ruby-on-rails - 检查关系是否存在 has_one mongoid

Question

class Question
  include Mongoid::Document
  include Mongoid::Timestamps

  field :title, :type => String

  has_one :response
end

class Response
  include Mongoid::Document
  include Mongoid::Timestamps

  field :content, :type => String

  belongs_to :question

end

控制台:

1.9.3p448 :014 > Question.where(:response => nil).size
 => 3 
1.9.3p448 :016 > Question.where(:response.ne => nil).size
 => 0 

然而，所有问题都有一个创建并关联的response!

谢谢!

Answer 1

ID 字段仅存储在子对象中，因此 Question 不知道它的 Response(没有 response_id 字段)。

你可以这样实现目标:

Response.ne(question_id: nil).map(&:question)

或者，获取没有回复的问题:

Question.not.in(id: Response.pluck(:question_id))