Composing Observables

As we explained earlier, an Observable interface is defined in a way that allows us to chain and combine different Observables to create complex tasks in a functional and declarative way.

Starting from our previous work, in our next example, we will make use of the RxJava composing feature and execute a second network call that depends on the previous Observable that will translate the text downloaded using a web service before we emit the translated text to the Subscriber.

To execute the translation on the network on a logically separate unit, we will create a new Observable that receives the text to translate, executes the task on the network, and emits the translated text as a String to the following Observable:

Observable<String> translateOnNetwork(final String url,
                                      final String toTranslate) {
  return Observable.create(
    new Observable.OnSubscribe<String>() {
      @Override
      public void call(Subscriber&lt...