namespace Prueba\PruebaBundle\Form;

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

class PruebaType extends AbstractType {

    /**
     * @param FormBuilderInterface $builder
     * @param array $options
     */
    public function buildForm(FormBuilderInterface $builder, array $options) {
        $builder
                ->add('nombre')
                ->add('apellido')
                ->add('tipoDocumento', 'entity', array(
                    'class' => 'PruebaBundle:TipoDocumento',
                    'required' => false
                ))
        ;
    }

    /**
     * @param OptionsResolverInterface $resolver
     */
    public function setDefaultOptions(OptionsResolverInterface $resolver) {
        $resolver->setDefaults(array(
            'data_class' => 'Prueba\PruebaBundle\Entity\Prueba'
        ));
    }

    /**
     * @return string
     */
    public function getName() {
        return 'prueba_pruebabundle_prueba';
    }

}

namespace Prueba\PruebaBundle\Form;

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

class TipoDocumentoType extends AbstractType
{
    /**
     * @param FormBuilderInterface $builder
     * @param array $options
     */
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder
            ->add('descripcion')
        ;
    }

    /**
     * @param OptionsResolverInterface $resolver
     */
    public function setDefaultOptions(OptionsResolverInterface $resolver)
    {
        $resolver->setDefaults(array(
            'data_class' => 'Prueba\PruebaBundle\Entity\TipoDocumento'
        ));
    }

    /**
     * @return string
     */
    public function getName()
    {
        return 'prueba_pruebabundle_tipodocumento';
    }
}

public function createAction(Request $request)
    {
        $entity = new Prueba();
        $form = $this->createCreateForm($entity);
        $form->handleRequest($request);

        if ($form->isValid()) {
            $em = $this->getDoctrine()->getManager();
            $em->persist($entity);
            $em->flush();

            return $this->redirect($this->generateUrl('prueba_show', array('id' => $entity->getId())));
        }

        return $this->render('PruebaBundle:Prueba:new.html.twig', array(
            'entity' => $entity,
            'form'   => $form->createView(),
        ));
    }