validation on unbound form field - symfony-2.1

Question

I have a form with an extra unbound field added using 'property_path' => false.
I would like to have a simple validation on this field and I've found many answers that suggest to use something like
$builder->addValidator(...);
but I've seen that in symfony 2.1 $builder->addValidator is deprecated. Does anyone know what is the correct way to put a validation on an unbound field in Symfony 2.1?

Answer 1

Edit :
I've just made a more complete answer on topic Symfony validate form with mapped false form fields
Original answer
Validating unbound (non mapped) field in a form is not well documented and the fast evolving form and validator components make the few examples obsoletes (for Symfony 2.1.2).
For now I succeed in validated non mapped fields with event listener.
Here is my simplified code :
namespace Dj\TestBundle\Form;
use Symfony\Component\Form\AbstractType;
use Symfony\Component\Form\FormBuilderInterface;
use Symfony\Component\OptionsResolver\OptionsResolverInterface;
use Symfony\Component\Form\FormEvents;
use Dj\TestBundle\Form\EventListener\NewPostListener;
class PostType extends AbstractType
{
public function buildForm(FormBuilderInterface $builder, array $options)
{
$builder->add('lineNumber', 'choice', array(
'label' => 'How many lines :',
'choices' => array(
3 => '3 lines',
6 => '6 lines'
),
// 'data' => 3, // default value
'expanded' => true,
'mapped' => false
))
->add('body', 'textarea', array(
'label' => 'Your text',
'max_length' => 120));
// this listener will validate form datas
$listener = new NewPostListener;
$builder->addEventListener(FormEvents::POST_BIND, array($listener, 'postBind'));
}
// ... other methods
}
And the event listener :
namespace Dj\TestBundle\Form\EventListener;
use Symfony\Component\Form\FormEvent;
use Symfony\Component\Form\FormError;
/**
* listener used at Post creation time to validate non mapped fields
*/
class NewPostListener
{
/**
* Validates lineNumber and body length
* #param \Symfony\Component\Form\FormEvent $event
*/
public function postBind(FormEvent $event)
{
$form = $event->getForm();
$data = $event->getData();
if (!isset($data->lineNumber)) {
$msg = 'Please give a correct line number';
$form->get('lineNumber')->addError(new FormError($msg));
}
// ... other validations
}
}
This is how I validate my non mapped fields until I find out how to do this with validators.

Answer 2

I have the same problem from the docs we get this:
The interface FormValidatorInterface was deprecated and will be
removed in Symfony 2.3. If you implemented custom validators using
this interface, you can substitute them by event listeners listening
to the FormEvents::POST_BIND (or any other of the *BIND events). In
case you used the CallbackValidator class, you should now pass the
callback directly to addEventListener.
This suggest to use event listeners but I have not found and example.
https://github.com/symfony/symfony/blob/master/UPGRADE-2.1.md