FOSUserBundle permission form

I try add field: permission to edit group. I used: Add roles field to FOSUserBundle group form [Solved]

Now I have problem with save it.

First option:

public function editAction($groupname)
    {
        $group = $this->findGroupBy('name', $groupname);
        $form= $this->container->get('fos_user.group.form'); // I can't use fos_user.group.form.factory, why?
        $formHandler = $this->container->get('fos_user.group.form.handler');

        $process = $formHandler->process($group);
        if ($process) {
            $this->setFlash('fos_user_success', 'group.flash.updated');
            $groupUrl =  $this->container->get('router')->generate('fos_user_group_show', array('groupname' => $group->getName()));

            return new RedirectResponse($groupUrl);
        }
        $form->add('roles', 'choice', array(
            'choices' => $this->getExistingRoles(),
            'data' => $group->getRoles(),
            'label' => 'Uprawnienia',
            'expanded' => true,
            'multiple' => true,
            'mapped' => true,
        ));

        return $this->container->get('templating')->renderResponse('FOSUserBundle:Group:edit.html.'.$this->getEngine(), array(
            'form'      => $form->createview(),
            'groupname'  => $group->getName(),
        ));
    }

It nice show. See groups and checkbox's. But when I want sent this form (save date) I see:

You cannot add children to a submitted form

Second option:

I deleted $form->add('roles', 'choice', array... I changed the form: GroupFormType

public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder->add('name', null, array('label' => 'form.group_name', 'translation_domain' => 'FOSUserBundle'));
        $builder->addEventListener(FormEvents::PRE_SET_DATA, function (FormEvent $event) {
            $form   = $event->getForm();
            $entity = $event->getData(); 
            if ($entity instanceof Group) {
                $form->add('roles', 'choice', array(
                    'choices' => $entity[]....,
                    'data' => $entity[]....
                    'label' => 'Permission',
                    'expanded' => true,
                    'multiple' => true,
                    'mapped' => true,
                ));
            }

        });
    }

How I can sent $event with editAction() to addEventListener?? I tried: $this->createForm($group) but symfony2 won't let me