EventEmitter or RxJS Subject in angular service

Question

Is EventEmitter an RxJS Observable?
In the angular documentation, it explains how to communicate from child to parent component using EventEmitter. Should we use EventEmitter only in component or it can be used angular service also?
In the angular documentation, it explains how parent and children communicate via a shared service that uses observables RxJS Subject. Can we use EventEmitter instead of RxJS Subject in this MissionService example? Please help converting this example with EventEmitter if we can use EventEmitter at all in a service. I'm new to angular.

https://angular.io/guide/component-interaction#parent-and-children-communicate-via-a-service

I'm confused a bit after reading these related posts:

Kliment Ru Kliment Ru · Accepted Answer · 2018-09-04T15:07:42

EventEmiter extends from RxJs subject and you can use it as Observable.

    export declare class EventEmitter<T> extends Subject<T> {
      __isAsync: boolean;
      constructor(isAsync?: boolean);
      emit(value?: T): void;
      subscribe(generatorOrNext?: any, error?: any, complete?: any): any;
    }

The best practice to sharing data between parent and child components use @Input and @Output

When you need to use service for sharing. You need to use Subject or BehaviorSubject

service example

@Injectable()
export class MyService {
  private data: BehaviorSubject<MyData> = new BehaviorSubject(null);

  getData(): Observable<MyData> {
    return this.data;
  }

  setData(d: MyData): void {
    this.data.next(d);
  }
}

use in component

data: Observable<MyData>;

constructor(private myService: MyService) {}

ngOnInit() {
   this.data = this.myService.getData();
}

use in template

<div>{{data|async}}</div>

EventEmitter or RxJS Subject in angular service

2 Answers