CODEWITHSUNDEEP
androidrx-javarx-java2
Samuel Eminet
Samuel Eminet

Reputation: 4737

Handle empty response with retrofit and rxjava 2.x

When using rxjava 1.x i used to return Observable<Void> to handle empty response from retrofit:

@POST( "login" )
Observable<Void> getToken( @Header( "Authorization" ) String authorization,
                                       @Header( "username" ) String username,
                                       @Header( "password" ) String password );

But since rxjava 2.x won't emit anything with Void is there any good practice to handle those empty responses?

Upvotes: 24

Views: 11271

Answers (4)

Leo DroidCoder
Leo DroidCoder

Reputation: 15046

Another solution is:

@POST("login")
Observable<Response<Void>> getToken(@Header("Authorization") String authorization,
                                    @Header("username") String username,
                                    @Header("password") String password);

Update: But I would rather use Completable

Upvotes: 7

NickJ
NickJ

Reputation: 1

So the accepted answer is only partially correct. Completable will work in some cases where one and only one emission is expected, however, Completable will only emit once, and will not emit after that. It is similar to Single (except we ignore the value being emitted). Observable, on the other hand, can emit multiple times. So if the source observable will emit multiple times, the answer, at least in RxJava2, is to emit something like Observable<Irrelevant> (where Irrelevant is a static enum/class), or better yet Observable<Kotlin.Unit>.

public class Source {
    private PublishSubject<Kotlin.Unit> heartbeatOperation;
...
    void getHeartbeats() {
         while(getHeartbeatFromSource() != null) {
             hearbeatOperation.accept(Unit.INSTANCE);
         }  
    }

    public Observable<Unit> heartbeats() {
         return hearbeatOperation.hide();
    }
...
}


public class SourceConsumer {
   @Inject Source source;
...
    void printHearbeats() {
         source.heartbeats()
         .subscribe(unused -> {
             System.out.println("Heartbeat received at " + DateTime.now());
         });
    }
}

Upvotes: 0

Maksim Ostrovidov
Maksim Ostrovidov

Reputation: 11058

Completable was designed for such cases. It available since RxJava 1.1.1. From the official docs:

Represents a deferred computation without any value but only indication for completion or exception. The class follows a similar event pattern as Reactive-Streams: onSubscribe (onError|onComplete)?

So just change your method's return type:

@POST("login")
Completable getToken(@Header("Authorization") String authorization,
                     @Header("username")      String username,
                     @Header("password")      String password);

And rewrite your subscriber, e.g.:

apiManager.getToken(auth, name, pass)
    ...
    .subscribe(() -> {
        //success
    }, exception -> {
        //error
    });

Upvotes: 46

Ionut Negru
Ionut Negru

Reputation: 6314

Did you try using Observable<Object> ?

This is from the official documentation of RxJava 2:

enum Irrelevant { INSTANCE; }

Observable<Object> source = Observable.create((ObservableEmitter<Object> emitter) -> {
   System.out.println("Side-effect 1");
   emitter.onNext(Irrelevant.INSTANCE);

   System.out.println("Side-effect 2");
   emitter.onNext(Irrelevant.INSTANCE);

   System.out.println("Side-effect 3");
   emitter.onNext(Irrelevant.INSTANCE);
});

source.subscribe(e -> { /* Ignored. */ }, Throwable::printStackTrace);

Upvotes: -1

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