title: What is a Grouped Flux and how exactly do we work with one?
body: <p>I am working on a Flux of some object lets say <code>Flux &lt; MovieReservation &gt;</code> . This contains info like movie id,name, timing, title etc. So I wanted to extract the info that can help in creating a new <br/> <code>Flux &lt; MovieShowDetail &gt;</code> . My intent was to group all reservations by the movie id and break the Flux down into a set of smaller and multiple Flux(fluxes if that's thing at all). Something like </p>
  
  <pre><code>Flux {
     movie1 -&gt; Flux&lt;MovieShowDetail&gt;
     movie2 -&gt; Flux&lt;MovieShowDetail&gt;
     ... and so on
  }
  </code></pre>
  
  <p>So I came across this groupBy method which is supposed to do something like this only. However the documentation is really out of content on this, especially on how to iterate over each movie and its respective Flux.</p>
  
  <p>Moreover when I try to learn by try and error, the processing stops after working on the operation before the groupBy method.</p>
  
  <p>I have tried to do </p>
  
  <pre><code>fluxOfSomething
  .groupBy( movieReservation -&gt; movieReservation.getMovieId ,
  movieReservation -&gt; movieReservation) 
  </code></pre>
  
  <p>so that i can iterate over each of the flux and create the new flux of MovieShowDetail. However, processing never gets in this block. I tried logging stuff but the flow never entered it.</p>
  
  <pre><code>flux
      .map( movieSomething -&gt; do something)
      .groupBy( movieReservation -&gt; 
          movieReservation.getMovieId , movieReservation -&gt;
      movieReservation)
      .subscribe("This text doesn't get printed");
  </code></pre>
  
  <p>I really need as much info as you can give about this.</p>