Tutorial by Examples: ar

// class declaration with a list of parameters for a primary constructor type Car (model: string, plates: string, miles: int) = // secondary constructor (it must call primary constructor) new (model, plates) = let miles = 0 new Car(model, plates, miles) ...

One can clear the user data of a specific app using adb: adb shell pm clear <package> This is the same as to browse the settings on the phone, select the app and press on the clear data button. pm invokes the package manager on the device clear deletes all data associated with a packag...

Create SharedPreferences BuyyaPref SharedPreferences pref = getApplicationContext().getSharedPreferences("BuyyaPref", MODE_PRIVATE); Editor editor = pref.edit(); Storing data as KEY/VALUE pair editor.putBoolean("key_name1", true); // Saving boolean - true/false ...

In contrast to segue that lets you pass data "forward" from current view controller to destination view controller: (VC1) -> (VC2) Using "unwind" you can do the opposite, pass data from the destination or current view controller to its presenting view controller: (VC1) <...

There are cases, where custom objects need to be created and defined in the resources of the application. Such objects can be composed of Java simple types, for example Integer, Float, String. Here is the example of how to import an object defined in application resources. The object Category cons...

Let's say you have a User model class User < ActiveRecord::Base end Now to update the first_name and last_name of a user with id = 1, you can write the following code. user = User.find(1) user.update(first_name: 'Kashif', last_name: 'Liaqat') Calling update will attempt to update the gi...

\documentclass{report} \begin{document} \title{I want to be a Wombat} \author{Carl Capybara} \maketitle \end{document} This will create a title page with no other content:

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); ...

#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. ...

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...

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...

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(...

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...

LISP and Scheme's greatest advantage over other mainstream programming language is their macro system. Unlike the C preprocessor and other macro languages, Scheme macros take parsed code as input and return expanded code as output. This is one of the applications of Scheme's “code is data” phrase, a...

Converting an integer type to the corresponding promoted type is better than converting it to some other integer type. void f(int x); void f(short x); signed char c = 42; f(c); // calls f(int); promotion to int is better than conversion to short short s = 42; f(s); // calls f(short); exact mat...

Like most scripting languages, vimscript has variables. One can define a variable with the :let command: let variable = value and delete it with :unlet: unlet variable In Vim, variables can be scoped by prepending a single letter and a colon to their name. Plugin authors use that feature to...