request.java

  public class request{

    public void test1(){

      //ServiceA() --> return list object {"id":1,"name":""}
      //ServiceB(id) --> return detail for object
      service.getAllGeneros("movie","list","da0d692f7f62a1dc687580f79dc1e6a0")
                 .subscribeOn(Schedulers.newThread())
                 .observeOn(AndroidSchedulers.mainThread())
                 .flatMap(userResponse -> Observable.just(userResponse.getGenres()))      //get list from response
                 .flatMapIterable(baseDatas -> baseDatas)                          //make the list iterable
                 .flatMap(baseData ->                                               //on each project, get the details

                                 service.getAllMovies(baseData.getId(),"movies","key","created_at.asc")
                                 .subscribeOn(Schedulers.io())                     //get network call off the main thread
                                 .observeOn(AndroidSchedulers.mainThread())

                 )
                 .subscribe(
                         (dataResponse) -> {
                             for (Result resMovie: dataResponse.getResults()) {
                                 Log.e( "Got Data Details:   " , resMovie.getTitle());
                             }
                         },
                         (error) -> {
                             Log.e( "Got Error:" ,error.getMessage());
                         },
                         () -> {
                             Log.e("Completed Data Details","finished");
                         }
                 );
    }


  }