rails 4有很多通过关联查询

Question

我有这些模型，但是当我执行Message.last.people或Message.last.recipient_lists时，我收到错误。如何引用收件人列表或附加到有活动记录的邮件的人？我需要做RecipientList.where(:message => Message.last)吗？似乎应该有更好的方法通过.message来做到这一点？

class Message < ActiveRecord::Base
    has_many   :people, through: :recipient_list
end

class Person < ActiveRecord::Base
  has_many :messages, through: :recipient_list
end

class RecipientList < ActiveRecord::Base
    belongs_to :person
    belongs_to :message
end

我收到此错误

  

Message.last.recipient_lists
  消息加载（0.7ms）SELECT   ＆＃34;消息＆＃34;。* FROM＆＃34;消息＆＃34;订购消息＆＃34;消息＆＃34;。＆＃34; id＆＃34; DESC限制1   NoMethodError：未定义的方法`recipient_lists＆＃39;对

     

来自/home/nick/.rvm/gems/ruby-2.0.0-p598/gems/activemodel-4.0.9/lib/active_model/attribute_methods.rb:439:in

     

method_missing' from /home/nick/.rvm/gems/ruby-2.0.0-p598/gems/activerecord-4.0.9/lib/active_record/attribute_methods.rb:168:in 的method_missing＆＃39;来自（irb）：1来自   /home/nick/.rvm/gems/ruby-2.0.0-p598/gems/railties-4.0.9/lib/rails/commands/console.rb:90:in   start' from /home/nick/.rvm/gems/ruby-2.0.0-p598/gems/railties-4.0.9/lib/rails/commands/console.rb:9:in 开始＆＃39;从   /home/nick/.rvm/gems/ruby-2.0.0-p598/gems/railties-4.0.9/lib/rails/commands.rb:62:in   <top (required)>' from bin/rails:4:in需要＆＃39;来自bin / rails：4：in   `＆＃39;

     

Message.last.people消息加载（1.0ms）SELECT＆＃34;消息＆＃34;。* FROM   ＆＃34;消息＆＃34;订购消息＆＃34;消息＆＃34;。＆＃34; id＆＃34; DESC限制1   ActiveRecord :: HasManyThroughAssociationNotFoundError：找不到   关联：模型消息中的recipient_list

Answer 1

您需要在Message和Person中明确包含has_many :recipient_lists，并在:recipient_lists选项中正确复制through:，如下所示：

class Message < ActiveRecord::Base
  has_many :recipient_lists
  has_many :people, through: :recipient_lists
end

class Person < ActiveRecord::Base
  has_many :recipient_lists
  has_many :messages, through: :recipient_lists
end

class RecipientList < ActiveRecord::Base
  belongs_to :person
  belongs_to :message
end