symfony3:为具有多对一关系的列的实体创建表单

我有一个"任务"表,引用一个"Estados"表,其中包含从Tasks.taskestado列到Estados.estado的外键.

这是任务的相关XML映射:

  

...

  
    
  

...

而对于Estados:

  


  
    
  

...

鉴于此,我正在尝试创建一个动作(novaAction())来创建任务.这是Controller代码:

public function novaAction(Request $request)
{
    $task = new Tasks();
    $em = $this->getDoctrine()->getManager();

    dump($task);
    #$task->setTaskEstado(new Estados());
    $form = $this->createForm(TasksType::class, $task);
    $form->handleRequest($request);

    if ($form->isSubmitted()) {
        if ($form->isValid()) {
            // Criar a tarefa na BD
            $em->persist($form->getData());
            $em->flush();
            $this->addFlash('notice', 'app.nova_tarefa.mensagem_sucesso');

            return $this->redirectToRoute('nova_tarefa');
        }

        $this->addFlash('error', 'app.nova_tarefa.mensagem_erro');
    }

以及相关的TasksType代码:

class TasksType extends AbstractType
{

public function buildForm(FormBuilderInterface $builder, array $options)
{
    $builder
        ->add('taskid', HiddenType::class)
        ...
        #->add('taskestado')
        ->add('taskestado', EntityType::class, [ 'class' => 'AppBundle:Estados' ])
        ...
}

/**
 * @param OptionsResolver $resolver
 */
public function configureOptions(OptionsResolver $resolver)
{
    $resolver->setDefaults(array(
        'data_class' => 'AppBundle\Entity\Tasks',
        #'empty_data' => function (\Symfony\Component\Form\FormInterface $form) {
        #    #return new Tasks($form->get('tasks')->getData());
        #    return new Tasks();
        #},
    ));
}
}

'empty_data'选项是尝试创建表单而不向其传递任务实例.另外,当我使用注释代码添加taskestado时,我也有相同的结果,即没有参数.

这是相关的任务实体:

namespace AppBundle\Entity;

use Doctrine\Common\Collections\ArrayCollection;

/**
 * Tasks
 */
class Tasks
{
    /**
     * @var integer
     */
    protected $taskid;

    /**
     * @var \AppBundle\Entity\Estados
     */
    protected $taskestado;

    ...

    /**
     * Get taskid
     *
     * @return integer
     */
    public function getTaskid()
    {
        return $this->taskid;
    }

    /**
     * Set taskestado
     *
     * @param \AppBundle\Entity\Estados $taskestado
     *
     * @return Tasks
     */
    public function setTaskestado(\AppBundle\Entity\Estados $taskestado = null)
    {
        $this->taskestado = $taskestado;

        return $this;
    }

    /**
     * Get taskestado
     *
     * @return \AppBundle\Entity\Estados
     */
    public function getTaskestado()
    {
        return $this->taskestado;
    }

    ...
}

当我打开页面时,出现以下错误:

必须管理传递到选择字段的实体.也许坚持他们在实体经理？

我还生成了CRUD(bin/console doctrine:generate:crud --filter=Tasks),以便我可以检查它是如何完成的,但代码是相似的,以及结果(在某些日期时间列的TasksType中修复了一些问题之后).

我究竟做错了什么？