModel, you can hand it over to a designer who can make it look very artsy :). MVVM Light adds some functionality to make Blend recognize your ViewModel. For the most part, you can do just about everything you want to in the ViewModel to affect the view.

If anyone reads this, I hope you find this helpful. If you have questions, please let me know. I used MVVM Light in this example, but you could do this without MVVM Light.

~Cheers

Cannot assign requested address using ServerSocket.socketBind

I came across this error when copying configurations from one server to another.

I had the old host's hostname in my ${JETTY_BASE}/start.ini jetty.host property. Setting the correct jetty.host property value solved the issue for me.

Hope this helps someone in the future who has to work on multiple servers at once.

How to add Tomcat Server in eclipse

If by mistake, you have deleted your Tomcat Server and Eclipse is not showing more options (Next button will be inactive) then in this case follow the bellow steps:

  1. First remove the two files from the following path:

    • Path : workspace/.metadata/.plugins/org.eclipse.runtime/.settings/
    • And that two files are :

      1. org.eclipse.wst.server.core.prefs
      2. org.eclipse.jst/server.tomcat.core.prefs
    • After deleting/removing the above two files from the workspace, Restart the Eclipse IDE.

    • Change to the Server View, Right Click 'New', Window 'Define a New Server' is shown, --> Select the Apache Folder, choose Tomcat-Version

    • Browse to the unzipped 'Apache-Tomcat folder', choose the second level

    • Now you are able to add/configure your new Tomcat Server. (Now you will see the 'Next' button will become active, and you can then follow the normal instructions)

How can I join multiple SQL tables using the IDs?

You want something more like this:

SELECT TableA.*, TableB.*, TableC.*, TableD.*
FROM TableA
    JOIN TableB
        ON TableB.aID = TableA.aID
    JOIN TableC
        ON TableC.cID = TableB.cID
    JOIN TableD
        ON TableD.dID = TableA.dID
WHERE DATE(TableC.date)=date(now()) 

In your example, you are not actually including TableD. All you have to do is perform another join just like you have done before.

A note: you will notice that I removed many of your parentheses, as they really are not necessary in most of the cases you had them, and only add confusion when trying to read the code. Proper nesting is the best way to make your code readable and separated out.

Why use ICollection and not IEnumerable or List<T> on many-many/one-many relationships?

Responding to your question about List<T>:

List<T> is a class; specifying an interface allows more flexibility of implementation. A better question is "why not IList<T>?"

To answer that question, consider what IList<T> adds to ICollection<T>: integer indexing, which means the items have some arbitrary order, and can be retrieved by reference to that order. This is probably not meaningful in most cases, since items probably need to be ordered differently in different contexts.

Multidimensional arrays in Swift

You are creating an array of three elements and assigning all three to the same thing, which is itself an array of three elements (three Doubles).

When you do the modifications you are modifying the floats in the internal array.

Unbound classpath container in Eclipse

The problem happens when you

  • Import project folders into the eclipse workspace.(when projects use different Jre).
  • Update or Reinstall eclipse
  • Change Jre or Build related Settings.
  • Or by there is a configuration mismatch.

You get two errors for each misconfigured files.

  • The project cannot be built until build path errors are resolved.
  • Unbound classpath container: 'JRE System Library.

If the no. of projects having problem is few:

  1. Select each project and apply Quick fix(Ctrl+1)
  2. Either Replace the project's JRE with default JRE or Specify Alternate JRE (or JDK).

You can do the same by right-click project-->Properties(from context menu)-->Java Build Path-->Libraries-->select current unbound library -->Remove-->Add Libraries-->Jre System library-->select default or alternate Jre.

Or directly choose Build Path-->Add libraries in project's context menu.


But the best way to get rid of such problem when you have many projects is:

EITHER

  1. Open the current workspace (in which your project is) in File Explorer.
  2. Delete all org.eclipse.jdt.core.prefs file present in .settings folder of your imported projects.(Be careful while deleting. Don't delete any files or folders inside .metadata folder.)**
  3. Now,Select the .classpath files of projects (those with errors) and open them in a powerful text editor(such as Notepad++).
  4. Find the line similar to <classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER/org.eclipse.jdt.internal.debug.ui.launcher.StandardVMType/JavaSE-1.6"/> and replace it with <classpathentry kind="con" path="org.eclipse.jdt.launching.JRE_CONTAINER"/>
  5. Save all the files. And Refresh or restart Eclipse IDE. All the problems are gone.

OR

Get the JRE used by the projects and install on your computer and then specify it..

Disable/Enable Submit Button until all forms have been filled

I just posted this on Disable Submit button until Input fields filled in. Works for me.

Use the form onsubmit. Nice and clean. You don't have to worry about the change and keypress events firing. Don't have to worry about keyup and focus issues.

http://www.w3schools.com/jsref/event_form_onsubmit.asp

<form action="formpost.php" method="POST" onsubmit="return validateCreditCardForm()">
   ...
</form>

function validateCreditCardForm(){
    var result = false;
    if (($('#billing-cc-exp').val().length > 0) &&
        ($('#billing-cvv').val().length  > 0) &&
        ($('#billing-cc-number').val().length > 0)) {
            result = true;
    }
    return result;
}

What is the equivalent of bigint in C#?

That corresponds to the long (or Int64), a 64-bit integer.

Although if the number from the database happens to be small enough, and you accidentally use an Int32, etc., you'll be fine. But the Int64 will definitely hold it.

And the error you get if you use something smaller and the full size is needed? A stack overflow! Yay!

Combining a class selector and an attribute selector with jQuery

I think you just need to remove the space. i.e.

$(".myclass[reference=12345]").css('border', '#000 solid 1px');

There is a fiddle here http://jsfiddle.net/xXEHY/

PHP move_uploaded_file() error?

Check that the web server has permissions to write to the "images/" directory

How to enable C++11 in Qt Creator?

add to your qmake file

QMAKE_CXXFLAGS+= -std=c++11
QMAKE_LFLAGS +=  -std=c++11

.aspx vs .ashx MAIN difference

.aspx is a rendered page. If you need a view, use an .aspx page. If all you need is backend functionality but will be staying on the same view, use an .ashx page.

