Mongoid使用has_one将一个对象与同一类的两个不同对象相关联

我已经看到了1：N这类问题的解决方案，但它们看起来并没有读到1：1，这是使用MongoDB 1.8，Mongoid 2.0.0.rc.8来说，Rails 3.0.5Mongoid使用has_one将一个对象与同一类的两个不同对象相关联

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：

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！

来源

2011-04-13 Indigo

定义Coach时，您正在引用类Team，但该类尚不存在。你有两个选择：

声明class_name作为一个字符串，而不是不断例如:class_name => 'Team'（首选，请参阅gist）
完全删除:class_name => Team选项并让Mongoid找出参与关联的正确类。 有一点需要注意：您将需要确保该类Team是类Coach之前宣布（加载你的源代码的顺序现在最重要的，所以这种解决方案并不理想）

来源

2011-04-14 09:16:51 Matt

良好，即不它非常感谢 – Indigo 2011-04-17 09:50:57

+1以上的答案，如果有人看到错误，它抱怨NoMethodError，那么它很可能与加载问题有关。将class_name声明为字符串可以解决问题。 – 2013-10-31 19:10:00

Mongoid使用has_one将一个对象与同一类的两个不同对象相关联

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