RxJava：过滤Observable中的列表（就地）

Question

I want to call an API that retrieves a list of hotels. The response comes back as an Observable<Response> . Within the Response object there is a List<HotelAvailability> , and within the HotelAvailability object, there is HotelInfo object. If HotelInfo is null , I want to remove the HotelAvailability from the list. I have got halfway with Rx, and then had to default back to a plain-old iterator and while loop. Can anyone help me make this entirely RX? (Note: I am coding on Android and for a relatively low SDK, so JDK8 solutions won't work for me).

availabilityApi.getAvailability(hotelName)
            .doOnNext(response -> {
                Iterator<HotelAvailability> hotelAvailabilityIterator = availabilityResponse.hotelAvailabilities().iterator();
                while (hotelAvailabilityIterator.hasNext()) {
                    if (hotelAvailabilityIterator.next().hotelInfo() == null) {
                        hotelAvailabilityIterator.remove();
                    }
                }
            })
            .subscribeOn(Schedulers.io())
            .observeOn(AndroidSchedulers.mainThread());

Answer 1

You can flatMap your list so you get separate stream events so you can filter them out one by one and then you can aggregate them back into a single list.

availabilityApi.getAvailability(hotelName)
        .map(Response::hotelAvailabilities)
        .flatMap(Observable::from)
        .filter(hotelAvailability -> hotelAvailability != null)
        .toList()
        .subscribeOn(Schedulers.io())
        .observeOn(AndroidSchedulers.mainThread());

If you want you can even flatMap the list from one single call:

flatMap(response -> Observable.from(response.hotelAvailabilities()))

Answer 2

Just use the JDK8 API:

availabilityApi.getAvailability(hotelName)
        .doOnNext(availabilityResponse ->
           availabilityResponse.hotelAvailabilities().removeIf(
              availability -> availability.hotelInfo() == null
           )
        )
        .subscribeOn(Schedulers.io())
        .observeOn(AndroidSchedulers.mainThread());

Edit: Doing it completely in RxJava, but maybe not necessarily better:

availabilityApi.getAvailability(hotelName)
        .flatMap(response -> Observable
            .from(availabilityResponse.hotelAvailabilities())
            .filter(availability -> availability.hotelInfo() != null)
            .toList()
            .doOnNext(availabilityResponse::setHotelAvailabilities)
            .map(any -> response)
        )
        .subscribeOn(Schedulers.io())
        .observeOn(AndroidSchedulers.mainThread());