Rails: :source => 之间的区别??和 :class_name =>??在模型中 [英] Rails: difference between :source => ?? and :class_name => ?? in models

问题描述

您好，对于更复杂的模型，我无法确定何时使用 :source 以及何时使用 :class.

Hi I'm having trouble conceptualizing when to use :source and when to use :class for my more complex models.

这里我有一个用户和朋友的例子.

Here I have an example of users with friends.

class User < ActiveRecord::Base
  ...
  has_many :friendships, :dependent => :destroy
  has_many :friends, :through => :friendships, :conditions => "status = 'accepted'"
  has_many :requested_friends, :through => :friendships, :source => :friend, :conditions => "status = 'requested'", :order => :created_at
  has_many :pending_friends, :through => :friendships, :source => :friend, :conditions => "status = 'pending'", :order => :created_at
end


class Friendship < ActiveRecord::Base
  attr_accessible :friend_id, :user_id, :status

  belongs_to :user
  belongs_to :friend, :class_name => "User", :foreign_key => 'friend_id'
end

有人能解释一下为什么 Friendship 是 :class_name 而不是 :source 吗?这是因为那只是配对(has_many + :source ，belongs_to + :class_name)?

Can someone explain why for Friendship it's :class_name instead of :source? Is this because that's just the pairing (has_many + :source , belongs_to + :class_name)?

推荐答案

它们在概念上是相同的，只是针对不同的用途而有所不同.

They are conceptually the same, just need to be different for different uses.

:source 用于(可选)在您使用 has_many through 时定义关联的模型名称；:class_name 用于(可选)在一个简单的 has many 关系中.仅当 Rails 无法自行找出类名时才需要两者.请参阅此处 API 中 has_many 的文档.

:source is used (optionally) to define the associated model name when you're using has_many through; :class_name is used (optionally) in a simple has many relationship. Both are needed only if Rails cannot figure out the class name on its own. See the documentation for has_many in the API here.

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