modifica entity manager

AutocompleteType.php

<?php

namespace PUGX\AutocompleterBundle\Form\Type;

use Doctrine\Common\Persistence\ManagerRegistry;
use Doctrine\Common\Persistence\ObjectManager;
use PUGX\AutocompleterBundle\Form\Transformer\ObjectToIdTransformer;
use Symfony\Component\Form\AbstractType;
use Symfony\Component\Form\Exception\InvalidConfigurationException;
use Symfony\Component\Form\FormBuilderInterface;
use Symfony\Component\OptionsResolver\OptionsResolverInterface;

class AutocompleteType extends AbstractType
{
    private $managerRegistry;

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

    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        if (empty($options['class'])) {
            throw new InvalidConfigurationException('Option "class" must be set.');
        }
        $entityManager = $this->managerRegistry->getManagerForClass($options['class']);
        $transformer = new ObjectToIdTransformer($entityManager, $options['class']);
        $builder->addModelTransformer($transformer);
    }

    public function setDefaultOptions(OptionsResolverInterface $resolver)
    {
        $resolver->setDefaults(array(
            'class'           => '',
            'invalid_message' => 'The selected item does not exist',
        ));
    }

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

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