[0.16.x] Unable to subscribe several times to a GroupedObservable produced by groupBy

[amazari]

It seems impossible to subscribe several Observers to the same GroupedObservable, as demonstrated in the following snipet:

Observable.range(1, 100).groupBy(new Func1<Integer, String>() {
  public String call(final Integer integer) {
    return integer > 50 ? "big" : "small";
  }
}).subscribe(new Action1<GroupedObservable<String, Integer>>() {
  public void call(final GroupedObservable<String, Integer> objectIntegerGroupedObservable) {

    // First subscription, if left alone works flawlessly
    objectIntegerGroupedObservable.subscribe(new Action1<Integer>() {
      public void call(final Integer integer) {
        System.out.println("first subscriber: "+integer);
      }
    });

    // Second subscription, fails and break the first one too
    objectIntegerGroupedObservable.subscribe(new Observer<Integer>() {
      public void onCompleted() {}
      public void onError(final Throwable e) { System.out.println(e); }
      public void onNext(final Integer args) { }
    });
  }
});

When providing an onError implementation to the second subscription, we can see a "java.lang.IllegalStateException: Can not set subscription more than once."
This seems unique to GroupedObservable, as other Observables (direct, or resulting of transformation) can be subscribed to multiples times.
Is this a bug or a desired behavior ? In the latter case, I am interested in the rationals and alternatives.
I am currently using publish and/or replay on the resulting GroupedObservables before any further processing but it clutters the code with implemetation detailsm imho.

Thanks for your time and energy !

[akarnokd]

Hi. Yes, it is the common single-subscription bug. If you can, upgrade to the most recent version (0.17).

A few of the older operators have this issue. For a workaround, I suggest using groupByUntil() with a Observable.never() duration selector. However, this operator has a synchronization bug, therefore, don't use it with any other kind of duration selector.

[amazari]

Thanks for your answer. I am gonna look into the alternatives you suggest.