protected function appendScopeChoices(FormBuilderInterface $builder, 
            Role $role, Center $center, User $user,
            AuthorizationHelper $authorizationHelper, 
            TranslatableStringHelper $translatableStringHelper,
            ObjectManager $om, $name = 'scope')
    {
        $reachableScopes = $authorizationHelper
              ->getReachableScopes($user, $role, $center);
        
        $choices = array();
        foreach($reachableScopes as $scope) {
            $choices[$scope->getId()] = $translatableStringHelper
                  ->localize($scope->getName());
        }
        
        $dataTransformer = new ScopeTransformer($om);
        
        $builder->addEventListener(FormEvents::PRE_SET_DATA, 
                function (FormEvent $event) use ($choices, $name, $dataTransformer, $builder) {
                    $form = $event->getForm();
                    $form->add(
                            $builder
                            ->create($name, 'choice', array(
                                'choices' => $choices,
                                'auto_initialize' => false
                                )
                            )
                            ->addModelTransformer($dataTransformer)
                            ->getForm()
                    );
                });
    }