takeUntil does not work with BehaviorSubject

Question

I have the following BehaviorSubject defined:

  private posts = new BehaviorSubject<any[]>([]);

and on init:

ngOnInit() {
  this.posts
    .takeUntil(!this._postsLoaded)
    .subscribe(x => {
       this._postsLoaded = true;
        // do something
    });
}

But it gets the following error, although it should work:

Property 'takeUntil' does not exist on type 'BehaviorSubject<any>'

Then you must use pipes. See this [takeUntil](https://www.learnrxjs.io/operators/filtering/takeuntil.html) example — Silvermind, Oct 21 '18 at 23:30

score 3 · Accepted Answer · answered Oct 21 '18 at 23:52

3

If you want to use like a chain syntax , You have to install rxjs compat also for backward comptability.

npm install --save rxjs-compat

But I would suggest use pipes

import { takeUntil } from 'rxjs/operators';
ngOnInit() {
  this.posts.pipe(
    takeUntil(!this._postsLoaded)
    ).subscribe(x => {
       this._postsLoaded = true;
        // do something
    };
}

Sample Stackblitz

https://stackblitz.com/edit/rxjs-takeuntilexample?file=index.ts

answered Oct 21 '18 at 23:52

Jameel Moideen

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this works, with one exception, thought - should only use takeUntil from rxjs, not from compact, as it throws an error – Yuvals Oct 23 '18 at 09:21
@Yuvals if you are using pipe , not need to install compat package – Jameel Moideen Oct 23 '18 at 19:49

score 0 · Answer 2 · answered Oct 22 '18 at 08:59

There're two things:

In RxJS 6 you should use pipable operators. If you have to use the old "patch" style of operators you'll need to include rxjs-compat package
The takeUntil() operator takes as a parameter another Observable so what you have now will throw an error anyway.

Maybe you should use takeWhile() instead. See this answer (RxJS takeWhile but include the last value) if you want to also include the last value that completed the chain.

takeUntil does not work with BehaviorSubject

2 Answers2