title: How do I get object id in sonata_type_collection associated admin
body: <p>I have a Symfony 2.0 with SonataAdminBundle 2.0. This is a method from one of my admin controllers.</p>
  
  <pre><code>protected function configureFormFields(FormMapper $formMapper)
  {
      $formMapper
          -&gt;add('name')
          -&gt;add('events', 'sonata_type_collection', array(), array(
              'edit'      =&gt; 'inline',
              'inline'    =&gt; 'table'
          ))
      ;
  
      $this-&gt;getFormFieldDescription('events')
          -&gt;setAssociationAdmin($this-&gt;getConfigurationPool() &gt;getInstance('platform.admin.events'));
  }
  </code></pre>
  
  <p>and I have associated eventsAdmin controller with this method</p>
  
  <pre><code>protected function configureFormFields(FormMapper $formMapper)
  {
      $currentObjectId = '' // this is what I want???
  
      $formMapper
          -&gt;add('name')
          -&gt;add('time')
          -&gt;add('trigger')
      ;
  }
  </code></pre>
  
  <p>So my parent form looks like<br></p>
  
  <p><strong>Name</strong>: blablabla<br>
  <strong>Events</strong>:<br> 
  1. - delete1 - name1 - time1 - trigger<br>
  2. - delete2 - name2 - time2 - trigger<br>
  3. - delete3 - name3 - time3 - trigger<br></p>
  
  <p>What I want is to get an ID of current object in associated admin.. "Trigger" is a select box and it's dependent on current object id. I have to make a query with it.</p>
  
  <p>There is a method <strong>->getSubject()</strong> in <strong>Sonata\AdminBundle\Admin\Admin</strong> but it always returns the first "event" object.</p>
  
  <p>Any suggestions?</p>