Rxjava Android how to use the Zip operator

Question

I am having a lot of trouble understanding the zip operator in RxJava for my android project. Problem I need to be able to send a network request to upload a video Then i need to send a network request to upload a picture to go with it finally i need to add a description and use the responses from the previous two requests to upload the location urls of the video and picture along with the description to my server.

I assumed that the zip operator would be perfect for this task as I understood we could take the response of two observables (video and picture requests) and use them for my final task. But I cant seem to get this to occur how I envision it.

I am looking for someone to answer how this can be done conceptually with a bit of psuedo code. Thank you

Answer 1

Zip operator strictly pairs emitted items from observables. It waits for both (or more) items to arrive then merges them. So yes this would be suitable for your needs.

I would use Func2 to chain the result from the first two observables. Notice this approach would be simpler if you use Retrofit since its api interface may return an observable. Otherwise you would need to create your own observable.

// assuming each observable returns response in the form of String
Observable<String> movOb = Observable.create(...);
// if you use Retrofit
Observable<String> picOb = RetrofitApiManager.getService().uploadPic(...),
Observable.zip(movOb, picOb, new Func2<String, String, MyResult>() {
      @Override
      public MyResult call(String movieUploadResponse, String picUploadResponse) {
          // analyze both responses, upload them to another server
          // and return this method with a MyResult type
          return myResult;
      }
   }
)
// continue chaining this observable with subscriber
// or use it for something else