Programs & Examples On #Isolation

Spring @Transactional - isolation, propagation

Enough explanation about each parameter is given by other answers; However you asked for a real world example, here is the one that clarifies the purpose of different propagation options:

Suppose you're in charge of implementing a signup service in which a confirmation e-mail is sent to the user. You come up with two service objects, one for enrolling the user and one for sending e-mails, which the latter is called inside the first one. For example something like this:

/* Sign Up service */
@Service
@Transactional(Propagation=REQUIRED)
class SignUpService{
 ...
 void SignUp(User user){
    ...
    emailService.sendMail(User);
 }
}

/* E-Mail Service */
@Service
@Transactional(Propagation=REQUIRES_NEW)
class EmailService{
 ...
 void sendMail(User user){
  try{
     ... // Trying to send the e-mail
  }catch( Exception)
 }
}

You may have noticed that the second service is of propagation type REQUIRES_NEW and moreover chances are it throws an exception (SMTP server down ,invalid e-mail or other reasons).You probably don't want the whole process to roll-back, like removing the user information from database or other things; therefore you call the second service in a separate transaction.

Back to our example, this time you are concerned about the database security, so you define your DAO classes this way:

/* User DAO */
@Transactional(Propagation=MANDATORY)
class UserDAO{
 // some CRUD methods
}

Meaning that whenever a DAO object, and hence a potential access to db, is created, we need to reassure that the call was made from inside one of our services, implying that a live transaction should exist; otherwise an exception occurs.Therefore the propagation is of type MANDATORY.

SSL certificate is not trusted - on mobile only

The most likely reason for the error is that the certificate authority that issued your SSL certificate is trusted on your desktop, but not on your mobile.

If you purchased the certificate from a common certification authority, it shouldn't be an issue - but if it is a less common one it is possible that your phone doesn't have it. You may need to accept it as a trusted publisher (although this is not ideal if you are pushing the site to the public as they won't be willing to do this.)

You might find looking at a list of Trusted CAs for Android helps to see if yours is there or not.

Need to ZIP an entire directory using Node.js

To include all files and directories:

archive.bulk([
  {
    expand: true,
    cwd: "temp/freewheel-bvi-120",
    src: ["**/*"],
    dot: true
  }
]);

It uses node-glob(https://github.com/isaacs/node-glob) underneath, so any matching expression compatible with that will work.

setup android on eclipse but don't know SDK directory

May be i am too much late here and question is already answered, but this may help those who still cannot find sdk location. Open eclipse, click window tab it will show a drop down menu, click preferences, in preferences window click Android, here u go Sdk location is right in front of u copy the address :)

Correct redirect URI for Google API and OAuth 2.0

There's no problem with using a localhost url for Dev work - obviously it needs to be changed when it comes to production.

You need to go here: https://developers.google.com/accounts/docs/OAuth2 and then follow the link for the API Console - link's in the Basic Steps section. When you've filled out the new application form you'll be asked to provide a redirect Url. Put in the page you want to go to once access has been granted.

When forming the Google oAuth Url - you need to include the redirect url - it has to be an exact match or you'll have problems. It also needs to be UrlEncoded.

NPM: npm-cli.js not found when running npm

I run into this problem when installing node9.0.0 on windows7 at the end the solution was to just remove npm npm.cmd npx npx.cmd from C:\Program Files\nodejs\node_modules\npm\bin before doing this a workaround was to run C:\Program Files\nodejs\npm so that is one way so see if you have the same problem I had.

Where are the Android icon drawables within the SDK?

  1. Right click on Drawable folder

  2. click on new

  3. click on image asset

Then you can select an icon type

Entity Framework 5 Updating a Record

Depending on your use case, all the above solutions apply. This is how i usually do it however :

For server side code (e.g. a batch process) I usually load the entities and work with dynamic proxies. Usually in batch processes you need to load the data anyways at the time the service runs. I try to batch load the data instead of using the find method to save some time. Depending on the process I use optimistic or pessimistic concurrency control (I always use optimistic except for parallel execution scenarios where I need to lock some records with plain sql statements, this is rare though). Depending on the code and scenario the impact can be reduced to almost zero.

For client side scenarios, you have a few options

  1. Use view models. The models should have a property UpdateStatus(unmodified-inserted-updated-deleted). It is the responsibility of the client to set the correct value to this column depending on the user actions (insert-update-delete). The server can either query the db for the original values or the client should send the original values to the server along with the changed rows. The server should attach the original values and use the UpdateStatus column for each row to decide how to handle the new values. In this scenario I always use optimistic concurrency. This will only do the insert - update - delete statements and not any selects, but it might need some clever code to walk the graph and update the entities (depends on your scenario - application). A mapper can help but does not handle the CRUD logic

  2. Use a library like breeze.js that hides most of this complexity (as described in 1) and try to fit it to your use case.

Hope it helps

How to show alert message in mvc 4 controller?

You cannot show an alert from a controller. There is one way communication from the client to the server.The server can therefore not tell the client to do anything. The client requests and the server gives a response.

You therefore need to use javascript when the response returns to show a messagebox of some sort.

OR

using jquery on the button that calls the controller action

<script>
 $(document).ready(function(){
  $("#submitButton").on("click",function()
  {
   alert('Your Message');
  });

});
<script>

Caused By: java.lang.NoClassDefFoundError: org/apache/log4j/Logger

During runtime your application is unable to find the jar.

Taken from this answer by Jared:

It is important to keep two different exceptions straight in our head in this case:

  1. java.lang.ClassNotFoundException This an Exception, it indicates that the class was not found on the classpath. This indicates that we were trying to load the class definition, and the class did not exist on the classpath.

  2. java.lang.NoClassDefFoundError This is Error, it indicates that the JVM looked in its internal class definition data structure for the definition of a class and did not find it. This is different than saying that it could not be loaded from the classpath. Usually this indicates that we previously attempted to load a class from the classpath, but it failed for some reason - now we're trying again, but we're not even going to try to load it, because we failed loading it earlier. The earlier failure could be a ClassNotFoundException or an ExceptionInInitializerError (indicating a failure in the static initialization block) or any number of other problems. The point is, a NoClassDefFoundError is not necessarily a classpath problem.

for similarities and differences

Using await outside of an async function

As of Node.js 14.3.0 the top-level await is supported.

Required flag: --experimental-top-level-await.

Further details: https://v8.dev/features/top-level-await

How do I prevent DIV tag starting a new line?

Add style="display: inline" to your div.

How to detect DIV's dimension changed?

Pure Javascript solution, but works only if the element is resized with the css resize button:

  1. store element size with offsetWidth and offsetHeight;
  2. add an onclick event listener on this element;
  3. when triggered, compare curent offsetWidth and offsetHeight with stored values, and if different, do what you want and update these values.

Large WCF web service request failing with (400) HTTP Bad Request

For what it is worth, an additional consideration when using .NET 4.0 is that if a valid endpoint is not found in your configuration, a default endpoint will be automatically created and used.

The default endpoint will use all default values so if you think you have a valid service configuration with a large value for maxReceivedMessageSize etc., but there is something wrong with the configuration, you would still get the 400 Bad Request since a default endpoint would be created and used.

This is done silently so it is hard to detect. You will see messages to this effect (e.g. 'No Endpoint found for Service, creating Default Endpoint' or similar) if you turn on tracing on the server but there is no other indication (to my knowledge).

sql insert into table with select case values

You need commas after end finishing the case statement. And, the "as" goes after the case statement, not inside it:

Insert into TblStuff(FullName, Address, City, Zip)
    Select (Case When Middle is Null Then Fname + LName
                 Else Fname +' ' + Middle + ' '+ Lname
            End)  as FullName,
           (Case When Address2 is Null Then Address1
                 else Address1 +', ' + Address2
            End)  as  Address,
           City as City,
           Zip as Zip
    from tblImport

What is the difference between <section> and <div>?

<div>—the generic flow container we all know and love. It’s a block-level element with no additional semantic meaning (W3C:Markup, WhatWG)

<section>—a generic document or application section. A normally has a heading (title) and maybe a footer too. It’s a chunk of related content, like a subsection of a long article, a major part of the page (eg the news section on the homepage), or a page in a webapp’s tabbed interface. (W3C:Markup, WhatWG)

My suggestion: div: used lower version( i think 4.01 to still) html element(lot of designers handled that). section: recently comming (html5) html element.

GitHub "fatal: remote origin already exists"

In case you want to do via GUI do the following:

  1. Ensure "hidden files" are visible in your project folder
  2. Go to .git directory
  3. Edit the url file in the config.txt file and save the file!

Correct way to read a text file into a buffer in C?

char source[1000000];

FILE *fp = fopen("TheFile.txt", "r");
if(fp != NULL)
{
    while((symbol = getc(fp)) != EOF)
    {
        strcat(source, &symbol);
    }
    fclose(fp);
}

There are quite a few things wrong with this code:

  1. It is very slow (you are extracting the buffer one character at a time).
  2. If the filesize is over sizeof(source), this is prone to buffer overflows.
  3. Really, when you look at it more closely, this code should not work at all. As stated in the man pages:

The strcat() function appends a copy of the null-terminated string s2 to the end of the null-terminated string s1, then add a terminating `\0'.

You are appending a character (not a NUL-terminated string!) to a string that may or may not be NUL-terminated. The only time I can imagine this working according to the man-page description is if every character in the file is NUL-terminated, in which case this would be rather pointless. So yes, this is most definitely a terrible abuse of strcat().

The following are two alternatives to consider using instead.

If you know the maximum buffer size ahead of time:

#include <stdio.h>
#define MAXBUFLEN 1000000

char source[MAXBUFLEN + 1];
FILE *fp = fopen("foo.txt", "r");
if (fp != NULL) {
    size_t newLen = fread(source, sizeof(char), MAXBUFLEN, fp);
    if ( ferror( fp ) != 0 ) {
        fputs("Error reading file", stderr);
    } else {
        source[newLen++] = '\0'; /* Just to be safe. */
    }

    fclose(fp);
}

Or, if you do not:

#include <stdio.h>
#include <stdlib.h>

char *source = NULL;
FILE *fp = fopen("foo.txt", "r");
if (fp != NULL) {
    /* Go to the end of the file. */
    if (fseek(fp, 0L, SEEK_END) == 0) {
        /* Get the size of the file. */
        long bufsize = ftell(fp);
        if (bufsize == -1) { /* Error */ }

        /* Allocate our buffer to that size. */
        source = malloc(sizeof(char) * (bufsize + 1));

        /* Go back to the start of the file. */
        if (fseek(fp, 0L, SEEK_SET) != 0) { /* Error */ }

        /* Read the entire file into memory. */
        size_t newLen = fread(source, sizeof(char), bufsize, fp);
        if ( ferror( fp ) != 0 ) {
            fputs("Error reading file", stderr);
        } else {
            source[newLen++] = '\0'; /* Just to be safe. */
        }
    }
    fclose(fp);
}

free(source); /* Don't forget to call free() later! */

Checking if object is empty, works with ng-show but not from controller?

you can check length of items

ng-show="items.length"

JSLint is suddenly reporting: Use the function form of "use strict"

Add a file .jslintrc (or .jshintrc in the case of jshint) at the root of your project with the following content:

{
    "node": true
}

Losing Session State

Your session is lost becoz....

I have found a scenario where session is lost - In a asp.net page, for a amount text box field has invalid characters, and followed by a session variable retrieval for other purpose.After posting the invalid number parsing through Convert.ToInt32 or double raises a first chance exception, but error does not show at that line, Instead of that, Session being null because of unhandled exception, shows error at session retrieval, thus deceiving the debugging...

HINT: Test your system to fail it- DESTRUCTIVE.. enter enough junk in unrelated scenarios for ex: after search results shown enter junk in search criteria and goto details of search result... , you would be able to reproduce this machine on your local code base too...:)

Hope it Helps, hydtechie

PHP mail function doesn't complete sending of e-mail

If you are using an SMTP configuration for sending your email, try using PHPMailer instead. You can download the library from https://github.com/PHPMailer/PHPMailer.

I created my email sending this way:

function send_mail($email, $recipient_name, $message='')
{
    require("phpmailer/class.phpmailer.php");

    $mail = new PHPMailer();

    $mail->CharSet = "utf-8";
    $mail->IsSMTP();                                      // Set mailer to use SMTP
    $mail->Host = "mail.example.com";  // Specify main and backup server
    $mail->SMTPAuth = true;     // Turn on SMTP authentication
    $mail->Username = "myusername";  // SMTP username
    $mail->Password = "p@ssw0rd"; // SMTP password

    $mail->From = "[email protected]";
    $mail->FromName = "System-Ad";
    $mail->AddAddress($email, $recipient_name);

    $mail->WordWrap = 50;                                 // Set word wrap to 50 characters
    $mail->IsHTML(true);                                  // Set email format to HTML (true) or plain text (false)

    $mail->Subject = "This is a Sampleenter code here Email";
    $mail->Body    = $message;
    $mail->AltBody = "This is the body in plain text for non-HTML mail clients";
    $mail->AddEmbeddedImage('images/logo.png', 'logo', 'logo.png');
    $mail->addAttachment('files/file.xlsx');

    if(!$mail->Send())
    {
       echo "Message could not be sent. <p>";
       echo "Mailer Error: " . $mail->ErrorInfo;
       exit;
    }

    echo "Message has been sent";
}

How to update all MySQL table rows at the same time?

just use UPDATE query without condition like this

 UPDATE tablename SET online_status=0;

Get an image extension from an uploaded file in Laravel

Yet another way to do it:

//Where $file is an instance of Illuminate\Http\UploadFile
$extension = $file->getClientOriginalExtension();

OperationalError, no such column. Django

You did not migrated all changes you made in model. so 1) python manage.py makemigrations 2) python manage.py migrate 3) python manag.py runserver it works 100%

new DateTime() vs default(DateTime)

No, they are identical.

default(), for any value type (DateTime is a value type) will always call the parameterless constructor.

C# error: Use of unassigned local variable

The compiler only knows that the code is or isn't reachable if you use "return". Think of Environment.Exit() as a function that you call, and the compiler don't know that it will close the application.

Wait for a void async method

If you can change the signature of your function to async Task then you can use the code presented here

How to split a string in two and store it in a field

I would suggest the following:

String[] parsedInput = str.split("\n"); String firstName = parsedInput[0].split(": ")[1]; String lastName = parsedInput[1].split(": ")[1]; myMap.put(firstName,lastName); 

Python Replace \\ with \

path = "C:\\Users\\Programming\\Downloads"
# Replace \\ with a \ along with any random key multiple times
path.replace('\\', '\pppyyyttthhhooonnn')
# Now replace pppyyyttthhhooonnn with a blank string
path.replace("pppyyyttthhhooonnn", "")

print(path)

#Output... C:\Users\Programming\Downloads

How to get Current Directory?

I guess, that the easiest way to locate the current directory is to cut it from command line args.

#include <string>
#include <iostream>

int main(int argc, char* argv[])
{
  std::string cur_dir(argv[0]);
  int pos = cur_dir.find_last_of("/\\");

  std::cout << "path: " << cur_dir.substr(0, pos) << std::endl;
  std::cout << "file: " << cur_dir.substr(pos+1) << std::endl;
  return 0;
}

You may know that every program gets its executable name as first command line argument. So you can use this.

How to reformat JSON in Notepad++?

For Notepad++ v.7.6 and above Plugins Admin... is available.

  1. Open Menu Plugins > Plugins Admin...

  2. Search JSON Viewer

  3. Check JSON Viewer in List

  4. Click on Install Button

  5. Restart Notepad++

  6. Select JSON text

  7. Go to Plugins > JSON Viewer > Format JSON ( Ctrl + Alt + Shift + M )

We can install any Notepad++ supported plugins using Plugins Admin...

LinearLayout not expanding inside a ScrollView

I know this post is very old, For those who don't want to use android:fillViewport="true" because it sometimes doesn't bring up the edittext above keyboard. Use Relative layout instead of LinearLayout it solves the purpose.

Mercurial: how to amend the last commit?

Assuming that you have not yet propagated your changes, here is what you can do.

  • Add to your .hgrc:

    [extensions]
    mq =
    
  • In your repository:

    hg qimport -r0:tip
    hg qpop -a
    

    Of course you need not start with revision zero or pop all patches, for the last just one pop (hg qpop) suffices (see below).

  • remove the last entry in the .hg/patches/series file, or the patches you do not like. Reordering is possible too.

  • hg qpush -a; hg qfinish -a
  • remove the .diff files (unapplied patches) still in .hg/patches (should be one in your case).

If you don't want to take back all of your patch, you can edit it by using hg qimport -r0:tip (or similar), then edit stuff and use hg qrefresh to merge the changes into the topmost patch on your stack. Read hg help qrefresh.

