angular - 如何检查是否有人订阅了 Angular 中的 EventEmitter？

Question

有一个事件发射器:

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

如何检查是否有人订阅了 Angular 中的 EventEmitter？

Answer 1

Angular EventEmitter 是 RXJS Subject :

class EventEmitter<T> extends Subject

因此您可以调用 .observers属性(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.
 *
 * @class Subject<T>
 */
export class Subject<T> extends Observable<T> implements SubscriptionLike {

  [rxSubscriberSymbol]() {
    return new SubjectSubscriber(this);
  }

  observers: Observer<T>[] = [];

备注 EventEmitter而不是使用 EventEmitter , 考虑 BehaviorSubject或 ReplaySubject .
见: Delegation: EventEmitter or Observable in Angular