Get values of an Array from an Observable

Question

I have an Observable<MoviesResponse>. My MovieResponse class contains a getResults() methods returning a List<Result>. This Result class has a getTitle() methods returning a String. I want to call the getTitle() methods of all my Result objects to get all the titles of my movies.

I achieved this with the code below using a foreach loop but I think there is a better way to do this by chaining RxJava operators, I just can't figure it out...

Subscription :

Observable<MoviesResponse> moviesResponseObservable = apiService.getTopRatedMoviesObservable(API_KEY);

subscription = moviesResponseObservable
                .subscribeOn(Schedulers.io())
                .observeOn(AndroidSchedulers.mainThread())
                .subscribe(new Observer<MoviesResponse>() {
                    @Override
                    public void onCompleted() {

                    }

                    @Override
                    public void onError(Throwable e) {

                    }

                    @Override
                    public void onNext(MoviesResponse moviesResponse) {
                        List<Result> results = moviesResponse.getResults();
                        for (Result r:results) {
                            Log.d(LOG_TAG,r.getTitle());
                        }
                    }
                });

Interface :

public interface ApiService {           
    @GET("movie/top_rated")
    Observable<MoviesResponse> getTopRatedMoviesObservable(@Query("api_key") String apiKey);
}

zsmb13 · Accepted Answer · 2017-03-28 04:42:26Z

3

You can use a flatmap to transform your observable into an Observable<Result> and then use map to turn that into Observable<String>, which you can then subscribe to.

moviesReponseObservable
    .subscribeOn(Schedulers.io())
    .flatMapIterable(new Function<MoviesResponse, Iterable<Result>>() {
        @Override
        public Iterable<Result> apply(@NonNull MoviesResponse moviesResponse) throws Exception {
            return moviesResponse.getResults();
        }
    })
    .map(new Function<Result, String>() {
        @Override
        public String apply(@NonNull Result result) throws Exception {
            return result.getTitle();
        }
    })
    .observeOn(AndroidSchedulers.mainThread())
    .subscribe(new Observer<String>() {

        @Override
        public void onNext(String s) {
            Log.d("TAG", s);
        }

        /* ... */    

    });

answered Mar 28, 2017 at 4:42

zsmb13

90k11 gold badges236 silver badges239 bronze badges

Sign up to request clarification or add additional context in comments.

1 Comment

Laurent Over a year ago

Thank you for your answer, it was very useful. I got this error on both new Function :

map (rx.functions.Func1<? super com.example.reactiveprog.network.apimodel.Result,? extends R>) in Observable cannot be applied to (anonymous java.util.function.Function<com.example.reactiveprog.network.apimodel.Result,java.lang.String>)reason: no instance(s) of type variable(s) R exist so that Function<Result, String> conforms to Func1<? super Result, ? extends R>

but find a way with Func1 following Android Studio suggestions.

Laurent · Accepted Answer · 2017-03-28 07:20:04Z

I got the following error with @zsmb13 answer :

new Function : map (rx.functions.Func1) in Observable cannot be applied to (anonymous java.util.function.Function)reaso‌n: no instance(s) of type variable(s) R exist so that Function conforms to Func1

Anyway this answer was very helpul I just replaced Function with Func1 and used call method.

subscription = moviesResponseObservable
                .subscribeOn(Schedulers.io())
                .flatMapIterable(new Func1<MoviesResponse, Iterable<Result>>() {
                    @Override
                    public Iterable<Result> call(MoviesResponse moviesResponse) {
                        return moviesResponse.getResults();
                    }

                })
                .map(new Func1<Result, String>() {

                    @Override
                    public String call(Result result) {
                        return result.getTitle();
                    }
                })
                .observeOn(AndroidSchedulers.mainThread())
                .subscribe(new Observer<String>() {


                    @Override
                    public void onCompleted() {

                    }

                    @Override
                    public void onError(Throwable e) {

                    }

                    @Override
                    public void onNext(String s) {
                        Log.d(LOG_TAG, s);
                    }
                });

Collectives™ on Stack Overflow

Get values of an Array from an Observable

2 Answers 2

1 Comment

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Related