主义实体继承

Question

I have an entity which I want to use as a base class for other entities (unknown at this time) and I need to store relationships in the base entity:

/**
 * @ORM\Entity
 * @ORM\Table(name="CMS_content")
 */
class BaseContent {
    /**
     * @ORM\ManyToOne(targetEntity="BaseContent")
     * @ORM\JoinColumn(name="parent", referencedColumnName="id", unique=false)
     */
    protected $parent;

    /**
     * @ORM\ManyToOne(targetEntity="ContentType")
     * @ORM\JoinColumn(name="content_type", referencedColumnName="id", unique=false)
     */
    protected $contentType;
    ...
};

/**
 * @ORM\Entity
 * @ORM\Table(name="CMS_whateverSpecializedContent")
 */
class WhateverSpecializedContent extends BaseContent {};

I cannot use@ORM\InheritanceType("JOINED") because I want to be able to create arbitrary number of subclasses later without touching the base class. I also need to have the base class in a separate database table so the relationship would make sense.

What other options do I have to manage these kind of structure?

Answer 1

Instead of using entity inheritance I ended up using the delegate design pattern. Both Content and BaseContent implements a common interface and the BaseContent delegate the functionality to a joined Content entity.

Now every subclass of this BaseContent will have a joined Content entity and can be used where an IContent is expected.

interface IContent {...}

/**
 * @ORM\Entity
 * @ORM\Table(name="CMS_content")
 */
class Content implements IContent {
    /**
     * @ORM\ManyToOne(targetEntity="BaseContent")
     * @ORM\JoinColumn(name="parent", referencedColumnName="id", unique=false)
     */
    protected $parent;

    /**
     * @ORM\ManyToOne(targetEntity="ContentType")
     * @ORM\JoinColumn(name="content_type", referencedColumnName="id", unique=false)
     */
    protected $contentType;
    ...
};

/**
 * @ORM\Entity
 * @ORM\Table(name="CMS_whateverSpecializedContent")
 */
class WhateverSpecializedContent extends BaseContent {};

/**
 * @ORM\MappedSuperclass
 */
abstract class BaseContent implements IContent {
    /**
     * @ORM\OneToOne(targetEntity="Content", cascade={"persist", "merge", "remove"})
     * @ORM\JoinColumn(name="content", referencedColumnName="id", unique=false)
     */
    private $content;

    public function implementedMethod() {
        $this->content->implementedMethod();
    }
};