Keylistener in Javascript

A bit more readable comparing is done by casting event.key to upper case (I used onkeyup - needed the event to fire once upon each key tap):

window.onkeyup = function(event) {
    let key = event.key.toUpperCase();
    if ( key == 'W' ) {
        // 'W' key is pressed
    } else if ( key == 'D' ) {
        // 'D' key is pressed
    }
}

Each key has it's own code, get it out by outputting value of "key" variable (eg for arrow up key it will be 'ARROWUP' - (casted to uppercase))

fs.writeFile in a promise, asynchronous-synchronous stuff

As of 2019...

...the correct answer is to use async/await with the native fs promises module included in node. Upgrade to Node.js 10 or 11 (already supported by major cloud providers) and do this:

const fs = require('fs').promises;

// This must run inside a function marked `async`:
const file = await fs.readFile('filename.txt', 'utf8');
await fs.writeFile('filename.txt', 'test');

Do not use third-party packages and do not write your own wrappers, that's not necessary anymore.

No longer experimental

Before Node 11.14.0, you would still get a warning that this feature is experimental, but it works just fine and it's the way to go in the future. Since 11.14.0, the feature is no longer experimental and is production-ready.

What if I prefer import instead of require?

It works, too - but only in Node.js versions where this feature is not marked as experimental.

import { promises as fs } from 'fs';

(async () => {
    await fs.writeFile('./test.txt', 'test', 'utf8');
})();

How to create a numeric vector of zero length in R

This isn't a very beautiful answer, but it's what I use to create zero-length vectors:

0[-1]     # numeric
""[-1]    # character
TRUE[-1]  # logical
0L[-1]    # integer

A literal is a vector of length 1, and [-1] removes the first element (the only element in this case) from the vector, leaving a vector with zero elements.

As a bonus, if you want a single NA of the respective type:

0[NA]     # numeric
""[NA]    # character
TRUE[NA]  # logical
0L[NA]    # integer

CSS transition between left -> right and top -> bottom positions

In more modern browsers (including IE 10+) you can now use calc():

.moveto {
  top: 0px;
  left: calc(100% - 50px);
}

Uncaught SyntaxError: Unexpected token :

In my case i ran into the same error, while running spring mvc application due to wrong mapping in my mvc controller

@RequestMapping(name="/private/updatestatus")

i changed the above mapping to

 @RequestMapping("/private/updatestatus")

or

 @RequestMapping(value="/private/updatestatus",method = RequestMethod.GET)

Echo off but messages are displayed

"echo off" is not ignored. "echo off" means that you do not want the commands echoed, it does not say anything about the errors produced by the commands.

The lines you showed us look okay, so the problem is probably not there. So, please show us more lines. Also, please show us the exact value of INSTALL_PATH.

add string to String array

Since Java arrays hold a fixed number of values, you need to create a new array with a length of 5 in this case. A better solution would be to use an ArrayList and simply add strings to the array.

Example:

ArrayList<String> scripts = new ArrayList<String>();
scripts.add("test3");
scripts.add("test4");
scripts.add("test5");

// Then later you can add more Strings to the ArrayList
scripts.add("test1");
scripts.add("test2");

MySQL: NOT LIKE

I don't know why

cfg_name_unique NOT LIKE '%categories%' 

still returns those two values, but maybe exclude them explicit:

SELECT *
    FROM developer_configurations_cms

    WHERE developer_configurations_cms.cat_id = '1'
    AND developer_configurations_cms.cfg_variables LIKE '%parent_id=2%'
    AND developer_configurations_cms.cfg_name_unique NOT LIKE '%categories%'
    AND developer_configurations_cms.cfg_name_unique NOT IN ('categories_posts', 'categories_news')

Javascript (+) sign concatenates instead of giving sum of variables

Since you are concatenating numbers on to a string, the whole thing is treated as a string. When you want to add numbers together, you either need to do it separately and assign it to a var and use that var, like this:

i = i + 1;
divID = "question-" + i;

Or you need to specify the number addition like this:

divID = "question-" + Number(i+1);

EDIT

I should have added this long ago, but based on the comments, this works as well:

divID = "question-" + (i+1);

How do I build JSON dynamically in javascript?

As myJSON is an object you can just set its properties, for example:

myJSON.list1 = ["1","2"];

If you dont know the name of the properties, you have to use the array access syntax:

myJSON['list'+listnum] = ["1","2"];

If you want to add an element to one of the properties, you can do;

myJSON.list1.push("3");

Add content to a new open window

When You want to open new tab/window (depends on Your browser configuration defaults):

output = 'Hello, World!';
window.open().document.write(output);

When output is an Object and You want get JSON, for example (also can generate any type of document, even image encoded in Base64)

output = ({a:1,b:'2'});
window.open('data:application/json;' + (window.btoa?'base64,'+btoa(JSON.stringify(output)):JSON.stringify(output)));

Update

Google Chrome (60.0.3112.90) block this code:

Not allowed to navigate top frame to data URL: data:application/json;base64,eyJhIjoxLCJiIjoiMiJ9

When You want to append some data to existing page

output = '<h1>Hello, World!</h1>';
window.open('output.html').document.body.innerHTML += output;

output = 'Hello, World!';
window.open('about:blank').document.body.innerText += output;

YAML mapping values are not allowed in this context

The elements of a sequence need to be indented at the same level. Assuming you want two jobs (A and B) each with an ordered list of key value pairs, you should use:

jobs:
 - - name: A
   - schedule: "0 0/5 * 1/1 * ? *"
   - - type: mongodb.cluster
     - config:
       - host: mongodb://localhost:27017/admin?replicaSet=rs
       - minSecondaries: 2
       - minOplogHours: 100
       - maxSecondaryDelay: 120
 - - name: B
   - schedule: "0 0/5 * 1/1 * ? *"
   - - type: mongodb.cluster
     - config:
       - host: mongodb://localhost:27017/admin?replicaSet=rs
       - minSecondaries: 2
       - minOplogHours: 100
       - maxSecondaryDelay: 120

Converting the sequences of (single entry) mappings to a mapping as @Tsyvarrev does is also possible, but makes you lose the ordering.

