Doctrine 分配错误：无法将 Doctrine\ORM\PersistentCollection 分配给属性

Question

我有一个上传，我想显示数据库中的所有类别，但我不断收到 EntityType 错误，我不知道为什么之前可以正常工作。

这是错误：

Cannot assign Doctrine\ORM\PersistentCollection to property App\Entity\Category::$posts  of type Doctrine\Common\Collections\ArrayCollection

<?php

declare(strict_types=1);

namespace App\Entity;

use App\Repository\CategoryRepository;
use Doctrine\Common\Collections\ArrayCollection;
use Doctrine\Common\Collections\Collection;
use Doctrine\ORM\Mapping as ORM;

/**
 * @ORM\Entity(repositoryClass=CategoryRepository::class)
 */
class Category
{
    /**
     * @ORM\Id
     * @ORM\GeneratedValue
     * @ORM\Column(type="integer")
     */
    private int $id;

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

    /**
     * @ORM\OneToMany(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 App\Form\Post;

use App\Entity\Category;
use App\Entity\Post;
use Symfony\Bridge\Doctrine\Form\Type\EntityType;
use Symfony\Component\Form\AbstractType;
use Symfony\Component\Form\Extension\Core\Type\FileType;
use Symfony\Component\Form\Extension\Core\Type\TextareaType;
use Symfony\Component\Form\Extension\Core\Type\TextType;
use Symfony\Component\Form\FormBuilderInterface;
use Symfony\Component\OptionsResolver\OptionsResolver;
use Symfony\Component\Validator\Constraints\File;
use Symfony\Component\Validator\Constraints\NotBlank;

class UploadType extends AbstractType
{
    /**
     * @param \Symfony\Component\Form\FormBuilderInterface $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 \Symfony\Component\OptionsResolver\OptionsResolver $resolver
     */
    public function configureOptions(OptionsResolver $resolver)
    {
        $resolver->setDefaults([
            'data_class' => Post::class,
        ]);
    }
}

在 Post 实体中

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

环境信息：

• Symfony 5.2.5（环境：开发，调试：true）
• PHP版本：8.0.3
• 数据库驱动程序和版本：8.0.23-0ubuntu0.20.04.1

Answer 1

经过一番挖掘，找到了答案，将 ArrayCollection 更改为 Collection 解决了我的问题

改变：

/**
 * @ORM\OneToMany(targetEntity=Post::class, mappedBy="Category_id")
 */
private \Doctrine\Common\Collections\ArrayCollection $posts;

至：

/**
 * @ORM\OneToMany(targetEntity=Post::class, mappedBy="Category_id")
 */
private \Doctrine\Common\Collections\Collection $posts;

Answer 2

问题在于类型提示（ArrayCollection => Collection）

改变：

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

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

作者：

/**
 * @ORM\OneToMany(targetEntity=Post::class, mappedBy="Category_id")
 */
private Collection $Posts;

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

Answer 3

$this->$posts[] = $posts;

看起来这一行应该是：

$this->$posts[] = $post;

Answer 4

private ArrayCollection $posts;

是对教义的直接依赖：

use Doctrine\Common\Collections\ArrayCollection;

如果你不同意，也许是因为它破坏了 SOLID “D”，请尝试使用纯 php 伪类型 Iterable (https://www.php.net/manual/en/language.types.iterable.php)，像这样：

private iterable $posts;

Answer 5

如果这可以帮助其他人，我在我的实体类中遇到了同样的问题。事实证明，由于某些原因，我的文件中缺少

Use

类的

Collection

声明。确保有这两行：

use Doctrine\Common\Collections\Collection;

使用 Doctrine\Common\Collections\ArrayCollection;