Form submission problems - symfony

Question

I want to create new user and give him a role from combo box but it doesn't work here is what have I done so far:
ROLE FORM
class RoleType extends AbstractType
{
/**
* #param FormBuilderInterface $builder
* #param array $options
*/
public function buildForm(FormBuilderInterface $builder, array $options)
{
$builder
->add('role','entity',array(
'class' => 'vendor\Bundle\Entity\Role',
'property'=>'role'
))
;
}
USER FORM
class UserType extends AbstractType
{
/**
* #param FormBuilderInterface $builder
* #param array $options
*/
public function buildForm(FormBuilderInterface $builder, array $options)
{
$builder
->add('username')
->add('password')
->add('email')
->add('firstname')
->add('lastname')
->add('role',new RoleType())
;
}
But I can't save my user to database I get this error
An exception occurred while executing 'UPDATE Roles SET role = ? WHERE role_id = ?' with params [{}, 1]:
CONTROLLER
private function createEditForm(User $entity)
{
$form = $this->createForm(new UserType(), $entity, array(
'action' => $this->generateUrl('user_update', array('id' => $entity->getId())),
'method' => 'PUT',
));
$form->add('submit', 'submit', array('label' => 'Update'));
return $form;
}
/**
* Edits an existing User entity.
*
*/
public function updateAction(Request $request, $id)
{
$em = $this->getDoctrine()->getManager();
$entity = $em->getRepository('myBundle:User')->find($id);
if (!$entity) {
throw $this->createNotFoundException('Unable to find User entity.');
}
$deleteForm = $this->createDeleteForm($id);
$editForm = $this->createEditForm($entity);
$editForm->handleRequest($request);
if ($editForm->isValid()) {
$em->flush();
return $this->redirect($this->generateUrl('user_edit', array('id' => $id)));
}
return $this->render('myBundle:User:edit.html.twig', array(
'entity' => $entity,
'edit_form' => $editForm->createView(),
'delete_form' => $deleteForm->createView(),
));
}

Answer 1

Why don't you just define the role field inside the UserType builder?
class UserType extends AbstractType
{
/**
* #param FormBuilderInterface $builder
* #param array $options
*/
public function buildForm(FormBuilderInterface $builder, array $options)
{
$builder
->add('username')
->add('password')
->add('email')
->add('firstname')
->add('lastname')
->add('role','entity',array(
'class' => 'vendor\Bundle\Entity\Role',
'property'=>'role'
))
;
}