Rxjava: PublishSubject does not emit values when single() is used

[dimsuz]

Better to illustrate this with code:

// use case: some api returns subject as an observable, subscription is made
// in other part of the app
// but here I put them together for illustration, to be easily reproducable

PublishSubject<Integer> subject = PublishSubject.create();
subject.single().subscribe(new Observer<Integer>() {
                       @Override
                       public void onCompleted() {

                       }

                       @Override
                       public void onError(Throwable throwable) {

                       }

                       @Override
                       public void onNext(Integer integer) {
                           System.out.println("on next" + integer);
                       }
                   });

 subject.onNext(2);

With the above snippet, nothing will be printed. Note that there is no threading involved, happens on the same thread.
If I remove single() call above, code starts working correctly,prints line.
Or If i add subject.onCompleted() right after subject.onNext(2) call - same, things start to work, even with single() in place, but this is an observation, not a proper fix I guess.

[dimsuz]

I am using rxjava 0.20.6

[zsxwing]

That's how single works. single won't emit the item until it confirms this Observable has exactly one item, or it will emit onError.

[akarnokd]

You may use take(1) instead to get the first value as soon as it is available and not wait for any other value.

[dimsuz]

Oh, I didn't know this, so it is not a bug... I just expected that single
would throw on attempt to emit a second item, didn't think that it does
those checks.
11 нояб. 2014 г. 14:52 пользователь "Shixiong Zhu" [email protected]
написал:

That's how single works. single won't emit the item until it confirms
this Observable has exactly one item, or it will emit onError.

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