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Angular 2 Dependency Injection

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

The basics Steps of Dependency injection,
1.     A class with @Injectable () to tell Angular2 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, InjectionToken } from '@angular/core';
import { Http, Response } from '@angular/http';
import 'rxjs/add/operator/map';

//BEGIN-REGION - USERSERVICE
@Injectable()
export class UserService {
    constructor(private _http: Http) {
    }

    getAPIUsers(apiUrl) {
        return this._http.get(apiUrl).map((data: Response) => data.json());
    }

    getAppUsers(apiUrl) {
        return this._http.get(apiUrl).map((data: Response) => data);
    }
}
//END BEGIN - USERSERVICE


Angular2 - Related Concepts

When use @Inject()? When Use @Injectable ()? @Injectable() vs. @Inject() ?
How to use Dependency Injection (DI) correctly in Angular 2? Dependency Injection (DI) in Angular 2?

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