By editing .hg/patches/series, you can even remove several patches, or reorder some. If your last revision is 99, you may just use hg qimport -r98:tip; hg qpop; [edit series file]; hg qpush -a; hg qfinish -a.

Of course, this procedure is highly discouraged and risky. Make a backup of everything before you do this!

As a sidenote, I've done it zillions of times on private-only repositories.

How do write IF ELSE statement in a MySQL query

You probably want to use a CASE expression.

They look like this:

SELECT col1, col2, (case when (action = 2 and state = 0) 
 THEN
      1 
 ELSE
      0 
 END)
 as state from tbl1;

How to test if a string is basically an integer in quotes using Ruby

You can use regular expressions. Here is the function with @janm's suggestions.

class String
    def is_i?
       !!(self =~ /\A[-+]?[0-9]+\z/)
    end
end

An edited version according to comment from @wich:

class String
    def is_i?
       /\A[-+]?\d+\z/ === self
    end
end

In case you only need to check positive numbers

  if !/\A\d+\z/.match(string_to_check)
      #Is not a positive number
  else
      #Is all good ..continue
  end  

Difference between `npm start` & `node app.js`, when starting app?

From the man page, npm start:

runs a package's "start" script, if one was provided. If no version is specified, then it starts the "active" version.

Admittedly, that description is completely unhelpful, and that's all it says. At least it's more documented than socket.io.

Anyhow, what really happens is that npm looks in your package.json file, and if you have something like

"scripts": { "start": "coffee server.coffee" }

then it will do that. If npm can't find your start script, it defaults to:

node server.js

 

No shadow by default on Toolbar?

Google released the Design Support library a few weeks ago and there is a nifty solution for this problem in this library.

Add the Design Support library as a dependency in build.gradle :

compile 'com.android.support:design:22.2.0'

Add AppBarLayout supplied by the library as a wrapper around your Toolbar layout to generate a drop shadow.

    <android.support.design.widget.AppBarLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content">
       <android.support.v7.widget.Toolbar
           .../>
    </android.support.design.widget.AppBarLayout>

Here is the result :

enter image description here

There are lots of other tricks with the design support library.

  1. http://inthecheesefactory.com/blog/android-design-support-library-codelab/en
  2. http://android-developers.blogspot.in/2015/05/android-design-support-library.html

AndroidX

As above but with dependency:

implementation 'com.google.android.material:material:1.0.0'

and com.google.android.material.appbar.AppBarLayout

Android Studio : How to uninstall APK (or execute adb command) automatically before Run or Debug?

A simple three-step process (checked on mac terminal)

  1. Connect your android device (please connect 1 android Device at a time), preferably by a cable & Confirm connection by (this will list Device's ID device ID)

    adb devices
    
  2. Then to list all app packages on the connected device by running, on terminal

    adb shell pm list packages -f -3 
    
  3. Then uninstall as explained earlier

    adb uninstall <package_name> 
    

Where is JAVA_HOME on macOS Mojave (10.14) to Lion (10.7)?

If you are in need to have multiple versions of JDK under Mac OS X (Yosemite), it might be helpful to add some scripting for automated switching between them.

What you do is to edit your ~/.bash_profile and add the following:

function setjdk() {
  if [ $# -ne 0 ]; then
   removeFromPath '/System/Library/Frameworks/JavaVM.framework/Home/bin'
   if [ -n "${JAVA_HOME+x}" ]; then
    removeFromPath $JAVA_HOME
   fi
   export JAVA_HOME=`/usr/libexec/java_home -v $@`
   export PATH=$JAVA_HOME/bin:$PATH
  fi
 }
 function removeFromPath() {
  export PATH=$(echo $PATH | sed -E -e "s;:$1;;" -e "s;$1:?;;")
 }
setjdk 1.7

What the script does is to first remove other JDK versions in the PATH so that they won’t interfere with our new JDK version. Then it makes some clever use of /usr/libexec/java_home which is a command that lists installed JDK versions. The -v argument tells java_home to return the path of the JDK with the supplied version, for example 1.7. We also update the PATH to point to the bin directory of the newly found JAVA_HOME directory. At the end we can simply execute the function using

setjdk 1.7

which selects the latest installed JDK version of the 1.7 branch. To select a specific version you can simply execute

setjdk 1.7.0_51

instead. Run /usr/libexec/java_home -V to get more details on how to choose versions.

P.S. Do not forget to source ~/.bash_profile after you save it.

How do I rename the android package name?

What I did was the following :

I simply created the package with the desired name , in the src folder , next to the current package with current name.

I dragged all contents of current package to new package , intellij popped a dialog box asking me if I want to refactor inside package references and project references to new package , I clicked 'yes' and TA-DAAA , worked like a charm.

How to encode text to base64 in python

Whilst you can of course use the base64 module, you can also to use the codecs module (referred to in your error message) for binary encodings (meaning non-standard & non-text encodings).

For example:

import codecs
my_bytes = b"Hello World!"
codecs.encode(my_bytes, "base64")
codecs.encode(my_bytes, "hex")
codecs.encode(my_bytes, "zip")
codecs.encode(my_bytes, "bz2")

This can come in useful for large data as you can chain them to get compressed and json-serializable values:

my_large_bytes = my_bytes * 10000
codecs.decode(
    codecs.encode(
        codecs.encode(
            my_large_bytes,
            "zip"
        ),
        "base64"),
    "utf8"
)

Refs:

Simple proof that GUID is not unique

If the number of UUID being generated follows Moore's law, the impression of never running out of GUID in the foreseeable future is false.

With 2 ^ 128 UUIDs, it will only take 18 months * Log2(2^128) ~= 192 years, before we run out of all UUIDs.

And I believe (with no statistical proof what-so-ever) in the past few years since mass adoption of UUID, the speed we are generating UUID is increasing way faster than Moore's law dictates. In other words, we probably have less than 192 years until we have to deal with UUID crisis, that's a lot sooner than end of universe.

But since we definitely won't be running them out by the end of 2012, we'll leave it to other species to worry about the problem.

How to add data via $.ajax ( serialize() + extra data ) like this

Personally, I'd append the element to the form instead of hacking the serialized data, e.g.

moredata = 'your custom data here';

// do what you like with the input
$input = $('<input type="text" name="moredata"/>').val(morevalue);

// append to the form
$('#myForm').append($input);

// then..
data: $('#myForm').serialize()

That way, you don't have to worry about ? or &

How to get DATE from DATETIME Column in SQL?

Simply cast your timestamp AS DATE, like this:

SELECT CAST(tstamp AS DATE)

SQLFiddle Demo

In other words, your statement would look like this:

SELECT SUM(transaction_amount)
FROM mytable
WHERE Card_No='123'
  AND CAST(transaction_date AS DATE) = target_date

What is nice about CAST is that it works exactly the same on most SQL engines (SQL Server, PostgreSQL, MySQL), and is much easier to remember how to use it. Methods using CONVERT() or TO_DATE() are specific to each SQL engine and make your code non-portable.

Unnamed/anonymous namespaces vs. static functions

A compiler specific difference between anonymous namespaces and static functions can be seen compiling the following code.

#include <iostream>

namespace
{
    void unreferenced()
    {
        std::cout << "Unreferenced";
    }

    void referenced()
    {
        std::cout << "Referenced";
    }
}

static void static_unreferenced()
{
    std::cout << "Unreferenced";
}

static void static_referenced()
{
    std::cout << "Referenced";
}

int main()
{
    referenced();
    static_referenced();
    return 0;
}

Compiling this code with VS 2017 (specifying the level 4 warning flag /W4 to enable warning C4505: unreferenced local function has been removed) and gcc 4.9 with the -Wunused-function or -Wall flag shows that VS 2017 will only produce a warning for the unused static function. gcc 4.9 and higher, as well as clang 3.3 and higher, will produce warnings for the unreferenced function in the namespace and also a warning for the unused static function.

Live demo of gcc 4.9 and MSVC 2017

How do I create a round cornered UILabel on the iPhone?

In Monotouch / Xamarin.iOS I solved the same problem like this:

UILabel exampleLabel = new UILabel(new CGRect(0, 0, 100, 50))
        {
            Text = "Hello Monotouch red label"
        };
        exampleLabel.Layer.MasksToBounds = true;
        exampleLabel.Layer.CornerRadius = 8;
        exampleLabel.Layer.BorderColor = UIColor.Red.CGColor;
        exampleLabel.Layer.BorderWidth = 2;

What is the use of ObservableCollection in .net?

From Pro C# 5.0 and the .NET 4.5 Framework

The ObservableCollection<T> class is very useful in that it has the ability to inform external objects when its contents have changed in some way (as you might guess, working with ReadOnlyObservableCollection<T> is very similar, but read-only in nature). In many ways, working with the ObservableCollection<T> is identical to working with List<T>, given that both of these classes implement the same core interfaces. What makes the ObservableCollection<T> class unique is that this class supports an event named CollectionChanged. This event will fire whenever a new item is inserted, a current item is removed (or relocated), or if the entire collection is modified. Like any event, CollectionChanged is defined in terms of a delegate, which in this case is NotifyCollectionChangedEventHandler. This delegate can call any method that takes an object as the first parameter, and a NotifyCollectionChangedEventArgs as the second. Consider the following Main() method, which populates an observable collection containing Person objects and wires up the CollectionChanged event:

class Program
{
   static void Main(string[] args)
   {
     // Make a collection to observe and add a few Person objects.
     ObservableCollection<Person> people = new ObservableCollection<Person>()
     {
        new Person{ FirstName = "Peter", LastName = "Murphy", Age = 52 },
        new Person{ FirstName = "Kevin", LastName = "Key", Age = 48 },
     };
     // Wire up the CollectionChanged event.
     people.CollectionChanged += people_CollectionChanged;
     // Now add a new item.
     people.Add(new Person("Fred", "Smith", 32));

     // Remove an item.
     people.RemoveAt(0);

     Console.ReadLine();
   }
   static void people_CollectionChanged(object sender, System.Collections.Specialized.NotifyCollectionChangedEventArgs e)
   {
       // What was the action that caused the event?
        Console.WriteLine("Action for this event: {0}", e.Action);

        // They removed something. 
        if (e.Action == System.Collections.Specialized.NotifyCollectionChangedAction.Remove)
        {
            Console.WriteLine("Here are the OLD items:");
            foreach (Person p in e.OldItems)
            {
                Console.WriteLine(p.ToString());
            }
            Console.WriteLine();
        }

        // They added something. 
        if (e.Action == System.Collections.Specialized.NotifyCollectionChangedAction.Add)
        {
            // Now show the NEW items that were inserted.
            Console.WriteLine("Here are the NEW items:");
            foreach (Person p in e.NewItems)
            {
                Console.WriteLine(p.ToString());
            }
        }
   }
}

The incoming NotifyCollectionChangedEventArgs parameter defines two important properties, OldItems and NewItems, which will give you a list of items that were currently in the collection before the event fired, and the new items that were involved in the change. However, you will want to examine these lists only under the correct circumstances. Recall that the CollectionChanged event can fire when items are added, removed, relocated, or reset. To discover which of these actions triggered the event, you can use the Action property of NotifyCollectionChangedEventArgs. The Action property can be tested against any of the following members of the NotifyCollectionChangedAction enumeration:

public enum NotifyCollectionChangedAction
{
Add = 0,
Remove = 1,
Replace = 2,
Move = 3,
Reset = 4,
}

Members of System.Collections.ObjectModel

How do you update Xcode on OSX to the latest version?

You DO NOT need to upgrade Xcode.

Just open the file /usr/local/Homebrew/Library/Homebrew/extend/os/mac/diagnostic.rb ,

then remove this line check_xcode_minimum_version in the following function.

def fatal_build_from_source_checks
    %w[
      check_xcode_license_approved
      check_xcode_minimum_version //<-- this one
      check_clt_minimum_version
      check_if_xcode_needs_clt_installed
    ].freeze
    end

Then brew install should works fine.

What is the difference between sed and awk?

1) What is the difference between awk and sed ?

Both are tools that transform text. BUT awk can do more things besides just manipulating text. Its a programming language by itself with most of the things you learn in programming, like arrays, loops, if/else flow control etc You can "program" in sed as well, but you won't want to maintain the code written in it.

2) What kind of application are best use cases for sed and awk tools ?

Conclusion: Use sed for very simple text parsing. Anything beyond that, awk is better. In fact, you can ditch sed altogether and just use awk. Since their functions overlap and awk can do more, just use awk. You will reduce your learning curve as well.

How do you add an in-app purchase to an iOS application?

Swift Answer

This is meant to supplement my Objective-C answer for Swift users, to keep the Objective-C answer from getting too big.

Setup

First, set up the in-app purchase on appstoreconnect.apple.com. Follow the beginning part of my Objective-C answer (steps 1-13, under the App Store Connect header) for instructions on doing that.

It could take a few hours for your product ID to register in App Store Connect, so be patient.

Now that you've set up your in-app purchase information on App Store Connect, we need to add Apple's framework for in-app-purchases, StoreKit, to the app.

Go into your Xcode project, and go to the application manager (blue page-like icon at the top of the left bar where your app's files are). Click on your app under targets on the left (it should be the first option), then go to "Capabilities" at the top. On the list, you should see an option "In-App Purchase". Turn this capability ON, and Xcode will add StoreKit to your project.

Coding

Now, we're going to start coding!

First, make a new swift file that will manage all of your in-app-purchases. I'm going to call it IAPManager.swift.

In this file, we're going to create a new class, called IAPManager that is a SKProductsRequestDelegate and SKPaymentTransactionObserver. At the top, make sure you import Foundation and StoreKit

import Foundation
import StoreKit

public class IAPManager: NSObject, SKProductsRequestDelegate,
                         SKPaymentTransactionObserver {
}

Next, we're going to add a variable to define the identifier for our in-app purchase (you could also use an enum, which would be easier to maintain if you have multiple IAPs).

// This should the ID of the in-app-purchase you made on AppStore Connect.
// if you have multiple IAPs, you'll need to store their identifiers in
// other variables, too (or, preferably in an enum).
let removeAdsID = "com.skiplit.removeAds"

Let's add an initializer for our class next:

// This is the initializer for your IAPManager class
//
// A better, and more scaleable way of doing this
// is to also accept a callback in the initializer, and call
// that callback in places like the paymentQueue function, and
// in all functions in this class, in place of calls to functions
// in RemoveAdsManager (you'll see those calls in the code below).

let productID: String
init(productID: String){
    self.productID = productID
}

Now, we're going to add the required functions for SKProductsRequestDelegate and SKPaymentTransactionObserver to work:

We'll add the RemoveAdsManager class later

// This is called when a SKProductsRequest receives a response
public func productsRequest(_ request: SKProductsRequest, didReceive response: SKProductsResponse){
    // Let's try to get the first product from the response
    // to the request
    if let product = response.products.first{
        // We were able to get the product! Make a new payment
        // using this product
        let payment = SKPayment(product: product)

        // add the new payment to the queue
        SKPaymentQueue.default().add(self)
        SKPaymentQueue.default().add(payment)
    }
    else{
        // Something went wrong! It is likely that either
        // the user doesn't have internet connection, or
        // your product ID is wrong!
        //
        // Tell the user in requestFailed() by sending an alert,
        // or something of the sort

        RemoveAdsManager.removeAdsFailure()
    }
}

// This is called when the user restores their IAP sucessfully
private func paymentQueueRestoreCompletedTransactionsFinished(_ queue: SKPaymentQueue){
    // For every transaction in the transaction queue...
    for transaction in queue.transactions{
        // If that transaction was restored
        if transaction.transactionState == .restored{
            // get the producted ID from the transaction
            let productID = transaction.payment.productIdentifier

            // In this case, we have only one IAP, so we don't need to check
            // what IAP it is. However, this is useful if you have multiple IAPs!
            // You'll need to figure out which one was restored
            if(productID.lowercased() == IAPManager.removeAdsID.lowercased()){
                // Restore the user's purchases
                RemoveAdsManager.restoreRemoveAdsSuccess()
            }

            // finish the payment
            SKPaymentQueue.default().finishTransaction(transaction)
        }
    }
}

// This is called when the state of the IAP changes -- from purchasing to purchased, for example.
// This is where the magic happens :)
public func paymentQueue(_ queue: SKPaymentQueue, updatedTransactions transactions: [SKPaymentTransaction]){
    for transaction in transactions{
        // get the producted ID from the transaction
        let productID = transaction.payment.productIdentifier

        // In this case, we have only one IAP, so we don't need to check
        // what IAP it is.
        // However, if you have multiple IAPs, you'll need to use productID
        // to check what functions you should run here!

        switch transaction.transactionState{
        case .purchasing:
            // if the user is currently purchasing the IAP,
            // we don't need to do anything.
            //
            // You could use this to show the user
            // an activity indicator, or something like that
            break
        case .purchased:
            // the user successfully purchased the IAP!
            RemoveAdsManager.removeAdsSuccess()
            SKPaymentQueue.default().finishTransaction(transaction)
        case .restored:
                // the user restored their IAP!
                IAPTestingHandler.restoreRemoveAdsSuccess()
                SKPaymentQueue.default().finishTransaction(transaction)
        case .failed:
                // The transaction failed!
                RemoveAdsManager.removeAdsFailure()
                // finish the transaction
                SKPaymentQueue.default().finishTransaction(transaction)
        case .deferred:
                // This happens when the IAP needs an external action
                // in order to proceeded, like Ask to Buy
                RemoveAdsManager.removeAdsDeferred()
                break
        }
    }
}

Now let's add some functions that can be used to start a purchase or a restore purchases:

// Call this when you want to begin a purchase
// for the productID you gave to the initializer
public func beginPurchase(){
    // If the user can make payments
    if SKPaymentQueue.canMakePayments(){
        // Create a new request
        let request = SKProductsRequest(productIdentifiers: [productID])
        // Set the request delegate to self, so we receive a response
        request.delegate = self
        // start the request
        request.start()
    }
    else{
        // Otherwise, tell the user that
        // they are not authorized to make payments,
        // due to parental controls, etc
    }
}

// Call this when you want to restore all purchases
// regardless of the productID you gave to the initializer
public func beginRestorePurchases(){
    // restore purchases, and give responses to self
    SKPaymentQueue.default().add(self)
    SKPaymentQueue.default().restoreCompletedTransactions()
}

Next, let's add a new utilities class to manage our IAPs. All of this code could be in one class, but having it multiple makes it a little cleaner. I'm going to make a new class called RemoveAdsManager, and in it, put a few functions

public class RemoveAdsManager{

    class func removeAds()
    class func restoreRemoveAds()

    class func areAdsRemoved() -> Bool

    class func removeAdsSuccess()
    class func restoreRemoveAdsSuccess()
    class func removeAdsDeferred()
    class func removeAdsFailure()
}

The first three functions, removeAds, restoreRemoveAds, and areAdsRemoved, are functions that you'll call to do certain actions. The last four are one that will be called by IAPManager.

