Symfony FileType：class尝试更新时不起作用

Question

嘿，我有一个问题，我要如何解决这个问题：

the form's view data is expected to be 
an instance of class Symfony\Component\HttpFoundation\File\File,
but is a(n) resource. You can avoid this error by setting the "data_class" 
option to null or by adding a view transformer that transforms a(n) 
resource to an instance of Symfony\Component\HttpFoundation\File\File.

当我尝试更新它时发生这种情况，但不适用于FileType :: class

这是我的代码：

<?php
    namespace XInteractive\Bundle\LeadsBundle\Form;


    use Symfony\Component\Form\Extension\Core\Type\FileType;
    use Symfony\Component\Form\AbstractType;
    use Symfony\Component\Form\FormBuilderInterface;
    use Symfony\Component\OptionsResolver\OptionsResolver;
    use XInteractive\Bundle\LeadsBundle\Entity\Document;

    class DocumentType extends AbstractType
    {
        public function buildForm(FormBuilderInterface $builder, array $options)
        {
            $builder
            ->add('name', null)
            ->add('file', FileType::class);

        }

        public function configureOptions(OptionsResolver $resolver)
        {
            $resolver->setDefaults([
                'data_class' => Document::class
            ]);
        }
    }

Answer 1

将data_class设置为空！

public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder
        ->add('name', null)
        ->add('file', FileType::class, array(
            'data_class' => null));
    }

Answer 2

显示您的控制者和实体的代码与此表单有什么关系

并阅读官方文档：

• How to Upload Files
• All about Uploading Files in Symfony

对我来说最好的方法：

->add('file', FileType::class, ['mapped' => false])

然后将自己的关系文件逻辑写入数据库。