How to add a field to a symfony2 form on preSetData

AddMarkValueSubscriber.php

<?php

namespace MyNamespace\ReviewBundle\Form\EventListener;

use Symfony\Component\EventDispatcher\EventSubscriberInterface,
    Symfony\Component\Form\FormFactoryInterface,
    Symfony\Component\Form\FormEvents,
    Symfony\Component\Form\Event\DataEvent;

/**
* Add Mark Value Subscriber.
*
*/
class AddMarkValueSubscriber implements EventSubscriberInterface
{
    /**
* @var \Symfony\Component\Form\FormFactoryInterface The form factory.
*/
    private $factory;

    /**
* Constructor.
*
* @param \Symfony\Component\Form\FormFactoryInterface $factory The form factory.
*/
    public function __construct(FormFactoryInterface $factory)
    {
        $this->factory = $factory;
    }

    /**
* Add the label to the mark.
*
* @param \Symfony\Component\Form\Event\DataEvent $event The form event.
*/
    public function preSetData(DataEvent $event)
    {
        $data = $event->getData();
        $form = $event->getForm();

        if (null === $data) {
            return;
        }

        $form->add($this->factory->createNamed('value', 'interactivemark', null, array(
            'label' => $data->getCriteria()->getName(),
            'invalid_message' => 'mark.value.invalid',
        )));
    }

    /**
* {@inheritdoc}
*/
    static public function getSubscribedEvents()
    {
        return array(FormEvents::PRE_SET_DATA => 'preSetData');
    }
}