Tutorial by Examples: construct

Default Constructor

When a type is defined without a constructor: public class Animal { } then the compiler generates a default constructor equivalent to the following: public class Animal { public Animal() {} } The definition of any constructor for the type will suppress the default constructor genera...

C# Language • Constructors and Finalizers

Calling a constructor from another constructor

public class Animal { public string Name { get; set; } public Animal() : this("Dog") { } public Animal(string name) { Name = name; } } var dog = new Animal(); // dog.Name will be set to "Dog" by default. var cat = new Ani...

C# Language • Constructors and Finalizers

Static constructor

A static constructor is called the first time any member of a type is initialized, a static class member is called or a static method. The static constructor is thread safe. A static constructor is commonly used to: Initialize static state, that is state which is shared across different instan...

C# Language • Constructors and Finalizers

Calling the base class constructor

A constructor of a base class is called before a constructor of a derived class is executed. For example, if Mammal extends Animal, then the code contained in the constructor of Animal is called first when creating an instance of a Mammal. If a derived class doesn't explicitly specify which constru...

C# Language • Constructors and Finalizers

Singleton constructor pattern

public class SingletonClass { public static SingletonClass Instance { get; } = new SingletonClass(); private SingletonClass() { // Put custom constructor code here } } Because the constructor is private, no new instances of SingletonClass can be made by consum...

C# Language • Constructors and Finalizers

Initializing Property in Constructor

class Example { public string Foobar { get; set; } public List<string> Names { get; set; } public Example() { Foobar = "xyz"; Names = new List<string>(){"carrot","fox","ball"}; } }

C# Language • Initializing Properties

Enums with constructors

An enum cannot have a public constructor; however, private constructors are acceptable (constructors for enums are package-private by default): public enum Coin { PENNY(1), NICKEL(5), DIME(10), QUARTER(25); // usual names for US coins // note that the above parentheses and the constructor...

Java Language • Enums

Class Constructor

The fundamental part of most classes is its constructor, which sets up each instance's initial state and handles any parameters that were passed when calling new. It's defined in a class block as though you're defining a method named constructor, though it's actually handled as a special case. cla...

JavaScript • Classes

The dict() constructor

The dict() constructor can be used to create dictionaries from keyword arguments, or from a single iterable of key-value pairs, or from a single dictionary and keyword arguments. dict(a=1, b=2, c=3) # {'a': 1, 'b': 2, 'c': 3} dict([('d', 4), ('e', 5), ('f', 6)]) # {'d': 4, 'e': ...

Python Language • Dictionary

Creating an Array with the literal constructor [ ]

Arrays can be created by enclosing a list of elements in square brackets ([ and ]). Array elements in this notation are separated with commas: array = [1, 2, 3, 4] Arrays can contain any kind of objects in any combination with no restrictions on type: array = [1, 'b', nil, [3, 4]]

Ruby Language • Arrays

Constructor

A class can have only one constructor, that is a method called initialize. The method is automatically invoked when a new instance of the class is created. class Customer def initialize(name) @name = name.capitalize end end sarah = Customer.new('sarah') sarah.name #=> 'Sarah' ...

Ruby Language • Classes

Constructors In A Subclass

When you make a subclass of a base class, you can construct the base class by using : base after the subclass constructor's parameters. class Instrument { string type; bool clean; public Instrument (string type, bool clean) { this.type = type; this.clean = c...

C# Language • Inheritance

Constructing collections from existing data

Standard Collections Java Collections framework A simple way to construct a List from individual data values is to use java.utils.Arrays method Arrays.asList: List<String> data = Arrays.asList("ab", "bc", "cd", "ab", "bc", "cd"); ...

Java Language • Collections

Constructor Injection

Constructor injection is the safest way of injecting dependencies that a whole class depends upon. Such dependencies are often referred to as invariants, since an instance of the class cannot be created without supplying them. By requiring the dependency to be injected at construction, it is guara...

unit-testing • Dependency Injection

Showcasing all common Angular constructs

The following example shows common AngularJS constructs in one file: <!DOCTYPE html> <html ng-app="myDemoApp"> <head> <style>.started { background: gold; }</style> <script src="https://code.angularjs.org/1.5.8/angular.min.js">&lt...

AngularJS • Getting started with AngularJS

Default Constructor

The "default" for constructors is that they do not have any arguments. In case you do not specify any constructor, the compiler will generate a default constructor for you. This means the following two snippets are semantically equivalent: public class TestClass { private String tes...

Java Language • Constructors

Constructor with Arguments

Constructors can be created with any kinds of arguments. public class TestClass { private String testData; public TestClass(String testData) { this.testData = testData; } } Called like this: TestClass testClass = new TestClass("Test Data"); A class can ...

Java Language • Constructors

Parsing and constructing an object from standard input

readFloat :: IO Float readFloat = fmap read getLine main :: IO () main = do putStr "Type the first number: " first <- readFloat putStr "Type the second number: " second <- readFloat putStrLn $ show first ++ " + " ++ show se...

Haskell Language • IO

Usage with non-default constructors

You can combine object initializers with constructors to initialize types if necessary. Take for example a class defined as such: public class Book { public string Title { get; set; } public string Author { get; set; } public Book(int id) { //do things } // the...

C# Language • Object initializers

Inheritance. Constructors' calls sequence

Consider we have a class Animal which has a child class Dog class Animal { public Animal() { Console.WriteLine("In Animal's constructor"); } } class Dog : Animal { public Dog() { Console.WriteLine("In Dog's constructor"); } ...

C# Language • Inheritance