I'm not sure what you are doing wrong here, when I build a form using form classes Symfony takes care of selecting the correct option in the list. Here's an example of one of my forms that works.
In the controller for the edit action:
$entity = $em->getRepository('FooBarBundle:CampaignEntity')->find($id);
if (!$entity) {
throw $this->createNotFoundException('Unable to find CampaignEntity entity.');
}
$editForm = $this->createForm(new CampaignEntityType(), $entity);
$deleteForm = $this->createDeleteForm($id);
return $this->render('FooBarBundle:CampaignEntity:edit.html.twig', array(
'entity' => $entity,
'edit_form' => $editForm->createView(),
'delete_form' => $deleteForm->createView(),
));
The campaign entity type class (src: Foo\BarBundle\Form\CampaignEntityType.php):
namespace Foo\BarBundle\Form;
use Symfony\Component\Form\AbstractType;
use Symfony\Component\Form\FormBuilder;
use Doctrine\ORM\EntityRepository;
class CampaignEntityType extends AbstractType
{
public function buildForm(FormBuilder $builder, array $options)
{
$builder
->add('store', 'entity', array('class'=>'FooBarBundle:Store', 'property'=>'name', 'em'=>'my_non_default_em','required' => true, 'query_builder' => function(EntityRepository $er) {return $er->createQueryBuilder('s')->orderBy('s.name', 'ASC');}))
->add('reward');
}
public function getName()
{
return 'foo_barbundle_campaignentitytype';
}
}