Question

我已经看到1：N的这类问题的解决方案，但他们似乎没有读到1：1，这是使用MongoDB 1.8，Mongoid 2.0.0.rc.8，Rails 3.0.5

class Coach  
  include Mongoid::Document 
  field :name, :type => String 
  belongs_to :coached, :class_name => Team, :inverse_of => :coach, :foreign_key => "coach_id" 
  belongs_to :assisted, :class_name => Team, :inverse_of => :assist, :foreign_key => "assist_id" 
end 


class Team 
  include Mongoid::Document 
  field :name, :type => String 
  has_one :coach, :class_name => Coach, :inverse_of => :coached 
  has_one :assist, :class_name => Coach, :inverse_of => :assisted 
end

然后我开始和Rails控制台会话和：

irb(main):001:0> c = Coach.new(:name => "Tom")  
=> #<Coach _id: da18348d298ca47ad000001, _type: nil, _id: BSON::ObjectId('4da18348d298ca47ad000001'), name: "Tom", coach_id: nil, assist_id: nil> 

irb(main):002:0> a = Coach.new(:name => "Dick") 
=> #<Coach _id: 4da18352d298ca47ad000002, _type: nil, _id: BSON::ObjectId('4da18352d298ca47ad000002'), name: "Dick", coach_id: nil, assist_id: nil> 

irb(main):003:0> t = Team.new(:name => "Allstars") 
=> #<Team _id: 4da18362d298ca47ad000003, _type: nil, _id: BSON::ObjectId('4da18362d298ca47ad000003'), name: "Allstars"> 

irb(main):005:0> t.coach = c 
NoMethodError: undefined method `constantize' for Coach:Class 

irb(main):005:0> c.coached = t 
NoMethodError: undefined method `constantize' for Team:Class

任何建议将不胜感激！

Answer 1

您在定义Team时引用了类Coach，但该类尚不存在。您有两种选择：

将class_name声明为字符串而不是常量，例如:class_name => 'Team'（首选，请参阅gist）
完全删除:class_name => Team选项，让Mongoid找出参与关联的正确类。 有一点需要注意：您需要确保在类Team之前声明类Coach（加载源代码的顺序现在很重要，因此此解决方案并不理想）

Mongoid使用has_one将一个对象与同一个类的两个不同对象相关联

1 个答案: