What Is The Difference between ngOnInit And Constructor

Confused between Constructor and ngOnInit in Angular? Don’t know where to use these methods? We got everything covered in this tutorial.

ngOnInit is a method provided by Angular while the constructor is not an insider of the framework. If you’re already familiar with object-oriented programming, you must have known that Constructor is a special method used in instances when a class is created. Even though the constructor name is the same as the class name in languages such as Java and a few other languages.

In ECMAScript 6, (ECMAScript is a standard for JavaScript) the classes were introduced in which the constructor method is used to initialize the properties of the class. You should note that in Javascript, the constructor method name is constructor only, it is not given a class name.

class Sport {

constructor(name, type) {

this.name = name;

this.type = type;

}

}

sportObj = new Sport(‘cricket’, ‘outdoor’);

When creating an instance the constructor is invoked. Whether it is implemented or not in the class since the typescript class is compiled to a function.

// Compiled version of above code

function Sport(name, type) {

this.name = name;

this.type = type;

}

In the case of the absence of a constructor, an empty function is created in transpired JavaScript.

class Sport {

}

function Sport() {

}

Let’s move to the important part. The usage of constructors in Angular is dependency injection. The dependencies of the component can be injected in the constructor which makes it available in the component class.

import { Router } from ‘@angular/router’;

export class ProductComponent {

constructor(private router: Router) {

}

}

Then the router can be accessed as this.router

A constructor is a good place to inject dependencies that are available outside the component. Setting up the dependencies in the constructor makes those available for initialization work in the class. Constructor can be generally used to initialize properties as well.

#angular #programming #javascript #ecmascript #ngoninit

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#javascript #functions #constructor #constructor functions #javascript constructor functions

What Is The Difference between ngOnInit And Constructor

Confused between Constructor and ngOnInit in Angular? Don’t know where to use these methods? We got everything covered in this tutorial.

ngOnInit is a method provided by Angular while the constructor is not an insider of the framework. If you’re already familiar with object-oriented programming, you must have known that Constructor is a special method used in instances when a class is created. Even though the constructor name is the same as the class name in languages such as Java and a few other languages.

In ECMAScript 6, (ECMAScript is a standard for JavaScript) the classes were introduced in which the constructor method is used to initialize the properties of the class. You should note that in Javascript, the constructor method name is constructor only, it is not given a class name.

class Sport {

constructor(name, type) {

this.name = name;

this.type = type;

}

}

sportObj = new Sport(‘cricket’, ‘outdoor’);

When creating an instance the constructor is invoked. Whether it is implemented or not in the class since the typescript class is compiled to a function.

// Compiled version of above code

function Sport(name, type) {

this.name = name;

this.type = type;

}

In the case of the absence of a constructor, an empty function is created in transpired JavaScript.

class Sport {

}

function Sport() {

}

Let’s move to the important part. The usage of constructors in Angular is dependency injection. The dependencies of the component can be injected in the constructor which makes it available in the component class.

import { Router } from ‘@angular/router’;

export class ProductComponent {

constructor(private router: Router) {

}

}

Then the router can be accessed as this.router

A constructor is a good place to inject dependencies that are available outside the component. Setting up the dependencies in the constructor makes those available for initialization work in the class. Constructor can be generally used to initialize properties as well.

#angular #programming #javascript #ecmascript #ngoninit

Private Constructor in Java: Use Cases Explained with Example

Introduction

A private constructor in Java is used in restricting object creation. It is a special instance constructor used in static member-only classes. If a constructor is declared as private, then its objects are only accessible from within the declared class. You cannot access its objects from outside the constructor class.

Private Constructor Use-Cases

Private constructors in Java are accessed only from within the class. You cannot access a private constructor from any other class. If the object is yet not initialised, then you can write a public function to call the private instructor. If the object is already initialised, then you can only return the instance of that object. A private constructor in Java has the following use-cases:

• You can use it with static members-only classes.
• You can use it with static utility or constant classes.
• You can use it to serve singleton classes.
• You can use it to assign a name, for instance, creation by utilising factory methods.
• You can use it to prevent subclassing.

Singleton Class

The private constructor in Java is used to create a singleton class. A singleton class is a class in Java that limits the number of objects of the declared class to one. A private constructor in Java ensures that only one object is created at a time. It restricts the class instances within the declared class so that no class instance can be created outside the declared class. You can use the singleton class in networking and database connectivity concepts.

#full stack development #java #private constructor #private constructor java #private constructor in java: use cases explained with example #use cases explained with example

Move Constructors in C++ with Examples

Prerequisites: l-value and r-value references in C++, Copy Constructor in C++.

What is a Move Constructor?

The copy constructors in C++ work with the l-value references and copy semantics(copy semantics means coping the actual data of the object to another object rather than making another object to point the already existing object in the heap). While move constructors work on the r-value references and move semantics(move semantics involves pointing to the already existing object in the memory).

On declaring the new object and assigning it with the r-value, firstly a temporary object is created, and then that temporary object is used to assign the values to the object. Due to this the copy constructor is called several times and increases the overhead and decreases the computational power of the code. To avoid this overhead and make the code more efficient we use move constructors.

Why Move Constructors are used?

Move constructor moves the resources in the heap, i.e., unlike copy constructors which copy the data of the existing object and assigning it to the new object move constructor just makes the pointer of the declared object to point to the data of temporary object and nulls out the pointer of the temporary objects. Thus, move constructor prevents unnecessarily copying data in the memory.

Work of move constructor looks a bit like default member-wise copy constructor but in this case, it nulls out the pointer of the temporary object preventing more than one object to point to same memory location.

#constructors #cpp-constructor #programming-c #cplusplus #c++

Constructor Overloading In C++ Tutorial With Example

Constructor Overloading in C++ is today’s topic. Before understanding constructor overloading, we first need to understand what are constructors.  Constructors are unique methods which are invoked automatically when we create an object of the class. The primary purpose of the constructors is to initialize data members of the new  object.

Constructor Overloading In C++

In C++, We can have more than one  constructor in the class with the same name, as long as each has a different list of arguments. This concept is known as Constructor Overloading and is quite similar to  function overloading.

There are three types of constructors:

1. Default constructors – A constructor with no arguments is known as default constructors.
2. Parameterized constructors – A constructor which has parameters are known as parameterized constructors.
3. Copy Constructor – A copy constructor is the member function which initializes an object using another object of the same class.

#c++ #constructor overloading #constructors