没有外键的 ActiveRecord 关联

发布于 2024-09-29 02:17:28 字数 723 浏览 2 评论 0原文

我正在尝试建立用户之间的关系模型。用户可以发起关系，或者从另一个用户接收关系。因此，数据库中的关系表具有外键“initiator_id”和“recipient_id”。
现在，我可以使用以下关联来计算用户发起或接收的关系：

has_many :initiated_relations, :foreign_key => :initiator_id, :class_name => 'Relation', :dependent => :destroy
has_many :received_relations,  :foreign_key => :recipient_id, :class_name => 'Relation', :dependent => :destroy

我想做的是建立一个关联，该关联将获取属于用户的所有关系（发起或接收）。尝试以下方法不起作用，并抱怨缺少“user_id”字段：

has_many :relations, :conditions => 'recipient_id = #{id} or initiator_id = #{id}'

How can I create an Association that is only based on the criteria field, without waiting for the defaultforeign_key?或者是否有一种完全不同的方法来解决这个问题？

原文

I am trying to build a relationship model between users. A user can either initiate a relation, or receive a relation from another user. Therefore, the relations table in the db has the foreign keys "initiator_id" and "recipient_id".
Now, I can figure what relations the user initiated or received using the following associations:

has_many :initiated_relations, :foreign_key => :initiator_id, :class_name => 'Relation', :dependent => :destroy
has_many :received_relations,  :foreign_key => :recipient_id, :class_name => 'Relation', :dependent => :destroy

What I am trying to do, is build an association that will fetch me all relations that belong to a user (either initiated or received). Trying the following does not work, and complains about the lack of "user_id" field:

has_many :relations, :conditions => 'recipient_id = #{id} or initiator_id = #{id}'

How can I create an association that is solely based on the conditions field, without looking for the default foreign_key? Or is there perhaps a completely different approach to solving this?

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染火枫林 2024-10-06 02:17:28

从你的评论到@neutrino的回答我明白，你只需要这个“关系”来进行只读操作。如果您使用 Rails 3，您可以利用它使用延迟获取的事实。 where() 方法返回 ActiveRecord::Relation 对象，您可以稍后修改该对象。所以你可以定义一个这样的方法：

def User < ActiveRecord::Base
  def all_relations
    Relation.where("initiator_id => ? OR recipient_id = ?", id, id)
  end
end

然后你可以这样做：

User.all_relations.where(:confirmed => true).all

From your comments to @neutrino's answer I understand, that you only need this "relation" for read only operations. If you're on Rails 3 you can utilize the fact, that it uses lazy fetching. The where() method returns ActiveRecord::Relation object, which you can later modify. So you can define a method like this:

def User < ActiveRecord::Base
  def all_relations
    Relation.where("initiator_id => ? OR recipient_id = ?", id, id)
  end
end

And then you can do:

User.all_relations.where(:confirmed => true).all

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辞别 2024-10-06 02:17:28

好吧，我可以考虑使用 finder_sql 来实现这一点：

has_many :relations, :finder_sql => 'select * from relations right outer join users
    on relations.recipient_id = #{id} or relations.initiator_id = #{id}'

除此之外，您可以编写一个方法来返回两个关系关联的统一数组，但您将失去关联的优势接口（唷）。

也许有人会想出更好的解决方案。

Well, I can think of using finder_sql for that:

has_many :relations, :finder_sql => 'select * from relations right outer join users
    on relations.recipient_id = #{id} or relations.initiator_id = #{id}'

Apart from that, you can just write a method that will return a united array of the two relations associations', but you will lose the advantage of an association interface (phew).

Perhaps someone will come up with a better solution.

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