Symfony2 Form Event Subscriber Example

IsAdminFieldSubscriber.php

<?php

namespace Acme\Bundle\AppBundle\Form\EventListener;

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

class IsAdminFieldSubscriber implements EventSubscriberInterface
{
    /**
     * @var FormFactoryInterface 
     */
    private $factory;

    /**
     * @param FormFactoryInterface $factory 
     */
    public function __construct(FormFactoryInterface $factory)
    {
        $this->factory = $factory;
    }

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

    /**
     * Called before form data is set
     *
     * @param DataEvent $event
     */
    public function preSetData(DataEvent $event)
    {
        $data = $event->getData();
        $form = $event->getForm();

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

        $checked = $data->hasRole('ROLE_ADMIN');
        
        $form->add($this->factory->createNamed('is_admin', 'checkbox', $checked, array(
            'property_path' => false,
            'required' => false
        )));
    }
    
    /**
     * Called when the form is bound to a request
     *
     * @param DataEvent $event
     */
    public function bind(DataEvent $event)
    {
        $data = $event->getData();
        $form = $event->getForm();

        if (null === $data) {
            return;
        }
        
        $value = $form->get('is_admin')->getData();
        
        if ($value) {
            $data->addRole('ROLE_ADMIN');
        } else {
            $data->removeRole('ROLE_ADMIN');
        }
    }
}

UserType.php

<?php

namespace Acme\Bundle\AppBundle\Form;

use Symfony\Component\Form\AbstractType;
use Symfony\Component\Form\FormBuilderInterface;
use Symfony\Component\OptionsResolver\OptionsResolverInterface;
use Acme\Bundle\AppBundle\Form\EventListener\IsAdminFieldSubscriber;

class UserType extends AbstractType
{
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder
            ->add('name')
            ->add('username')
            ->add('email')
        ;
        
        $subscriber = new IsAdminFieldSubscriber($builder->getFormFactory());
        $builder->addEventSubscriber($subscriber);
    }

    public function setDefaultOptions(OptionsResolverInterface $resolver)
    {
        $resolver->setDefaults(array(
            'data_class' => 'Acme\Bundle\AppBundle\Entity\User'
        ));
    }

    public function getName()
    {
        return 'user';
    }
}

does not seem to be working in Symfony 3