Tutorial by Examples: n

The android:process field defines the name of the process where the service is to run. Normally, all components of an application run in the default process created for the application. However, a component can override the default with its own process attribute, allowing you to spread your applicat...

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 default project layout creates a single settings.py. This is often useful to split it like this: myprojectroot/ myproject/ __init__.py settings/ __init__.py base.py dev.py prod.py tests.py This enables...

SELECT FIND_IN_SET('b','a,b,c'); Return value: 2 SELECT FIND_IN_SET('d','a,b,c'); Return value: 0

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...

To run a container interactively, pass in the -it options: $ docker run -it ubuntu:14.04 bash root@8ef2356d919a:/# echo hi hi root@8ef2356d919a:/# -i keeps STDIN open, while -t allocates a pseudo-TTY.

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...

You can nest quotes simply by including multiple > characters, like so: > Often makes no sense. > > Commenting above your quote… Often makes no sense. Commenting above your quote…

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...

Rcpp features two functions that enable code compilation inline and exportation directly into R: cppFunction() and evalCpp(). A third function called sourceCpp() exists to read in C++ code in a separate file though can be used akin to cppFunction(). Below is an example of compiling a C++ function w...

Within C++, one can set different compilation flags using: // [[Rcpp::plugins(name)]] List of the built-in plugins: // built-in C++11 plugin // [[Rcpp::plugins(cpp11)]] // built-in C++11 plugin for older g++ compiler // [[Rcpp::plugins(cpp0x)]] // built-in C++14 plugin for C++14 standa...

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...

Cloning a huge repository (like a project with multiple years of history) might take a long time, or fail because of the amount of data to be transferred. In cases where you don't need to have the full history available, you can do a shallow clone: git clone [repo_url] --depth 1 The above comman...

Similarly to the SimpleXML, you can use DOMDocument to parse XML from a string or from a XML file 1. From a string $doc = new DOMDocument(); $doc->loadXML($string); 2. From a file $doc = new DOMDocument(); $doc->load('books.xml');// use the actual file path. Absolute or relative Exa...

When you want to use user generated content in the SQL, it with done with parameters. For example for searching user with the name aminadav you should do: var username = 'aminadav'; var querystring = 'SELECT name, email from users where name = ?'; connection.query(querystring, [username], functi...

a. Running multiple queries at same time All queries in MySQL connection are done one after another. It means that if you want to do 10 queries and each query takes 2 seconds then it will take 20 seconds to complete whole execution. The solution is to create 10 connection and run each query in a di...

One of the easiest ways to connect to MySQL is by using mysql module. This module handles the connection between Node.js app and MySQL server. You can install it like any other module: npm install --save mysql Now you have to create a mysql connection, which you can later query. const mysql ...