Tutorial by Examples: r

If you are given a JSON string : val str = """{ | "name" : "Jsony McJsonface", | "age" : 18, | "hobbies" : [ "Fishing", "Hunting", "Camping" ], | "pet" : { | ...

C-style bit-manipulation A bit can be cleared using the bitwise AND operator (&). // Bit x will be cleared number &= ~(1LL << x); Using std::bitset reset(x) or set(x,false) - clears the bit at position x. std::bitset<5> num(std::string("01100")); num.reset(2); ...

Self-referential association is used to associate a model with itself. The most frequent example would be, to manage association between a friend and his follower. ex. rails g model friendship user_id:references friend_id:integer now you can associate models like; class User < ActiveRecord:...

The ng-required adds or removes the required validation attribute on an element, which in turn will enable and disable the require validation key for the input. It is used to optionally define if an input element is required to have a non-empty value. The directive is helpful when designing validat...

#include <stddef.h> // size_t, ptrdiff_t //----------------------------------- Machinery: using Size = ptrdiff_t; template< class Item, size_t n > constexpr auto n_items( Item (&)[n] ) noexcept -> Size { return n; } //----------------------------------- Us...

// Example of raw dynamic size array. It's generally better to use std::vector. #include <algorithm> // std::sort #include <iostream> using namespace std; auto int_from( istream& in ) -> int { int x; in >> x; return x; } auto main() -> int { ...

// Example of std::vector as an expanding dynamic size array. #include <algorithm> // std::sort #include <iostream> #include <vector> // std::vector using namespace std; int int_from( std::istream& in ) { int x = 0; in >> x; return x; } ...

// A fixed size raw array matrix (that is, a 2D raw array). #include <iostream> #include <iomanip> using namespace std; auto main() -> int { int const n_rows = 3; int const n_cols = 7; int const m[n_rows][n_cols] = // A raw array matrix. ...

Unfortunately as of C++14 there's no dynamic size matrix class in the C++ standard library. Matrix classes that support dynamic size are however available from a number of 3rd party libraries, including the Boost Matrix library (a sub-library within the Boost library). If you don't want a dependenc...

This is useful to see if there are any non-printable characters, or non-ASCII characters. e.g. If you have copy-pasted the code from web, you may have quotes like ” instead of standard ". $ cat -v file.txt $ cat -vE file.txt # Useful in detecting trailing spaces. e.g. $ echo '” ' | c...

Because in .NET 3.5 and older you don't have Lazy<T> class you use the following pattern: public class Singleton { private Singleton() // prevents public instantiation { } public static Singleton Instance { get { return Nested.instanc...

To create a new Rails 5 API, open a terminal and run the following command: rails new app_name --api The following file structure will be created: create create README.rdoc create Rakefile create config.ru create .gitignore create Gemfile create app create app/as...

RVM is a great tool to manage your ruby versions and set up your working environment. Assuming you already have RVM installed, to get the latest version of ruby, which is needed for these examples, open a terminal and run: $ rvm get stable $ rvm install ruby --latest Check your ruby version by...

PBKDF2 ("Password-Based Key Derivation Function 2") is one of the recommended hash-functions for password-hashing. It is part of rfc-2898. .NET's Rfc2898DeriveBytes-Class is based upon HMACSHA1. using System.Security.Cryptography; ... public const int SALT_SIZE = 24; //...

CanCan is a a popular authorization library for Ruby on Rails which restricts user access to specific resources. The latest gem (CanCanCan) is a continuation of the dead project CanCan. Permissions are defined in the Ability class and can be used from controllers, views, helpers, or any other place...

Once the number of abilities definitions start to grow in number, it becomes more and more difficult to handle the Ability file. The first strategy to handle these issue is to move abilities into meaningful methods, as per this example: class Ability include CanCan::Ability def initialize(...

Will select records in TableName that have records matching in TableName1. SELECT * FROM TableName t WHERE EXISTS ( SELECT 1 FROM TableName1 t1 where t.Id = t1.Id)

mount is used to mount another application (basically rack application) or rails engines to be used within the current application syntax: mount SomeRackApp, at: "some_route" Now you can access above mounted application using route helper some_rack_app_path or some_rack_app_url. But ...

Step 1: Create the controller, set the delegate, and conform to the protocol //Swift class ImageUploadViewController: UIViewController, UIImagePickerControllerDelegate, UINavigationControllerDelegate { let imagePickerController = UIImagePickerController() override func viewDi...

Build numberDescription15.0.4623.1001June 201415.0.4631.1001July 201415.0.4641.1001August 201415.0.4649.1001September 201415.0.4659.1001October 201415.0.4667.1000November 201415.0.4675.1000December 201415.0.4693.1001February 201515.0.4701.1001March 201515.0.4711.1000April 2015 (SP1 REQ)15.0.4719.100...