RxJava2：仅当所有 observable 都发出错误时才发出错误

Question

I have multiple observables doing network calls and I need to emit error from combiner observable only when all observables emitted error. If at least one observable completes then the result should be passed.

My current stream functions like this:

Observable.fromIterable(list)
.flatMap{networkObservable}
.reduce{combine result of all network observables to same list}

I could just do:

Observable.fromIterable(list)
.flatMap{networkObservable.onErrorReturnItem(errorItem)}
.reduce{check if all items are error items and return error item otherwise combine result of 
all network observables to same list}

But I wanted to know if there's a better way to handle this case.

Answer 1

If I understand correctly, if there is at least one item from any of the networkObservable s, errors should be ignored, right? In this case, you could detect the onNext s emitted, then in the error handler, suppress the error:

Observable.using(
    () -> new AtomicBoolean(),
    hasItem -> Observable.fromIterable(list)
                         .flatMap(v -> networkObservable, true) // delay errors
                         .doOnNext(v -> {
                              if (!hasItem.get()) {
                                   hasItem.set(true);
                              }
                         })
                         .onErrorResumeNext(error -> {
                              if (hasItem.get()) {
                                  return Observable.empty();
                              }
                              return Observable.error(error);
                         }),
    () -> { } // no need to clean up the AtomicBoolean
)