Use RxJava and Retrofit to iterate through list and augment results based on subqueries

Question

I\'m using retrofit and I feel like rxjava (with retrolambda) would be a good fit for the following flow:

1. get list of widgets (http)

2. for each widget

Answer 1

You could insert doOnNext at certain points of the stream to add side-effects:

apiService.getWidgets(token)
.flatMapIterable(v -> v)
.flatMap(w -> 
    apiService.getArticles(token, w.type)
    .flatMapIterable(a -> a)
    .doOnNext(a -> db.insert(a))
    .doOnNext(a -> {
         w.articleName = a.name;
         w.articleUrl = a.url;
    })
    .takeLast(1)
    .map(a -> w)
)
.toList()
.subscribe(
    modifiedWidgets -> saveWidgets(modifiedWidgets),
    throwable -> processWidgetError(throwable)
);

Here is runnable example of this.

Answer 2

akarnokd's answer is quite helpful but that may cause NetworkOnMainThreadException. To solve that I have added

.observeOn(AndroidSchedulers.mainThread())
.subscribeOn(Schedulers.io())

on every requests

apiService.getWidgets(token)
.observeOn(AndroidSchedulers.mainThread())      //added this
.subscribeOn(Schedulers.io())                   //added this
.flatMapIterable(v -> v)
.flatMap(w -> 
    apiService.getArticles(token, w.type)
    .observeOn(AndroidSchedulers.mainThread())  //added this
    .subscribeOn(Schedulers.io())               //added this
    .flatMapIterable(a -> a)
    .doOnNext(a -> db.insert(a))
    .doOnNext(a -> {
         w.articleName = a.name;
         w.articleUrl = a.url;
    })
    .takeLast(1)
    .map(a -> w)
)
.toList()
.subscribe(
    modifiedWidgets -> saveWidgets(modifiedWidgets),
    throwable -> processWidgetError(throwable)
);

Answer 3

adding this here since I couldn't find an example of iterating a list that is returned in an object as variable.

getUserAccount(token)
    .subscribeOn(Schedulers.newThread())
    .observeOn(AndroidSchedulers.mainThread())
    .flatMap(userResponse -> Observable.just(userResponse.list))      //get list from response
    .flatMapIterable(baseDatas -> baseDatas)                          //make the list iterable
    .flatMap(baseData ->                                              //on each project, get the details
            getProjectDetails(baseData.name,token)
                    .subscribeOn(Schedulers.io())                     //get network call off the main thread
                    .observeOn(AndroidSchedulers.mainThread()))
    .subscribe(
            (dataResponse) -> {
                Timber.d( "Got Data Details:" + dataResponse);
            },
            (error) -> {
                Timber.e( "Got Error:" + error.getMessage());
            },
            () -> {
                Timber.d("Completed Data Details");
            }
    );