Tutorial by Examples: an

Given the model: class MyModel(models.Model): name = models.CharField(max_length=10) model_num = models.IntegerField() flag = models.NullBooleanField(default=False) We can use Q objects to create AND , OR conditions in your lookup query. For example, say we want all objects that ...

Django manger is an interface through which the django model queries the database. The objects field used in most django queries is actually the default manager created for us by django (this is only created if we don't define custom managers). Why would we define a custom manager/queryset? To avo...

Assuming a class from django.db import models class Author(models.Model): name = models.CharField(max_length=50) def __str__(self): return self.name def get_absolute_url(self): return reverse('view_author', args=[str(self.id)]) class Book(models.Mo...

tl;dr : Create a base class that defines two user objects (say user and another_user). Create your other models and define three Client instances. self.client : Representing user logged in browser self.another_client : Representing another_user 's client self.unlogged_client : Representing unlo...

package main import ( "log" "text/template" "os" ) type Person struct{ MyName string MyAge int } var myTempContents string= ` This person's name is : {{.MyName}} And he is {{.MyAge}} years old. ` func main() { t,err := temp...

To assign variables from the command-line, -v can be used: $ awk -v myvar="hello" 'BEGIN {print myvar}' hello Note that there are no spaces around the equal sign. This allows to use shell variables: $ shell_var="hello" $ awk -v myvar="$shell_var" 'BEGIN {print m...

Node Version Manager, otherwise known as nvm, is a bash script that simplifies the management of multiple Node.js versions. To install nvm, use the provided install script: $ curl -o- https://raw.githubusercontent.com/creationix/nvm/v0.31.3/install.sh | bash For windows there is a nvm-windows p...

In some cases you may want to wrap a synchronous operation inside a promise to prevent repetition in code branches. Take this example: if (result) { // if we already have a result processResult(result); // process it } else { fetchResult().then(processResult); } The synchronous and async...

git checkout --orphan new-orphan-branch The first commit made on this new branch will have no parents and it will be the root of a new history totally disconnected from all the other branches and commits. source

You can use any element as an handle to drag another element around: <script> $(function() { $( "#draggable" ).draggable({ handle: ".handle" }); }); </script> <div id="draggable"> <span class="handle"&...

__call() and __callStatic() are called when somebody is calling nonexistent object method in object or static context. class Foo { /** * This method will be called when somebody will try to invoke a method in object * context, which does not exist, like: * * $foo->...

__sleep and __wakeup are methods that are related to the serialization process. serialize function checks if a class has a __sleep method. If so, it will be executed before any serialization. __sleep is supposed to return an array of the names of all variables of an object that should be serializ...

In case you have a Named Range in your Sheet, and you want to dynamically get the last row of that Dynamic Named Range. Also covers cases where the Named Range doesn't start from the first Row. Sub FindingLastRow() Dim sht As Worksheet Dim LastRow As Long Dim FirstRow As Long Set sht =...

import { Http, Request, RequestOptionsArgs, Response, RequestOptions, ConnectionBackend, Headers } from '@angular/http'; import { Router } from '@angular/router'; import { Observable } from 'rxjs/Observable'; import 'rxjs/add/observable/empty'; import 'rxjs/add/observable/throw'; import 'rxjs/a...

After extending the Http class, we need to tell angular to use this class instead of Http class. In order to do this, in our main module(or depending on the needs, just a particular module), we need to write in the providers section: export function httpServiceFactory(xhrBackend: XHRBackend, reque...

There are several ways to create an Observable in RxJava. The most powerful way is to use the Observable.create method. But it's also the most complicated way. So you must avoid using it, as much as possible. Emitting an exiting value If you already have a value, you can use Observable.just to emi...

SharedPreferences Manager (Singleton) class to read and write all types of data. import android.content.Context; import android.content.SharedPreferences; import android.util.Log; import com.google.gson.Gson; import java.lang.reflect.Type; /** * Singleton Class for accessing SharedPref...

A request for the top 10 most recently active StackOverflow posts using the Stack Exchange API. package main import ( "encoding/json" "fmt" "net/http" "net/url" ) const apiURL = "https://api.stackexchange.com/2.2/posts?" ...

If you want to cancel an alarm, and you don't have a reference to the original PendingIntent used to set the alarm, you need to recreate a PendingIntent exactly as it was when it was originally created. An Intent is considered equal by the AlarmManager: if their action, data, type, class, and ca...

Executing code after 1.5 seconds: Handler handler = new Handler(); handler.postDelayed(new Runnable() { @Override public void run() { //The code you want to run after the time is up } }, 1500); //the time you want to delay in milliseconds Executing code repeatedly every...