Dynamic validation_groups based on choice value

CatchmentAreaType.php

<?php

namespace Ormigo\Bundle\OrmigoBundle\Form\CatchmentArea\Type;

use Symfony\Component\Form\AbstractType;
use Symfony\Component\Form\FormBuilderInterface;
use Symfony\Component\Form\FormInterface;
use Symfony\Component\OptionsResolver\OptionsResolverInterface;

use Ormigo\Bundle\OrmigoBundle\Form\CatchmentArea\DataTransformer\CatchmentAreaModelTransformer;
use Ormigo\Bundle\OrmigoBundle\Form\CatchmentArea\Extension\TypeChoiceList;

class CatchmentAreaType extends AbstractType
{
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        /*
         * The validation groups are defined by the chosen type of CatchmentArea.
         *
         * We use the default validation of the respective form types.
         * The avaiable choices for the type match the names of the form types.
         *
         * Only the selected child form will be set to validate.
         */
        $validationGroups = function(FormInterface $form) {
            /* @var $data \Ormigo\Bundle\OrmigoBundle\Form\CatchmentArea\Model\CatchmentArea */
            $data = $form->getParent()->getViewData();

            if ($form->getName() === $data->type) {
                return array('Default');
            }

            return array();
        };

        $areaOptions = array(
            'validation_groups' => $validationGroups,
            'error_bubbling' => false,
        );

        $builder
            ->add('type', 'choice', array(
                'choice_list' => new TypeChoiceList(),
                'expanded' => true,
            ))
            ->add('zipcode_area', 'zipcode_area', $areaOptions)
            ->add('ambit_area', 'ambit_area', $areaOptions)
            ->add('country_area', 'country_area', $areaOptions)
        ;

        $builder->addModelTransformer(new CatchmentAreaModelTransformer());
    }

    public function setDefaultOptions(OptionsResolverInterface $resolver)
    {
        $resolver->setDefaults(array(
            'data_class' => 'Ormigo\Bundle\OrmigoBundle\Form\CatchmentArea\Model\CatchmentArea',
            'invalid_message' => 'catchment_area.invalid',
        ));
    }

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