我怎样才能使原则2忽略通过关系发现的新实体? - How can I make Doctrine 2 ignore new entities found through relationships?

How can I make Doctrine 2 ignore new entities found through relationships?

例如，我有以下两个类(为简洁起见省略了getter/setter)，它们在映射中是双向链接的:

class Form
{
    private $elements = array();
    public function addElement($element)
    {
        $this->elements[] = $element
        $element->setForm($this);
    }
}
class Element
{
    private $form;
    private $name;
}
<one-to-many field="elements" target-entity="Element" mapped-by="form"/>
<many-to-one field="form" target-entity="Form" inversed-by="elements">
    <join-column name="formId" referenced-column-name="id" on-delete="CASCADE" on-update="CASCADE"/>
</many-to-one>

如果我执行以下操作;向表单添加两个元素，但只持久化一个元素，我希望发生的是实体管理器完全忽略未持久化的元素，但将另一个元素和表单插入到数据库中:

$form = new Form;
$em->persist($form);
$element = new Element;
$element->setName('firstName');
$form->addElement($element);
$em->persist($element);
$element2 = new Element;
$element2->setName('lastName');
$form->addElement($element2);
$em->flush();

目前得到以下错误:

exception 'Doctrine'ORM'ORMInvalidArgumentException' with message 'A new entity was found through the relationship 'Form#elements' that was not configured to cascade persist operations for entity Element@0000000019217f52000000009c20d747. To solve this issue: Either explicitly call EntityManager#persist() on this unknown entity or configure cascade persist this association in the mapping for example @ManyToOne(..,cascade={"persist"}). If you cannot find out which entity causes the problem implement 'Element#__toString()' to get a clue

据我所知，没有级联选项来忽略新实体(http://docs.doctrine-project.org/projects/doctrine-orm/en/latest/reference/working-with-associations.html#transitive-persistence-cascade-operations)，并且使用preUpdate生命周期回调从$elements数组中删除违规实体也不起作用，因为在回调运行之前抛出异常。

有什么办法吗?

尝试只刷新需要的实体:

$form = new Form;
$em->persist($form);
$em->flush($form);
$element = new Element;
$element->setName('firstName');
$form->addElement($element);
$em->persist($element);
$em->flush($element);
//ignored element
$element2 = new Element;
$element2->setName('lastName');
$form->addElement($element2);

因为这是我能找到的唯一与这个问题相关的页面，所以我将添加我自己想到的解决方案。(在我的项目中，它基本上也是一个带有答案的表单，在那里我手动保存已更新的答案，但不完整的答案不应该在持久化表单时保存到数据库。)

基本上，您为关系创建了两个属性:一个仅用于加载持久化的相关元素($subEntities)，另一个将向公众提供($chachedSubEntities)。

这个$cachedSubEntities成员将在你第一次调用getSubEntities时被持久化的子实体初始化。

class MyEntity extends AbstractEntity
{
    /**
     * @ORM'OneToMany(targetEntity="SubEntity", mappedBy="parent", indexBy="id")
     */
    protected $subEntities;
    
    protected $cachedSubEntities;
    public function __construct()
    {
        $this->subEntities = new ArrayCollection();
    }
    
    public function getSubEntities()
    {
        if (is_null($this->cachedSubEntities)) {
            $this->cachedSubEntities = new ArrayCollection($this->subEntities->toArray());
        }
        return $this->cachedSubEntities;
    }
}