How to convert rxJava2's Observable to Completable?

Question

I have Observable stream, and I want to convert it to Completable, how I could do that?

Griffie

Answer 1

The fluent way is to use Observable.ignoreElements().

Observable.just(1, 2, 3)
.ignoreElements()

Convert it back via toObservable if needed.

Officialdom

More conversions can be found here. speakerdeck.com/jakewharton/… – Beecher

Note that RxJava 1 does not automatically convert this to a Completable. This functionality is achieved in v1 using Observable.toCompletable(). v1's ignoreElements() just creates another Observable without elements. – Victual

flatMapCompletable can also help in this situation depending on your needs – Olnee

Answer 2

You can do something like below.

Observable<Integer> observable = Observable.just(1, 2, 3);
Completable completable = Completable.fromObservable(observable);

Like on an Observable, you will have to subscribe to the completable to start the asynchronous process that Observable wraps.

More details can be found here in the Java doc for the method.

Beecher

Answer 3

As I understand all this solutions will work only if Observable call onComplete, which is not enough if you want your result Completable to trigger after first onNext or onError, so for this case I'd recommend this:

Observable<Integer> observable = Observable.just(1, 2, 3);
Completable completable = observable.firstOrError().ignoreElement()

Weismannism

Answer 4

Use Completable.merge(YourObservable()...

Ozzy

Answer 5

You could use Completable.fromObservable(xx). That is worked fine on my project.

Coinstantaneous