foo.subscribe with bar not always working

Question

Imagine we have foo$ and bar$ and both of them are BehaviorSubjects.

I have a bug in angular that sometimes in some cases foo$.subscribe(bar$) works fine, in most casses actually.

But sometimes I have a bug and its not working until I do foo$.subscribe(foo => bar$.next(foo)), and even worse it seems like it works the first time and then the second time it dose not work.

I experienced this bug sometimes but still rearly. Not sure even how to make a proper minimal reproduction. I would like to understand what makes this causing the bug? And is the angular team aware of it? I didn't see anywhere so far anyone posting about it.

Have checked if it solves anything by removing zonejs and it dose not.

I tougth maybe its a very very general issue which I'm just not aware of. I'll try to make a repo. — Muhamed Karajic
– Muhamed Karajic, Commented Mar 20 at 12:38
@MatthieuRiegler here is a minimal repo stackblitz.com/edit/… You can see in the console hello... is logged once when doing it the first way, and doing it the second way its logged as many times as you click the button. — Muhamed Karajic
– Muhamed Karajic, Commented Mar 20 at 13:10
After looking it however myself I see the issue is actully in the this.onDestroy$.next(); call. but still strange that it works fine when changing the line of code. — Muhamed Karajic
– Muhamed Karajic, Commented Mar 20 at 13:12

Matthieu Riegler · Accepted Answer · 2025-03-20 13:23:57Z

2

When you do this.foo$.pipe(takeUntil(this.onDestroy$)).subscribe(this.bar$);

The bar$ subject actually completes when the foo$ subscription completes (because if the takeUntil).

This is become subscribe(this.bar$) implies

foo$.subscribe({
  next: value => bar$.next(value),
  error: error => bar$.error(error),
  complete: () => bar$.complete(),
})

answered Mar 20 at 13:23

Matthieu Riegler

59.9k27 gold badges158 silver badges208 bronze badges

Sign up to request clarification or add additional context in comments.

2 Comments

Muhamed Karajic Mar 20 at 13:27

So to clarify, the issue is that foo$.subscribe(foo => bar$.next(foo)) and foo$.subscribe(bar$) are in fact different. I tougth its just the shortform. So it makes sense that it will complete bar if foo completes. I think that answers all my questions. Thank you Matthieu.

Muhamed Karajic Mar 20 at 13:30

One more question, if foo$ throws an error and I used foo$.subscribe(foo => bar$.next(foo)) then if I catch the error when piping bar$ I won't see the error? Is there any shorthand to forward the next as well as the error but not complete it?

Collectives™ on Stack Overflow

foo.subscribe with bar not always working

1 Answer 1

2 Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

2 Comments

Your Answer

Sign up or log in

Post as a guest

Related