在同一页面上发布/重定向/获取之后的 symfony 表单渲染异常

这段代码工作得很好：

use Symfony'Bundle'FrameworkBundle'Controller'Controller;
use Symfony'Component'HttpFoundation'Request;
use Symfony'Component'HttpKernel'Exception'NotFoundHttpException;
abstract class TableManagerController extends Controller
{
    public function listAndAddAction(Request $request)
    {
        // We get the Entity Manager
        $entityManager = $this->getDoctrine()->getManager();
        // We get the entity repository
        $repository = $entityManager->getRepository($this->entityRepository);
        // We build the new form through Form Factory service
        $form = $this->get('form.factory')->create($this->entityFormObject, $this->entityObject);
        // If user sent the form and sent data is valid
        if ($form->handleRequest($request)->isValid())
        {
            // We set the position of the new entity to the higher existing one + 1
            $newPosition = $repository->higherPosition() + 1;
            $this->entityObject->setPosition($newPosition);
            // We insert the data in DB
            $entityManager->persist($this->entityObject);
            $entityManager->flush();
            // We redirect user to the defined homepage
            return $this->redirect($this->generateUrl($this->routeHomePage));
        }
        return $this->render($this->renderIndexTemplate, array(
            'dataList' => $repository->listAll(),
            'form' => $form->createView()
        ));
    }
}

但是当我把它分成 3 种方法时，就像这样：

use Symfony'Bundle'FrameworkBundle'Controller'Controller;
use Symfony'Component'HttpFoundation'Request;
use Symfony'Component'HttpKernel'Exception'NotFoundHttpException;
abstract class TableManagerController extends Controller
{
    public function listAndAddAction(Request $request)
    {
        $dataList = $this->listMethod();
        $form = $this->addMethod($request);
        return $this->render($this->renderIndexTemplate, array(
            'dataList' => $dataList,
            'form' => $form
        ));
    }
    protected function listMethod()
    {
        // We get the Entity Manager
        $entityManager = $this->getDoctrine()->getManager();
        // We get the entity repository
        $repository = $entityManager->getRepository($this->entityRepository);
        // We generate the entity management homepage view (list + add form)
        return $repository->listAll();
    }
    protected function addMethod(Request $request)
    {
        // We get the Entity Manager
        $entityManager = $this->getDoctrine()->getManager();
        // We get the entity repository
        $repository = $entityManager->getRepository($this->entityRepository);
        // We build the new form through Form Factory service
        $form = $this->get('form.factory')->create($this->entityFormObject, $this->entityObject);
        // If user sent the form and sent data is valid
        if ($form->handleRequest($request)->isValid())
        {
            // We set the position of the new entity to the higher existing one + 1
            $newPosition = $repository->higherPosition() + 1;
            $this->entityObject->setPosition($newPosition);
            // We insert the data in DB
            $entityManager->persist($this->entityObject);
            $entityManager->flush();
            // We redirect user to the defined homepage
            return $this->redirect($this->generateUrl($this->routeHomePage));
        }
        // We return the generated form
        return $form->createView();
    }
}

我发送了表格，就会出现此错误：

An exception has been thrown during the rendering of a template ("Catchable Fatal Error: Argument 1 passed to Symfony'Component'Form'FormRenderer::renderBlock() must be an instance of Symfony'Component'Form'FormView, instance of Symfony'Component'HttpFoundation'RedirectResponse given, called in D:'Websites'CPG-2015'app'cache'dev'twig'd6'80'0e5eee6c7aa1859cedb4cd0cc7317a0ebbdd61af7e80f217ce1d2cf86771.php on line 61 and defined in D:'Websites'CPG-2015'vendor'symfony'symfony'src'Symfony'Component'Form'FormRenderer.php line 106") in IBCPGAdministrationBundle:CourseLevel:index.html.twig at line 19.

我知道表格有问题。但我真的不明白为什么，因为从同一角度来看，同样的表格在我发送之前看起来非常好。