How to chain calls, depending on result ?

Hello,

In my webapp, I have to chain two async calls : The first call gives me a list of dog ids. The second call gives me a Dog (found by its id).

In my code, i’d like to write something like :

final Observable<RxMessage<String>> observable1 = asyncCallForDogIds(..);

final List<Dog> dogs = new ArrayList<>();
observable1.subscribe(
    // onNext
    (RxMessage<String> message) -> {
        final String id = readId(message);

        final Observable<RxMessage<String>> observable2 = someAsyncCallForOneDogId(id, ..);

        final Dog dog = readFromSomeMessage2(...);
        dogs.add(dog);
    },

    // onError
    (Throwable err) -> error(err, ..),

    // onCompleted
    () -> resume(dogs, ..));

What would be the best way to do that ? Th.

[benjchristensen]

If you want to handle errors for each call you put the onErrorResumeNext or similar handlers on each of the async calls.

asyncCallForDogIds(..)
    .map(this::readId)
    .flatMap(dogId -> {
             return someAsyncCallForOneDogId(id, ..)
                             .onErrorResumeNext(errorHandlingHere)
    })
    .map(this::readFromSomeMessage2)

[hamidp]

You want flatMap so roughly:

asyncCallForDogIds(..)
    .map(this::readId)
    .flatMap(dogId -> someAsyncCallForOneDogId(id, ..))
    .map(this::readFromSomeMessage2)