Votable

post.rb

# app/models/post

class Post < ActiveRecord::Base
  include Votable
  
end

votable.rb

# app/models/concerns/votable.rb

module Votable
  extend ActiveSupport::Concern
  
  included do
    has_many :votes
  end
  
  def update_vote_count!
    update_attributes(vote_count: votes.size) if has_attribute?(:vote_count)
  end
end

vote.rb

# app/models/vote

class Vote < ActiveRecord::Base
  belongs_to :item, polymorphic: true
  
  after_save :update_item_vote_count
  
private

  def update_item_vote_count
    if item.present?
      item.update_vote_count!
    end
  end
  
end