Let's add some code to the first two functions, removeAds and restoreRemoveAds:

// Call this when the user wants
// to remove ads, like when they
// press a "remove ads" button
class func removeAds(){
    // Before starting the purchase, you could tell the
    // user that their purchase is happening, maybe with
    // an activity indicator

    let iap = IAPManager(productID: IAPManager.removeAdsID)
    iap.beginPurchase()
}

// Call this when the user wants
// to restore their IAP purchases,
// like when they press a "restore
// purchases" button.
class func restoreRemoveAds(){
    // Before starting the purchase, you could tell the
    // user that the restore action is happening, maybe with
    // an activity indicator

    let iap = IAPManager(productID: IAPManager.removeAdsID)
    iap.beginRestorePurchases()
}

And lastly, let's add some code to the last five functions.

// Call this to check whether or not
// ads are removed. You can use the
// result of this to hide or show
// ads
class func areAdsRemoved() -> Bool{
    // This is the code that is run to check
    // if the user has the IAP.

    return UserDefaults.standard.bool(forKey: "RemoveAdsPurchased")
}

// This will be called by IAPManager
// when the user sucessfully purchases
// the IAP
class func removeAdsSuccess(){
    // This is the code that is run to actually
    // give the IAP to the user!
    //
    // I'm using UserDefaults in this example,
    // but you may want to use Keychain,
    // or some other method, as UserDefaults
    // can be modified by users using their
    // computer, if they know how to, more
    // easily than Keychain

    UserDefaults.standard.set(true, forKey: "RemoveAdsPurchased")
    UserDefaults.standard.synchronize()
}

// This will be called by IAPManager
// when the user sucessfully restores
//  their purchases
class func restoreRemoveAdsSuccess(){
    // Give the user their IAP back! Likely all you'll need to
    // do is call the same function you call when a user
    // sucessfully completes their purchase. In this case, removeAdsSuccess()

    removeAdsSuccess()
}

// This will be called by IAPManager
// when the IAP failed
class func removeAdsFailure(){
    // Send the user a message explaining that the IAP
    // failed for some reason, and to try again later
}

// This will be called by IAPManager
// when the IAP gets deferred.
class func removeAdsDeferred(){
    // Send the user a message explaining that the IAP
    // was deferred, and pending an external action, like
    // Ask to Buy.
}

Putting it all together, we get something like this:

import Foundation
import StoreKit

public class RemoveAdsManager{

    // Call this when the user wants
    // to remove ads, like when they
    // press a "remove ads" button
    class func removeAds(){
        // Before starting the purchase, you could tell the
        // user that their purchase is happening, maybe with
        // an activity indicator

        let iap = IAPManager(productID: IAPManager.removeAdsID)
        iap.beginPurchase()
    }

    // Call this when the user wants
    // to restore their IAP purchases,
    // like when they press a "restore
    // purchases" button.
    class func restoreRemoveAds(){
        // Before starting the purchase, you could tell the
        // user that the restore action is happening, maybe with
        // an activity indicator

        let iap = IAPManager(productID: IAPManager.removeAdsID)
        iap.beginRestorePurchases()
    }

    // Call this to check whether or not
    // ads are removed. You can use the
    // result of this to hide or show
    // ads
    class func areAdsRemoved() -> Bool{
        // This is the code that is run to check
        // if the user has the IAP.

        return UserDefaults.standard.bool(forKey: "RemoveAdsPurchased")
    }

    // This will be called by IAPManager
    // when the user sucessfully purchases
    // the IAP
    class func removeAdsSuccess(){
        // This is the code that is run to actually
        // give the IAP to the user!
        //
        // I'm using UserDefaults in this example,
        // but you may want to use Keychain,
        // or some other method, as UserDefaults
        // can be modified by users using their
        // computer, if they know how to, more
        // easily than Keychain

        UserDefaults.standard.set(true, forKey: "RemoveAdsPurchased")
        UserDefaults.standard.synchronize()
    }

    // This will be called by IAPManager
    // when the user sucessfully restores
    //  their purchases
    class func restoreRemoveAdsSuccess(){
        // Give the user their IAP back! Likely all you'll need to
        // do is call the same function you call when a user
        // sucessfully completes their purchase. In this case, removeAdsSuccess()
        removeAdsSuccess()
    }

    // This will be called by IAPManager
    // when the IAP failed
    class func removeAdsFailure(){
        // Send the user a message explaining that the IAP
        // failed for some reason, and to try again later
    }

    // This will be called by IAPManager
    // when the IAP gets deferred.
    class func removeAdsDeferred(){
        // Send the user a message explaining that the IAP
        // was deferred, and pending an external action, like
        // Ask to Buy.
    }

}

public class IAPManager: NSObject, SKProductsRequestDelegate, SKPaymentTransactionObserver{

    // This should the ID of the in-app-purchase you made on AppStore Connect.
    // if you have multiple IAPs, you'll need to store their identifiers in
    // other variables, too (or, preferably in an enum).
    static let removeAdsID = "com.skiplit.removeAds"

    // This is the initializer for your IAPManager class
    //
    // An alternative, and more scaleable way of doing this
    // is to also accept a callback in the initializer, and call
    // that callback in places like the paymentQueue function, and
    // in all functions in this class, in place of calls to functions
    // in RemoveAdsManager.
    let productID: String
    init(productID: String){
        self.productID = productID
    }

    // Call this when you want to begin a purchase
    // for the productID you gave to the initializer
    public func beginPurchase(){
        // If the user can make payments
        if SKPaymentQueue.canMakePayments(){
            // Create a new request
            let request = SKProductsRequest(productIdentifiers: [productID])
            request.delegate = self
            request.start()
        }
        else{
            // Otherwise, tell the user that
            // they are not authorized to make payments,
            // due to parental controls, etc
        }
    }

    // Call this when you want to restore all purchases
    // regardless of the productID you gave to the initializer
    public func beginRestorePurchases(){
        SKPaymentQueue.default().add(self)
        SKPaymentQueue.default().restoreCompletedTransactions()
    }

    // This is called when a SKProductsRequest receives a response
    public func productsRequest(_ request: SKProductsRequest, didReceive response: SKProductsResponse){
        // Let's try to get the first product from the response
        // to the request
        if let product = response.products.first{
            // We were able to get the product! Make a new payment
            // using this product
            let payment = SKPayment(product: product)

            // add the new payment to the queue
            SKPaymentQueue.default().add(self)
            SKPaymentQueue.default().add(payment)
        }
        else{
            // Something went wrong! It is likely that either
            // the user doesn't have internet connection, or
            // your product ID is wrong!
            //
            // Tell the user in requestFailed() by sending an alert,
            // or something of the sort

            RemoveAdsManager.removeAdsFailure()
        }
    }

    // This is called when the user restores their IAP sucessfully
    private func paymentQueueRestoreCompletedTransactionsFinished(_ queue: SKPaymentQueue){
        // For every transaction in the transaction queue...
        for transaction in queue.transactions{
            // If that transaction was restored
            if transaction.transactionState == .restored{
                // get the producted ID from the transaction
                let productID = transaction.payment.productIdentifier

                // In this case, we have only one IAP, so we don't need to check
                // what IAP it is. However, this is useful if you have multiple IAPs!
                // You'll need to figure out which one was restored
                if(productID.lowercased() == IAPManager.removeAdsID.lowercased()){
                    // Restore the user's purchases
                    RemoveAdsManager.restoreRemoveAdsSuccess()
                }

                // finish the payment
                SKPaymentQueue.default().finishTransaction(transaction)
            }
        }
    }

    // This is called when the state of the IAP changes -- from purchasing to purchased, for example.
    // This is where the magic happens :)
    public func paymentQueue(_ queue: SKPaymentQueue, updatedTransactions transactions: [SKPaymentTransaction]){
        for transaction in transactions{
            // get the producted ID from the transaction
            let productID = transaction.payment.productIdentifier

            // In this case, we have only one IAP, so we don't need to check
            // what IAP it is.
            // However, if you have multiple IAPs, you'll need to use productID
            // to check what functions you should run here!

            switch transaction.transactionState{
            case .purchasing:
                // if the user is currently purchasing the IAP,
                // we don't need to do anything.
                //
                // You could use this to show the user
                // an activity indicator, or something like that
                break
            case .purchased:
                // the user sucessfully purchased the IAP!
                RemoveAdsManager.removeAdsSuccess()
                SKPaymentQueue.default().finishTransaction(transaction)
            case .restored:
                // the user restored their IAP!
                RemoveAdsManager.restoreRemoveAdsSuccess()
                SKPaymentQueue.default().finishTransaction(transaction)
            case .failed:
                // The transaction failed!
                RemoveAdsManager.removeAdsFailure()
                // finish the transaction
                SKPaymentQueue.default().finishTransaction(transaction)
            case .deferred:
                // This happens when the IAP needs an external action
                // in order to proceeded, like Ask to Buy
                RemoveAdsManager.removeAdsDeferred()
                break
            }
        }
    }

}

Lastly, you need to add some way for the user to start the purchase and call RemoveAdsManager.removeAds() and start a restore and call RemoveAdsManager.restoreRemoveAds(), like a button somewhere! Keep in mind that, per the App Store guidelines, you do need to provide a button to restore purchases somewhere.

Submitting for review

The last thing to do is submit your IAP for review on App Store Connect! For detailed instructions on doing that, you can follow the last part of my Objective-C answer, under the Submitting for review header.

What is a simple command line program or script to backup SQL server databases?

Microsoft's answer to backing up all user databases on SQL Express is here:

The process is: copy, paste, and execute their code (see below. I've commented some oddly non-commented lines at the top) as a query on your database server. That means you should first install the SQL Server Management Studio (or otherwise connect to your database server with SSMS). This code execution will create a stored procedure on your database server.

Create a batch file to execute the stored procedure, then use Task Scheduler to schedule a periodic (e.g. nightly) run of this batch file. My code (that works) is a slightly modified version of their first example:

sqlcmd -S .\SQLEXPRESS -E -Q "EXEC sp_BackupDatabases @backupLocation='E:\SQLBackups\', @backupType='F'" 

This worked for me, and I like it. Each time you run it, new backup files are created. You'll need to devise a method of deleting old backup files on a routine basis. I already have a routine that does that sort of thing, so I'll keep a couple of days' worth of backups on disk (long enough for them to get backed up by my normal backup routine), then I'll delete them. In other words, I'll always have a few days' worth of backups on hand without having to restore from my backup system.

I'll paste Microsoft's stored procedure creation script below:

--// Copyright © Microsoft Corporation.  All Rights Reserved.
--// This code released under the terms of the
--// Microsoft Public License (MS-PL, http://opensource.org/licenses/ms-pl.html.)

USE [master] 
GO 

/****** Object:  StoredProcedure [dbo].[sp_BackupDatabases] ******/ 

SET ANSI_NULLS ON 
GO 

SET QUOTED_IDENTIFIER ON 
GO 

 
-- ============================================= 
-- Author: Microsoft 
-- Create date: 2010-02-06
-- Description: Backup Databases for SQLExpress
-- Parameter1: databaseName 
-- Parameter2: backupType F=full, D=differential, L=log
-- Parameter3: backup file location
-- =============================================

CREATE PROCEDURE [dbo].[sp_BackupDatabases]  
            @databaseName sysname = null,
            @backupType CHAR(1),
            @backupLocation nvarchar(200) 
AS 

       SET NOCOUNT ON; 

            DECLARE @DBs TABLE
            (
                  ID int IDENTITY PRIMARY KEY,
                  DBNAME nvarchar(500)
            )
           
             -- Pick out only databases which are online in case ALL databases are chosen to be backed up

             -- If specific database is chosen to be backed up only pick that out from @DBs

            INSERT INTO @DBs (DBNAME)
            SELECT Name FROM master.sys.databases
            where state=0
            AND name=@DatabaseName
            OR @DatabaseName IS NULL
            ORDER BY Name

 
           -- Filter out databases which do not need to backed up
 
           IF @backupType='F'
                  BEGIN
                  DELETE @DBs where DBNAME IN ('tempdb','Northwind','pubs','AdventureWorks')
                  END
            ELSE IF @backupType='D'
                  BEGIN
                  DELETE @DBs where DBNAME IN ('tempdb','Northwind','pubs','master','AdventureWorks')
                  END
            ELSE IF @backupType='L'
                  BEGIN
                  DELETE @DBs where DBNAME IN ('tempdb','Northwind','pubs','master','AdventureWorks')
                  END
            ELSE
                  BEGIN
                  RETURN
                  END
           

            -- Declare variables

            DECLARE @BackupName varchar(100)
            DECLARE @BackupFile varchar(100)
            DECLARE @DBNAME varchar(300)
            DECLARE @sqlCommand NVARCHAR(1000) 
        DECLARE @dateTime NVARCHAR(20)
            DECLARE @Loop int                  
                       
            -- Loop through the databases one by one

            SELECT @Loop = min(ID) FROM @DBs
       WHILE @Loop IS NOT NULL
      BEGIN
 
-- Database Names have to be in [dbname] format since some have - or _ in their name

      SET @DBNAME = '['+(SELECT DBNAME FROM @DBs WHERE ID = @Loop)+']'


-- Set the current date and time n yyyyhhmmss format

      SET @dateTime = REPLACE(CONVERT(VARCHAR, GETDATE(),101),'/','') + '_' +  REPLACE(CONVERT(VARCHAR, GETDATE(),108),':','')  
 

-- Create backup filename in path\filename.extension format for full,diff and log backups

      IF @backupType = 'F'
            SET @BackupFile = @backupLocation+REPLACE(REPLACE(@DBNAME, '[',''),']','')+ '_FULL_'+ @dateTime+ '.BAK'
      ELSE IF @backupType = 'D'
            SET @BackupFile = @backupLocation+REPLACE(REPLACE(@DBNAME, '[',''),']','')+ '_DIFF_'+ @dateTime+ '.BAK'
      ELSE IF @backupType = 'L'
            SET @BackupFile = @backupLocation+REPLACE(REPLACE(@DBNAME, '[',''),']','')+ '_LOG_'+ @dateTime+ '.TRN'
 

-- Provide the backup a name for storing in the media

      IF @backupType = 'F'
            SET @BackupName = REPLACE(REPLACE(@DBNAME,'[',''),']','') +' full backup for '+ @dateTime

      IF @backupType = 'D'
            SET @BackupName = REPLACE(REPLACE(@DBNAME,'[',''),']','') +' differential backup for '+ @dateTime

      IF @backupType = 'L'
            SET @BackupName = REPLACE(REPLACE(@DBNAME,'[',''),']','') +' log backup for '+ @dateTime


-- Generate the dynamic SQL command to be executed

       IF @backupType = 'F' 
                  BEGIN
               SET @sqlCommand = 'BACKUP DATABASE ' +@DBNAME+  ' TO DISK = '''+@BackupFile+ ''' WITH INIT, NAME= ''' +@BackupName+''', NOSKIP, NOFORMAT'
                  END

       IF @backupType = 'D'
                  BEGIN
               SET @sqlCommand = 'BACKUP DATABASE ' +@DBNAME+  ' TO DISK = '''+@BackupFile+ ''' WITH DIFFERENTIAL, INIT, NAME= ''' +@BackupName+''', NOSKIP, NOFORMAT'        
                  END

       IF @backupType = 'L' 
                  BEGIN
               SET @sqlCommand = 'BACKUP LOG ' +@DBNAME+  ' TO DISK = '''+@BackupFile+ ''' WITH INIT, NAME= ''' +@BackupName+''', NOSKIP, NOFORMAT'        
                  END
 

-- Execute the generated SQL command

       EXEC(@sqlCommand)

 
-- Goto the next database

SELECT @Loop = min(ID) FROM @DBs where ID>@Loop
 

END?

