学说：在国外复合键

Question

我有以下实体授权NULL：

/** 
* SeriesAuthorRole 
* 
* @ORM\Table() 
* @ORM\Entity(repositoryClass="Blog\Bundle\CoreBundle\Entity\SeriesAuthorRoleRepository") 
*/ 
class SeriesAuthorRole extends AuthorRoleAbstract 
{ 
    /** 
    * @var Series 
    * 
    * @ORM\ManyToOne(targetEntity="Blog\Bundle\CoreBundle\Entity\Series", inversedBy="authors") 
    * @ORM\JoinColumn(name="series", referencedColumnName="id", nullable=false) 
    * @ORM\Id 
    */ 
    private $series; 

    /** 
    * @var Author 
    * 
    * @ORM\ManyToOne(targetEntity="Blog\Bundle\CoreBundle\Entity\Author") 
    * @ORM\JoinColumn(name="author", referencedColumnName="id", nullable=false) 
    * @ORM\Id 
    */ 
    protected $author; 

    /** 
    * @var Role 
    * 
    * @todo Must be nullable 
    * 
    * @ORM\ManyToOne(targetEntity="Blog\Bundle\CoreBundle\Entity\Role") 
    * @ORM\JoinColumn(name="role", referencedColumnName="id", nullable=true) 
    * @ORM\Id 
    */ 
    protected $role; 

    // ... Getters, setters 
} 

背后的想法很简单：我们有作家，作用和一系列的实体。一个系列可以有几个不同角色的作者。同一作者可以在一个系列中实现多个角色。

有时，我们并不确切知道作者的作用。在这种情况下，NULL值将用于角色，NULL值代表“我不知道”。

我被教导不要在外国复合键中使用NULL，除非它有意义。那么它在这里有意义，我知道这可以在没有Doctrine的情况下实现。然而，现在，Symfony 2抛出该错误：

Entity of type Blog\Bundle\CoreBundle\Entity\BandAuthorRole is missing an assigned ID for field 'role'. The identifier generation strategy for this entity requires the ID field to be populated before EntityManager#persist() is called. If you want automatically generated identifiers instead you need to adjust the metadata mapping accordingly. 
500 Internal Server Error - ORMException 

那么我怎样才能授权外国复合键的NULL值？ Doctrine有没有可能？

Answer 1

你@JoinColumn注释是正确与引用到http://docs.doctrine-project.org/projects/doctrine-orm/en/latest/reference/annotations-reference.html#annref-joincolumn

然而，

Every entity with a composite key cannot use an id generator other than “ASSIGNED”. That means the ID fields have to have their values set before you call EntityManager#persist($entity).

http://docs.doctrine-project.org/en/2.0.x/tutorials/composite-primary-keys.html#general-considerations