RxJavaMulti

Implementation of multi-valued observables supporting more than one value passed to subscribers via onNext. This library includes operators and static methods to convert to and from the various observable arities including the mono-observable as defined in the core RxJava library.

When a BiObservable is subscribed to by a BiSubscriber the onNext(T0, T1) method will be called passing a pair of elements.

Creating a BiObservable

Generate

Emits bi-values of an Integer and its String representation. The BiObservable's behavior upon subscription is to subscribe to the source mono-observable once to generate the string representation.

Observable<Integer> intRange = Observable.range(0,99);
BiObservable<Integer, String> pairs = BiObservable.generate(intRange, (Integer i) -> {return i.toString()});

Attach

Emits bi-values of an Integer and a java.io.File where all bi-value's second element are ==.

Observable<Integer> intRange = Observable.range(0,99);
BiObservable<Integer, File> withFile = BiObservable.attach(intRange, new File("log.txt"));

Product

Emits bi-values of a Movie and a Language. There will be 1 bi-value for each movie and language combination.

Observable<Movie> movies = movieService.getMovies();
Observable<Language> langs = geo.getAllLanguages();
BiObservable<Movie, Language> pairs = BiObservable.product(movies, langs);

Sparse Product

Emits bi-values of a Movie and a Language. Each movie will have one bi-value for each Language emitted by the Observable<Language> returned by the generator function provided.

Observable<Movie> movies = movieService.getMovies();
BiObservable<Movie, Language> pairs = BiObservable.sparseProduct(movies, (Movie m) -> { 
  List<Languages> langs = subtitleService.getLanguagesForMovie(m);
  return from(langs);
});

Usage

Filtering

A filter predicate can be written for the first, second, or both elements of a bi-value. The following example filters all bi-values but one based on the second element.

BiObservable.generate(Observable.range(0,100), (Integer i) -> { return i == 42 ? “yep” : “nope”; })
    .filter2((Boolean isAnswer) -> { return isAnswer.equals(“yep”); });

Mono-Mapping

Bi-values can be mapped back to a single valued Observable using the bimap operator.

Observable<Integer> nums = Observable.range(0,99);
Observable<Integer> factorsOf3 = nums.map((Integer i) -> {return i * 3;});
Observable<Integer> factorsOf5 = BiObservable.attach(nums, 5).biMap((Integer i, Integer factor) -> {return i * factor;});

Bi-Mapping

You can replace a single element of a bi-value at a time. The map1(Func1) and map1(Func2) overloads replace the first element of the bi-values, while the map2(Func1) and map2(Func2) replace the second.

BiObservable<String, MyMovieService> pair = BiObservable.attach(getAllMovies(), MyMovieService())
    .map1((Movie m, MyMovieService service) -> { return service.getSynopsis(m); });

Scanning

The scan1 and scan2 operators will replace the first or second element of a bi-value respectively with the result of the provided accumulator function. This will preserve the second element for each bi-value. Note that scanning over a bi-value cannot emit the provided seed value as the pre-computation onNext because there is no second element of the bi-value to emit.