Currently, I am in the process of implementing dialogs using Angular 9 and I encountered a scenario where I need to unsubscribe from a Subject after its first emission.
Initially, my approach was to use the take(1) or first() operators to transform the Subject and automatically handle unsubscription after the initial emission. This is because when an observable completes, the unsubscription logic is triggered. Here's an example:
const subject = new Subject();
subject.pipe(take(1)).subscribe(console.log);
subject.next("hello");
However, I also stumbled upon a "hack" that seems to work. Can someone verify this for me?
const subject = new Subject();
const subscription = subject.subscribe((value) => {
console.log(value);
subscription.unsubscribe(); // <----- this line seems magical
}
subject.next("hello");
This unconventional method caught my attention, and I believe it could be useful in certain scenarios. What puzzles me is that the observer is calling the subscription on the same line where it's defined. Is this considered good practice? Are there alternative approaches to achieve the same result?
Thank you!