如何在呈现主窗体之前向嵌入对象添加值

Question

我有3个实体。 “挑战”/“团队”/“用户” 我正在尝试向嵌入式表单添加值，如下所示：

class ChallengeController extends Controller
{    
    public function newAction($id, Request $request)
    {
        // 1. Get known users
        $user = $this->container->get('security.context')->getToken()->getUser();
        $challengedUser = $this->getDoctrine()->getRepository('ApplicationSonataUserBundle:User')->find($id);

        // 2. Create new team
        $team = new Team();
        $teamOpponent = new Team();

        // 3. Add known players to corresponding teams
        $team->addUser($user);
        $teamOpponent->addUser($challengedUser);

        // 4. Create new challenge and add teams
        $challenge = new Challenge();
        $challenge->addTeam($team);
        $challenge->addTeam($teamOpponent);

        // 5. Create new form 
        $form = $this->createForm(new ChallengeType(), $challenge);

        return $this->render('TennisconnectDashboardBundle:Challenge:new.html.twig', array('form' => $form->createView(), 'challengedUser' => $challengedUser));
    }
}

//编辑：添加了challengeType

class ChallengeType extends AbstractType
{
    public function buildForm(FormBuilder $builder, array $options)
    {
        $builder
            ->add('teams', 'collection', array(
                'type' => new TeamType(),
                'allow_add' => true
            ))
            ->add('place')
            ->add('date');
    }

    public function getName()
    {
        return 'challenge';
    }

    public function getDefaultOptions(array $options)
    {
        return array('data_class' => 'Tennisconnect\DashboardBundle\Entity\Challenge');
    }
}

当提出挑战表格时，我会期望填写2名球员的价值。但他们只是空白。我做错了什么？

THX。