How to deal with ModalDialog using selenium webdriver?

Try this code, include your object names & variable to work.

Set<String> windowids = driver.getWindowHandles();
Iterator<String> iter= windowids.iterator();
for (int i = 1; i < sh.getRows(); i++)
{   
while(iter.hasNext())
{
System.out.println("Main Window ID :"+iter.next());
}
driver.findElement(By.id("lgnLogin_UserName")).clear();
driver.findElement(By.id("lgnLogin_UserName")).sendKeys(sh.getCell(0, 
i).getContents());
driver.findElement(By.id("lgnLogin_Password")).clear();
driver.findElement(By.id("lgnLogin_Password")).sendKeys(sh.getCell(1, 
i).getContents());
driver.findElement(By.id("lgnLogin_LoginButton")).click();
Thread.sleep(5000L);
            windowids = driver.getWindowHandles();
    iter= windowids.iterator();
    String main_windowID=iter.next();
    String tabbed_windowID=iter.next();
    System.out.println("Main Window ID :"+main_windowID);
    //switch over to pop-up window
    Thread.sleep(1000);
    driver.switchTo().window(tabbed_windowID);
    System.out.println("Pop-up window Title : "+driver.getTitle());

How do C++ class members get initialized if I don't do it explicitly?

If you example class is instantiated on the stack, the contents of uninitialized scalar members is random and undefined.

For a global instance, uninitialized scalar members will be zeroed.

For members which are themselves instances of classes, their default constructors will be called, so your string object will get initialized.

  • int *ptr; //uninitialized pointer (or zeroed if global)
  • string name; //constructor called, initialized with empty string
  • string *pname; //uninitialized pointer (or zeroed if global)
  • string &rname; //compilation error if you fail to initialize this
  • const string &crname; //compilation error if you fail to initialize this
  • int age; //scalar value, uninitialized and random (or zeroed if global)

Why GDB jumps unpredictably between lines and prints variables as "<value optimized out>"?

Im using QtCreator with gdb.

Adding

QMAKE_CXXFLAGS += -O0
QMAKE_CXXFLAGS -= -O1
QMAKE_CXXFLAGS -= -O2
QMAKE_CXXFLAGS -= -O3

Works well for me

Using CMake to generate Visual Studio C++ project files

CMake produces Visual Studio Projects and Solutions seamlessly. You can even produce projects/solutions for different Visual Studio versions without making any changes to the CMake files.

Adding and removing source files is just a matter of modifying the CMakeLists.txt which has the list of source files and regenerating the projects/solutions. There is even a globbing function to find all the sources in a directory (though it should be used with caution).

The following link explains CMake and Visual Studio specific behavior very well.

CMake and Visual Studio

Key value pairs using JSON

I see what you are trying to ask and I think this is the simplest answer to what you are looking for, given you might not know how many key pairs your are being sent.

Simple Key Pair JSON structure

var data = {
    'XXXXXX' : '100.0',
    'YYYYYYY' : '200.0',
    'ZZZZZZZ' : '500.0',
}

Usage JavaScript code to access the key pairs

for (var key in data) 
  { if (!data.hasOwnProperty(key))
    { continue; } 
    console.log(key + ' -> ' +  data[key]);
  };

Console output should look like this

XXXXXX -> 100.0 
YYYYYYY -> 200.0 
ZZZZZZZ -> 500.0

Here is a JSFiddle to show how it works.

how I can show the sum of in a datagridview column?

//declare the total variable
int total = 0;
//loop through the datagrid and sum the column 
for(int i=0;i<datagridview1.Rows.Count;i++)
{
    total +=int.Parse(datagridview1.Rows[i].Cells["CELL NAME OR INDEX"].Value.ToString());

}
string tota

Java "user.dir" property - what exactly does it mean?

user.dir is the "User working directory" according to the Java Tutorial, System Properties

How to align a <div> to the middle (horizontally/width) of the page

In my case, the phone screen size is unknown, and here is what I did.

HTML

<div class="loadingImg"></div>

CSS

.loadingImg{
    position: fixed;
    top: 0px;
    left: 0px;
    z-index: 9999999;
    border: 0;
    background: url('../images/loading.gif') no-repeat center;
    background-size: 50px 50px;
    display: block;
    margin: 0 auto;
    -webkit-border-radius: 50px;
    border-radius: 50px;
}

JavaScript (before you need to show this DIV)

$(".loadingImg").css("height",$(document).height());
$(".loadingImg").css("width",$(document).width());
$(".loadingImg").show();

Python float to int conversion

>>> x = 2.51
>>> x*100
250.99999999999997

the floating point numbers are inaccurate. in this case, it is 250.99999999999999, which is really close to 251, but int() truncates the decimal part, in this case 250.

you should take a look at the Decimal module or maybe if you have to do a lot of calculation at the mpmath library http://code.google.com/p/mpmath/ :),

How do I redirect with JavaScript?

window.location.replace('http://sidanmor.com');

It's better than using window.location.href = 'http://sidanmor.com';

Using replace() is better because it does not keep the originating page in the session history, meaning the user won't get stuck in a never-ending back-button fiasco.

If you want to simulate someone clicking on a link, use window.location.href

If you want to simulate an HTTP redirect, use window.location.replace

For example:

// similar behavior as an HTTP redirect
window.location.replace("http://sidanmor.com");

// similar behavior as clicking on a link
window.location.href = "http://sidanmor.com";

Taken from here: How to redirect to another page in jQuery?

Assignment makes pointer from integer without cast

As others already noted, in one case you are attempting to return cString (which is a char * value in this context - a pointer) from a function that is declared to return a char (which is an integer). In another case you do the reverse: you are assigning a char return value to a char * pointer. This is what triggers the warnings. You certainly need to declare your return values as char *, not as char.

