comment_methods.rb

module ActsAsCommentable
  # including this module into your Comment model will give you finders and named scopes
  # useful for working with Comments.
  # The named scopes are:
  #   in_order: Returns comments in the order they were created (created_at ASC).
  #   recent: Returns comments by how recently they were created (created_at DESC).
  #   limit(N): Return no more than N comments.
  module Comment
    
    def self.included(comment_model)
      comment_model.extend Finders
      comment_model.scope :in_order, comment_model.order('created_at ASC')
      comment_model.scope :recent,   comment_model.order('created_at DESC')
    end
    
    module Finders
      # Helper class method to lookup all comments assigned
      # to all commentable types for a given user.
      def find_comments_by_user(user)
        where(["user_id = ?", user.id]).order("created_at DESC")
      end

      # Helper class method to look up all comments for 
      # commentable class name and commentable id.
      def find_comments_for_commentable(commentable_str, commentable_id)
        where(["commentable_type = ? and commentable_id = ?", commentable_str, commentable_id]).order("created_at DESC")
      end

      # Helper class method to look up a commentable object
      # given the commentable class name and id 
      def find_commentable(commentable_str, commentable_id)
        model = commentable_str.constantize
        model.respond_to?(:find_comments_for) ? model.find(commentable_id) : nil
			end
    end
  end
end