Figuring out who is listening to your output(s) sounds complicated but it’s pretty straight forward. Every Observable has a “observers” property which is an array of Subscriber’s.
Observable.observers
Observable.observers is just an array of Subjects:
@Component({
selector: 'app-components-sharing-a',
templateUrl: './components-sharing-a.component.html',
styleUrls: [ './components-sharing-a.component.scss' ]
})
export class ComponentsSharingAComponent implements OnInit {
@Output() public outputOne = new EventEmitter();
public ngOnInit(): void {
console.log('this.outputOne.observers.length: ' + this.outputOne.observers.length);
// output: this.outputOne.observers.length: 3
}
public isAnybodyListeningToMe(): boolean {
return !!this.outputOne.observers.length;
}
}We can send a message directly to a specific observer with stream$.observers[0].next(event).
Component @Output()
Take the following component and see how you’re able to get the length of the observers array:
@Component({
selector: 'app-components-sharing-a',
templateUrl: './components-sharing-a.component.html',
styleUrls: [ './components-sharing-a.component.scss' ]
})
export class ComponentsSharingAComponent implements OnInit {
@Output() public outputOne = new EventEmitter();
public ngOnInit(): void {
console.log('this.outputOne.observers.length: ' + this.outputOne.observers.length);
// outputs: this.outputOne.observers.length: 1
}
}