How to check if anyone is subscribed to EventEmitter in Angular?

Question

There is a EventEmitter:

@Output() edit: EventEmitter<any> = new EventEmitter();

You can't. That's not how observables work. Please share what the original problem was that gave you this idea as the solution. — Reactgular, Aug 13 '19 at 13:28

Christopher Peisert · Accepted Answer · 2022-11-25T21:39:59.630

4

Angular EventEmitter is an RXJS Subject:

class EventEmitter<T> extends Subject

Therefore you can use the currentObservers property.

RXJS Source Code

/**
 * A Subject is a special type of Observable that allows values to be
 * multicasted to many Observers. Subjects are like EventEmitters.
 *
 * Every Subject is an Observable and an Observer. You can subscribe to a
 * Subject, and you can call next to feed values as well as error and complete.
 */
export class Subject<T> extends Observable<T> implements SubscriptionLike {
  closed = false;

  private currentObservers: Observer<T>[] | null = null;

Notes

RxJs API changed property name from observers to currentObservers
Rather than using an EventEmitter, consider BehaviorSubject or ReplaySubject.

See: Delegation: EventEmitter or Observable in Angular

edited Nov 25 '22 at 21:39

answered Aug 13 '19 at 13:31

Christopher Peisert

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I was using this technique but I have this "depreacation" warning: "Internal implementation detail, do not use directly. Will be made internal in v8." Anyone knows how to replace this ? – Tonio Feb 21 '22 at 11:04
1

@Tonio: Use `.observed`. – Victor Zakharov Nov 22 '22 at 12:47
1

@Tonio Answer updated to reflect new RxJS `Subject` API. The property is now called `currentObservers` – Christopher Peisert Nov 22 '22 at 13:47

How to check if anyone is subscribed to EventEmitter in Angular?

1 Answers1

RXJS Source Code

Notes