CODEWITHSUNDEEP
rxjs
burnt1ce
burnt1ce

Reputation: 14917

Why can't I pipe a BehaviourSubject?

I'm not sure why subscribe works with BehaviourSubject but not pipe.

For example, the code below prints out?

subscribe: 123
subscribe: 456

Why doesn't it also print

pipe: 123
pipe: 456

Code:

import {tap } from 'rxjs/operators';
import { BehaviorSubject } from 'rxjs';

const subject = new BehaviorSubject(123);
subject.subscribe(p => console.log("subscribe: " + p));
subject.pipe(
  tap(p => {console.log("pipe:" + p);})
)
subject.next(456);

Upvotes: 1

Views: 2678

Answers (1)

jamilsiam
jamilsiam

Reputation: 71

subject.pipe(
  tap(p => {console.log("pipe:" + p);})
)

You are only tapping into the observable here. You will need to subscribe separately in this subject for the tapping to work. The following code will give you the desired console log:

subject.pipe(
  tap(p => {console.log("pipe:" + p);})
).subscribe();

If you must subscribe only once, then you could try the following code:

const abc$ = new BehaviorSubject(123).asObservable().pipe(
  tap((val) => console.log('pipe: ', val))
);
abc$.subscribe((val) => console.log('subscribe: ', val));

Upvotes: 2

Related Questions