Subtracting Dates in Oracle - Number or Interval Datatype?

Ok, I don't normally answer my own questions but after a bit of tinkering, I have figured out definitively how Oracle stores the result of a DATE subtraction.

When you subtract 2 dates, the value is not a NUMBER datatype (as the Oracle 11.2 SQL Reference manual would have you believe). The internal datatype number of a DATE subtraction is 14, which is a non-documented internal datatype (NUMBER is internal datatype number 2). However, it is actually stored as 2 separate two's complement signed numbers, with the first 4 bytes used to represent the number of days and the last 4 bytes used to represent the number of seconds.

An example of a DATE subtraction resulting in a positive integer difference:

select date '2009-08-07' - date '2008-08-08' from dual;

Results in:

DATE'2009-08-07'-DATE'2008-08-08'
---------------------------------
                              364

select dump(date '2009-08-07' - date '2008-08-08') from dual;

DUMP(DATE'2009-08-07'-DATE'2008
-------------------------------
Typ=14 Len=8: 108,1,0,0,0,0,0,0

Recall that the result is represented as a 2 seperate two's complement signed 4 byte numbers. Since there are no decimals in this case (364 days and 0 hours exactly), the last 4 bytes are all 0s and can be ignored. For the first 4 bytes, because my CPU has a little-endian architecture, the bytes are reversed and should be read as 1,108 or 0x16c, which is decimal 364.

An example of a DATE subtraction resulting in a negative integer difference:

select date '1000-08-07' - date '2008-08-08' from dual;

Results in:

DATE'1000-08-07'-DATE'2008-08-08'
---------------------------------
                          -368160

select dump(date '1000-08-07' - date '2008-08-08') from dual;

DUMP(DATE'1000-08-07'-DATE'2008-08-0
------------------------------------
Typ=14 Len=8: 224,97,250,255,0,0,0,0

Again, since I am using a little-endian machine, the bytes are reversed and should be read as 255,250,97,224 which corresponds to 11111111 11111010 01100001 11011111. Now since this is in two's complement signed binary numeral encoding, we know that the number is negative because the leftmost binary digit is a 1. To convert this into a decimal number we would have to reverse the 2's complement (subtract 1 then do the one's complement) resulting in: 00000000 00000101 10011110 00100000 which equals -368160 as suspected.

An example of a DATE subtraction resulting in a decimal difference:

select to_date('08/AUG/2004 14:00:00', 'DD/MON/YYYY HH24:MI:SS'
 - to_date('08/AUG/2004 8:00:00', 'DD/MON/YYYY HH24:MI:SS') from dual;

TO_DATE('08/AUG/200414:00:00','DD/MON/YYYYHH24:MI:SS')-TO_DATE('08/AUG/20048:00:
--------------------------------------------------------------------------------
                                                                             .25

The difference between those 2 dates is 0.25 days or 6 hours.

select dump(to_date('08/AUG/2004 14:00:00', 'DD/MON/YYYY HH24:MI:SS')
 - to_date('08/AUG/2004 8:00:00', 'DD/MON/YYYY HH24:MI:SS')) from dual;

DUMP(TO_DATE('08/AUG/200414:00:
-------------------------------
Typ=14 Len=8: 0,0,0,0,96,84,0,0

Now this time, since the difference is 0 days and 6 hours, it is expected that the first 4 bytes are 0. For the last 4 bytes, we can reverse them (because CPU is little-endian) and get 84,96 = 01010100 01100000 base 2 = 21600 in decimal. Converting 21600 seconds to hours gives you 6 hours which is the difference which we expected.

Hope this helps anyone who was wondering how a DATE subtraction is actually stored.


You get the syntax error because the date math does not return a NUMBER, but it returns an INTERVAL:

SQL> SELECT DUMP(SYSDATE - start_date) from test;

DUMP(SYSDATE-START_DATE)
-------------------------------------- 
Typ=14 Len=8: 188,10,0,0,223,65,1,0

You need to convert the number in your example into an INTERVAL first using the NUMTODSINTERVAL Function

For example:

SQL> SELECT (SYSDATE - start_date) DAY(5) TO SECOND from test;

(SYSDATE-START_DATE)DAY(5)TOSECOND
----------------------------------
+02748 22:50:04.000000

SQL> SELECT (SYSDATE - start_date) from test;

(SYSDATE-START_DATE)
--------------------
           2748.9515

SQL> select NUMTODSINTERVAL(2748.9515, 'day') from dual;

NUMTODSINTERVAL(2748.9515,'DAY')
--------------------------------
+000002748 22:50:09.600000000

SQL>

Based on the reverse cast with the NUMTODSINTERVAL() function, it appears some rounding is lost in translation.

Conditional HTML Attributes using Razor MVC3

Note you can do something like this(at least in MVC3):

<td align="left" @(isOddRow ? "class=TopBorder" : "style=border:0px") >

What I believed was razor adding quotes was actually the browser. As Rism pointed out when testing with MVC 4(I haven't tested with MVC 3 but I assume behavior hasn't changed), this actually produces class=TopBorder but browsers are able to parse this fine. The HTML parsers are somewhat forgiving on missing attribute quotes, but this can break if you have spaces or certain characters.

<td align="left" class="TopBorder" >

OR

<td align="left" style="border:0px" >

What goes wrong with providing your own quotes

If you try to use some of the usual C# conventions for nested quotes, you'll end up with more quotes than you bargained for because Razor is trying to safely escape them. For example:

<button type="button" @(true ? "style=\"border:0px\"" : string.Empty)>

This should evaluate to <button type="button" style="border:0px"> but Razor escapes all output from C# and thus produces:

style=&quot;border:0px&quot;

You will only see this if you view the response over the network. If you use an HTML inspector, often you are actually seeing the DOM, not the raw HTML. Browsers parse HTML into the DOM, and the after-parsing DOM representation already has some niceties applied. In this case the Browser sees there aren't quotes around the attribute value, adds them:

style="&quot;border:0px&quot;"

But in the DOM inspector HTML character codes display properly so you actually see:

style=""border:0px""

In Chrome, if you right-click and select Edit HTML, it switch back so you can see those nasty HTML character codes, making it clear you have real outer quotes, and HTML encoded inner quotes.

So the problem with trying to do the quoting yourself is Razor escapes these.

If you want complete control of quotes

Use Html.Raw to prevent quote escaping:

<td @Html.Raw( someBoolean ? "rel='tooltip' data-container='.drillDown a'" : "" )>

Renders as:

<td rel='tooltip' title='Drilldown' data-container='.drillDown a'>

The above is perfectly safe because I'm not outputting any HTML from a variable. The only variable involved is the ternary condition. However, beware that this last technique might expose you to certain security problems if building strings from user supplied data. E.g. if you built an attribute from data fields that originated from user supplied data, use of Html.Raw means that string could contain a premature ending of the attribute and tag, then begin a script tag that does something on behalf of the currently logged in user(possibly different than the logged in user). Maybe you have a page with a list of all users pictures and you are setting a tooltip to be the username of each person, and one users named himself '/><script>$.post('changepassword.php?password=123')</script> and now any other user who views this page has their password instantly changed to a password that the malicious user knows.

XMLHttpRequest status 0 (responseText is empty)

Edit: Please read Malvolio's comments below as this answer's knowledge is outdated.

You cannot do cross-domain XMLHttpRequests.

The call to 127.0.0.1 works because your test page is located at 127.0.0.1, and the local test also works since, well... it's a local test.

The other two tests fail because JavaScript cannot communicate with a distant server through XMLHttpRequest.

You might instead consider either:

  • XMLHttp-request your own server to fetch your remote XML content for you (php script, for example)
  • Trying to use a service like GoogleAppEngine if you want to keep it full JavaScript.

Hope that helps

How to plot two columns of a pandas data frame using points?

Pandas uses matplotlib as a library for basic plots. The easiest way in your case will using the following:

import pandas as pd
import numpy as np

#creating sample data 
sample_data={'col_name_1':np.random.rand(20),
      'col_name_2': np.random.rand(20)}
df= pd.DataFrame(sample_data)
df.plot(x='col_name_1', y='col_name_2', style='o')

enter image description here

However, I would recommend to use seaborn as an alternative solution if you want have more customized plots while not going into the basic level of matplotlib. In this case you the solution will be following:

import pandas as pd
import seaborn as sns
import numpy as np

#creating sample data 
sample_data={'col_name_1':np.random.rand(20),
      'col_name_2': np.random.rand(20)}
df= pd.DataFrame(sample_data)
sns.scatterplot(x="col_name_1", y="col_name_2", data=df)

enter image description here

How to make canvas responsive

You can have a responsive canvas in 3 short and simple steps:

  1. Remove the width and height attributes from your <canvas>.

    <canvas id="responsive-canvas"></canvas>
    
  2. Using CSS, set the width of your canvas to 100%.

    #responsive-canvas {
      width: 100%;
    }
    
  3. Using JavaScript, set the height to some ratio of the width.

    var canvas = document.getElementById('responsive-canvas');
    var heightRatio = 1.5;
    canvas.height = canvas.width * heightRatio;
    

Asp.NET Web API - 405 - HTTP verb used to access this page is not allowed - how to set handler mappings

Change Your Web.Config file as below. It will act like charm.

In node <system.webServer> add below portion of code

<modules runAllManagedModulesForAllRequests="true">
  <remove name="WebDAVModule"/>
</modules>

After adding, your Web.Config will look like below

<system.webServer>
    <validation validateIntegratedModeConfiguration="false" />
    <modules runAllManagedModulesForAllRequests="true">
        <remove name="WebDAVModule"/>
    </modules>
    <httpProtocol>
    <customHeaders>
        <add name="Access-Control-Allow-Origin" value="*" />
        <add name="Access-Control-Allow-Headers" value="Content-Type" />
        <add name="Access-Control-Allow-Methods" value="GET, POST, PUT, DELETE, OPTIONS" />
    </customHeaders>
    </httpProtocol>
    <handlers>
      <remove name="ExtensionlessUrlHandler-ISAPI-4.0_32bit" />
      <remove name="ExtensionlessUrlHandler-ISAPI-4.0_64bit" />
      <remove name="ExtensionlessUrlHandler-Integrated-4.0" />
      <add name="ExtensionlessUrlHandler-ISAPI-4.0_32bit" path="*." verb="GET,HEAD,POST,DEBUG,PUT,DELETE,PATCH,OPTIONS" modules="IsapiModule" scriptProcessor="%windir%\Microsoft.NET\Framework\v4.0.30319\aspnet_isapi.dll" preCondition="classicMode,runtimeVersionv4.0,bitness32" responseBufferLimit="0" />
      <add name="ExtensionlessUrlHandler-ISAPI-4.0_64bit" path="*." verb="GET,HEAD,POST,DEBUG,PUT,DELETE,PATCH,OPTIONS" modules="IsapiModule" scriptProcessor="%windir%\Microsoft.NET\Framework64\v4.0.30319\aspnet_isapi.dll" preCondition="classicMode,runtimeVersionv4.0,bitness64" responseBufferLimit="0" />
      <add name="ExtensionlessUrlHandler-Integrated-4.0" path="*." verb="GET,HEAD,POST,DEBUG,PUT,DELETE,PATCH,OPTIONS" type="System.Web.Handlers.TransferRequestHandler" preCondition="integratedMode,runtimeVersionv4.0" />
    </handlers>
</system.webServer>

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

The key difference is that Const is the C equivalent of #DEFINE. The number literally gets substituted a-la precompiler. Readonly is actually treated as a variable.

This distinction is especially relevant when you have Project A depending on a Public constant from Project B. Suppose the public constant changes. Now your choice of const/readonly will impact the behavior on project A:

Const: project A does not catch the new value (unless it is recompiled with the new const, of course) because it was compiled with the constants subtituted in.

ReadOnly: Project A will always ask project B for it's variable value, so it will pick up the new value of the public constant in B.

Honestly, I would recommend you use readonly for nearly everything except truly universal constants ( e.g. Pi, Inches_To_Centimeters). For anything that could possibly change, I say use readonly.

Hope this helps, Alan.

Open file by its full path in C++

A different take on this question, which might help someone:

I came here because I was debugging in Visual Studio on Windows, and I got confused about all this / vs \\ discussion (it really should not matter in most cases).

For me, the problem was: the "current directory" was not set to what I wanted in Visual Studio. It defaults to the directory of the executable (depending on how you set up your project).

Change it via: Right-click the solution -> Properties -> Working Directory

I only mention it because the question seems Windows-centric, which generally also means VisualStudio-centric, which tells me this hint might be relevant (:

Using module 'subprocess' with timeout

I don't know much about the low level details; but, given that in python 2.6 the API offers the ability to wait for threads and terminate processes, what about running the process in a separate thread?

import subprocess, threading

class Command(object):
    def __init__(self, cmd):
        self.cmd = cmd
        self.process = None

    def run(self, timeout):
        def target():
            print 'Thread started'
            self.process = subprocess.Popen(self.cmd, shell=True)
            self.process.communicate()
            print 'Thread finished'

        thread = threading.Thread(target=target)
        thread.start()

        thread.join(timeout)
        if thread.is_alive():
            print 'Terminating process'
            self.process.terminate()
            thread.join()
        print self.process.returncode

command = Command("echo 'Process started'; sleep 2; echo 'Process finished'")
command.run(timeout=3)
command.run(timeout=1)

The output of this snippet in my machine is:

Thread started
Process started
Process finished
Thread finished
0
Thread started
Process started
Terminating process
Thread finished
-15

where it can be seen that, in the first execution, the process finished correctly (return code 0), while the in the second one the process was terminated (return code -15).

I haven't tested in windows; but, aside from updating the example command, I think it should work since I haven't found in the documentation anything that says that thread.join or process.terminate is not supported.

Default text which won't be shown in drop-down list

Kyle's solution worked perfectly fine for me so I made my research in order to avoid any Js and CSS, but just sticking with HTML. Adding a value of selected to the item we want to appear as a header forces it to show in the first place as a placeholder. Something like:

<option selected disabled>Choose here</option>

The complete markup should be along these lines:

<select>
    <option selected disabled>Choose here</option>
    <option value="1">One</option>
    <option value="2">Two</option>
    <option value="3">Three</option>
    <option value="4">Four</option>
    <option value="5">Five</option>
</select>

You can take a look at this fiddle, and here's the result:

enter image description here

If you do not want the sort of placeholder text to appear listed in the options once a user clicks on the select box just add the hidden attribute like so:

<select>
    <option selected disabled hidden>Choose here</option>
    <option value="1">One</option>
    <option value="2">Two</option>
    <option value="3">Three</option>
    <option value="4">Four</option>
    <option value="5">Five</option>
</select>

Check the fiddle here and the screenshot below.

enter image description here


Here is the solution:

<select>
    <option style="display:none;" selected>Select language</option>
    <option>Option 1</option>
    <option>Option 2</option>
</select>

Instantly detect client disconnection from server socket

Using the method SetSocketOption, you will be able to set KeepAlive that will let you know whenever a Socket gets disconnected

Socket _connectedSocket = this._sSocketEscucha.EndAccept(asyn);
                _connectedSocket.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.KeepAlive, 1);

http://msdn.microsoft.com/en-us/library/1011kecd(v=VS.90).aspx

Hope it helps! Ramiro Rinaldi

jQuery multiselect drop down menu

  • Download jquery.multiselect

  • Include the jquery.multiselect.js and jquery.multiselect.css files

    <script src="jquery-ui-multiselect-widget-master/src/jquery.multiselect.js" type="text/javascript"></script> <link rel="stylesheet" href="jquery-ui-multiselect-widget-master/jquery.multiselect.css" />

  • Populate your select input

  • Add the multiselect

    $('#' + Field).multiselect({ checkAllText: "Your text for CheckAll", uncheckAllText: "Your text for UncheckCheckAll", noneSelectedText: "Your text for NoOptionHasBeenSelected", selectedText: "You selected # of #" //The multiselect knows to display the second # as the total });

  • You may change the style

    ui-multiselect { //The button background:#fff !important; //background-color wouldn't work here text-align: right !important; } ui-multiselect-header { //The CheckAll/ UncheckAll line) background: lightgray !important; text-align: right !important; } ui-multiselect-menu { //The options text-align: right !important; }

  • If you want to repopulate the select, you must refresh it:

    $('#' + Field).multiselect('refresh');

  • To get the selected values (comma separated):

    var SelectedOptions = $('#' + Field).multiselect("getChecked").map(function () { return this.value; }).get();

  • To clear all selected values:

    $('#' + Field).multiselect("uncheckAll");

Sum one number to every element in a list (or array) in Python

If you don't want list comprehensions:

a = [1,1,1,1,1]
b = []
for i in a:
    b.append(i+1)

How to update and delete a cookie?

http://www.quirksmode.org/js/cookies.html

function createCookie(name,value,days) {
    if (days) {
        var date = new Date();
        date.setTime(date.getTime()+(days*24*60*60*1000));
        var expires = "; expires="+date.toGMTString();
    }
    else var expires = "";
    document.cookie = name+"="+value+expires+"; path=/";
}

function readCookie(name) {
    var nameEQ = name + "=";
    var ca = document.cookie.split(';');
    for(var i=0;i < ca.length;i++) {
        var c = ca[i];
        while (c.charAt(0)==' ') c = c.substring(1,c.length);
        if (c.indexOf(nameEQ) == 0) return c.substring(nameEQ.length,c.length);
    }
    return null;
}

function eraseCookie(name) {
    createCookie(name,"",-1);
}

Find all files in a directory with extension .txt in Python

Functional solution with sub-directories:

from fnmatch import filter
from functools import partial
from itertools import chain
from os import path, walk

print(*chain(*(map(partial(path.join, root), filter(filenames, "*.txt")) for root, _, filenames in walk("mydir"))))

How do I make a relative reference to another workbook in Excel?

