For the Angular router events Observable, why is there no unsubscribe()?

Question

In my ngOnInit method I am subscribing to the Router like this:

this.router.events.subscribe(
  event => {
    if (event instanceof NavigationEnd) this.clearMessages();
  }
);

Normally, for Observables outside of the HttpClient package I call unsubscribe in the ngOnDestroy method but when I tried that here I discovered that this.router.events does not have such a method. Am I mistaken or is there something different about this Observable? Why would unsubscribe not be implemented?

Answer 1

I discovered that this.router.events does not have such a method

You call unsubscribe on subscriptions, not observables. And this.router.events is an observable, not subscription. So the following would work:

const subscription = this.router.events.subscribe(...);   
subscription.unsubscribe();

Answer 2

You are right, some observables need no manual unsubscription from, observables like:

1. Router, HTTP, HTTPClient, because these are single emission observables, although implicitly, and
2. Explicit single emission observables (e.g., finite), like first()

Similar information can be found on this reddit site also. This also means that no need to worry about memory leaks from observables in these classes.