Styjun

Please look at this code:

 Disposable disposable = mcityService.authLogin(request,Utils.prepareHeaders())
 .subscribeOn(Schedulers.io())
 .observeOn(AndroidSchedulers.mainThread())
 .subscribe(resp ->
 
 mCompositeDisposable.add(mcityService.getUserDetails(selectedCity.id,Utils.prepareHeaders(resp.tokenType,resp.accessToken))
 .subscribeOn(Schedulers.io())
 .observeOn(AndroidSchedulers.mainThread())
 .subscribe(userDetails ->
 
 /*process resp and user details*/

 ));


 , throwable ->
 
 process errors
 );

 mCompositeDisposable.add(disposable);
 }

So basically I need to call authLogin, if it succedes, call getUserDetails (some fields from authLogin call results are required), if getUserDetails succeded, chain is finished and I need some additional processing result from both calls. If authLogin fails or getUserDetails fails, error processing should be performed (for example, get http error code or message from throwable).

As my approach works, I know it's not goot approach, how to optimize it? Can I use flatMap operator instead nested observables?

edit: Methods declarations:

public static Map<String, String> prepareHeaders(String tokenType, String accessToken);
Observable<UserDetails> getUserDetails(@Path(value = "cityId", encoded = true) String cityId, @HeaderMap Map<String, String> headers);

Final attempt:

mcityService.authLogin(request, Utils.prepareHeaders())
 .concatMap(response ->
 
 final Map<String, String> headers = Utils.prepareHeaders(response.tokenType,response.accessToken);
 return mcityService.getUserDetails(selectedCity.id, headers)
 .map(userDetails -> new Object()
 
 public AuthResponse ar = response;
 public UserDetails ud = userDetails;
 );
 )
 .doOnNext(responseDetails ->
 
 AuthResponse ar = responseDetails.ar; 
 UserDetails ud = responseDetails.ud; 


 )
 .doOnError(throwable ->
 

 final String message = throwable.getMessage();

 );

Results: .doOnNext never called, mcityService.getUserDetails seems to be never called, .doOnError also never called (so there was no error). First mcityService.authLogin call returns Observable<AuthResponse> don't I really need subscribe?

Yes, you can, and should use flatMap / concatMap / switchMap.

Also, sorry if it is not coded well, I primarily use RxJS, which has pipable operators (much better!).

mcityService.authLogin(request, Utils.prepareHeaders())
 .concatMap(response -> 
 final Map<String, String> headers = Utils.prepareHeaders(resp.tokenType,resp.accessToken);
 return mcityService.getUserDetails(selectedCity.id, headers)
 .map(userDetails -> ResponseUserDetails.of(response, userDetails));
 )
 .doOnNext(responseDetails -> 
 // Hanlde ResponseUserDetails object
 )
 .doOnError(throwable -> 
            // Handle exception
 final String message = throwable.getMessage();
 ...
       )
 .subscribe(
 responseDetails -> ... ,
 throwable -> ... 
 );

If you don't want to use an additional class, you can create an Object on the fly

return mcityService.getUserDetails(selectedCity.id, headers)
 .map(userDetails -> new Object() 
 public Response r = response;
 public UserDetails ud = userDetails;
 );

And access its fields via

.doOnNext(responseDetails -> 
 final Response r = responseDetails.r;
 final UserDetails ud = responseDetails.ud;
 ...
)

static class ResponseUserDetails 
 final Response response;
 final UserDetails userDetails;

 ResponseUserDetails(
 final Response response,
 final UserDetails userDetails) 
 this.response = response;
 this.userDetails = userDetails;
 

 static ResponseUserDetails of(
 final Response response,
 final UserDetails userDetails) 
 return new ResponseUserDetails(response, userDetails);