Presume you linking to a shared drive for example the S drive? If so, other people may have mapped the drive differently. You probably need to use the "official" drive name //euhkj002/forecasts/bla bla. Instead of S// in your link

How can I add comments in MySQL?

You can use single line comments:

-- this is a comment
# this is also a comment

Or a multiline comment:

/*
   multiline
   comment
*/

How to delete all files from a specific folder?

You can do it via FileInfo or DirectoryInfo:

DirectoryInfo di = new DirectoryInfo("TempDir");
di.Delete(true);

And then recreate the directory

Exponentiation in Python - should I prefer ** operator instead of math.pow and math.sqrt?

math.sqrt is the C implementation of square root and is therefore different from using the ** operator which implements Python's built-in pow function. Thus, using math.sqrt actually gives a different answer than using the ** operator and there is indeed a computational reason to prefer numpy or math module implementation over the built-in. Specifically the sqrt functions are probably implemented in the most efficient way possible whereas ** operates over a large number of bases and exponents and is probably unoptimized for the specific case of square root. On the other hand, the built-in pow function handles a few extra cases like "complex numbers, unbounded integer powers, and modular exponentiation".

See this Stack Overflow question for more information on the difference between ** and math.sqrt.

In terms of which is more "Pythonic", I think we need to discuss the very definition of that word. From the official Python glossary, it states that a piece of code or idea is Pythonic if it "closely follows the most common idioms of the Python language, rather than implementing code using concepts common to other languages." In every single other language I can think of, there is some math module with basic square root functions. However there are languages that lack a power operator like ** e.g. C++. So ** is probably more Pythonic, but whether or not it's objectively better depends on the use case.

Image comparison - fast algorithm

My company has about 24million images come in from manufacturers every month. I was looking for a fast solution to ensure that the images we upload to our catalog are new images.

I want to say that I have searched the internet far and wide to attempt to find an ideal solution. I even developed my own edge detection algorithm.
I have evaluated speed and accuracy of multiple models. My images, which have white backgrounds, work extremely well with phashing. Like redcalx said, I recommend phash or ahash. DO NOT use MD5 Hashing or anyother cryptographic hashes. Unless, you want only EXACT image matches. Any resizing or manipulation that occurs between images will yield a different hash.

For phash/ahash, Check this out: imagehash

I wanted to extend *redcalx'*s post by posting my code and my accuracy.

What I do:

from PIL import Image
from PIL import ImageFilter
import imagehash

img1=Image.open(r"C:\yourlocation")
img2=Image.open(r"C:\yourlocation")
if img1.width<img2.width:
    img2=img2.resize((img1.width,img1.height))
else:
    img1=img1.resize((img2.width,img2.height))
img1=img1.filter(ImageFilter.BoxBlur(radius=3))
img2=img2.filter(ImageFilter.BoxBlur(radius=3))
phashvalue=imagehash.phash(img1)-imagehash.phash(img2)
ahashvalue=imagehash.average_hash(img1)-imagehash.average_hash(img2)
totalaccuracy=phashvalue+ahashvalue

Here are some of my results:

item1  item2  totalsimilarity
desk1  desk1       3
desk1  phone1     22
chair1 desk1      17
phone1 chair1     34

Hope this helps!

How can I pass data from Flask to JavaScript in a template?

You can use {{ variable }} anywhere in your template, not just in the HTML part. So this should work:

<html>
<head>
  <script>
    var someJavaScriptVar = '{{ geocode[1] }}';
  </script>
</head>
<body>
  <p>Hello World</p>
  <button onclick="alert('Geocode: {{ geocode[0] }} ' + someJavaScriptVar)" />
</body>
</html>

Think of it as a two-stage process: First, Jinja (the template engine Flask uses) generates your text output. This gets sent to the user who executes the JavaScript he sees. If you want your Flask variable to be available in JavaScript as an array, you have to generate an array definition in your output:

<html>
  <head>
    <script>
      var myGeocode = ['{{ geocode[0] }}', '{{ geocode[1] }}'];
    </script>
  </head>
  <body>
    <p>Hello World</p>
    <button onclick="alert('Geocode: ' + myGeocode[0] + ' ' + myGeocode[1])" />
  </body>
</html>

Jinja also offers more advanced constructs from Python, so you can shorten it to:

<html>
<head>
  <script>
    var myGeocode = [{{ ', '.join(geocode) }}];
  </script>
</head>
<body>
  <p>Hello World</p>
  <button onclick="alert('Geocode: ' + myGeocode[0] + ' ' + myGeocode[1])" />
</body>
</html>

You can also use for loops, if statements and many more, see the Jinja2 documentation for more.

Also, have a look at Ford's answer who points out the tojson filter which is an addition to Jinja2's standard set of filters.

Edit Nov 2018: tojson is now included in Jinja2's standard set of filters.

Getting a map() to return a list in Python 3.x

Using list comprehension in python and basic map function utility, one can do this also:

chi = [x for x in map(chr,[66,53,0,94])]

Positive Number to Negative Number in JavaScript?

var x = 100;
var negX = ( -x ); // => -100

Add button to navigationbar programmatically

To add search button on navigation bar use this code:

 UIBarButtonItem *searchButton = [[UIBarButtonItem alloc] initWithBarButtonSystemItem:UIBarButtonSystemItemSearch target:self action:@selector(toggleSearch:)];
self.navigationController.navigationBar.topItem.rightBarButtonItem = searchButton;

and implement following method:

- (IBAction)toggleSearch:(id)sender
{
    // do something or handle Search Button Action.
}

How do you put an image file in a json object?

I can think of doing it in two ways:

1.

Storing the file in file system in any directory (say dir1) and renaming it which ensures that the name is unique for every file (may be a timestamp) (say xyz123.jpg), and then storing this name in some DataBase. Then while generating the JSON you pull this filename and generate a complete URL (which will be http://example.com/dir1/xyz123.png )and insert it in the JSON.

2.

Base 64 Encoding, It's basically a way of encoding arbitrary binary data in ASCII text. It takes 4 characters per 3 bytes of data, plus potentially a bit of padding at the end. Essentially each 6 bits of the input is encoded in a 64-character alphabet. The "standard" alphabet uses A-Z, a-z, 0-9 and + and /, with = as a padding character. There are URL-safe variants. So this approach will allow you to put your image directly in the MongoDB, while storing it Encode the image and decode while fetching it, it has some of its own drawbacks:

  • base64 encoding makes file sizes roughly 33% larger than their original binary representations, which means more data down the wire (this might be exceptionally painful on mobile networks)
  • data URIs aren’t supported on IE6 or IE7.
  • base64 encoded data may possibly take longer to process than binary data.

Source

Converting Image to DATA URI

A.) Canvas

Load the image into an Image-Object, paint it to a canvas and convert the canvas back to a dataURL.

function convertToDataURLviaCanvas(url, callback, outputFormat){
    var img = new Image();
    img.crossOrigin = 'Anonymous';
    img.onload = function(){
        var canvas = document.createElement('CANVAS');
        var ctx = canvas.getContext('2d');
        var dataURL;
        canvas.height = this.height;
        canvas.width = this.width;
        ctx.drawImage(this, 0, 0);
        dataURL = canvas.toDataURL(outputFormat);
        callback(dataURL);
        canvas = null; 
    };
    img.src = url;
}

Usage

convertToDataURLviaCanvas('http://bit.ly/18g0VNp', function(base64Img){
    // Base64DataURL
});

Supported input formats image/png, image/jpeg, image/jpg, image/gif, image/bmp, image/tiff, image/x-icon, image/svg+xml, image/webp, image/xxx

B.) FileReader

Load the image as blob via XMLHttpRequest and use the FileReader API to convert it to a data URL.

function convertFileToBase64viaFileReader(url, callback){
    var xhr = new XMLHttpRequest();
    xhr.responseType = 'blob';
    xhr.onload = function() {
      var reader  = new FileReader();
      reader.onloadend = function () {
          callback(reader.result);
      }
      reader.readAsDataURL(xhr.response);
    };
    xhr.open('GET', url);
    xhr.send();
}

This approach

  • lacks in browser support
  • has better compression
  • works for other file types as well.

Usage

convertFileToBase64viaFileReader('http://bit.ly/18g0VNp', function(base64Img){
    // Base64DataURL
});

Source

How to control border height?

I was just looking for this... By using David's answer, I used a span and gave it some padding (height won't work + top margin issue)... Works like a charm;

See fiddle

<ul>
  <li><a href="index.php">Home</a></li><span class="divider"></span>
  <li><a href="about.php">About Us</a></li><span class="divider"></span>
  <li><a href="#">Events</a></li><span class="divider"></span>
  <li><a href="#">Forum</a></li><span class="divider"></span>
  <li><a href="#">Contact</a></li>
</ul>

.divider {
    border-left: 1px solid #8e1537;
    padding: 29px 0 24px 0;
}

Pure CSS scroll animation

You can do it with anchor tags using css3 :target pseudo-selector, this selector is going to be triggered when the element with the same id as the hash of the current URL get an match. Example

Knowing this, we can combine this technique with the use of proximity selectors like "+" and "~" to select any other element through the target element who id get match with the hash of the current url. An example of this would be something like what you are asking.

Disabling browser print options (headers, footers, margins) from page?

This worked for me with about 1cm margin

@page 
{
    size:  auto;   /* auto is the initial value */
    margin: 0mm;  /* this affects the margin in the printer settings */
}
html
{
    background-color: #FFFFFF; 
    margin: 0mm;  /* this affects the margin on the html before sending to printer */
}
body
{
    padding:30px; /* margin you want for the content */
}

implementing merge sort in C++

I know this question has already been answered, but I decided to add my two cents. Here is code for a merge sort that only uses additional space in the merge operation (and that additional space is temporary space which will be destroyed when the stack is popped). In fact, you will see in this code that there is not usage of heap operations (no declaring new anywhere).

Hope this helps.

    void merge(int *arr, int size1, int size2) {
        int temp[size1+size2];
        int ptr1=0, ptr2=0;
        int *arr1 = arr, *arr2 = arr+size1;

        while (ptr1+ptr2 < size1+size2) {
            if (ptr1 < size1 && arr1[ptr1] <= arr2[ptr2] || ptr1 < size1 && ptr2 >= size2)
                temp[ptr1+ptr2] = arr1[ptr1++];

            if (ptr2 < size2 && arr2[ptr2] < arr1[ptr1] || ptr2 < size2 && ptr1 >= size1)
                temp[ptr1+ptr2] = arr2[ptr2++];
        }   

        for (int i=0; i < size1+size2; i++)
            arr[i] = temp[i];
    }   

    void mergeSort(int *arr, int size) {
        if (size == 1)
            return;

        int size1 = size/2, size2 = size-size1;
        mergeSort(arr, size1);
        mergeSort(arr+size1, size2);
        merge(arr, size1, size2);
    } 

    int main(int argc, char** argv) {
         int num;
         cout << "How many numbers do you want to sort: ";
         cin >> num;
         int a[num];
         for (int i = 0; i < num; i++) {
           cout << (i + 1) << ": ";
           cin >> a[i];
         }   

         // Start merge sort
         mergeSort(a, num);

         // Print the sorted array
         cout << endl;
         for (int i = 0; i < num; i++) {
           cout << a[i] << " ";
         }   
         cout << endl;

         return 0;
    } 

How to save traceback / sys.exc_info() values in a variable?

The object can be used as a parameter in Exception.with_traceback() function:

except Exception as e:
    tb = sys.exc_info()
    print(e.with_traceback(tb[2]))

how to log in to mysql and query the database from linux terminal

1.- How do I get mysql prompt in linux terminal?

mysql -u root -p

At the Enter password: prompt, well, enter root's password :)

You can find further reference by typing mysql --help or at the online manual.

2. How I stop the mysql server from linux terminal?

It depends. Red Hat based distros have the service command:

service mysqld stop

Other distros require to call the init script directly:

/etc/init.d/mysqld stop

3. How I start the mysql server from linux terminal?

Same as #2, but with start.

4. How do I get mysql prompt in linux terminal?

Same as #1.

5. How do I login to mysql server from linux terminal?

Same as #1.

6. How do I solve following error?

Same as #1.

How to vertically center an image inside of a div element in HTML using CSS?

In your example, the div's height is static and the image's height is static. Give the image a margin-top value of ( div_height - image_height ) / 2

If the image is 50px, then

img {
    margin-top: 25px;
}

Random number c++ in some range

int random(int min, int max) //range : [min, max]
{
   static bool first = true;
   if (first) 
   {  
      srand( time(NULL) ); //seeding for the first time only!
      first = false;
   }
   return min + rand() % (( max + 1 ) - min);
}

Pandas join issue: columns overlap but no suffix specified

This error indicates that the two tables have the 1 or more column names that have the same column name. The error message translates to: "I can see the same column in both tables but you haven't told me to rename either before bringing one of them in"

You either want to delete one of the columns before bringing it in from the other on using del df['column name'], or use lsuffix to re-write the original column, or rsuffix to rename the one that is being brought it.

df_a.join(df_b, on='mukey', how='left', lsuffix='_left', rsuffix='_right')

How is OAuth 2 different from OAuth 1?

From a security point of view, I'd go for OAuth 1. See OAuth 2.0 and the road to hell

quote from that link: "If you are currently using 1.0 successfully, ignore 2.0. It offers no real value over 1.0 (I’m guessing your client developers have already figured out 1.0 signatures by now).

If you are new to this space, and consider yourself a security expert, use 2.0 after careful examination of its features. If you are not an expert, either use 1.0 or copy the 2.0 implementation of a provider you trust to get it right (Facebook’s API documents are a good place to start). 2.0 is better for large scale, but if you are running a major operation, you probably have some security experts on site to figure it all out for you."

Using an array as needles in strpos

<?php
$Words = array("hello","there","world");
$c = 0;

    $message = 'Hi hello';
     foreach ($Words as $word):
        $trial = stripos($message,$word);
        
        if($trial != true){
            $c++;
            echo 'Word '.$c.' didnt match <br> <br>';
        }else{
            $c++;
            echo 'Word '.$c.' matched <br> <br>';
        }
     endforeach;
     ?>

I used this kind of code to check for hello, It also Has a numbering feature. You can use this if you want to do content moderation practices in websites that need the user to type

SSIS Text was truncated with status value 4

I've had this problem before, you can go to "advanced" tab of "choose a data source" page and click on "suggested types" button, and set the "number of rows" as much as you want. after that, the type and text qualified are set to the true values.

i applied the above solution and can convert my data to SQL.

Opening new window in HTML for target="_blank"

You don't have that kind of control with a bare a tag. But you can hook up the tag's onclick handler to call window.open(...) with the right parameters. See here for examples: https://developer.mozilla.org/En/DOM/Window.open

I still don't think you can force window over tab directly though-- that depends on the browser and the user's settings.

Why am I getting this error Premature end of file?

