我有一个上传文件，我想从那里显示数据库中的所有类别，但我一直收到 EntityType 错误，我不知道之前为什么工作。

这是错误： Cannot assign DoctrineORMPersistentCollection to property AppEntityCategory::$posts of type DoctrineCommonCollectionsArrayCollection

<?php

declare(strict_types=1);

namespace AppEntity;

use AppRepositoryCategoryRepository;
use DoctrineCommonCollectionsArrayCollection;
use DoctrineCommonCollectionsCollection;
use DoctrineORMMapping as ORM;

/**
 * @ORMEntity(repositoryClass=CategoryRepository::class)
 */
class Category
{
    /**
     * @ORMId
     * @ORMGeneratedValue
     * @ORMColumn(type="integer")
     */
    private int $id;

    /**
     * @ORMColumn(type="string", length=255)
     */
    private string $name;

    /**
     * @ORMOneToMany(targetEntity=Post::class, mappedBy="Category_id")
     */
    private ArrayCollection $Posts;

    public function __construct()
    {
        $this->posts = new ArrayCollection();
    }

    public function getId(): ?int
    {
        return $this->id;
    }

    public function getName(): ?string
    {
        return $this->name;
    }

    public function setName(string $name): self
    {
        $this->name = $name;

        return $this;
    }

    /**
     * @return Collection|Post[]
     */
    public function gePosts(): Collection
    {
        return $this->posts;
    }

    public function addPost(Post $post): self
    {
        if (!$this->posts->contains($post)) {
            $this->$posts[] = $posts;
            $post->setCategoryId($this);
        }

        return $this;
    }

    public function removePost(Post $post): self
    {
        if ($this->posts->removeElement($post)) {
            // set the owning side to null (unless already changed)
            if ($post->getCategoryId() === $this) {
                $post->setCategoryId(null);
            }
        }

        return $this;
    }
    public function __toString(): string
    {
        return (string) $this->getName();
    }
}

我收到错误的上传表单

<?php

declare(strict_types=1);

namespace AppFormPost;

use AppEntityCategory;
use AppEntityPost;
use SymfonyBridgeDoctrineFormTypeEntityType;
use SymfonyComponentFormAbstractType;
use SymfonyComponentFormExtensionCoreTypeFileType;
use SymfonyComponentFormExtensionCoreTypeTextareaType;
use SymfonyComponentFormExtensionCoreTypeTextType;
use SymfonyComponentFormFormBuilderInterface;
use SymfonyComponentOptionsResolverOptionsResolver;
use SymfonyComponentValidatorConstraintsFile;
use SymfonyComponentValidatorConstraintsNotBlank;

class UploadType extends AbstractType
{
    /**
     * @param SymfonyComponentFormFormBuilderInterface $builder
     * @param array                                        $options
     */
    public function buildForm(FormBuilderInterface $builder, array $options)
    {
        $builder
            ->add('title', TextType::class, [
                
                'constraints' => [
                    new NotBlank([
                        'message' => 'Please enter a valid Title. '
                    ])
                ]
            ])
            ->add('category', EntityType::class, [
                'mapped' => false,
                'class' => Category::class,
                'choice_label' => 'name',
                'expanded' => true
            ])
            ->add('poster', FileType::class, [
                'required' => false,
                'constraints' => [
                    new File([
                        'maxSize' => '6000K',
                        'mimeTypes' => [
                            'image/x-png',
                            'image/jpeg',
                        ],
                        'mimeTypesMessage' => 'Please upload a image file.'
                    ])
                ]
            ])
            ->add('description', TextareaType::class, [
                'constraints' => [
                    new NotBlank([
                        'message' => 'Please enter a valid Title. '
                    ])
                ]
            ])
            ->add('mediainfo', TextareaType::class, [
                'required' => false,
            ]);
    }
    
    /**
     * @param SymfonyComponentOptionsResolverOptionsResolver $resolver
     */
    public function configureOptions(OptionsResolver $resolver)
    {
        $resolver->setDefaults([
            'data_class' => Post::class,
        ]);
    }
}

在 Post 实体中

   /**
     * @ORMManyToOne(targetEntity=Category::class, inversedBy="posts")
     */
    private Category $Category_id;

环境信息：

• Symfony 5.2.5 (env: dev, debug: true)
• PHP 版本：8.0.3
• 数据库驱动和版本：8.0.23-0ubuntu0.20.04.1

回答

change:
     /**
         * @ORMOneToMany(targetEntity=Post::class, mappedBy="Category_id")
         */
        private DoctrineCommonCollectionsArrayCollection $posts;

to: 
 /**
         * @ORMOneToMany(targetEntity=Post::class, mappedBy="Category_id")
         */
        private DoctrineCommonCollectionsCollection $posts;