"Filter" with combineLatest

[Dave Jensen]

I have a situation where I want to use combineLatest (actually withLatestFrom) and filter some of the combinations.

Let's say I have Observable<Temperature> and Observable<Boolean>. I would like to use something like combineLatest to only emit Temperature when the Boolean is true. I'd rather not have to use an intermediary object like Pair<Temperature, Boolean>.

i.e., is there a better way than this:

Observable<Temperature> observableTemperature = getTemp();

Observable<Boolean> observableBoolean = getTempPrefs();

Observable

  .combineLatest(observableTemperature, observableBoolean, (Func2) (thing, aBoolean) -> {

      return new Pair<Thing, Boolean>(thing, aBoolean);

  })

  .filter((Func1) (thingBooleanPair) -> {

      return thingBooleanPair.second;

  })

  .map((Func1) (thingBooleanPair) -> {

      return thingBooleanPair.first;

  });

[Dave Jensen]

Correction Thing should be Temperature.

I'm also not too happy with this solution either. I just don't like having to use the intermediate Pair object to do this task.

Observable

  .combineLatest(observableTemperature, observableBoolean, (Func2) (temperature, aBoolean) -> {

      return new Pair<Temperature, Boolean>(temperature, aBoolean);

  })

  .flatMap((Func1) (temperatureBooleanPair) -> {

    if (temperatureBooleanPair.second)

      return Observable.just(temperatureBooleanPair.first);

    else

      return Observable.just(temperatureBooleanPair.first).skip(1);

  });

[Dávid Karnok]

Unfortunately, one can't filter and map with a single function (without out parameters like in C#) so all solution would wrap and allocate. However, the withLatestFrom is so simple you could just create a version of it with filter+map and lift it into your stream: https://gist.github.com/akarnokd/3b97ce85079f431addc2