Question

可能重复：
HABTM Polymorphic Relationship

目前，我通过定义关系模型，然后通过关系模型设置has_many关系来实现多对多关系。像这样的东西：

class WorldCup < ActiveRecord::Base
  has_many :country_taggings#, :as => :entity
  has_many :countries, :through => :country_taggings
end

class Country < ActiveRecord::Base
  has_many :country_taggings
end

class CountryTaggings < ActiveRecord::Base
   belongs_to :country
   belongs_to :world_cup
   # belongs_to :entity, :polymorphic => true
end

当然，这很容易转换成has_and_belongs_to_many，如果它不是我在那里注释的东西。因此，从父母到关系模型的关系是多态的。实际定义中间关系模型的详细程度正在扼杀我。难道没有办法重新发现has_and_belongs_to_many并以某种方式找到了一种方法来实现多态性吗？

Answer 1

试试这个 -

http://ruby-on-rails-dipak-panchal.blogspot.in/2012/10/has-many-through-relationship.html

class WorldCup < ActiveRecord::Base
  has_many :country_taggings
  has_many :countries, :through => :country_taggings
end

class Country < ActiveRecord::Base
  has_many :country_taggings
  has_many :worldcups, :through => :country_taggings
end

class CountryTaggings < ActiveRecord::Base
  belongs_to :country
  belongs_to :world_cup
end

也看到了这个

http://guides.rubyonrails.org/association_basics.html#the-has_many-through-association

Answer 2

class WorldCup < ActiveRecord::Base

  has_many :country_taggings

 has_many :countries, :through => :country_taggings

end

class Country &lt; ActiveRecord::Base
  has_many :country_taggings
end

class CountryTaggings < ActiveRecord::Base
  belongs_to :entity, :polymorphic => true

 belongs_to :country

 belongs_to :world_cup

end

has_many_and_belongs_to多态？

2 个答案: