Tutorial by Examples: s

Inheritance Modifiers (on properties and methods)

Overridable Allows a property or method in a class to be overridden in a derived class. Public Class Person Public Overridable Sub DoSomething() Console.WriteLine("Person") End Sub End Class Overrides Overrides an Overridable property or method defined in the base...

Visual Basic .NET Language • OOP Keywords

MyBase

The MyBase keyword behaves like an object variable that refers to the base class of the current instance of a class. Public Class Person Public Sub DoSomething() Console.WriteLine("Person") End Sub End Class Public Class Customer Inherits Person Public S...

Visual Basic .NET Language • OOP Keywords

Me vs MyClass

Me uses the current object instance. MyClass uses the memberdefinition in the class where the member is called Class Person Public Overridable Sub DoSomething() Console.WriteLine("Person") End Sub Public Sub useMe() Me.DoSomething() End Sub ...

Visual Basic .NET Language • OOP Keywords

Shadows

It redeclares a member that is not overridable. Only calls to the instance will be affected. Code inside the base classes will not be affected by this. Public Class Person Public Sub DoSomething() Console.WriteLine("Person") End Sub Public Sub UseMe() ...

Visual Basic .NET Language • OOP Keywords

Interfaces

Public Interface IPerson Sub DoSomething() End Interface Public Class Customer Implements IPerson Public Sub DoSomething() Implements IPerson.DoSomething Console.WriteLine("Customer") End Sub End Class

Visual Basic .NET Language • OOP Keywords

Installation or Setup

Chart.js can be included in several different ways: NPM Run the following command on your NPM project directory npm install chart.js --save CDN Include a script tag in your HTML linking to the chart.js CDN <html> <body> <script type="text/javascript" s...

chart.js • Getting started with chart.js

Using character constants instead of string literals, and vice versa

In C, character constants and string literals are different things. A character surrounded by single quotes like 'a' is a character constant. A character constant is an integer whose value is the character code that stands for the character. How to interpret character constants with multiple charac...

C Language • Common pitfalls

SQLite

SQLite is a lightweight, disk-based database. Since it does not require a separate database server, it is often used for prototyping or for small applications that are often used by a single user or by one user at a given time. import sqlite3 conn = sqlite3.connect("users.db") c = con...

Python Language • Database Access

Download a file from Server using Retrofit2

Interface declaration for downloading a file public interface ApiInterface { @GET("movie/now_playing") Call<MovieResponse> getNowPlayingMovies(@Query("api_key") String apiKey, @Query("page") int page); // option 1: a resource relative to your bas...

Android • Retrofit2

Sample to get user profile path

# will retrieve my home path ENV['HOME'] # => "/Users/username" # will try retrieve the 'FOO' environment variable. If failed, will get 'bar' ENV.fetch('FOO', 'bar')

Ruby Language • Environment Variables

Accessing Singleton Class

There are two ways to get singleton class of an object singleton_class method. Reopening singleton class of an object and returning self. object.singleton_class singleton_class = class << object self end

Ruby Language • Singleton Class

Accessing Instance/Class Variables in Singleton Classes

Singleton classes share their instance/class variables with their object. class Example @@foo = :example end def Example.foo class_variable_get :@@foo end Example.foo #=> :example class Example def initialize @foo = 1 end def foo @foo end end e = Ex...

Ruby Language • Singleton Class

Delete a range of lines into a named register

In Normal, type the following to delete a range of lines into a named register :10,20d a This will delete lines 10,20 in register "a. We can verify this by typing :reg This will show the text that was delete in register "a. To paste the contents in "a, just type "ap ...

vim • Vim Registers

Flowing execution context with AsyncLocal

When you need to pass some data from the parent task to its children tasks, so it logically flows with the execution, use AsyncLocal class: void Main() { AsyncLocal<string> user = new AsyncLocal<string>(); user.Value = "initial user"; // this does not aff...

.NET Framework • Task Parallel Library (TPL)

Formatting console output

Many of the console's print methods can also handle C-like string formatting, using % tokens: console.log('%s has %d points', 'Sam', 100); Displays Sam has 100 points. The full list of format specifiers in Javascript is: SpecifierOutput%sFormats the value as a string%i or %dFormats the value a...

JavaScript • Console

Basic subscription to Time.every event with 'unsubscribe'

0.18.0 Model is passed to subscriptions which means that every state change can modify subscriptions. import Html exposing ( Html, div, text, button ) import Html.Events exposing ( onClick ) import Time main : Program Never Model Msg main = Html.program { init = init ,...

Elm Language • Subscriptions

Basic loading and playing a video on the canvas.

The canvas can be used to display video from a variety of sources. This example shows how to load a video as a file resource, display it and add a simple click on screen play/pause toggle. This stackoverflow self answered question How do I display a video using HTML5 canvas tag shows the following ...

html5-canvas • Media types and the canvas

StackOverflowError & recursion to loop

If a recursive call goes "too deep", this results in a StackOverflowError. Java allocates a new frame for every method call on its thread's stack. However, the space of each thread's stack is limited. Too many frames on the stack leads to the Stack Overflow (SO). Example public static vo...

Java Language • Recursion

Message tagging with Html.App.map

Components define their own Messages, sent after emitted DOM Events, eg. CounterMsg from Parent-child communication type CounterMsg = Increment | Decrement | Reset The view of this component will send messages of CounterMsg type, therefore the view type signature is Html CounterMs...

Elm Language • The Elm Architecture

Limit DOM Updates

A common mistake seen in JavaScript when run in a browser environment is updating the DOM more often than necessary. The issue here is that every update in the DOM interface causes the browser to re-render the screen. If an update changes the layout of an element in the page, the entire page layout...

JavaScript • Performance Tips