php – Symfony doctrine repository(findOneBy)结果不是对象

我有一个简单的表单,并在最终创建表单的请求中发送参数.

/**
 * Displays a form to create a new Comment entity.
 *
 * @Route("/saveComment/",name="comment_new")
 * @Method("POST")
 * @Template()
 */
public function newAction(Request $request)
{
    $entity = new Comment();
    $form  = $this->createCreateForm($entity,$request);

    return array(
        'entity' => $entity,'form'   => $form->createView(),);
}

现在我得到我的参数并尝试在学说中找到对象.

/**
 * Creates a form to create a Comment entity.
 *
 * @param Comment $entity The entity
 *
 * @return SymfonyComponentFormForm The form
 */
private function createCreateForm(Comment $entity,Request $request)
{
    $em = $this->getDoctrine()->getManager();

    $commentForUserRequest = $request->request->get('commentForUser');
    $commentForUser = $em->getRepository('ApplicationSonataUserBundle:User')->findOneBy(array('username' => $commentForUserRequest ));

    $auctionRequest = $request->request->getInt('auction');

    $auction = $em->getRepository('AppBundle:Auction')->find(1);  // **ALL FINE**
    $auction = $em->getRepository('AppBundle:Auction')->find($auctionRequest); //**PROBLEM**

    $auction->addComment($entity);
    $entity->setAuction($auction);

    $form = $this->createForm(new CommentType(),$entity,array(
                'action' => $this->generateUrl('comment_create'),'method' => 'POST',));
}

当我给出一个数字而不是我的请求参数时,一切正常.
仅针对第二种情况发生以下错误消息：

Error: Call to a member function addComment() on a non-object

我不明白我做错了什么.

编辑：

并且comment_create

/**
 * Creates a new Comment entity.
 *
 * @Route("/comment/",name="comment_create")
 * @Method("POST")
 * @Template("AppBundle:Comment:new.html.twig")
 */
public function createAction(Request $request)
{

    $entity = new Comment();

    $form = $this->createCreateForm($entity,$request);
    $form->handleRequest($request);

    if ($form->isValid()) {
        $em = $this->getDoctrine()->getManager();
        $em->persist($entity);
        $em->flush();

        return $this->redirect($this->generateUrl('comment_show',array('id' => $entity->getId())));
    }

    return array(
        'entity' => $entity,);
}