RxJava: chaining observables

Question

Is it possible to implement something like next chaining using RxJava:

loginObservable()    .then( (someData) -> {       // returns another Observable<T> with some long operation       return fetchUserDataObservable(someData);     }).then( (userData) -> {       // it should be called when fetching user data completed (with userData of type T)       cacheUserData(userData);     }).then( (userData) -> {       // it should be called after all previous operations completed       displayUserData()     }).doOnError( (error) -> {       //do something    }) 

I found this library very interesting, but can't figure our how to chain requests where each other depends on previous.

Answer 1

Sure, RxJava supports .map which does this. From the RxJava Wiki:

Basically, it'd be:

loginObservable()    .switchMap( someData -> fetchUserDataObservable(someData) )    .map( userData -> cacheUserData(userData) )    .subscribe(new Subscriber<YourResult>() {         @Override         public void onCompleted() {            // observable stream has ended - no more logins possible         }         @Override         public void onError(Throwable e) {             // do something         }         @Override         public void onNext(YourType yourType) {             displayUserData();         }     });