Tutorial by Examples: on

Traits to facilitate horizontal code reuse

Let's say we have an interface for logging: interface Logger { function log($message); } Now say we have two concrete implementations of the Logger interface: the FileLogger and the ConsoleLogger. class FileLogger implements Logger { public function log($message) { // Append...

PHP • Traits

Calling a function from another C file

foo.h #ifndef FOO_DOT_H /* This is an "include guard" */ #define FOO_DOT_H /* prevents the file from being included twice. */ /* Including a header file twice causes all kinds */ /* of interesting problems.*/ /** * This is a functi...

C Language • Declarations

onUpgrade() method

SQLiteOpenHelper is a helper class to manage database creation and version management. In this class, the onUpgrade() method is responsible for upgrading the database when you make changes to the schema. It is called when the database file already exists, but its version is lower than the one spec...

Android • SQLite

Forcing a static constructor to be called

While static constructors are always called before the first usage of a type it's sometimes useful to be able to force them to be called and the RuntimeHelpers class provide an helper for it: using System.Runtime.CompilerServices; // ... RuntimeHelpers.RunClassConstructor(typeof(Foo).TypeHand...

C# Language • Constructors and Finalizers

Installation or Setup

To prepare your web site or web application to use Kendo UI, simply add the style and script files in the <head> section of your page. CDN services are provided for the minified versions of official Kendo UI releases, for both HTTP and HTTPS protocols. JQuery is also required to use Kendo UI...

kendo-ui • Getting started with kendo-ui

Singleton Class

What is a Singleton Class? A singleton class returns the same instance no matter how many times an application requests it. Unlike a regular class, A singleton object provides a global point of access to the resources of its class. When to Use Singleton Classes? Singletons are used in situations ...

Objective-C Language • Classes and Objects

Creating a new program using Mono

First install Mono by going through the install instructions for the platform of your choice as described in their installation section. Mono is available for Mac OS X, Windows and Linux. After installation is done, create a text file, name it HelloWorld.cs and copy the following content into it: ...

C# Language • Getting started with C# Language

Drop Constraint

ALTER TABLE Employees DROP CONSTRAINT DefaultSalary This Drops a constraint called DefaultSalary from the employees table definition. Note:- Ensure that constraints of the column are dropped before dropping a column.

SQL • ALTER TABLE

Add Constraint

ALTER TABLE Employees ADD CONSTRAINT DefaultSalary DEFAULT ((100)) FOR [Salary] This adds a constraint called DefaultSalary which specifies a default of 100 for the Salary column. A constraint can be added at the table level. Types of constraints Primary Key - prevents a duplicate record in...

SQL • ALTER TABLE

Installation or Setup

Executable File Download the .exe from http://dev.sitecore.net/ and double-click to start. This .exe will do everything for you - attach databases, modify host file, and set folder permissions. The only downside is that it leaves an entry in the registry under [HKEY_LOCAL_MACHINE\SOFTWARE\Sitecore...

sitecore • Getting started with sitecore

Construct a string from Array

The String.Join method will help us to construct a string From array/list of characters or string. This method accepts two parameters. The first one is the delimiter or the separator which will help you to separate each element in the array. And the second parameter is the Array itself. String from...

C# Language • Common String Operations

Finalization

A Java object may declare a finalize method. This method is called just before Java releases the memory for the object. It will typically look like this: public class MyClass { //Methods for the class @Override protected void finalize() throws Throwable { // Cleanup co...

Java Language • Java Memory Management

Installation

To start development with Elm, you need to install a set of tools called elm-platform. It includes: elm-make, elm-reactor, elm-repl and elm-package. All of these tools are available through CLI, in other words you can use them from your terminal. Pick one of the following methods to install Elm: ...

Elm Language • Getting started with Elm Language

Using position: absolute

Working in old browsers (IE >= 8) Automatic margins, paired with values of zero for the left and right or top and bottom offsets, will center an absolutely positioned elements within its parent. View Result HTML <div class="parent"> <img class="center" src=&quo...

CSS • Centering

Installation or Setup

Detailed instructions on getting kentico set up or installed.

kentico • Getting started with kentico

Type Comparison

There are two types of comparison: loose comparison with == and strict comparison with ===. Strict comparison ensures both the type and value of both sides of the operator are the same. // Loose comparisons var_dump(1 == 1); // true var_dump(1 == "1"); // true var_dump(1 == true); // t...

PHP • Types

Installation

Download and unzip the GWT SDK. This contains the core libraries, compiler, and development server that you need to write web applications. On Windows, extract the files from the compressed folder gwt-2.7.0.zip. On Mac or Linux, you can unpack the package with a command like: unzip gwt-2.7.0.zip ...

gwt • Getting started with gwt

Creating an enum (Python 2.4 through 3.3)

Enums have been backported from Python 3.4 to Python 2.4 through Python 3.3. You can get this the enum34 backport from PyPI. pip install enum34 Creation of an enum is identical to how it works in Python 3.4+ from enum import Enum class Color(Enum): red = 1 green = 2 blue = 3 ...

Python Language • Enum

Simple cross compilation with go build

From your project directory, run the go build command and specify the operating system and architecture target with the GOOS and GOARCH environment variables: Compiling for Mac (64-bit): GOOS=darwin GOARCH=amd64 go build Compiling for Windows x86 processor: GOOS=windows GOARCH=386 go build ...

Go • Cross Compilation

Guards (if expressions)

Case statements can be combined with if expressions to provide extra logic when pattern matching. def checkSign(x: Int): String = { x match { case a if a < 0 => s"$a is a negative number" case b if b > 0 => s"$b is a positive number" case c ...

Scala Language • Pattern Matching