Question

I have the following database setup:

Tag (Integer id)
ItemTag (Integer id, Integer tag_id, Integer item_id, Integer item_type)
Artwork (Integer id)
Photo (Integer id)

I tried using the item_id field in ItemTag for both the Artwork id and Photo id like below

class ItemTag {
/**
 * @Id @GeneratedValue
 * @Column(type="integer")
 */
private $id;

/**
 * @Column(type="integer")
 */
private $item_type;

/**
 * @ManyToOne(targetEntity="Artwork")
 * @JoinColumn(name="item_id", referencedColumnName="id")
 */
private $artwork;

/**
 * @ManyToOne(targetEntity="Photo")
 * @JoinColumn(name="item_id", referencedColumnName="id")
 */
private $photo;

/**
 * @ManyToOne(targetEntity="Tag")
 */
private $tag;
}

The setup above does not produce any errors and works fine when I try to save a “photo item”, however when saving an “artwork item” the item_id is NULL.

Is there a way to be able to save both relations into a single item_id field?

Answer 1

Yes, you can use inheritance.

You can define an abstract class “Item” and have both Photo and Artwork extend it.

http://www.doctrine-project.org/docs/orm/2.0/en/reference/inheritance-mapping.html

This requires you to change your schema slightly though.