title: Select multiple into a Symfony2 FORM
body: <p>I have this scenario</p>
  
  <p><code>EntityA</code> related to <code>EntityB</code> into a <strong>one-to-many</strong> fashion. I have created a form for <code>EntityB</code> and I want to select (with checkboxes) some of <code>EntityA</code> element.<br/></p>
  
  <p>How can I achieve this?</p>
  
  <p>UPDATE</p>
  
  <pre><code>public function viewAction()
  {
      $id_struttura = 9;
      $channel_rates = $this-&gt;getDoctrine()-&gt;getRepository('SestanteChannelManagerBundle:StrutturaCanaleTariffa')-&gt;findByStruttura($id_struttura);
      $list = array();
      foreach ($channel_rates as $channel_rate) {
          $list[$channel_rate-&gt;getId()] = $channel_rate-&gt;getNomeCameraTariffa();
      }
      $view = new View();
      $view-&gt;addChannelRate($channel_rates);
      $form = $this-&gt;createForm(new ViewType(), $view);
      $request = $this-&gt;getRequest();
      if ($request-&gt;getMethod() == 'POST') {
          $form-&gt;bindRequest($request);
          if ($form-&gt;isValid()) {
              $dateRange = new DateRange($date_from, $date_to);
              $channelDisp = $this-&gt;get('channel_dispatcher');
              $inventories = $channelDisp-&gt;queryAvailabilityRates($dateRange, $channelRateList);
              return $this-&gt;render('SestanteCDTestBundle:Main:view_result.html.twig', array('inventories' =&gt; $inventories));
          }
      }
      return $this-&gt;render('SestanteCDTestBundle:Main:view.html.twig', array('form' =&gt; $form-&gt;createView()));
  }
  </code></pre>
  
  <p>This is my entity</p>
  
  <pre><code>&lt;?php
  
  namespace Sestante\CDTestBundle\Entity;
  
  use Doctrine\Common\Collections\ArrayCollection;
  
  class View
  {
      protected $channel_rate;
  
      function __construct()
      {
          $this-&gt;channel_rate = new ArrayCollection();
      }
  
  
      /**
       * @return the $date_from
       */
      public function getDateFrom() {
          return $this-&gt;date_from;
      }
  
      /**
       * @return the $date_to
       */
      public function getDateTo() {
          return $this-&gt;date_to;
      }
  
      /**
       * @return the $channel_rate
       */
      public function getChannelRate() {
          return $this-&gt;channel_rate;
      }
  
      /**
       * @param field_type $date_from
       */
      public function setDateFrom($date_from) {
          $this-&gt;date_from = $date_from;
      }
  
      /**
       * @param field_type $date_to
       */
      public function setDateTo($date_to) {
          $this-&gt;date_to = $date_to;
      }
  
      /**
       * @param field_type $channel_rate
       */
      public function addChannelRate($channel_rate) {
            $this-&gt;channel_rate[] = $channel_rate;
      }
  }
  </code></pre>
  
  <p>And this is my form</p>
  
  <pre><code>&lt;?php
  
  namespace Sestante\CDTestBundle\Form;
  
  use Symfony\Component\Form\AbstractType;
  use Symfony\Component\Form\FormBuilderInterface;
  
  class ViewType extends AbstractType
  {
      public function buildForm(FormBuilderInterface $builder, array $options)
      {
          $builder-&gt;add('date_from', 'date', array('widget' =&gt; 'single_text','format' =&gt; 'yyyy-MM-dd'));
          $builder-&gt;add('date_to', 'date', array('widget' =&gt; 'single_text','format' =&gt; 'yyyy-MM-dd'));
          $builder-&gt;add('channel_rate', 'entity', array('class'=&gt;'SestanteChannelManagerBundle:StrutturaCanaleTariffa', 'multiple'=&gt;true, 'expanded'=&gt;true));
      }
  
      public function getName()
      {
          return 'view';
      }
  }
  </code></pre>
  
  <p>If I add a statement like this (into entity) all works good:</p>
  
  <pre><code>foreach ($channel_rate as $ch)
  {
  $this-&gt;channel_rate[] = $ch;
  }
  </code></pre>