RxJava：使用Builder对象链接Observables

Question

I'm using a Builder pattern to build upon a model object which combines data from different network calls and I'm having a hard time understanding the best way to take the model object from the first network call and combine the data from the second network call into the original model object.

My actual subscription:

myFirstApiRepository.getFirstModelObjectBuilder()
    .flatmap(firstModelObjectBuilder -> mySecondApiRepository.getSomeExtraData(firstModelObjectBuilder))
    .observable.subscribeOn(Schedulers.io())
    .observeOn(AndroidSchedulers.mainThread())
    .subscribe(getMySubscriber());

First network call:

public Observable<FirstModelObject.Builder> getFirstModelObjectBuilder() {
    return myFirstApiResource.getSomeData(...)
            .flatMap(someData -> Observable.just(new FirstModelObject.Builder()
                .setFirstAttribute(someData.getFirstAttribute())
                .setSecondAttribute(someData.getSecondAttribute())));
}

Second network call:

public Observable<FirstModelObject> getSomeExtraData(FirstModelObject.Builder builder) {
    return mySecondApiResource.getSomeData(...)
        .flatMap(aString -> builder.setSomeStringValue(aString)
                                   .build());
}

The problem here is that I have to pass the builder object into the second network call's observable. This makes it very rigid and I'd rather not have my SecondApiRepository rely on and reference a data type which it shouldn't need to reference. It also makes this second method here " .build() " the object, which is not good. So, how can I use the firstModelObject and add data to it from the second network call in a clean way ?

If this is just bad design, please let me know. I'm still trying to learn more about RxJava best practices. :)

Answer 1

If your second request relies on first request's result, then check my answer - https://stackoverflow.com/a/41820372/7045114 .

If not - just use zip operator:

Combines the emissions of multiple Observables together via a specified function and emit single items for each combination based on the results of this function.

Observable.zip(firstRequest, secondRequest, (firstResult, secondResult) -> {
    //process results
})