[Angular services & dependency injection] #angular

dependency.md

Links

https://angular.io/guide/dependency-injection#injectable-ngmodule-or-component

Create service

  $ng generate service heroes/hero


  import { Injectable } from '@angular/core';

  @Injectable({
    // we declare that this service should be created
    // by the root application injector.
    providedIn: 'root',
  })

  @Injectable({
    // we declare that this service should be created
    // by any injector that includes HeroModule.
    providedIn: HeroModule,
  })

Component level and child

  @Component({
  selector: 'app-unsorted-heroes',
  template: `<div *ngFor="let hero of heroes">{{hero.name}}</div>`,
  providers: [HeroService]
})
export class HeroesBaseComponent implements OnInit {
  constructor(private heroService: HeroService) { }
}

Sets or overrides the provider for MyService to the MyMockService class.

{ provide: MyService, useClass: MyMockService } 	

Sets or overrides the provider for MyService to the myFactory factory function.

{ provide: MyService, useFactory: myFactory } 	

Sets or overrides the provider for MyValue to the value 41.

{ provide: MyValue, useValue: 41 }