code: public function updateAction($id)
      {
          $em = $this->getDoctrine()->getEntityManager();
  
          $group = $em->getRepository('Orkestra\Bundle\ApplicationBundle\Entity\Group')->find($id);
  
          if (!$group) {
              throw $this->createNotFoundException('Unable to locate Group');
          }
  
          $form = $this->createForm(GroupType::class, $group);
  
          $form->bindRequest($this->getRequest());
  
          if ($form->isValid()) {
              $em->persist($group);
              $em->flush();
  
              $this->get('session')->getFlashBag()->set('success', 'Your changes have been saved.');
  
              return $this->redirect($this->generateUrl('orkestra_group_show', array('id' => $id)));
          }
  
          return array(
              'group' => $group,
              'form' => $form->createView(),
          );
      }
docs: Edits an existing Group entity.
  
  @Route("/{id}/update", name="orkestra_group_update")
  @Method("post")
  @Template("OrkestraApplicationBundle:Group:edit.html.twig")
  @Secure(roles="ROLE_GROUP_WRITE")