Note BTW that these assignments are in fact constraint violations from the language point of view (i.e. they are "errors"), since it is illegal to mix pointers and integers in C like that (aside from integral constant zero). Your compiler is simply too forgiving in this regard and reports these violations as mere "warnings".

What I also wanted to note is that in several answers you might notice the relatively strange suggestion to return void from your functions, since you are modifying the string in-place. While it will certainly work (since you indeed are modifying the string in-place), there's nothing really wrong with returning the same value from the function. In fact, it is a rather standard practice in C language where applicable (take a look at the standard functions like strcpy and others), since it enables "chaining" of function calls if you choose to use it, and costs virtually nothing if you don't use "chaining".

That said, the assignments in your implementation of compareString look complete superfluous to me (even though they won't break anything). I'd either get rid of them

int compareString(char cString1[], char cString2[]) { 
    // To lowercase 
    strToLower(cString1); 
    strToLower(cString2); 

    // Do regular strcmp 
    return strcmp(cString1, cString2); 
} 

or use "chaining" and do

int compareString(char cString1[], char cString2[]) { 
    return strcmp(strToLower(cString1), strToLower(cString2)); 
} 

(this is when your char * return would come handy). Just keep in mind that such "chained" function calls are sometimes difficult to debug with a step-by-step debugger.

As an additional, unrealted note, I'd say that implementing a string comparison function in such a destructive fashion (it modifies the input strings) might not be the best idea. A non-destructive function would be of a much greater value in my opinion. Instead of performing as explicit conversion of the input strings to a lower case, it is usually a better idea to implement a custom char-by-char case-insensitive string comparison function and use it instead of calling the standard strcmp.

oracle.jdbc.driver.OracleDriver ClassNotFoundException

Method 1: Download ojdbc.jar

add ojdbc6.jar to deployment assembly. Right click on project->properties->select deployment assembly->click on 'Add' ->select 'Archives from File System'->browse to the folder where ojdbc6.jar is saved.->add the jar->click finish->Apply/OK.

Method 2:

if you want to add ojdbc.jar to your maven dependencies you follow this link: http://www.mkyong.com/maven/how-to-add-oracle-jdbc-driver-in-your-maven-local-repository/ . . Even if you're using a maven project it is not necessary to add ojdbc to maven dependencies(method 2), method 1 (adding directly to deployment assembly) works just fine.

TestNG ERROR Cannot find class in classpath

Was facing a similar issue using IntelliJ and in case it may be helpful to someone else what fixed it for me was to change the Use classpath of module field, to have it as the one that shows the package name.

enter image description here

How to change Git log date formats

git log -n1 --format="Last committed item in this release was by %an, `git log -n1 --format=%at | awk '{print strftime("%y%m%d%H%M",$1)}'`, message: %s (%h) [%d]"

Find the number of downloads for a particular app in apple appstore

I think developers can do this for their own apps via iTunes Connect but this doesn't help you if you are looking for stats on other peoples apps.

148Apps also have some aggregate AppStore metrics on their web site that could be useful to you but, again, doesn't really give a low-level breakdown of numbers.

You could also scrape some stats from the RSS feeds generated by the iTunes Store RSS Generator but, again, this just gets currently popular apps rather than actual download numbers.

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

You should use datetime object, not str.

>>> from datetime import datetime
>>> cr_date = datetime(2013, 10, 31, 18, 23, 29, 227)
>>> cr_date.strftime('%m/%d/%Y')
'10/31/2013'

To get the datetime object from the string, use datetime.datetime.strptime:

>>> datetime.strptime(cr_date, '%Y-%m-%d %H:%M:%S.%f')
datetime.datetime(2013, 10, 31, 18, 23, 29, 227)
>>> datetime.strptime(cr_date, '%Y-%m-%d %H:%M:%S.%f').strftime('%m/%d/%Y')
'10/31/2013'

git checkout master error: the following untracked working tree files would be overwritten by checkout

With Git 2.23 (August 2019), that would be, using git switch -f:

git switch -f master

That avoids the confusion with git checkout (which deals with files or branches).

And that will proceeds, even if the index or the working tree differs from HEAD.
Both the index and working tree are restored to match the switching target.
If --recurse-submodules is specified, submodule content is also restored to match the switching target.
This is used to throw away local changes.

How to make shadow on border-bottom?

Try:

_x000D_
_x000D_
div{_x000D_
-webkit-box-shadow:0px 1px 1px #de1dde;_x000D_
 -moz-box-shadow:0px 1px 1px #de1dde;_x000D_
 box-shadow:0px 1px 1px #de1dde;_x000D_
  }
_x000D_
<div>wefwefwef</div>
_x000D_
_x000D_
_x000D_

It generally adds a 1px blurred shadow 1px from the bottom of the box

box-shadow: [horizontal offset] [vertical offset] [blur radius] [color];

Git: How configure KDiff3 as merge tool and diff tool

For Mac users

Here is @Joseph's accepted answer, but with the default Mac install path location of kdiff3

(Note that you can copy and paste this and run it in one go)

git config --global --add merge.tool kdiff3 
git config --global --add mergetool.kdiff3.path  "/Applications/kdiff3.app/Contents/MacOS/kdiff3" 
git config --global --add mergetool.kdiff3.trustExitCode false

git config --global --add diff.guitool kdiff3
git config --global --add difftool.kdiff3.path "/Applications/kdiff3.app/Contents/MacOS/kdiff3"
git config --global --add difftool.kdiff3.trustExitCode false

What is the best way to return different types of ResponseEntity in Spring MVC or Spring-Boot

I used to use a class like this. The statusCode is set when there is an error with the error message set in message. Data is stored either in the Map or in a List as and when appropriate.

