Tutorial by Examples: o

Patterns can be matched based on values independent to the value being matched using if guards: // Let's imagine a simplistic web app with the following pages: enum Page { Login, Logout, About, Admin } // We are authenticated let is_authenticated = true; // But we aren't admins...

To select the children of an element you can use the children() method. <div class="parent"> <h2>A headline</h2> <p>Lorem ipsum dolor sit amet...</p> <p>Praesent quis dolor turpis...</p> </div> Change the color of all the ...

By default the Python random module use the Mersenne Twister PRNG to generate random numbers, which, although suitable in domains like simulations, fails to meet security requirements in more demanding environments. In order to create a cryptographically secure pseudorandom number, one can use Syst...

docker restart <container> [<container>...] Option --time : Seconds to wait for stop before killing the container (default 10) docker restart <container> --time 10

public class Singleton { private readonly static Singleton instance = new Singleton(); private Singleton() { } public static Singleton Instance => instance; } This implementation is thread-safe because in this case instance object is initialized in the static constructor. The ...

This thread-safe version of a singleton was necessary in the early versions of .NET where static initialization was not guaranteed to be thread-safe. In more modern versions of the framework a statically initialized singleton is usually preferred because it is very easy to make implementation mistak...

To avoid repetition in nested routes, concerns provide a great way of sharing common resources that are reusable. To create a concern use the method concern within the routes.rb file. The method expects a symbol and block: concern :commentable do resources :comments end While not creating a...

git shortlog summarizes git log and groups by author If no parameters are given, a list of all commits made per committer will be shown in chronological order. $ git shortlog Committer 1 (<number_of_commits>): Commit Message 1 Commit Message 2 ... Committer 2 (<number_of_...

The flow of execution of a Ruby block may be controlled with the break, next, and redo statements. break The break statement will exit the block immediately. Any remaining instructions in the block will be skipped, and the iteration will end: actions = %w(run jump swim exit macarena) index = 0 ...

When assigning named methods to delegates, they will refer to the same underlying object if: They are the same instance method, on the same instance of a class They are the same static method on a class public class Greeter { public void WriteInstance() { Console.Write...

The System namespace contains Func<..., TResult> delegate types with between 0 and 15 generic parameters, returning type TResult. private void UseFunc(Func<string> func) { string output = func(); // Func with a single generic type parameter returns that type Console.WriteLine...

Named methods can be assigned to delegates with matching signatures: public static class Example { public static int AddOne(int input) { return input + 1; } } Func<int,int> addOne = Example.AddOne Example.AddOne takes an int and returns an int, its signature ...

Lambdas can be used to create anonymous methods to assign to a delegate: Func<int,int> addOne = x => x+1; Note that the explicit declaration of type is required when creating a variable this way: var addOne = x => x+1; // Does not work

In Python 2, exec is a statement, with special syntax: exec code [in globals[, locals]]. In Python 3 exec is now a function: exec(code, [, globals[, locals]]), and the Python 2 syntax will raise a SyntaxError. As print was changed from statement into a function, a __future__ import was also added. ...

SwiftyJSON is a Swift framework built to remove the need for optional chaining in normal JSON serialization. You can download it here: https://github.com/SwiftyJSON/SwiftyJSON Without SwiftyJSON, your code would look like this to find the name of the first book in a JSON object: if let jsonObject...

Do-loops are useful when you always want to run a codeblock at least once. A Do-loop will evaluate the condition after executing the codeblock, unlike a while-loop which does it before executing the codeblock. You can use do-loops in two ways: Loop while the condition is true: Do { code_...

Closures in Python are created by function calls. Here, the call to makeInc creates a binding for x that is referenced inside the function inc. Each call to makeInc creates a new instance of this function, but each instance has a link to a different binding of x. def makeInc(x): def inc(y): ...

On either Linux/UNIX or Windows, a script can be passed as an argument to the PHP executable, with that script's options and arguments following: php ~/example.php foo bar c:\php\php.exe c:\example.php foo bar This passes foo and bar as arguments to example.php. On Linux/UNIX, the preferred me...

The for keyword is also used for conditional loops, traditionally while loops in other programming languages. package main import ( "fmt" ) func main() { i := 0 for i < 3 { // Will repeat if condition is true i++ fmt.Println(i) } } play ...

In Python 2, when a property raise a error, hasattr will ignore this property, returning False. class A(object): @property def get(self): raise IOError class B(object): @property def get(self): return 'get in b' a = A() b = B() print 'a hasattr get:...