Hey guys, question about wiring observables throug...

# rx

[Maciek]

Hey guys, question about wiring observables through subjects. My cold finite observable will not come down the downstream unless I'll make subscription with lambda and call manual onNext on subject. Can someone explain why `subscribe`method on observable where you pass whole subject object is not working the same way? Also what is happening with disposable from such subscribe? Is it the same disposable when you make subscription on the subject?

Untitled.kt

[arekolek]

Probably because observable.subscribe(subject) will forward onComplete to the subject as well [1], and to quote David Karnok: “When a BehaviorProcessor is terminated, the cached value is no longer available to late Subscribers.” [2]

[1] https://github.com/JakeWharton/RxRelay

[2] https://stackoverflow.com/questions/47982511/test-that-rxjava-behaviorprocessor-emits-a-value

[arekolek]

either call observable.subscribe(subject::onNext) (like you did in first example), or use a Relay and observable.subscribe(relay) will work as you expect (which is still like the first example, because it implements Consumer)

[Maciek]

Thanks a ton for explanation! As you said Relay is working as expected, but it actually uses the same method as lambda subscribe. It's the one with the Consumer, when you're calling subscribe with normal subject it's using overload with Observer which is few methods down the line after subscribe with Consumer. Difference is still that subscribe from subject won't return disposable and from relay and lambda will.