/**
* 
*/
package com.test.presentation.response;

import java.util.Collection;
import java.util.Map;

/**
 * A simple POJO to send JSON response to ajax requests. This POJO enables  us to
 * send messages and error codes with the actual objects in the application.
 * 
 * 
 */
@SuppressWarnings("rawtypes")
public class GenericResponse {

/**
 * An array that contains the actual objects
 */
private Collection rows;

/**
 * An Map that contains the actual objects
 */
private Map mapData;

/**
 * A String containing error code. Set to 1 if there is an error
 */
private int statusCode = 0;

/**
 * A String containing error message.
 */
private String message;

/**
 * An array that contains the actual objects
 * 
 * @return the rows
 */
public Collection getRows() {
    return rows;
}

/**
 * An array that contains the actual objects
 * 
 * @param rows
 *            the rows to set
 */
public void setRows(Collection rows) {
    this.rows = rows;
}

/**
 * An Map that contains the actual objects
 * 
 * @return the mapData
 */
public Map getMapData() {
    return mapData;
}

/**
 * An Map that contains the actual objects
 * 
 * @param mapData
 *            the mapData to set
 */
public void setMapData(Map mapData) {
    this.mapData = mapData;
}

/**
 * A String containing error code.
 * 
 * @return the errorCode
 */
public int getStatusCode() {
    return statusCode;
}

/**
 * A String containing error code.
 * 
 * @param errorCode
 *            the errorCode to set
 */
public void setStatusCode(int errorCode) {
    this.statusCode = errorCode;
}

/**
 * A String containing error message.
 * 
 * @return the errorMessage
 */
public String getMessage() {
    return message;
}

/**
 * A String containing error message.
 * 
 * @param errorMessage
 *            the errorMessage to set
 */
public void setMessage(String errorMessage) {
    this.message = errorMessage;
}

}

Hope this helps.

How to put individual tags for a scatter plot

Perhaps use plt.annotate:

import numpy as np
import matplotlib.pyplot as plt

N = 10
data = np.random.random((N, 4))
labels = ['point{0}'.format(i) for i in range(N)]

plt.subplots_adjust(bottom = 0.1)
plt.scatter(
    data[:, 0], data[:, 1], marker='o', c=data[:, 2], s=data[:, 3] * 1500,
    cmap=plt.get_cmap('Spectral'))

for label, x, y in zip(labels, data[:, 0], data[:, 1]):
    plt.annotate(
        label,
        xy=(x, y), xytext=(-20, 20),
        textcoords='offset points', ha='right', va='bottom',
        bbox=dict(boxstyle='round,pad=0.5', fc='yellow', alpha=0.5),
        arrowprops=dict(arrowstyle = '->', connectionstyle='arc3,rad=0'))

plt.show()

enter image description here

Visual Studio debugger error: Unable to start program Specified file cannot be found

I had the same problem :) Verify the "Source code" folder on the "Solution Explorer", if it doesn't contain any "source code" file then :

Right click on "Source code" > Add > Existing Item > Choose the file You want to build and run.

Good luck ;)

Ways to iterate over a list in Java

In Java 8 we have multiple ways to iterate over collection classes.

Using Iterable forEach

The collections that implement Iterable (for example all lists) now have forEach method. We can use method-reference introduced in Java 8.

Arrays.asList(1,2,3,4).forEach(System.out::println);

Using Streams forEach and forEachOrdered

We can also iterate over a list using Stream as:

Arrays.asList(1,2,3,4).stream().forEach(System.out::println);
Arrays.asList(1,2,3,4).stream().forEachOrdered(System.out::println);

We should prefer forEachOrdered over forEach because the behaviour of forEach is explicitly nondeterministic where as the forEachOrdered performs an action for each element of this stream, in the encounter order of the stream if the stream has a defined encounter order. So forEach does not guarantee that the order would be kept.

The advantage with streams is that we can also make use of parallel streams wherever appropriate. If the objective is only to print the items irrespective of the order then we can use parallel stream as:

Arrays.asList(1,2,3,4).parallelStream().forEach(System.out::println);

How to output to the console and file?

Here's a small improvement that to @UltraInstinct's Tee class, modified to be a context manager and also captures any exceptions.

import traceback
import sys

# Context manager that copies stdout and any exceptions to a log file
class Tee(object):
    def __init__(self, filename):
        self.file = open(filename, 'w')
        self.stdout = sys.stdout

    def __enter__(self):
        sys.stdout = self

    def __exit__(self, exc_type, exc_value, tb):
        sys.stdout = self.stdout
        if exc_type is not None:
            self.file.write(traceback.format_exc())
        self.file.close()

    def write(self, data):
        self.file.write(data)
        self.stdout.write(data)

    def flush(self):
        self.file.flush()
        self.stdout.flush()

To use the context manager:

print("Print")
with Tee('test.txt'):
    print("Print+Write")
    raise Exception("Test")
print("Print")

What is makeinfo, and how do I get it?

If you build packages from scratch:

Specifically, if you build bash from source, install docs, including man pages, will fail (silently) without makeinfo available.

Format timedelta to string

timedelta to string, use for print running time info.

def strfdelta_round(tdelta, round_period='second'):
  """timedelta to string,  use for measure running time
  attend period from days downto smaller period, round to minimum period
  omit zero value period  
  """
  period_names = ('day', 'hour', 'minute', 'second', 'millisecond')
  if round_period not in period_names:
    raise Exception(f'round_period "{round_period}" invalid, should be one of {",".join(period_names)}')
  period_seconds = (86400, 3600, 60, 1, 1/pow(10,3))
  period_desc = ('days', 'hours', 'mins', 'secs', 'msecs')
  round_i = period_names.index(round_period)
  
  s = ''
  remainder = tdelta.total_seconds()
  for i in range(len(period_names)):
    q, remainder = divmod(remainder, period_seconds[i])
    if int(q)>0:
      if not len(s)==0:
        s += ' '
      s += f'{q:.0f} {period_desc[i]}'
    if i==round_i:
      break
    if i==round_i+1:
      s += f'{remainder} {period_desc[round_i]}'
      break
    
  return s

e.g. auto omit zero leading period:

