摧毁自我参照关联双方的最佳方法是什么？

发布于 2024-10-11 05:25:49 字数 501 浏览 5 评论 0原文

在我的项目中，我有一个自我参照关联。

我有一个用户模型：

class User < ActiveRecord::Base
  has_many :relationships, :dependent => :destroy
  has_many :peers, :through => :relationships
end

和一个关系模型：

class Relationship < ActiveRecord::Base
  belongs_to :user
  belongs_to :peer, :class_name => "User"
end

当两个用户彼此对等时，数据库中显然有两条记录。

当一个用户选择结束关系时，我希望这会销毁两条记录 - 而不仅仅是关系的一侧。

有没有更好的方法来执行此操作，而不是在控制器中加载关系两次（关系的每一方一次）？

原文

In my project, I have a self-referential association.

I have a User model:

class User < ActiveRecord::Base
  has_many :relationships, :dependent => :destroy
  has_many :peers, :through => :relationships
end

And a Relationship model:

class Relationship < ActiveRecord::Base
  belongs_to :user
  belongs_to :peer, :class_name => "User"
end

When two users are peers with one another, there are obviously two records in the database.

When one user opts to end a relationship, I'd like this to destroy both records - not just one side of the relationship.

Is there a better way to go about doing this rather than loading the relationship twice in the controller (once for each side of the relationship)?

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只等公子 2024-10-18 05:25:49

有几种方法可以做到这一点

首先是删除后触发器，如果您相信数据库不可知论的错误承诺，这是一种非常有争议的做事方式，但本质上是一种有效的方式，您查看 old.peer_id 和 old.user_id，然后执行删除但反转角色。如果您想走这条路，您应该查阅数据库手册以了解如何实现触发器。

第二种方法是 after_destroy callback ，您可以在其中执行

after_destroy do |record| 
  other = Relationship.find_by_user_id_and_peer_id(record.peer_id, record.user_id)
  other.destroy if other
end

另一个 - 可能更激烈的措施是重新设计模型，以便它有一个布尔接受字段，其中双方由于关系的一部分由数据库中的一条记录建模，因此对 (peer_id, user_id) = (user_id, peer_id) 的记录存在约束。这样您就不必担心删除两侧，也不必担心重复记录。

Couple of ways this can be done

Firstly is an after delete trigger, this is a pretty controversial way of doing things if you believe in the false promise of database agnosticism, however is one that works - in essence, you look at old.peer_id and old.user_id and then do a delete but reversing the roles. If you want to go down this route, you should consult your database manual as how to implement a trigger.

The second way is an after_destroy callback where you do a

after_destroy do |record| 
  other = Relationship.find_by_user_id_and_peer_id(record.peer_id, record.user_id)
  other.destroy if other
end

The other - and probably more drastic measure is to rework the model, so that it has a boolean accepted field wherein both sides of the relationship are modelled by one record in the database, there is a constraint on records where (peer_id, user_id) = (user_id, peer_id). That way you wont have to worry about deleting both sides, nor having duplicate records.

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