You are getting the error because the SAXBuilder is not intelligent enough to deal with "blank states". So it looks for at least an <xml ..> declaration, and when that causes a no data response it creates the exception you see rather than report the empty state.

creating a new list with subset of list using index in python

Suppose

a = ['a', 'b', 'c', 3, 4, 'd', 6, 7, 8]

and the list of indexes is stored in

b= [0, 1, 2, 4, 6, 7, 8]

then a simple one-line solution will be

c = [a[i] for i in b]

How to find the remainder of a division in C?

All the above answers are correct. Just providing with your dataset to find perfect divisor:

#include <stdio.h>

int main() 
{

int arr[7] = {3,5,7,8,9,17,19};
int j = 51;
int i = 0;

for (i=0 ; i < 7; i++) {
    if (j % arr[i] == 0)
        printf("%d is the perfect divisor of %d\n", arr[i], j);
}

return 0;
}

apache not accepting incoming connections from outside of localhost

Try with below setting in iptables.config table

iptables -A INPUT -p tcp --dport 80 -j ACCEPT

Run the below command to restart the iptable service

service iptables restart

change the httpd.config file to

Listen 192.170.2.1:80

re-start the apache.

Try now.

How to validate a date?

My function returns true if is a valid date otherwise returns false :D

_x000D_
_x000D_
function isDate  (day, month, year){_x000D_
 if(day == 0 ){_x000D_
  return false;_x000D_
 }_x000D_
 switch(month){_x000D_
  case 1: case 3: case 5: case 7: case 8: case 10: case 12:_x000D_
   if(day > 31)_x000D_
    return false;_x000D_
   return true;_x000D_
  case 2:_x000D_
   if (year % 4 == 0)_x000D_
    if(day > 29){_x000D_
     return false;_x000D_
    }_x000D_
    else{_x000D_
     return true;_x000D_
    }_x000D_
   if(day > 28){_x000D_
    return false;_x000D_
   }_x000D_
   return true;_x000D_
  case 4: case 6: case 9: case 11:_x000D_
   if(day > 30){_x000D_
    return false;_x000D_
   }_x000D_
   return true;_x000D_
  default:_x000D_
   return false;_x000D_
 }_x000D_
}_x000D_
_x000D_
console.log(isDate(30, 5, 2017));_x000D_
console.log(isDate(29, 2, 2016));_x000D_
console.log(isDate(29, 2, 2015));
_x000D_
_x000D_
_x000D_

Regular expression to extract numbers from a string

^\s*(\w+)\s*\(\s*(\d+)\D+(\d+)\D+\)\s*$

should work. After the match, backreference 1 will contain the month, backreference 2 will contain the first number and backreference 3 the second number.

Explanation:

^     # start of string
\s*   # optional whitespace
(\w+) # one or more alphanumeric characters, capture the match
\s*   # optional whitespace
\(    # a (
\s*   # optional whitespace
(\d+) # a number, capture the match
\D+   # one or more non-digits
(\d+) # a number, capture the match
\D+   # one or more non-digits
\)    # a )
\s*   # optional whitespace
$     # end of string

How to handle ETIMEDOUT error?

This is caused when your request response is not received in given time(by timeout request module option).

Basically to catch that error first, you need to register a handler on error, so the unhandled error won't be thrown anymore: out.on('error', function (err) { /* handle errors here */ }). Some more explanation here.

In the handler you can check if the error is ETIMEDOUT and apply your own logic: if (err.message.code === 'ETIMEDOUT') { /* apply logic */ }.

If you want to request for the file again, I suggest using node-retry or node-backoff modules. It makes things much simpler.

If you want to wait longer, you can set timeout option of request yourself. You can set it to 0 for no timeout.

UIImage resize (Scale proportion)

This change worked for me:

// The size returned by CGImageGetWidth(imgRef) & CGImageGetHeight(imgRef) is incorrect as it doesn't respect the image orientation!
// CGImageRef imgRef = [image CGImage];
// CGFloat width = CGImageGetWidth(imgRef);
// CGFloat height = CGImageGetHeight(imgRef);
//
// This returns the actual width and height of the photo (and hence solves the problem
CGFloat width = image.size.width; 
CGFloat height = image.size.height;
CGRect bounds = CGRectMake(0, 0, width, height);

How to disable XDebug

In Linux Ubuntu(maybe also another - it's not tested) distribution with PHP 5 on board, you can use:

sudo php5dismod xdebug

And with PHP 7

sudo phpdismod xdebug

And after that, please restart the server:

sudo service apache2 restart

SQL Stored Procedure set variables using SELECT

select @currentTerm = CurrentTerm, @termID = TermID, @endDate = EndDate
    from table1
    where IsCurrent = 1

what does Error "Thread 1:EXC_BAD_INSTRUCTION (code=EXC_I386_INVOP, subcode=0x0)" mean?

I got this on WatchOS Sim. The issue persisted even after:

  • Deleting the app
  • Restarting Xcode
  • Deleting Derived Data

...and was finally fixed by "Erase all Content and Settings" in the simulator.

Reordering arrays

With ES6 you can do something like this:

const swapPositions = (array, a ,b) => {
  [array[a], array[b]] = [array[b], array[a]]
}

let array = [1,2,3,4,5];
swapPositions(array,0,1);

/// => [2, 1, 3, 4, 5]

Include an SVG (hosted on GitHub) in MarkDown

This will work. Link to your SVG using the following pattern:

https://cdn.rawgit.com/<repo-owner>/<repo>/<branch>/path/to.svg

The downside is hardcoding the owner and repo in the path, meaning the svg will break if either of those are renamed.

Change Button color onClick

Every time setColor gets hit, you are setting count = 1. You would need to define count outside of the scope of the function. Example:

var count=1;
function setColor(btn, color){
    var property = document.getElementById(btn);
    if (count == 0){
        property.style.backgroundColor = "#FFFFFF"
        count=1;        
    }
    else{
        property.style.backgroundColor = "#7FFF00"
        count=0;
    }

}

How to Cast Objects in PHP

It sounds like what you really want to do is implement an interface.

Your interface will specify the methods that the object can handle and when you pass an object that implements the interface to a method that wants an object that supports the interface, you just type the argument with the name of the interface.

Default visibility for C# classes and members (fields, methods, etc.)?

By default, the access modifier for a class is internal. That means to say, a class is accessible within the same assembly. But if we want the class to be accessed from other assemblies then it has to be made public.

Alert handling in Selenium WebDriver (selenium 2) with Java

Write the following method:

public boolean isAlertPresent() {
    try {
        driver.switchTo().alert();
        return true;
    } // try
    catch (Exception e) {
        return false;
    } // catch
}

Now, you can check whether alert is present or not by using the method written above as below:

if (isAlertPresent()) {
    driver.switchTo().alert();
    driver.switchTo().alert().accept();
    driver.switchTo().defaultContent();
}

JUnit: how to avoid "no runnable methods" in test utils classes

I was also facing a similar issue ("no runnable methods..") on running the simplest of simple piece of code (Using @Test, @Before etc.) and found the solution nowhere. I was using Junit4 and Eclipse SDK version 4.1.2. Resolved my problem by using the latest Eclipse SDK 4.2.2. I hope this helps people who are struggling with a somewhat similar issue.

how to output every line in a file python

Did you try

for line in open("masters", "r").readlines(): print line

?

readline() 

only reads "a line", on the other hand

readlines()

reads whole lines and gives you a list of all lines.

call javascript function on hyperlink click

Use the onclick HTML attribute.

The onclick event handler captures a click event from the users’ mouse button on the element to which the onclick attribute is applied. This action usually results in a call to a script method such as a JavaScript function [...]

How to compare dates in datetime fields in Postgresql?

Use the range type. If the user enter a date:

select *
from table
where
    update_date
    <@
    tsrange('2013-05-03', '2013-05-03'::date + 1, '[)');

If the user enters timestamps then you don't need the ::date + 1 part

http://www.postgresql.org/docs/9.2/static/rangetypes.html

http://www.postgresql.org/docs/9.2/static/functions-range.html

Similarity String Comparison in Java

You can achieve this using the apache commons java library. Take a look at these two functions within it:
- getLevenshteinDistance
- getFuzzyDistance

How to listen to route changes in react router v4?

For functional components try useEffect with props.location.

import React, {useEffect} from 'react';

const SampleComponent = (props) => {

      useEffect(() => {
        console.log(props.location);
      }, [props.location]);

}

export default SampleComponent;

How to sum all values in a column in Jaspersoft iReport Designer?

iReports Custom Fields for columns (sum, average, etc)

  1. Right-Click on Variables and click Create Variable

  2. Click on the new variable

    a. Notice the properties on the right

  3. Rename the variable accordingly

  4. Change the Value Class Name to the correct Data Type

    a. You can search by clicking the 3 dots

  5. Select the correct type of calculation

  6. Change the Expression

    a. Click the little icon

    b. Select the column you are looking to do the calculation for

    c. Click finish

  7. Set Initial Value Expression to 0

  8. Set the increment type to none

  9. Leave Incrementer Factory Class Name blank
  10. Set the Reset Type (usually report)

  11. Drag a new Text Field to stage (Usually in Last Page Footer, or Column Footer)

  12. Double Click the new Text Field
  13. Clear the expression “Text Field”
  14. Select the new variable

  15. Click finish

  16. Put the new text in a desirable position ?

Combine [NgStyle] With Condition (if..else)

I have used the below code in my existing project

<div class="form-group" [ngStyle]="{'border':isSubmitted && form_data.controls.first_name.errors?'1px solid red':'' }">
</div>

how to get the first and last days of a given month

Print only current month week:

function my_week_range($date) {
    $ts = strtotime($date);
    $start = (date('w', $ts) == 0) ? $ts : strtotime('last sunday', $ts);
    echo $currentWeek = ceil((date("d",strtotime($date)) - date("w",strtotime($date)) - 1) / 7) + 1;
    $start_date = date('Y-m-d', $start);$end_date=date('Y-m-d', strtotime('next saturday', $start));
    if($currentWeek==1)
        {$start_date = date('Y-m-01', strtotime($date));}
    else if($currentWeek==5)
       {$end_date = date('Y-m-t', strtotime($date));}
    else
       {}
    return array($start_date, $end_date );
}

$date_range=list($start_date, $end_date) = my_week_range($new_fdate);

Double Iteration in List Comprehension

Gee, I guess I found the anwser: I was not taking care enough about which loop is inner and which is outer. The list comprehension should be like:

[x for b in a for x in b]

to get the desired result, and yes, one current value can be the iterator for the next loop.

How to create a zip file in Java

If you want decompress without software better use this code. Other code with pdf files sends error on manually decompress

byte[] buffer = new byte[1024];     
    try
    {   
        FileOutputStream fos = new FileOutputStream("123.zip");
        ZipOutputStream zos = new ZipOutputStream(fos);
        ZipEntry ze= new ZipEntry("file.pdf");
        zos.putNextEntry(ze);
        FileInputStream in = new FileInputStream("file.pdf");
        int len;
        while ((len = in.read(buffer)) > 0) 
        {
            zos.write(buffer, 0, len);
        }
        in.close();
        zos.closeEntry();
        zos.close();
    }
    catch(IOException ex)
    {
       ex.printStackTrace();
    }

How to pass a value to razor variable from javascript variable?

But it would be possible if one were used in place of the variable in @html.Hidden field. As in this example.

@Html.Hidden("myVar", 0);

set the field per script:

<script>
function setMyValue(value) {
     $('#myVar').val(value);       
}
</script>

I hope I can at least offer no small Workaround.

javascript: calculate x% of a number

Harder Way (learning purpose) :

var number = 150
var percent= 10
var result = 0
for (var index = 0; index < number; index++) {
   const calculate = index / number * 100
   if (calculate == percent) result += index
}
return result

Is False == 0 and True == 1 an implementation detail or is it guaranteed by the language?

In Python 2.x, it is not guaranteed at all:

>>> False = 5
>>> 0 == False
False

So it could change. In Python 3.x, True, False, and None are reserved words, so the above code would not work.

In general, with booleans you should assume that while False will always have an integer value of 0 (so long as you don't change it, as above), True could have any other value. I wouldn't necessarily rely on any guarantee that True==1, but on Python 3.x, this will always be the case, no matter what.

Finding the index of elements based on a condition using python list comprehension

Even if it's a late answer: I think this is still a very good question and IMHO Python (without additional libraries or toolkits like numpy) is still lacking a convenient method to access the indices of list elements according to a manually defined filter.

You could manually define a function, which provides that functionality:

def indices(list, filtr=lambda x: bool(x)):
    return [i for i,x in enumerate(list) if filtr(x)]

print(indices([1,0,3,5,1], lambda x: x==1))

Yields: [0, 4]

In my imagination the perfect way would be making a child class of list and adding the indices function as class method. In this way only the filter method would be needed:

class MyList(list):
    def __init__(self, *args):
        list.__init__(self, *args)
    def indices(self, filtr=lambda x: bool(x)):
        return [i for i,x in enumerate(self) if filtr(x)]

my_list = MyList([1,0,3,5,1])
my_list.indices(lambda x: x==1)

I elaborated a bit more on that topic here: http://tinyurl.com/jajrr87

Get a list of all git commits, including the 'lost' ones

@bsimmons

git fsck --lost-found | grep commit

Then create a branch for each one:

$ git fsck --lost-found | grep commit
Checking object directories: 100% (256/256), done.
dangling commit 2806a32af04d1bbd7803fb899071fcf247a2b9b0
dangling commit 6d0e49efd0c1a4b5bea1235c6286f0b64c4c8de1
dangling commit 91ca9b2482a96b20dc31d2af4818d69606a229d4

$ git branch  branch_2806a3 2806a3
$ git branch  branch_6d0e49 6d0e49
$ git branch  branch_91ca9b 91ca9b

Now many tools will show you a graphical visualization of those lost commits.

Change a Rails application to production

You can also pass the environment to script/server:

$ script/server -e production

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

Here is a link to W3Schools that answers your question https://www.w3schools.com/bootstrap/bootstrap_ref_js_modal.asp

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

I hope that helps

Java 8 - Best way to transform a list: map or foreach?

If you use Eclipse Collections you can use the collectIf() method.

MutableList<Integer> source =
    Lists.mutable.with(1, null, 2, null, 3, null, 4, null, 5);

MutableList<String> result = source.collectIf(Objects::nonNull, String::valueOf);

Assert.assertEquals(Lists.immutable.with("1", "2", "3", "4", "5"), result);

It evaluates eagerly and should be a bit faster than using a Stream.

Note: I am a committer for Eclipse Collections.

Exit/save edit to sudoers file? Putty SSH

Just open file by nano /file_name

Once done, press CTRL+O and then Enter to save. Then press CTRL+X to return.

Here CTRL+O : is CTRL and O for Orange Not 0 Zero

Verifying a specific parameter with Moq

Had one of these as well, but the parameter of the action was an interface with no public properties. Ended up using It.Is() with a seperate method and within this method had to do some mocking of the interface

public interface IQuery
{
    IQuery SetSomeFields(string info);
}

void DoSomeQuerying(Action<IQuery> queryThing);

mockedObject.Setup(m => m.DoSomeQuerying(It.Is<Action<IQuery>>(q => MyCheckingMethod(q)));

private bool MyCheckingMethod(Action<IQuery> queryAction)
{
    var mockQuery = new Mock<IQuery>();
    mockQuery.Setup(m => m.SetSomeFields(It.Is<string>(s => s.MeetsSomeCondition())
    queryAction.Invoke(mockQuery.Object);
    mockQuery.Verify(m => m.SetSomeFields(It.Is<string>(s => s.MeetsSomeCondition(), Times.Once)
    return true
}

error: package javax.servlet does not exist

maybe doesnt exists javaee-api-7.0.jar. download this jar and on your project right clik

  1. on your project right click
  2. build path
  3. Configure build path
  4. Add external Jars
  5. javaee-api-7.0.jar choose
  6. Apply and finish

Cannot assign requested address using ServerSocket.socketBind

Just for others who may look at this answer in the hope of solving a similar problem, I got a similar message because my ip address changed.

java.net.BindException: Cannot assign requested address: bind
    at sun.nio.ch.Net.bind(Native Method)
    at sun.nio.ch.ServerSocketChannelImpl.bind(ServerSocketChannelImpl.java:126)
    at sun.nio.ch.ServerSocketAdaptor.bind(ServerSocketAdaptor.java:59)
    at org.eclipse.jetty.server.nio.SelectChannelConnector.open(SelectChannelConnector.java:182)
    at org.eclipse.jetty.server.AbstractConnector.doStart(AbstractConnector.java:311)
    at org.eclipse.jetty.server.nio.SelectChannelConnector.doStart(SelectChannelConnector.java:260)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:59)
    at org.eclipse.jetty.server.Server.doStart(Server.java:273)
    at org.eclipse.jetty.util.component.AbstractLifeCycle.start(AbstractLifeCycle.java:59)

Java 8 stream map on entry set

Question might be a little dated, but you could simply use AbstractMap.SimpleEntry<> as follows:

private Map<String, AttributeType> mapConfig(
    Map<String, String> input, String prefix) {
       int subLength = prefix.length();
       return input.entrySet()
          .stream()
          .map(e -> new AbstractMap.SimpleEntry<>(
               e.getKey().substring(subLength),
               AttributeType.GetByName(e.getValue()))
          .collect(Collectors.toMap(Map.Entry::getKey, Map.Entry::getValue));

any other Pair-like value object would work too (ie. ApacheCommons Pair tuple).