>>> td = timedelta(days=0, hours=2, minutes=5, seconds=8, microseconds=3549)
>>> strfdelta_round(td, 'second')
'2 hours 5 mins 8 secs'

or omit middle zero period:

>>> td = timedelta(days=2, hours=0, minutes=5, seconds=8, microseconds=3549)
>>> strfdelta_round(td, 'millisecond')
'2 days 5 mins 8 secs 3 msecs'

or round to minutes, omit below minutes:

>>> td = timedelta(days=1, hours=2, minutes=5, seconds=8, microseconds=3549)
>>> strfdelta_round(td, 'minute')
'1 days 2 hours 5 mins'

The name 'ViewBag' does not exist in the current context

After trying different things, it turns out it was VS cache. You can resolve it by deleting the cache files located in:

C:\Users\your.name.here\AppData\Local\Microsoft\VisualStudio\14.0\ComponentModelCache

I closed my project, deleted the files on that path and reopened my project, cleaned the solution and built it again and the problem was solved

The files will be recreated when you next launch Visual Studio

Converting a string to a date in a cell

I was struggling with this for some time and after some help on a post I was able to come up with this formula =(DATEVALUE(LEFT(XX,10)))+(TIMEVALUE(MID(XX,12,5))) where XX is the cell in reference.

I've come across many other forums with people asking the same thing and this, to me, seems to be the simplest answer. What this will do is return text that is copied in from this format 2014/11/20 11:53 EST and turn it in to a Date/Time format so it can be sorted oldest to newest. It works with short date/long date and if you want the time just format the cell to display time and it will show. Hope this helps anyone who goes searching around like I did.

Storing query results into a variable and modifying it inside a Stored Procedure

Yup, this is possible of course. Here are several examples.

-- one way to do this
DECLARE @Cnt int

SELECT @Cnt = COUNT(SomeColumn)
FROM TableName
GROUP BY SomeColumn

-- another way to do the same thing
DECLARE @StreetName nvarchar(100)
SET @StreetName = (SELECT Street_Name from Streets where Street_ID = 123)

-- Assign values to several variables at once
DECLARE @val1 nvarchar(20)
DECLARE @val2 int
DECLARE @val3 datetime
DECLARE @val4 uniqueidentifier
DECLARE @val5 double

SELECT @val1 = TextColumn,
@val2 = IntColumn,
@val3 = DateColumn,
@val4 = GuidColumn,
@val5 = DoubleColumn
FROM SomeTable

Android Completely transparent Status Bar?

Just add this line of code to your main java file:

getWindow().setFlags(
    WindowManager.LayoutParams.FLAG_LAYOUT_NO_LIMITS,
    WindowManager.LayoutParams.FLAG_LAYOUT_NO_LIMITS
);

Error: Cannot find module '../lib/utils/unsupported.js' while using Ionic

In my case it was $NODE_PATH missing:

NODE="/home/ubuntu/local/node" #here your user account after home
NODE_PATH="/usr/local/lib/node_modules" 
PATH="$PATH:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/games:$NODE/bin:$NODE/lib/node_modules"

To check just echo $NODE_PATH empty means it is not set. Add them to .bashrc is recommended.

Laravel - Form Input - Multiple select for a one to many relationship

A multiple select is really just a select with a multiple attribute. With that in mind, it should be as easy as...

Form::select('sports[]', $sports, null, array('multiple'))

The first parameter is just the name, but post-fixing it with the [] will return it as an array when you use Input::get('sports').

The second parameter is an array of selectable options.

The third parameter is an array of options you want pre-selected.

The fourth parameter is actually setting this up as a multiple select dropdown by adding the multiple property to the actual select element..

How can I monitor the thread count of a process on linux?

Newer JDK distributions ship with JConsole and VisualVM. Both are fantastic tools for getting the dirty details from a running Java process. If you have to do this programmatically, investigate JMX.

Xcode: failed to get the task for process

I had this issue when trying to debug an App on a device I hadn't used before. Developer profile was correctly set. The device was part of our teams account but wasn't included in my profile.

Simply had to open Organizer -> Select the Device -> Add to Member Center

How to merge a transparent png image with another image using PIL

from PIL import Image

background = Image.open("test1.png")
foreground = Image.open("test2.png")

background.paste(foreground, (0, 0), foreground)
background.show()

First parameter to .paste() is the image to paste. Second are coordinates, and the secret sauce is the third parameter. It indicates a mask that will be used to paste the image. If you pass a image with transparency, then the alpha channel is used as mask.

Check the docs.

Array of arrays (Python/NumPy)

a=np.array([[1,2,3],[4,5,6]])

a.tolist()

tolist method mentioned above will return the nested Python list

Change color of Button when Mouse is over

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

Can I have onScrollListener for a ScrollView?

Beside accepted answer, you need to hold a reference of listener and remove when you don't need it. Otherwise you will get a null pointer exception for your ScrollView and memory leak (mentioned in comments of accepted answer).

  1. You can implement OnScrollChangedListener in your activity/fragment.

    MyFragment : ViewTreeObserver.OnScrollChangedListener
    
  2. Add it to scrollView when your view is ready.

    scrollView.viewTreeObserver.addOnScrollChangedListener(this)
    
  3. Remove listener when no longer need (ie. onPause())

    scrollView.viewTreeObserver.removeOnScrollChangedListener(this)
    

Select first occurring element after another element

I use latest CSS and "+" didn't work for me so I end up with

:first-child

Getting raw SQL query string from PDO prepared statements

You can use sprintf(str_replace('?', '"%s"', $sql), ...$params);

Here is an example:

function mysqli_prepared_query($link, $sql, $types='', $params=array()) {
    echo sprintf(str_replace('?', '"%s"', $sql), ...$params);
    //prepare, bind, execute
}

$link = new mysqli($server, $dbusername, $dbpassword, $database);
$sql = "SELECT firstname, lastname FROM users WHERE userage >= ? AND favecolor = ?";
$types = "is"; //integer and string
$params = array(20, "Brown");

if(!$qry = mysqli_prepared_query($link, $sql, $types, $params)){
    echo "Failed";
} else {
    echo "Success";
}

Note this only works for PHP >= 5.6

javascript regex - look behind alternative?

