Observables have the subscribe method we call with a callback function to get the values emitted into the Observable aloso we can unsubscribe from Observables. In Angular, we use it in Components/Directives especially in the router module, NgRx, HTTP module.
Before closing a component , we must unsubscribe from all the existing observables . Of cores the observable have a unsubscribe method that we call in the ngOnDestroy() witch is a part of the lifecycle of the component to cancel the executions
Example :
@Component({...})
export class AppComponent implements OnInit, OnDestroy {
subscription: Subscription
ngOnInit () {
var observable = Rx.Observable.interval(1000);
this.subscription = observable.subscribe(x => console.log(x));
}
ngOnDestroy() {
this.subscription.unsubscribe()
}
}