如何创建这个`through``协会？

Question

Organization和Link通过Node关联。

Organization：

has_many :nodes
has_many :links, through: :nodes, source: :where_first_links

Node：

belongs_to :organization
has_many :where_first_links, class_name:  "Link",
                             foreign_key: "first_node_id"
has_many :where_second_links, class_name:  "Link",
                              foreign_key: "second_node_id"

Link：

belongs_to :first_node,  class_name: "Node"
belongs_to :second_node, class_name: "Node"

问题：如何将Link与Organization关联？我尝试了以下这一行，但这似乎不起作用（ArgumentError: Unknown key: :through.）：

belongs_to :organization, 
           through: :first_node, 
           source: :where_first_links, 
           inverse_of: :links

Answer 1

belongs_to association not not key by key

你应该使用has_one association

has_one :first_node_organization, 
        through: :first_node, 
        class_name: 'Organization', 
        source: :organization

Answer 2

使用has_one代替belongs_to。

class Link < ActiveRecord::Base
  belongs_to :first_node,  class_name: "Node"
  belongs_to :second_node, class_name: "Node"

  has_one :organization, through: :first_node
end