Let's suppose you want to find all int not preceded by unsigned:

With support for negative look-behind:

(?<!unsigned )int

Without support for negative look-behind:

((?!unsigned ).{9}|^.{0,8})int

Basically idea is to grab n preceding characters and exclude match with negative look-ahead, but also match the cases where there's no preceeding n characters. (where n is length of look-behind).

So the regex in question:

(?<!filename)\.js$

would translate to:

((?!filename).{8}|^.{0,7})\.js$

You might need to play with capturing groups to find exact spot of the string that interests you or you want't to replace specific part with something else.

How to connect android emulator to the internet

Thanks for the pointers. They really helped. The "Firewall" word clicked an idea in my mind.

I have a Windows XP machine with WIFI connection and no proxy. I have Norton Internet Security running on my machine which has a Smart Firewall. This Smart Firewall manages programs' access to network, including emulator.exe. I went into Settings -> Program Control and then granted full access to emulator.exe. After this I started Android Emulator and bang... I could connect to internet.

Hope this helps new folks.

~Saggy

How to Update Multiple Array Elements in mongodb

This can also be accomplished with a while loop which checks to see if any documents remain that still have subdocuments that have not been updated. This method preserves the atomicity of your updates (which many of the other solutions here do not).

var query = {
    events: {
        $elemMatch: {
            profile: 10,
            handled: { $ne: 0 }
        }
    }
};

while (db.yourCollection.find(query).count() > 0) {
    db.yourCollection.update(
        query,
        { $set: { "events.$.handled": 0 } },
        { multi: true }
    );
}

The number of times the loop is executed will equal the maximum number of times subdocuments with profile equal to 10 and handled not equal to 0 occur in any of the documents in your collection. So if you have 100 documents in your collection and one of them has three subdocuments that match query and all the other documents have fewer matching subdocuments, the loop will execute three times.

This method avoids the danger of clobbering other data that may be updated by another process while this script executes. It also minimizes the amount of data being transferred between client and server.

Return back to MainActivity from another activity

instead of starting MainActivity again via startActivity, call finish() instead in the other activities to get back to MainActivity... as MainActivity is already in stack

"TypeError: (Integer) is not JSON serializable" when serializing JSON in Python?

You have Numpy Data Type, Just change to normal int() or float() data type. it will work fine.

Check if a String contains a special character

Visit each character in the string to see if that character is in a blacklist of special characters; this is O(n*m).

The pseudo-code is:

for each char in string:
  if char in blacklist:
    ...

The complexity can be slightly improved by sorting the blacklist so that you can early-exit each check. However, the string find function is probably native code, so this optimisation - which would be in Java byte-code - could well be slower.

How to set a string's color

If you're printing to stdout, it depends on the terminal you're printing to. You can use ansi escape codes on xterms and other similar terminal emulators. Here's a bash code snippet that will print all 255 colors supported by xterm, putty and Konsole:

 for ((i=0;i<256;i++)); do echo -en "\e[38;5;"$i"m"$i" "; done

You can use these escape codes in any programming language. It's better to rely on a library that will decide which codes to use depending on architecture and the content of the TERM environment variable.

Why does typeof array with objects return "object" and not "array"?

Try this example and you will understand also what is the difference between Associative Array and Object in JavaScript.

Associative Array

var a = new Array(1,2,3); 
a['key'] = 'experiment';
Array.isArray(a);

returns true

Keep in mind that a.length will be undefined, because length is treated as a key, you should use Object.keys(a).length to get the length of an Associative Array.

Object

var a = {1:1, 2:2, 3:3,'key':'experiment'}; 
Array.isArray(a)

returns false

JSON returns an Object ... could return an Associative Array ... but it is not like that

What is limiting the # of simultaneous connections my ASP.NET application can make to a web service?

See the "Threading" section of this page: http://msdn.microsoft.com/en-us/library/ff647786.aspx, in conjunction with the "Connections" section.

Have you tried upping the maxconnection attribute of your processModel setting?

How to get length of a list of lists in python

if the name of your list is listlen then just type len(listlen). This will return the size of your list in the python.

Excel to JSON javascript code?

The answers are working fine with xls format but, in my case, it didn't work for xlsx format. Thus I added some code here. it works both xls and xlsx format.

I took the sample from the official sample link.

Hope it may help !

function fileReader(oEvent) {
        var oFile = oEvent.target.files[0];
        var sFilename = oFile.name;

        var reader = new FileReader();
        var result = {};

        reader.onload = function (e) {
            var data = e.target.result;
            data = new Uint8Array(data);
            var workbook = XLSX.read(data, {type: 'array'});
            console.log(workbook);
            var result = {};
            workbook.SheetNames.forEach(function (sheetName) {
                var roa = XLSX.utils.sheet_to_json(workbook.Sheets[sheetName], {header: 1});
                if (roa.length) result[sheetName] = roa;
            });
            // see the result, caution: it works after reader event is done.
            console.log(result);
        };
        reader.readAsArrayBuffer(oFile);
}

// Add your id of "File Input" 
$('#fileUpload').change(function(ev) {
        // Do something 
        fileReader(ev);
}

How can I query for null values in entity framework?

Workaround for Linq-to-SQL:

var result = from entry in table
             where entry.something.Equals(value)
             select entry;

Workaround for Linq-to-Entities (ouch!):

var result = from entry in table
             where (value == null ? entry.something == null : entry.something == value)
             select entry;

This is a nasty bug which has bitten me several times. If this bug has affected you too, please visit the bug report on UserVoice and let Microsoft know that this bug has affected you as well.


Edit: This bug is being fixed in EF 4.5! Thanks everyone for upvoting this bug!

For backwards compatibility, it will be opt-in - you need manually enable a setting to make entry == value work. No word yet on what this setting is. Stay tuned!


