title: Symfony2 EntityType field persist
body: <p>I have Entity: <code>AdWCType</code> and <code>AdWallType</code>. These entities contains static data like directory.</p>
  
  <p><strong>AdWallType</strong></p>
  
  <pre><code>index  title
  -----  -----
  1      Brick
  2      Plate
  </code></pre>
  
  <p>Entity <code>Ad</code> contains columns <code>wallType</code> and <code>wcType</code>.</p>
  
  <p><strong>AdType</strong></p>
  
  <pre><code>$builder-&gt;add('wallType', EntityType::class, array(
                  'class' =&gt; 'AdBundle:AdWallType',
                  'choice_label' =&gt; 'title',
                  'query_builder' =&gt; function(EntityRepository $er) {
                      return $er-&gt;createQueryBuilder('wt')
                          -&gt;where('wt.visible = :visible')
                          -&gt;setParameter('visible', true)
                          -&gt;orderBy('wt.weight', 'ASC')
                          -&gt;setCacheable(true);
                  }
              ))
              -&gt;add('wcType', EntityType::class, array(
                  'class' =&gt; 'AdBundle:AdWCType',
                  'choice_label' =&gt; 'title',
                  'query_builder' =&gt; function(EntityRepository $er) {
                      return $er-&gt;createQueryBuilder('wc')
                          -&gt;where('wc.visible = :visible')
                          -&gt;setParameter('visible', true)
                          -&gt;orderBy('wc.weight', 'ASC')
                          -&gt;setCacheable(true);
                  }
              ))
  </code></pre>
  
  <p>How I can persist <code>wcType</code> and <code>wallType</code> which I choosed into entity <code>Ad</code> on form submit?</p>