How to Extend Your Models in Rails

popular.rb

# create an extensions directory in models
# app/models/extensions/popular.rb

module Extensions
  module Popular
    extend ActiveSupport::Concern

    # you can include other things here
    included do
      include Extensions::OtherCoolStuff
      # or if you're using Mongoid you can also add fields
      field :points, :type => Integer, :default => 0
    end

    # include class methods here
    # like User.most_popular
    module ClassMethods
      def most_popular(limit=10)
         order_by(:points.desc).limit(limit).all
      end
    end

    # include Instance methods
    # like @user.popularity
    module InstanceMethods
      def popularity
        1+(self.points/100)
      end
    end
  end
end

# then you can include these is multiple models 
# so you can have DRY code (Don't Repeat Yourself)

class User
  include Extensions::Popular
end

class Tags
  include Extensions::Popular
end

# now all of the following work:

User.most_popular 
Tag.most_popular

@user = User.find(1)
@user.popularity #= 12

@tag = Tag.find(1)
@tag.popularity #=> 84