TextView - setting the text size programmatically doesn't seem to work

This fixed the issue for me. I got uniform font size across all devices.

 textView.setTextSize(TypedValue.COMPLEX_UNIT_PX,getResources().getDimension(R.dimen.font));

Controlling number of decimal digits in print output in R

One more solution able to control the how many decimal digits to print out based on needs (if you don't want to print redundant zero(s))

For example, if you have a vector as elements and would like to get sum of it

elements <- c(-1e-05, -2e-04, -3e-03, -4e-02, -5e-01, -6e+00, -7e+01, -8e+02)
sum(elements)
## -876.5432

Apparently, the last digital as 1 been truncated, the ideal result should be -876.54321, but if set as fixed printing decimal option, e.g sprintf("%.10f", sum(elements)), redundant zero(s) generate as -876.5432100000

Following the tutorial here: printing decimal numbers, if able to identify how many decimal digits in the certain numeric number, like here in -876.54321, there are 5 decimal digits need to print, then we can set up a parameter for format function as below:

decimal_length <- 5
formatC(sum(elements), format = "f", digits = decimal_length)
## -876.54321

We can change the decimal_length based on each time query, so it can satisfy different decimal printing requirement.

Replacing few values in a pandas dataframe column with another value

loc function can be used to replace multiple values, Documentation for it : loc

df.loc[df['BrandName'].isin(['ABC', 'AB'])]='A'

Laravel blank white screen

Sometimes it's because laravel 5.1 require PHP >= 5.5.9. Update php will solve the problem.

Convert double to float in Java

The problem is, your value cannot be stored accurately in single precision floating point type. Proof:

public class test{
    public static void main(String[] args){
        Float a = Float.valueOf("23423424666767");
        System.out.printf("%f\n", a); //23423424135168,000000
        System.out.println(a);        //2.34234241E13
    }
}

Another thing is: you don't get "2.3423424666767E13", it's just the visual representation of the number stored in memory. "How you print out" and "what is in memory" are two distinct things. Example above shows you how to print the number as float, which avoids scientific notation you were getting.

Replacing instances of a character in a string

This should cover a slightly more general case, but you should be able to customize it for your purpose

def selectiveReplace(myStr):
    answer = []
    for index,char in enumerate(myStr):
        if char == ';':
            if index%2 == 1: # replace ';' in even indices with ":"
                answer.append(":")
            else:
                answer.append("!") # replace ';' in odd indices with "!"
        else:
            answer.append(char)
    return ''.join(answer)

Hope this helps

How to show the last queries executed on MySQL?

SELECT * FROM  mysql.general_log  WHERE command_type ='Query' LIMIT total;

jQuery - Create hidden form element on the fly

$('<input>').attr('type','hidden').appendTo('form');

To answer your second question:

$('<input>').attr({
    type: 'hidden',
    id: 'foo',
    name: 'bar'
}).appendTo('form');

Gson: How to exclude specific fields from Serialization without annotations

Any fields you don't want serialized in general you should use the "transient" modifier, and this also applies to json serializers (at least it does to a few that I have used, including gson).

If you don't want name to show up in the serialized json give it a transient keyword, eg:

private transient String name;

More details in the Gson documentation

Name node is in safe mode. Not able to leave

safe mode on means (HDFS is in READ only mode)
safe mode off means (HDFS is in Writeable and readable mode)

In Hadoop 2.6.0, we can check the status of name node with help of the below commands:

TO CHECK THE name node status

$ hdfs dfsadmin -safemode get

TO ENTER IN SAFE MODE:

$ hdfs dfsadmin -safemode enter

TO LEAVE SAFE mode

~$ hdfs dfsadmin -safemode leave

Creating an index on a table variable

It should be understood that from a performance standpoint there are no differences between @temp tables and #temp tables that favor variables. They reside in the same place (tempdb) and are implemented the same way. All the differences appear in additional features. See this amazingly complete writeup: https://dba.stackexchange.com/questions/16385/whats-the-difference-between-a-temp-table-and-table-variable-in-sql-server/16386#16386

Although there are cases where a temp table can't be used such as in table or scalar functions, for most other cases prior to v2016 (where even filtered indexes can be added to a table variable) you can simply use a #temp table.

The drawback to using named indexes (or constraints) in tempdb is that the names can then clash. Not just theoretically with other procedures but often quite easily with other instances of the procedure itself which would try to put the same index on its copy of the #temp table.

To avoid name clashes, something like this usually works:

declare @cmd varchar(500)='CREATE NONCLUSTERED INDEX [ix_temp'+cast(newid() as varchar(40))+'] ON #temp (NonUniqueIndexNeeded);';
exec (@cmd);

This insures the name is always unique even between simultaneous executions of the same procedure.

Is there a "null coalescing" operator in JavaScript?

Note that React's create-react-app tool-chain supports the null-coalescing since version 3.3.0 (released 5.12.2019). From the release notes:

Optional Chaining and Nullish Coalescing Operators

We now support the optional chaining and nullish coalescing operators!

// Optional chaining
a?.(); // undefined if `a` is null/undefined
b?.c; // undefined if `b` is null/undefined

// Nullish coalescing
undefined ?? 'some other default'; // result: 'some other default'
null ?? 'some other default'; // result: 'some other default'
'' ?? 'some other default'; // result: ''
0 ?? 300; // result: 0
false ?? true; // result: false

This said, in case you use create-react-app 3.3.0+ you can start using the null-coalesce operator already today in your React apps.

Can the Android drawable directory contain subdirectories?

  1. Right click on Drawable
  2. Select New ---> Directory
  3. Enter the directory name. Eg: logo.png(the location will already show the drawable folder by default)
  4. Copy and paste the images directly into the drawable folder. While pasting you get an option to choose mdpi/xhdpi/xxhdpi etc for each of the images from a list. Select the appropriate option and enter the name of the image. Make sure to keep the same name as the directory name i.e logo.png
  5. Do the same for the remaining images. All of them will be placed under the logo.png main folder.

Bootstrap carousel resizing image

Use this code to set height of the image slider to the full screen / upto 100 view port height. This will helpful when using bootstrap carousel theme slider. I face some issue with height the i use following classes to set image width 100% & height 100vh.

<img class="d-block w-100" src="" alt="" > use this class in image tags & write following css code in style tags or style.css file

.carousel-inner > .carousel-item > img {
  height: 100vh;
}

is vs typeof

Does it matter which is faster, if they don't do the same thing? Comparing the performance of statements with different meaning seems like a bad idea.

is tells you if the object implements ClassA anywhere in its type heirarchy. GetType() tells you about the most-derived type.

Not the same thing.

Groovy write to file (newline)

As @Steven points out, a better way would be:

public void writeToFile(def directory, def fileName, def extension, def infoList) {
  new File("$directory/$fileName$extension").withWriter { out ->
    infoList.each {
      out.println it
    }
  }
}

As this handles the line separator for you, and handles closing the writer as well

(and doesn't open and close the file each time you write a line, which could be slow in your original version)

How do I implement IEnumerable<T>

make mylist into a List<MyObject>, is one option

Can I use wget to check , but not download

Yes easy.

wget --spider www.bluespark.co.nz

That will give you

Resolving www.bluespark.co.nz... 210.48.79.121
Connecting to www.bluespark.co.nz[210.48.79.121]:80... connected.
HTTP request sent, awaiting response... 200 OK
Length: unspecified [text/html]
200 OK

How to check if a column exists in a SQL Server table?

Tweak the below to suit your specific requirements:

if not exists (select
                     column_name
               from
                     INFORMATION_SCHEMA.columns
               where
                     table_name = 'MyTable'
                     and column_name = 'MyColumn')
    alter table MyTable add MyColumn int

Edit to deal with edit to question: That should work - take a careful look over your code for stupid mistakes; are you querying INFORMATION_SCHEMA on the same database as your insert is being applied to for example? Do you have a typo in your table/column name in either statement?

Socket accept - "Too many open files"

Use lsof -u `whoami` | wc -l to find how many open files the user has

Import PEM into Java Key Store

I used Keystore Explorer

  1. Open JKS with a private key
  2. Examine signed PEM from CA
  3. Import key
  4. Save JKS

Is it possible to validate the size and type of input=file in html5

if your using php for the backend maybe you can use this code.

// Validate image file size
if (($_FILES["file-input"]["size"] > 2000000)) {
    $msg = "Image File Size is Greater than 2MB.";
    header("Location: ../product.php?error=$msg");
    exit();
}  

Drawing an image from a data URL to a canvas

You might wanna clear the old Image before setting a new Image.

You also need to update the Canvas size for a new Image.

This is how I am doing in my project:

    // on image load update Canvas Image 
    this.image.onload = () => {

      // Clear Old Image and Reset Bounds
      canvasContext.clearRect(0, 0, this.canvas.width, this.canvas.height);
      this.canvas.height = this.image.height;
      this.canvas.width = this.image.width;

      // Redraw Image
      canvasContext.drawImage(
        this.image,
        0,
        0,
        this.image.width,
        this.image.height
      );
    };

Convert a Unicode string to a string in Python (containing extra symbols)

No answere worked for my case, where I had a string variable containing unicode chars, and no encode-decode explained here did the work.

If I do in a Terminal

echo "no me llama mucho la atenci\u00f3n"

or

python3
>>> print("no me llama mucho la atenci\u00f3n")

The output is correct:

output: no me llama mucho la atención

But working with scripts loading this string variable didn't work.

This is what worked on my case, in case helps anybody:

string_to_convert = "no me llama mucho la atenci\u00f3n"
print(json.dumps(json.loads(r'"%s"' % string_to_convert), ensure_ascii=False))
output: no me llama mucho la atención

Set Windows process (or user) memory limit

No way to do this that I know of, although I'm very curious to read if anyone has a good answer. I have been thinking about adding something like this to one of the apps my company builds, but have found no good way to do it.

The one thing I can think of (although not directly on point) is that I believe you can limit the total memory usage for a COM+ application in Windows. It would require the app to be written to run in COM+, of course, but it's the closest way I know of.

The working set stuff is good (Job Objects also control working sets), but that's not total memory usage, only real memory usage (paged in) at any one time. It may work for what you want, but afaik it doesn't limit total allocated memory.

Using jQuery to compare two arrays of Javascript objects

In my case compared arrays contain only numbers and strings. This solution worked for me:

function are_arrs_equal(arr1, arr2){
    return arr1.sort().toString() === arr2.sort().toString()
}

Let's test it!

arr1 = [1, 2, 3, 'nik']
arr2 = ['nik', 3, 1, 2]
arr3 = [1, 2, 5]

console.log (are_arrs_equal(arr1, arr2)) //true
console.log (are_arrs_equal(arr1, arr3)) //false

How to delete selected text in the vi editor

If you want to delete using line numbers you can use:

:startingline, last line d

Example:

:7,20 d

This example will delete line 7 to 20.

How to extract a floating number from a string

Python docs has an answer that covers +/-, and exponent notation

scanf() Token      Regular Expression
%e, %E, %f, %g     [-+]?(\d+(\.\d*)?|\.\d+)([eE][-+]?\d+)?
%i                 [-+]?(0[xX][\dA-Fa-f]+|0[0-7]*|\d+)

This regular expression does not support international formats where a comma is used as the separator character between the whole and fractional part (3,14159). In that case, replace all \. with [.,] in the above float regex.

                        Regular Expression
International float     [-+]?(\d+([.,]\d*)?|[.,]\d+)([eE][-+]?\d+)?

jackson deserialization json to java-objects

It looks like you are trying to read an object from JSON that actually describes an array. Java objects are mapped to JSON objects with curly braces {} but your JSON actually starts with square brackets [] designating an array.

What you actually have is a List<product> To describe generic types, due to Java's type erasure, you must use a TypeReference. Your deserialization could read: myProduct = objectMapper.readValue(productJson, new TypeReference<List<product>>() {});

A couple of other notes: your classes should always be PascalCased. Your main method can just be public static void main(String[] args) throws Exception which saves you all the useless catch blocks.

How to print colored text to the terminal?

I have a library called colorit. It is super simple.

Here are some examples:

from colorit import *

# Use this to ensure that ColorIt will be usable by certain command line interfaces
# Note: This clears the terminal
init_colorit()

# Foreground
print(color("This text is red", Colors.red))
print(color("This text is orange", Colors.orange))
print(color("This text is yellow", Colors.yellow))
print(color("This text is green", Colors.green))
print(color("This text is blue", Colors.blue))
print(color("This text is purple", Colors.purple))
print(color("This text is white", Colors.white))

# Background
print(background("This text has a background that is red", Colors.red))
print(background("This text has a background that is orange", Colors.orange))
print(background("This text has a background that is yellow", Colors.yellow))
print(background("This text has a background that is green", Colors.green))
print(background("This text has a background that is blue", Colors.blue))
print(background("This text has a background that is purple", Colors.purple))
print(background("This text has a background that is white", Colors.white))

# Custom
print(color("This color has a custom grey text color", (150, 150, 150)))
print(background("This color has a custom grey background", (150, 150, 150)))

# Combination
print(
    background(
        color("This text is blue with a white background", Colors.blue), Colors.white
    )
)

# If you are using Windows Command Line, this is so that it doesn't close immediately
input()

This gives you:

Picture of ColorIt

It's also worth noting that this is cross platform and has been tested on Mac, Linux, and Windows.

You might want to try it out: https://github.com/SuperMaZingCoder/colorit

colorit is now available to be installed with PyPi! You can install it with pip install color-it on Windows and pip3 install color-it on macOS and Linux.

How to implement onBackPressed() in Fragments?

In activity life cycle, always android back button deals with FragmentManager transactions when we used FragmentActivity or AppCompatActivity.

To handle the backstack we don't need to handle its backstack count or tag anything but we should keep focus while adding or replacing a fragment. Please find the following snippets to handle the back button cases,

    public void replaceFragment(Fragment fragment) {

        FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
        if (!(fragment instanceof HomeFragment)) {
            transaction.addToBackStack(null);
        }
        transaction.replace(R.id.activity_menu_fragment_container, fragment).commit();
    }

Here, I won't add back stack for my home fragment because it's home page of my application. If add addToBackStack to HomeFragment then app will wait to remove all the frament in acitivity then we'll get blank screen so I'm keeping the following condition,

if (!(fragment instanceof HomeFragment)) {
            transaction.addToBackStack(null);
}

Now, you can see the previously added fragment on acitvity and app will exit when reaching HomeFragment. you can also look on the following snippets.

@Override
public void onBackPressed() {

    if (mDrawerLayout.isDrawerOpen(Gravity.LEFT)) {
        closeDrawer();
    } else {
        super.onBackPressed();
    }
}

Anybody knows any knowledge base open source?

Since I don't have enough reputation points to comment on Bruno Shine's answer, I'll add this note as a new answer.

KBPublisher 2.0 is still available on Sourceforge: http://sourceforge.net/projects/kbpublisher/

The project hasn't been updated for years. I've been running it since v1.9 or something, and it works fine.

Need to combine lots of files in a directory

If you like to do this for open files on Notepad++, you can use Combine plugin: http://www.scout-soft.com/combine/

Bash Templating: How to build configuration files from templates with Bash?

Here's a modified perl script based on a few of the other answers:

perl -pe 's/([^\\]|^)\$\{([a-zA-Z_][a-zA-Z_0-9]*)\}/$1.$ENV{$2}/eg' -i template

Features (based on my needs, but should be easy to modify):

  • Skips escaped parameter expansions (e.g. \${VAR}).
  • Supports parameter expansions of the form ${VAR}, but not $VAR.
  • Replaces ${VAR} with a blank string if there is no VAR envar.
  • Only supports a-z, A-Z, 0-9 and underscore characters in the name (excluding digits in the first position).

Select Specific Columns from Spark DataFrame

Problem was to select columns of on dataframe after joining with other dataframe.

I tried below and select the columns of salaryDf from the joined dataframe.

Hope this will help

        val empDf=spark.read.option("header","true").csv("/data/tech.txt")

        val salaryDf=spark.read.option("header","true").csv("/data/salary.txt")

        val joinData= empDf.join(salaryDf,empDf.col("first") === salaryDf.col("first") and  empDf.col("last") === salaryDf.col("last"))

      //**below will select the colums of salaryDf only**

     val finalDF=joinData.select(salaryDf.columns map  salaryDf.col:_*)

//same way we can select the columns of empDf
joinData.select(empDf.columns map  empDf.col:_*)

How can I pass POST parameters in a URL?