Edit 2: According to this post by the EF team, this issue has been fixed in EF6! Woohoo!

We changed the default behavior of EF6 to compensate for three-valued logic.

This means that existing code that relies on the old behavior (null != null, but only when comparing to a variable) will either need to be changed to not rely on that behavior, or set UseCSharpNullComparisonBehavior to false to use the old broken behavior.

mysql alphabetical order

but result showing all records starting with a or c or d i want to show records only starting with b

You should use WHERE in that case:

select name from user where name = 'b' order by name

If you want to allow regex, you can use the LIKE operator there too if you want. Example:

select name from user where name like 'b%' order by name

That will select records starting with b. Following query on the other hand will select all rows where b is found anywhere in the column:

select name from user where name like '%b%' order by name

iOS 7's blurred overlay effect using CSS?

You made me want to try, so I did, check out the example here:

http://codepen.io/Edo_B/pen/cLbrt

Using:

  1. HW Accelerated CSS filters
  2. JS for class assigning and arrow key events
  3. Images CSS Clip property

that's it.

I also believe this could be done dynamically for any screen if using canvas to copy the current dom and blurring it.

back button callback in navigationController in iOS

Maybe it's a little too late, but I also wanted the same behavior before. And the solution I went with works quite well in one of the apps currently on the App Store. Since I haven't seen anyone goes with similar method, I would like to share it here. The downside of this solution is that it requires subclassing UINavigationController. Though using Method Swizzling might help avoiding that, I didn't go that far.

So, the default back button is actually managed by UINavigationBar. When a user taps on the back button, UINavigationBar ask its delegate if it should pop the top UINavigationItem by calling navigationBar(_:shouldPop:). UINavigationController actually implement this, but it doesn't publicly declare that it adopts UINavigationBarDelegate (why!?). To intercept this event, create a subclass of UINavigationController, declare its conformance to UINavigationBarDelegate and implement navigationBar(_:shouldPop:). Return true if the top item should be popped. Return false if it should stay.

There are two problems. The first is that you must call the UINavigationController version of navigationBar(_:shouldPop:) at some point. But UINavigationBarController doesn't publicly declare it conformance to UINavigationBarDelegate, trying to call it will result in a compile time error. The solution I went with is to use Objective-C runtime to get the implementation directly and call it. Please let me know if anyone has a better solution.

The other problem is that navigationBar(_:shouldPop:) is called first follows by popViewController(animated:) if the user taps on the back button. The order reverses if the view controller is popped by calling popViewController(animated:). In this case, I use a boolean to detect if popViewController(animated:) is called before navigationBar(_:shouldPop:) which mean that the user has tapped on the back button.

Also, I make an extension of UIViewController to let the navigation controller ask the view controller if it should be popped if the user taps on the back button. View controllers can return false and do any necessary actions and call popViewController(animated:) later.

class InterceptableNavigationController: UINavigationController, UINavigationBarDelegate {
    // If a view controller is popped by tapping on the back button, `navigationBar(_:, shouldPop:)` is called first follows by `popViewController(animated:)`.
    // If it is popped by calling to `popViewController(animated:)`, the order reverses and we need this flag to check that.
    private var didCallPopViewController = false

    override func popViewController(animated: Bool) -> UIViewController? {
        didCallPopViewController = true
        return super.popViewController(animated: animated)
    }

    func navigationBar(_ navigationBar: UINavigationBar, shouldPop item: UINavigationItem) -> Bool {
        // If this is a subsequence call after `popViewController(animated:)`, we should just pop the view controller right away.
        if didCallPopViewController {
            return originalImplementationOfNavigationBar(navigationBar, shouldPop: item)
        }

        // The following code is called only when the user taps on the back button.

        guard let vc = topViewController, item == vc.navigationItem else {
            return false
        }

        if vc.shouldBePopped(self) {
            return originalImplementationOfNavigationBar(navigationBar, shouldPop: item)
        } else {
            return false
        }
    }

    func navigationBar(_ navigationBar: UINavigationBar, didPop item: UINavigationItem) {
        didCallPopViewController = false
    }

    /// Since `UINavigationController` doesn't publicly declare its conformance to `UINavigationBarDelegate`,
    /// trying to called `navigationBar(_:shouldPop:)` will result in a compile error.
    /// So, we'll have to use Objective-C runtime to directly get super's implementation of `navigationBar(_:shouldPop:)` and call it.
    private func originalImplementationOfNavigationBar(_ navigationBar: UINavigationBar, shouldPop item: UINavigationItem) -> Bool {
        let sel = #selector(UINavigationBarDelegate.navigationBar(_:shouldPop:))
        let imp = class_getMethodImplementation(class_getSuperclass(InterceptableNavigationController.self), sel)
        typealias ShouldPopFunction = @convention(c) (AnyObject, Selector, UINavigationBar, UINavigationItem) -> Bool
        let shouldPop = unsafeBitCast(imp, to: ShouldPopFunction.self)
        return shouldPop(self, sel, navigationBar, item)
    }
}

extension UIViewController {
    @objc func shouldBePopped(_ navigationController: UINavigationController) -> Bool {
        return true
    }
}

And in you view controllers, implement shouldBePopped(_:). If you don't implement this method, the default behavior will be to pop the view controller as soon as the user taps on the back button just like normal.

class MyViewController: UIViewController {
    override func shouldBePopped(_ navigationController: UINavigationController) -> Bool {
        let alert = UIAlertController(title: "Do you want to go back?",
                                      message: "Do you really want to go back? Tap on \"Yes\" to go back. Tap on \"No\" to stay on this screen.",
                                      preferredStyle: .alert)
        alert.addAction(UIAlertAction(title: "No", style: .cancel, handler: nil))
        alert.addAction(UIAlertAction(title: "Yes", style: .default, handler: { _ in
            navigationController.popViewController(animated: true)
        }))
        present(alert, animated: true, completion: nil)
        return false
    }
}

You can look at my demo here.

enter image description here