How to unsubscribe from not initialized subscription in Angular

Question

I got following error:

ERROR Error: Uncaught (in promise): TypeError: Cannot read property 'unsubscribe' of undefined

I have subscription not on ngOnInit and that's why I got this error, because my property that holding the subscription is not yet initialized, but what's the 'proper way' in such a situation.

Here is my code:

Answer 1

You can use takeUntil() operator of rxjs with pipe() before subscribing to the observable.

 unsubscribeSignal: Subject<void> = new Subject();

 ngOnInit() {
    this.subscription = this.observableToSubscribe
    .pipe(
       takeUntil(this.unsubscribeSignal.asObservable()),
    )
    .subscribe(result => {

      //Do some fancy stuff here

      console.log(result );
    });
  }

  ngOnDestroy(){
    this.unsubscribeSignal.next();
  }

Another benefit of using takeUntil instead of manually unsubscribing the subscription is that you can use a single Subject to unsubscribe multiple subscriptions at once.

You can check out my another answer here