主义级联选项为OneToMany [英] Doctrine Cascade Options for OneToMany

问题描述

我很难理解教条手册说明级联操作，需要有人帮助我了解一个简单的ManyToOne关系的选项。

在我的应用程序中，我有一个名为Article的表/实体，其外键字段引用名为Topic的表/实体中的id字段。

当我创建一个新文章时，我从下拉菜单中选择主题。这将在文章表中的'topic_id'外键字段中插入一个整数。

我在文章实体中设置了$ topic关联，如下所示：

  / ** 
 * @ManyToOne（targetEntity =Topic）
 * @JoinColumn（name =topic_id ，referencedColumnName =id，nullable = false）
 * / 
 private $ topic; 
  

主题实体没有关于文章实体的任何往复注释。主题不关心什么文章引用它们，当引用主题的文章被删除时，主题就不需要发生。

因为我没有指定级联在文章实体中的操作，当我尝试创建一个新的文章时，Doctrine会引发错误：通过未配置为级联持久化操作的关系找到一个新实体，明确地保留新的实体或在关系上配置级联持久性操作。

所以我知道我需要选择一个级联操作来包含在文章实体中，但是我该如何知道在这种情况下选择哪个操作？ >

从阅读原则手册，分离听起来像正确的选项。但是研究他人的类似问题此处和这里使我想我想使用持久而不是

任何人都可以帮助我了解坚持，删除，合并和分离的意思，就像一个简单的ManyToOne关系'描述？

解决方案

在Doctrine2文档9.6。传递持久性/级联操作几乎没有关于如何配置您的实体的示例，你坚持$ article，$ topic也会持续存在。在你的情况下，我建议主题实体注释：

  / ** 
 * @OneToMany（targetEntity = article，mappedBy =topic，cascade = {persist，remove}）
 * / 
 private $ articles; 
  

此解决方案的缺点是您必须将$ articles集合包含在主题实体中，但您可以作为@ kurt-krueckeberg所提到的，你必须在创建新文章时通过真正的主题实体，即：

  $ topic = $ em-> getRepository（'Entity\Topic'） - > find（$ id）; 
 $ article = new Article（$ topic）; 
 $ em-> persist（$ article）; 
 $ em-> flush（）; 
 
 //也许，在这种情况下，您甚至不需要配置级联操作
  

$ b $祝你好运！

I'm having a hard time making sense of the Doctrine manual's explanation of cascade operations and need someone to help me understand the options in terms of a simple ManyToOne relationship.

In my application, I have a table/entity named Article that has a foreign key field referencing the 'id' field in a table/entity named Topic.

When I create a new Article, I select the Topic from a dropdown menu. This inserts an integer into the 'topic_id' foreign key field in the Article table.

I have the $topic association set up in the Article entity like this:

/**
 * @ManyToOne(targetEntity="Topic")
 * @JoinColumn(name="topic_id", referencedColumnName="id", nullable=false)
 */
private $topic;

The Topic entity doesn't have any reciprocating annotation regarding the Article entity. Topics don't care what Articles reference them and nothing needs to happen to a Topic when an Article that references the Topic is deleted.

Because I'm not specifying the cascade operation in the Article entity, Doctrine throws an error when I try to create a new Article: "A new entity was found through a relationship that was not configured to cascade persist operations. Explicitly persist the new entity or configure cascading persist operations on the relationship."

So I know I need to choose a cascade operation to include in the Article entity, but how do I know which operation to choose in this situation?

From reading the Doctrine manual, "detach" sounds like the right option. But researching others' similar questions here and here makes me think I want to use "persist" instead.

Can anyone help me understand what "persist," "remove," "merge," and "detach" mean in terms of a simple ManyToOne relationship like the one I've described?

解决方案

In the Doctrine2 documentation "9.6. Transitive persistence / Cascade Operations" there are few examples of how you should configure your entities so that when you persist $article, the $topic would be also persisted. In your case I'd suggest this annotation for Topic entity:

/**
 * @OneToMany(targetEntity="Article", mappedBy="topic", cascade={"persist", "remove"})
 */
 private $articles;  

The drawback of this solution is that you have to include $articles collection to Topic entity, but you can leave it private without getter/setter.

And as @kurt-krueckeberg mentioned, you must pass the real Topic entity when creating new Article, i.e.:

$topic = $em->getRepository('Entity\Topic')->find($id);
$article = new Article($topic);
$em->persist($article);
$em->flush();

// perhaps, in this case you don't even need to configure cascade operations

Good luck!

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