class Comment < ActiveRecord::Base
  belongs_to :user
  has_many :replies
  has_many :emotions,:as => :emotionable
end



class Reply < ActiveRecord::Base
  belongs_to :user
  belongs_to :comment
  has_many :emotions,:as => :emotionable
end

class Emotion < ActiveRecord::Base
  belongs_to :emotionable,:polymorphic => :true  
end

所以这一切都很好,但是我需要为Comment和Reply添加一个计数器缓存,以便获得每个对象的Agrees和Disagree的大小.在所有文档中,它都有使用正常多态关联进行计数器缓存的示例,而不是具有额外条件的计数缓存.作为参考,Emotion的模式如下所示：

create_table "emotions",:force => true do |t|
  t.integer  "user_id"
  t.string   "emotion"
  t.integer  "emotionable_id"
  t.string   "emotionable_type"
  t.datetime "created_at",:null => false
  t.datetime "updated_at",:null => false
end

TL：DR – 我需要能够通过计数器缓存对多态关联调用@commet.agrees_count,@ comment.disagrees_count,@ reply.agrees_count和@ reply.disagrees_count.所以评论和回复将需要2个计数器缓存.