ruby-on-rails – Mongoid使用has_one将一个对象与同一个类的两

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,: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,: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,_id: BSON::ObjectId('4da18352d298ca47ad000002'),name: "Dick",assist_id: nil> 

irb(main):003:0> t = Team.new(:name => "Allstars") 
=> #<Team _id: 4da18362d298ca47ad000003,_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！