Angular 2 @Inject vs. @Injectable [Why @Inject and @Injectable?]

@Inject() - Angular 2

Angular 2 @Inject() is a special technique for letting Angular know that a parameter must be injected.

Stayed Informed - Why @Injectable() in Angular 2?

Example as,

import { Inject } from '@angular/core';
import { Http } from '@angular/http';

class UserService {
  users:Array<any>;

  constructor(@Inject(Http) http:Http) {
    //TODO AS PER YOU.
  }
}

@Injectable() - Angular 2

@Injectable() marks a class as available to an injector for instantiation. An injector reports an error when trying to instantiate a class that is not marked as @Injectable().

How to use Dependency Injection (DI) correctly in Angular 2?

The basics Steps of Dependency injection,

1. A class with @Injectable() to tell angular 2 that it’s to be injected “UserService”.

2. A class with a constructor that accepts a type to be injected.

Example, UserService marked as @Injectable as,

import {Injectable, bind} from 'angular2/core';
import {Http} from 'angular2/http';

@Injectable() /* This is #Step 1 */
export class UserService {
  constructor(http: Http/* This is #Step 2 */ ) {
    this.http = Http;
  }
}

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