title: Symfony form - Access Entity inside child entry Type in a CollectionType
body: <p>I'm trying to access the entity for a given embedded form in the parent <code>CollectionType</code> inside <code>FormBuilder</code>:</p>
  
  <p><strong>ParentType</strong></p>
  
  <pre><code>Class ParentType extends AbstractType
  {
      public function buildForm(FormBuilderInterface $builder, array $options)
      {
          $builder-&gt;add('children', CollectionType::class, array(
              'entry_type' =&gt; ChildType::class
          );
      }
  }
  </code></pre>
  
  <p><strong>ChildType</strong>   </p>
  
  <pre><code>class ChildType extends AbstractType
  {
      public function buildForm(FormBuilderInterface $builder, array $options)
      {
          $child = $builder-&gt;getData(); // this returns null
      }
  
      public function getDefaultOptions(array $options)
      {
          return array(
              'data_class' =&gt; 'Vendor\Bundle\Entity\Child',
          );
      }
  }
  </code></pre>
  
  <p>While this works in a normal form, <code>$child</code> is being returned as null. How can I access the <code>Child</code> entity inside <code>ChildType</code>?</p>