Symfony2 Setting a default choice field selection

I am creating a form in the following manner:

$form = $this->createFormBuilder($breed)
             ->add('species', 'entity', array(
                  'class' => 'BFPEduBundle:Item',
                  'property' => 'name',
                  'query_builder' => function(ItemRepository $er){
                      return $er->createQueryBuilder('i')
                                ->where("i.type = 'species'")
                                ->orderBy('i.name', 'ASC');
                  }))
             ->add('breed', 'text', array('required'=>true))
             ->add('size', 'textarea', array('required' => false))
             ->getForm()

How can I set a default value for the species listbox?

Thank you for your response, I apologise, I think I should rephrase my question. Once I have a value that I retrieve from the model, how do I set that value as SELECTED="yes" for the corresponding value in the species choice list?

So, that select option output from the TWIG view would appear like so:

<option value="174" selected="yes">Dog</option>

Solution 1:

You can define the default value from the 'data' attribute. This is part of the Abstract "field" type (http://symfony.com/doc/2.0/reference/forms/types/field.html)

$form = $this->createFormBuilder()
            ->add('status', 'choice', array(
                'choices' => array(
                    0 => 'Published',
                    1 => 'Draft'
                ),
                'data' => 1
            ))
            ->getForm();

In this example, 'Draft' would be set as the default selected value.

Solution 2:

If you use Cristian's solution, you'll need to inject the EntityManager into your FormType class. Here is a simplified example:

class EntityType extends AbstractType{
    public function __construct($em) {
        $this->em = $em;
    }

    public function buildForm(FormBuilderInterface $builder, array $options){
         $builder
             ->add('MyEntity', 'entity', array(
                     'class' => 'AcmeDemoBundle:Entity',
                     'property' => 'name',
                     'query_builder' => function(EntityRepository $er) {
                         return $er->createQueryBuilder('e')
                             ->orderBy('e.name', 'ASC');
                     },
                     'data' => $this->em->getReference("AcmeDemoBundle:Entity", 3)
        ));
    }
}

And your controller:

 // ...    

 $form = $this->createForm(new EntityType($this->getDoctrine()->getManager()), $entity);

// ...

From Doctrine Docs:

The method EntityManager#getReference($entityName, $identifier) lets you obtain a reference to an entity for which the identifier is known, without loading that entity from the database. This is useful, for example, as a performance enhancement, when you want to establish an association to an entity for which you have the identifier.