You could use a form styled as a link. No JavaScript is required:

<form action="/do/stuff.php" method="post">
    <input type="hidden" name="user_id" value="123" />
    <button>Go to user 123</button>
</form>

CSS:

button {
    border: 0;
    padding: 0;
    display: inline;
    background: none;
    text-decoration: underline;
    color: blue;
}
button:hover {
    cursor: pointer;
}

See: http://jsfiddle.net/SkQRN/

Disabling Minimize & Maximize On WinForm?

you can simply disable maximize inside form constructor.

 public Form1(){
     InitializeComponent();
     MaximizeBox = false;
 }

to minimize when closing.

private void Form1_FormClosing(Object sender, FormClosingEventArgs e) {
    e.Cancel = true;
    WindowState = FormWindowState.Minimized;
}

Concatenate columns in Apache Spark DataFrame

In my case, I wanted a Tab delimited row.

from pyspark.sql import functions as F
df.select(F.concat_ws('|','_c1','_c2','_c3','_c4')).show()

This worked well like a hot knife over butter.

Double border with different color

Alternatively, you can use pseudo-elements to do so :) the advantage of the pseudo-element solution is that you can use it to space the inner border at an arbitrary distance away from the actual border, and the background will show through that space. The markup:

_x000D_
_x000D_
body {_x000D_
  background-image: linear-gradient(180deg, #ccc 50%, #fff 50%);_x000D_
  background-repeat: no-repeat;_x000D_
  height: 100vh;_x000D_
}_x000D_
.double-border {_x000D_
  background-color: #ccc;_x000D_
  border: 4px solid #fff;_x000D_
  padding: 2em;_x000D_
  width: 16em;_x000D_
  height: 16em;_x000D_
  position: relative;_x000D_
  margin: 0 auto;_x000D_
}_x000D_
.double-border:before {_x000D_
  background: none;_x000D_
  border: 4px solid #fff;_x000D_
  content: "";_x000D_
  display: block;_x000D_
  position: absolute;_x000D_
  top: 4px;_x000D_
  left: 4px;_x000D_
  right: 4px;_x000D_
  bottom: 4px;_x000D_
  pointer-events: none;_x000D_
}
_x000D_
<div class="double-border">_x000D_
  <!-- Content -->_x000D_
</div>
_x000D_
_x000D_
_x000D_

If you want borders that are consecutive to each other (no space between them), you can use multiple box-shadow declarations (separated by commas) to do so:

_x000D_
_x000D_
body {_x000D_
  background-image: linear-gradient(180deg, #ccc 50%, #fff 50%);_x000D_
  background-repeat: no-repeat;_x000D_
  height: 100vh;_x000D_
}_x000D_
.double-border {_x000D_
  background-color: #ccc;_x000D_
  border: 4px solid #fff;_x000D_
  box-shadow:_x000D_
    inset 0 0 0 4px #eee,_x000D_
    inset 0 0 0 8px #ddd,_x000D_
    inset 0 0 0 12px #ccc,_x000D_
    inset 0 0 0 16px #bbb,_x000D_
    inset 0 0 0 20px #aaa,_x000D_
    inset 0 0 0 20px #999,_x000D_
    inset 0 0 0 20px #888;_x000D_
  /* And so on and so forth, if you want border-ception */_x000D_
  margin: 0 auto;_x000D_
  padding: 3em;_x000D_
  width: 16em;_x000D_
  height: 16em;_x000D_
  position: relative;_x000D_
}
_x000D_
<div class="double-border">_x000D_
  <!-- Content -->_x000D_
</div>
_x000D_
_x000D_
_x000D_

How to use adb command to push a file on device without sd card

Follow these steps :

go to Android Sdk then 'platform-tools' path on your Terminal or Console

(on mac, default path is : /Users/USERNAME/Library/Android/sdk/platform-tools)

To check the SDCards(External and Internal) installed on your device fire these commands :

  • 1) ./adb shell (hit return/enter)
  • 2) cd -(hit return/enter)

now you will see the list of Directories and files from your android device there you may find /sdcard as well as /storage

  • 3) cd /storage (hit return/enter)
  • 4) ls (hit return/enter)

you may see sdcard0 (generally sdcard0 is internal storage) and sdcard1 (if External SDCard is present)

  • 5) exit (hit return/enter)

to come out of adb shell

  • 6) ./adb push '/Users/SML/Documents/filename.zip' /storage/sdcard0/path_to_store/ (hit return/enter)

to copy file

using favicon with css

There is no explicit way to change the favicon globally using CSS that I know of. But you can use a simple trick to change it on the fly.

First just name, or rename, the favicon to "favicon.ico" or something similar that will be easy to remember, or is relevant for the site you're working on. Then add the link to the favicon in the head as you usually would. Then when you drop in a new favicon just make sure it's in the same directory as the old one, and that it has the same name, and there you go!

It's not a very elegant solution, and it requires some effort. But dropping in a new favicon in one place is far easier than doing a find and replace of all the links, or worse, changing them manually. At least this way doesn't involve messing with the code.

Of course dropping in a new favicon with the same name will delete the old one, so make sure to backup the old favicon in case of disaster, or if you ever want to go back to the old design.

PHP: HTML: send HTML select option attribute in POST

You can do this with JQuery

Simply:

   <form name='add'>
   Age: <select id="age" name='age'>
   <option value='1' stud_name='sre'>23</option>
   <option value='2' stud_name='sam'>24</option>
   <option value='5' stud_name='john'>25</option>
   </select>
   <input type='hidden' id="name" name="name" value=""/>
   <input type='submit' name='submit'/>
   </form>

Add this code in Header section:

<script src="http://code.jquery.com/jquery-1.9.0.min.js"></script>

Now JQuery function

<script type="text/javascript" language="javascript">
$(function() {
      $("#age").change(function(){
      var studentNmae= $('option:selected', this).attr('stud_name');
      $('#name').val(studentNmae);
   });
});
</script>

you can use both values as

$name = $_POST['name'];
$value = $_POST['age'];

Get column from a two dimensional array

Taking a column is easy with the map function.

// a two-dimensional array
var two_d = [[1,2,3],[4,5,6],[7,8,9]];

// take the third column
var col3 = two_d.map(function(value,index) { return value[2]; });

Why bother with the slice at all? Just filter the matrix to find the rows of interest.

var interesting = two_d.filter(function(value,index) {return value[1]==5;});
// interesting is now [[4,5,6]]

Sadly, filter and map are not natively available on IE9 and lower. The MDN documentation provides implementations for browsers without native support.

angularjs to output plain text instead of html

Use ng-bind-html this is only proper and simplest way

The representation of if-elseif-else in EL using JSF

You can use "ELSE IF" using conditional operator in expression language as below:

 <p:outputLabel value="#{transaction.status.equals('PNDNG')?'Pending':
                                     transaction.status.equals('RJCTD')?'Rejected':
                                     transaction.status.equals('CNFRMD')?'Confirmed':
                                     transaction.status.equals('PSTD')?'Posted':''}"/>

Why is 1/1/1970 the "epoch time"?

Short answer: Why not?

Longer answer: The time itself doesn't really matter, as long as everyone who uses it agrees on its value. As 1/1/70 has been in use for so long, using it will make you code as understandable as possible for as many people as possible.

There's no great merit in choosing an arbitrary epoch just to be different.

Cannot read property 'getContext' of null, using canvas

You don't have to include JQuery.

In the index.html:
<canvas id="canvas" width="640" height="480"></canvas><script src="javascript/game.js"> This should work without JQuery...

Edit: You should put the script tag IN the body tag...

mysql select from n last rows

Last 5 rows retrieve in mysql

This query working perfectly

SELECT * FROM (SELECT * FROM recharge ORDER BY sno DESC LIMIT 5)sub ORDER BY sno ASC

or

select sno from(select sno from recharge order by sno desc limit 5) as t where t.sno order by t.sno asc

Counting Number of Letters in a string variable

You can simply use

int numberOfLetters = yourWord.Length;

or to be cool and trendy, use LINQ like this :

int numberOfLetters = yourWord.ToCharArray().Count();

and if you hate both Properties and LINQ, you can go old school with a loop :

int numberOfLetters = 0;
foreach (char letter in yourWord)
{
    numberOfLetters++;
}

How do I use the new computeIfAbsent function?

Recently I was playing with this method too. I wrote a memoized algorithm to calcualte Fibonacci numbers which could serve as another illustration on how to use the method.

We can start by defining a map and putting the values in it for the base cases, namely, fibonnaci(0) and fibonacci(1):

private static Map<Integer,Long> memo = new HashMap<>();
static {
   memo.put(0,0L); //fibonacci(0)
   memo.put(1,1L); //fibonacci(1)
}

And for the inductive step all we have to do is redefine our Fibonacci function as follows:

public static long fibonacci(int x) {
   return memo.computeIfAbsent(x, n -> fibonacci(n-2) + fibonacci(n-1));
}

As you can see, the method computeIfAbsent will use the provided lambda expression to calculate the Fibonacci number when the number is not present in the map. This represents a significant improvement over the traditional, tree recursive algorithm.

Multiline TextBox multiple newline

I had the same problem. If I add one Environment.Newline I get one new line in the textbox. But if I add two Environment.Newline I get one new line. In my web app I use a whitespace modul that removes all unnecessary white spaces. If i disable this module I get two new lines in my textbox. Hope that helps.

Accessing Websites through a Different Port?

You can only access a website throught the port that is bind with the http server. Example: i hava a web server and it is listening for connections on port 123, the you only can get my pages connecting to my 123 port.

How can I reload .emacs after changing it?

Keyboard shortcut:

(defun reload-init-file ()
  (interactive)
  (load-file user-init-file))

(global-set-key (kbd "C-c C-l") 'reload-init-file)    ; Reload .emacs file

What does collation mean?

Collation defines how you sort and compare string values

For example, it defines how to deal with

  • accents (äàa etc)
  • case (Aa)
  • the language context:
    • In a French collation, cote < côte < coté < côté.
    • In the SQL Server Latin1 default , cote < coté < côte < côté
  • ASCII sorts (a binary collation)

Disable dragging an image from an HTML page

I did the css properties shown here as well as monitor ondragstart with the following javascript:

handleDragStart: function (evt) {
    if (evt.target.nodeName.match(/^(IMG|DIV|SPAN|A)$/i)) {
      evt.preventDefault();
      return false;
    }
  },

Is there any use for unique_ptr with array?

Some people do not have the luxury of using std::vector, even with allocators. Some people need a dynamically sized array, so std::array is out. And some people get their arrays from other code that is known to return an array; and that code isn't going to be rewritten to return a vector or something.

By allowing unique_ptr<T[]>, you service those needs.

In short, you use unique_ptr<T[]> when you need to. When the alternatives simply aren't going to work for you. It's a tool of last resort.

How do I get Month and Date of JavaScript in 2 digit format?

Example for month:

function getMonth(date) {
  var month = date.getMonth() + 1;
  return month < 10 ? '0' + month : '' + month; // ('' + month) for string result
}  

You can also extend Date object with such function:

Date.prototype.getMonthFormatted = function() {
  var month = this.getMonth() + 1;
  return month < 10 ? '0' + month : '' + month; // ('' + month) for string result
}

FATAL ERROR in native method: JDWP No transports initialized, jvmtiError=AGENT_ERROR_TRANSPORT_INIT(197)

I had the same problem in Catalina.sh of my tomcat for JPDA Options:

JPDA_OPTS="-agentlib:jdwp=transport=$JPDA_TRANSPORT,address=$JPDA_ADDRESS,server=y,suspend=$JPDA_SUSPEND"

After removing JPDA option from my command to start the Tomcat server, I was able to start the server on local environment.

Android: Reverse geocoding - getFromLocation

I've heard that Geocoder is on the buggy side. I recently put together an example application that uses Google's http geocoding service to lookup location from lat/long. Feel free to check it out here

http://www.smnirven.com/?p=39

forEach() in React JSX does not output any HTML

You need to pass an array of element to jsx. The problem is that forEach does not return anything (i.e it returns undefined). So it's better to use map because map returns an array:

class QuestionSet extends Component {
render(){ 
    <div className="container">
       <h1>{this.props.question.text}</h1>
       {this.props.question.answers.map((answer, i) => {     
           console.log("Entered");                 
           // Return the element. Also pass key     
           return (<Answer key={answer} answer={answer} />) 
        })}
}

export default QuestionSet;

How can I use modulo operator (%) in JavaScript?

That would be the modulo operator, which produces the remainder of the division of two numbers.

Difference between shared objects (.so), static libraries (.a), and DLL's (.so)?

I've always thought that DLLs and shared objects are just different terms for the same thing - Windows calls them DLLs, while on UNIX systems they're shared objects, with the general term - dynamically linked library - covering both (even the function to open a .so on UNIX is called dlopen() after 'dynamic library').

They are indeed only linked at application startup, however your notion of verification against the header file is incorrect. The header file defines prototypes which are required in order to compile the code which uses the library, but at link time the linker looks inside the library itself to make sure the functions it needs are actually there. The linker has to find the function bodies somewhere at link time or it'll raise an error. It ALSO does that at runtime, because as you rightly point out the library itself might have changed since the program was compiled. This is why ABI stability is so important in platform libraries, as the ABI changing is what breaks existing programs compiled against older versions.

Static libraries are just bundles of object files straight out of the compiler, just like the ones that you are building yourself as part of your project's compilation, so they get pulled in and fed to the linker in exactly the same way, and unused bits are dropped in exactly the same way.

What is the canonical way to trim a string in Ruby without creating a new string?

If you are using Ruby on Rails there is a squish

> @title = " abc "
 => " abc " 

> @title.squish
 => "abc"
> @title
 => " abc "

> @title.squish!
 => "abc"
> @title
 => "abc" 

If you are using just Ruby you want to use strip

Herein lies the gotcha.. in your case you want to use strip without the bang !

while strip! certainly does return nil if there was no action it still updates the variable so strip! cannot be used inline. If you want to use strip inline you can use the version without the bang !

strip! using multi line approach

> tokens["Title"] = " abc "
 => " abc "
> tokens["Title"].strip!
 => "abc"
> @title = tokens["Title"]
 => "abc"

strip single line approach... YOUR ANSWER

> tokens["Title"] = " abc "
 => " abc "
> @title = tokens["Title"].strip if tokens["Title"].present?
 => "abc"

npm install error - unable to get local issuer certificate

Try

npm config set strict-ssl false

This is a alternative shared in this url https://github.com/nodejs/node/issues/3742

Access an arbitrary element in a dictionary in Python

to get a key

next(iter(mydict))

to get a value

next(iter(mydict.values()))

to get both

next(iter(mydict.items())) # or next(iter(mydict.viewitems())) in python 2

The first two are Python 2 and 3. The last two are lazy in Python 3, but not in Python 2.

JavaScript replace \n with <br />

Handles either type of line break

str.replace(new RegExp('\r?\n','g'), '<br />');

npm install vs. update - what's the difference?

The difference between npm install and npm update handling of package versions specified in package.json:

{
  "name":          "my-project",
  "version":       "1.0",                             // install   update
  "dependencies":  {                                  // ------------------
    "already-installed-versionless-module":  "*",     // ignores   "1.0" -> "1.1"
    "already-installed-semver-module":       "^1.4.3" // ignores   "1.4.3" -> "1.5.2"
    "already-installed-versioned-module":    "3.4.1"  // ignores   ignores
    "not-yet-installed-versionless-module":  "*",     // installs  installs
    "not-yet-installed-semver-module":       "^4.2.1" // installs  installs
    "not-yet-installed-versioned-module":    "2.7.8"  // installs  installs
  }
}

Summary: The only big difference is that an already installed module with fuzzy versioning ...

  • gets ignored by npm install
  • gets updated by npm update

Additionally: install and update by default handle devDependencies differently

  • npm install will install/update devDependencies unless --production flag is added
  • npm update will ignore devDependencies unless --dev flag is added

Why use npm install at all?

Because npm install does more when you look besides handling your dependencies in package.json. As you can see in npm install you can ...

  • manually install node-modules
  • set them as global (which puts them in the shell's PATH) using npm install -g <name>
  • install certain versions described by git tags
  • install from a git url
  • force a reinstall with --force

String comparison: InvariantCultureIgnoreCase vs OrdinalIgnoreCase?

You seem to be doing file name comparisons, so I would just add that OrdinalIgnoreCase is closest to what NTFS does (it's not exactly the same, but it's closer than InvariantCultureIgnoreCase)

Determine version of Entity Framework I am using?

If you open the references folder and locate system.data.entity, click the item, then check the runtime version number in the Properties explorer, you will see the sub version as well. Mine for instance shows v4.0.30319 with the Version property showing 4.0.0.0.