如何在 Angular 中一次取消订阅一个组件中的所有 observables

Question

In my angular project, I have multiple subscriptions in a few components. So I use properties inside of it to store subscriptions, and in destroy function, I unsubscribe all of them. The problem is that the code becomes larger unnecessary larger. My question is, is there any way to unsubscribe all subscriptions at ones?

Answer 1

I tend to store all my subscriptions in an array..

private subs: Subscription[] = []

ngOnInit() {
  this.subs.push(
     this.obs1.subscribe(),
     this.obs2.subscribe() // etc
  )
}

ngOnDestroy() {
  this.subs.forEach(s => s.unsubscribe())
}

other people prefer other methods. just be creative.

Answer 2

A recommanded way to unsubscribe to an observable is to call

ngOnDestroy () {
 this.obs.next();
 this.obs.complete();
}

To do it for all observable at once, you can declare a subject and use takeUntil from rxjs:

ngUnsubscribe = new Subject();

... code...

ngOnInit() {
  this.myObs.pipe(takeUntil(this.ngUnsubscribe))
  .subscribe(_ => ...);
}

ngOnDestroy() {
  this.ngUnsubscribe.next();
  this.ngUnsubscribe.complete();
}

I do it this way because I noticed that in my project, calling .unsubscribe() wasn't working as expected. Switching from component A to B and then back to A created a second (then third, etc.) subscription and finally fixed by applying advice from this thread ).

Answer 3

There is many ways to do that but we can't avoid the boilerplate, you can use the ways above or use a decorator for that but keep in mind that there are exceptions where you don't have to unsubscribe:

No Need of unsubscribe in these cases

1. In case of HttpClient calls because the observable emit one value (success or error) and complete automatically.

2. In case or ActivatedRoute subscription because the Router will destroy it when the component is destroyed automatically

3. use of Async pipe