RxJS Subscriber unsubscribe vs. complete

Question

I was reading through the RxJS docs and want to make sure I\'m understanding the difference between Subscriber.unsubscribe() and Subscriber.complete()

Answer 1

Subscribers don't call complete(). You can call complete() on a Subject or more typically it's called for you "indirectly" using operators such as take(), takeWhile(), ...

For example:

const s = new Subject();
const subscriber1 = s.subscribe(...);
const subscriber2 = s.subscribe(...);
s.complete(); // both subscribers will receive the complete notification

// or with `take(1)` operator it'll call `complete()` for you
const subscriber1 = s.take(1).subscribe(...);
const subscriber2 = s.take(1).subscribe(...);
s.next(42); // both subscribers will receive the complete notification

Note that calling complete() on a Subject changes its inner state and there's no way to make it non-complete again while just unsubscribing a subscriber has no effect on the Subject.

A little similar question: Observable Finally on Subscribe

Answer 2

From my experience with the API, the idea is that: you don't call the Observable, the Observable calls you. You are able to trigger things if you create a Subject and next/complete the Subject though.

That's why you will see some examples that have a "private" Subject as a class member, but the publicly exposed item is an Observable. The expectation is that you will subscribe to the Observable and the top level class will dispatch values through the Subject with next() and error(). The only way to complete the Observable/Subject is to complete() the Subject.

Additionally, Subscriber does not have an unsubscribe() method, a Subscription does.