Symfony2在FosUserBundle的RegistrationFormType中获取会话

我试图在我的RegistrationFormType中获取对象会话，但我得到了这个错误：Warning: Missing argument 2 for Meet'MembreBundle'Form'Type'RegistrationFormType::__construct()

我的注册表格类型：

namespace Meet'MembreBundle'Form'Type;
use Symfony'Component'Form'FormBuilder;
use Symfony'Component'Form'FormBuilderInterface;
use FOS'UserBundle'Form'Type'RegistrationFormType as BaseType;
    class RegistrationFormType extends BaseType
    {
        private $session;
        public function __construct($session, $class)
        {
            $this->session = $session;
            parent::__construct($class);
        }
        public function buildForm(FormBuilder $builder, array $options)
        {
            parent::buildForm($builder, $options);
            $locale = $this->session->getLocale();
            var_dump($locale);
        }
        public function getName()
        {
            return 'meet_user_registration';
        }
    }

我的配置yml

fos_user:
    db_driver: orm # other valid values are 'mongodb', 'couchdb' and 'propel'
    firewall_name: main
    # Permet de renseigner la nouvelle entity utilisateur
    user_class: Meet'MembreBundle'Entity'Membre
    registration:
        form:
            type: meet_user_registration
services:
  meet_user_registration:
    class: Meet'MembreBundle'Form'Type'RegistrationFormType
    arguments: [@session, %fos_user.model.user.class%]
    tags:
        - { name: form.type, alias: my_user_registration }