RxJava api call for every item in list and return list of extended items

Question

I use Retrofit 2 and I'm learning RxJava. I download a list of items from somewhere. I want to make an api call for each item and create a new list of extended items. Both calls return an Observable. It looks something like this:

getItemsService.getItems()
            .concatMap(Observable::from)
            .map(item -> new ExtendedItem(item, someOtherService.getDetails(item.somedetail)))
            .toList()
            .subscribeOn(Schedulers.io())
            .observeOn(AndroidSchedulers.mainThread())
            .subscribe(activity);

The details service:

public interface IGetDetailsService {
@GET(BuildConfig.GET_DETAILS_ENDPOINT)
Observable<Detail> getDetails(@Query("q") String someDetail);

}

The problem is that getDetails returns an Observable and I cannot use it to construct ExtendedItem. Changing the getDetails call to return an object does not work in the rxJava chain, I guess because it returns the result to the main thread. How do I get the object itself? I tried a lot of other things but nothing works so far.

AndroidEx · Accepted Answer · 2016-04-05 14:42:32Z

2

You can use one of the variants of flatMap:

...
            .concatMap(Observable::from)
            .flatMap(item -> someOtherService.getDetails(item.somedetail), (item, detail) -> new ExtendedItem(item, detail))
            .toList()
...

edited Apr 5, 2016 at 14:42

answered Apr 5, 2016 at 12:54

AndroidEx

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