FormType to use with Sonata + KNP DoctrineBehaviours translatable trait

PlaceAdmin.php

<?php

namespace App\PlaceBundle\Admin;

use App\PlaceBundle\Form;

use Sonata\AdminBundle\Admin\Admin;
use Sonata\AdminBundle\Datagrid\ListMapper;
use Sonata\AdminBundle\Datagrid\DatagridMapper;
use Sonata\AdminBundle\Form\FormMapper;

class PlaceAdmin extends Admin
{
    protected function configureFormFields(FormMapper $formMapper)
    {
        $formMapper
            ->add('telephone')
            ->add('address')
            ->add('translations', new Form\Type\TranslationType($this), array(
                'type' => new Form\PlaceTranslationType(),
            ))     
        ;
    }

    // ...
}

TranslationType.php

<?php

namespace App\PlaceBundle\Form\Type;

use App\PlaceBundle\Form;

use Symfony\Component\Form\AbstractType;
use Symfony\Component\Form\FormBuilderInterface;
use Symfony\Component\Form\FormEvents;
use Symfony\Component\Form\FormEvent;
use Symfony\Component\OptionsResolver\OptionsResolverInterface;

class TranslationType extends AbstractType
{
    protected $class;

    public function __construct($admin)
    {
        $this->class = $admin->getClass() . 'Translation';
    }

    /**
     * {@inheritDoc}
     */
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder->addEventListener(FormEvents::PRE_SET_DATA, function(FormEvent $event) use ($builder) {
            $form   = $event->getForm();
            $entity = $form->getParent()->getData();

            // Initialize
            foreach (['es', 'eu', 'it'] as $locale) {
                $entity->translate($locale);
            }

            $entity->mergeNewTranslations();
        });
    }

    /**
     * {@inheritDoc}
     */
    public function setDefaultOptions(OptionsResolverInterface $resolver)
    {
        $resolver->setDefaults(array(
            'allow_add' => false,
            'by_reference' => true,
            'options' => [
                'data_class' => $this->class,
            ]
        ));
    }

    public function getParent()
    {
        return 'collection';
    }

    /**
     * {@inheritDoc}
     */
    public function getName()
    {
        return 'sonata_type_translation';
    }
}