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I have two observables apiService.getFeed() & apiService.getProfile() I want to load both data in same screen & inorder to do that and handle errors I need to call apiService.getProfile() after apiService.getFeed().

I have looked up a lot of examples but most of it seem to use flatMap & am not sure if we can use it especially because the two observable are of different class types and both are independent in terms of values.

ColdFire
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Akshay Moorthy
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2 Answers2

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This is how I would nest two Retrofit calls with RxJava2's flatMap:

    apiService.getFeed(param1, param2, ...)
            .flatMap(result -> apiService.getProfile(param1, param2, ...))
            .subscribeOn(Schedulers.io())
            .observeOn(AndroidSchedulers.mainThread())
            .subscribe(result -> {
                //do something here
            }, throwable -> {
                view.showErrorMessage(throwable.getMessage());
            });

But if it's two different observable types, you can also use different variants of flatMap:

  • flatMap - returns a Single
  • flatMapCompletable - returns a Completable
  • flatMapMaybe - returns a Maybe
  • flatMapObservable - returns an Observable
  • flatMapPublisher - returns a Flowable
ppgdn
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Return your retrofit responses as Observable, then use the zip operator. http://reactivex.io/documentation/operators/zip.html

When one api call has dependency on the other api call, zip operator is the ideal since the Zip operator combines the emission of two observables in order. 

Observable <String> feed = apiService.getFeed("param");
Observable <String> profile = apiService.getProfile("param");

Observable.zip(
        feed, profile,
        new Func2<String, String, ResultType>() {

           @Override
           public ResultType call(String feedResponse, 
           String profileResponse) {
              // Do something with the feedResponse
              // Do something with the profileResponse
              // Return something with ResultType
              return something;
           }
        }).subscribe(
            //Once requests process are done
           new Consumer<Object>() {
               @Override
               public void accept(Object o) throws Exception {
                   //on successful completion of the request
               }
           },
           new Consumer<Throwable>() {
               @Override
               public void accept(Throwable e) throws Exception {
                   //on error 
               }
           });
javasnowman
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