title: Iterate list with RxJava/RxAndroid
body: <p>I'm new to RxJava/RxAndroid but I'm stuck with my use case.</p>
  
  <p>I try to iterate a <code>List&lt;A&gt;</code> to convert each <code>A</code> into an <code>B</code> asynchronously (because it needs call to database) and my <code>Observer</code> should be notified on every successful conversion (in <code>onNext()</code>) to do some jobs on the main thread. </p>
  
  <p>I successfully managed to convert the entire list and then received my <code>List&lt;B&gt;</code> in <code>onNext()</code>but I need to be notified at each item, not once all items are done.</p>
  
  <p>I tried something with the operator <code>from</code> but if I use <code>from(List&lt;A&gt;)</code> my <code>Observer</code> must receivied objects from the same type (<code>A</code> and not <code>B</code>).</p>
  
  <p>Here is how my code to convert entire <code>List&lt;A&gt;</code> to <code>list&lt;B&gt;</code> What should I change here?</p>
  
  <pre class="lang-java prettyprint-override"><code>private List&lt;A&gt; listOfA;
  
  private startConversion() {
      Observer observer = new Observer&lt;List&lt;B&gt;&gt;() {
          @Override
          public void onCompleted() {
  
          }
  
          @Override
          public void onError(Throwable e) {
              e.printStackTrace();
          }
  
          @Override
          public void onNext(List&lt;B&gt; convertedItems) {
              onConversionCompleted(convertedItems);
          }
      };
  
      Observable&lt;B&gt; observervable = Observable.fromCallable(new Callable&lt;List&lt;B&gt;&gt;() {
          @Override
          public List&lt;B&gt; call() throws Exception {
              return convertListOfAToListOfB(listOfA);
          }
      });
  
      subscription = observable
                  .subscribeOn(Schedulers.newThread())
                  .observeOn(AndroidSchedulers.mainThread())
                  .subscribe(observer);
  }
  </code></pre>
  
  <p>PS: this is pseudo code.</p>
  
  <p>Thank's for help !</p>