title: How to set up a listener for form.set_data event in Symfony 2?
body: <p>Seems like a pretty simple problem but I've been trying for a while and can't get it to work. I need to hook into the form.set_data event in Symfony 2 in order to modify the data being set in the form from an existing DB record.</p>
  
  <p>I'm trying the following:</p>
  
  <p>Config.yml:</p>
  
  <pre><code>services:
      Acme.DemoBundle.listener.set_data:
      class: Acme\DemoBundle\RequestListener
      tags:
          - { name: kernel.event_listener, event: form.set_data, method: onFormSetData }
  </code></pre>
  
  <p>RequestListener.php</p>
  
  <pre><code>namespace Acme\DemoBundle;
  ...
  class RequestListener {
      public function onFormSetData(GetResponseEvent $event) {
          echo 'Eureka!'; die();
      }
  }
  </code></pre>
  
  <p>I never get the <code>echo</code> or <code>die</code>. I am sure that the event is being dispatched (fired). I verified that using debugging (xDebug). Looks like the listener is not being registered.</p>
  
  <p>What am I doing wrong? Is there something obvious that I'm missing here?</p>