title: chaining requests with retrofit and rxjava
body: <p>I need to make about 5 chaining requests for example I have 5 different calls and I want to make them serial not parallel in specific order.</p>
  
  <p>Here are some examples of my observables </p>
  
  <pre><code>Observable&lt;ResponseBody&gt; textsCall=EndpointFactory.provideEndpoint().getTexts(textsTask.getLanguage())
          .subscribeOn(Schedulers.newThread())
          .observeOn(AndroidSchedulers.mainThread());
  
  Observable&lt;AirportCombo&gt; routesCall=EndpointFactory.provideEndpoint().getRoutes()
          .subscribeOn(Schedulers.newThread())
          .observeOn(AndroidSchedulers.mainThread());
  </code></pre>
  
  <p>Actually, I don't know what function does it on rx java. </p>
  
  <p>Earlier I've implemented parallel requests, now I need serial. </p>
  
  <p>If you need parallel approach here you are:</p>
  
  <pre><code>Observable&lt;ResponseResult&gt; combined = Observable.zip(textsCall, routesCall, (textsBody, airportCombo) -&gt; {
              //some parsing and other logic
              return new ResponseResult(flag);
          });
  </code></pre>