When we use providers in Angular 2?

Question

Some of examples From angular 2 documents they used for http also

import { HTTP_PROVIDERS }    from '@angular/http';
import { HeroService }       from './hero.service';
@Component({
  selector: 'my-toh',
  template: `
  <hero-list></hero-list>
  `,
  directives: [HeroListComponent],
  providers:  [
    HTTP_PROVIDERS,
    HeroService,
  ]
})

They are entry point to make dependencies available for component.. — Pankaj Parkar, May 18 '16 at 11:22

score 4 · Answer 1 · edited May 23 '17 at 12:32

4

Providers need to be used to provide a way to create instances to inject. For example, if you want to inject an Http instance you need to have define the HTTP_PROVIDERS (that contains the provider for the Http type.

An important thing to understand is that Angular2 supports hierarchical injectors for dependency injector. I mean an injector is associated with each component and the current injector is a child injector of the injector of the parent component.

This question could interest you:

What's the best way to inject one service into another in angular 2 (Beta)?

edited May 23 '17 at 12:32

Community

1
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answered May 18 '16 at 11:28

Thierry Templier

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Thanks @Thierry !!! Can You please explain me (source: string, subString: string): boolean; – Sarvesh Yadav May 18 '16 at 11:57
You're welcome! It's the TypeScript syntax for methods / functions. A method with two parameters (source of type string and subString of type string) that returns a boolean value. – Thierry Templier May 18 '16 at 12:11

When we use providers in Angular 2?

1 Answers1