angular 2: using a service to broadcast an event

Question

I\'m trying to get a button click in one component to put focus on an element on another component. (Frankly, I don\'t understand why this must be so complex, but I have not bee

Answer 1

EventEmitter should only be used in an actual component with an @Output directive. Anything else may not work in future.

For child-parent communication it is better to use a Subject or BehaviorSubject. This is an example from the angular guide.

https://angular.io/guide/component-interaction

@Injectable()
export class MissionService {

  // Observable string sources
  private missionAnnouncedSource = new Subject();
  private missionConfirmedSource = new Subject();

  // Observable string streams
  missionAnnounced$ = this.missionAnnouncedSource.asObservable();
  missionConfirmed$ = this.missionConfirmedSource.asObservable();

  // Service message commands
  announceMission(mission: string) {
    this.missionAnnouncedSource.next(mission);
  }

  confirmMission(astronaut: string) {
    this.missionConfirmedSource.next(astronaut);
  }
}

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Tip:

If you have an event that just signifies something has occurred or completed - and has no actual data associated with it - you can use a Subject(). This makes the signature of next() cleaner and you don't need to provide a dummy value for the sake of it.

Eg.

windowClosed = new Subject();

windowClosed.next() will emit the event