Extending models in Rails

gistfile1.rb

# See http://blog.waxman.me/extending-your-models-in-rails-3 for original post
module Extensions
  module Popular
    module ClassMethods
      def most_popular(limit=10)
        order('points desc').limit(limit).all
      end
    end

    def popularity
      1+(self.points/100)
    end

    def self.included(base)
      base.extend(ClassMethods)
      base.extend(Extensions::OtherCoolStuff)
    end
  end
end

class User
  include Extensions::Popular
end

class Tags
  include Extensions::Popular
end

gistfile2.rb

# GTK...
module Extensions
  module Ohai
    def self.included(base)
      base.class_eval do
        # share an association (vs. using STI)
        belongs_to :parent

        # share a scope
        scope :recent, where(:created_at => 1.day.ago..Time.now)
      end
    end
  end
end

gistfile3.rb

# Another take, if you want things leaner
module Extensions
  module Popular
    def popularity
      1+(self.points/100)
    end
    
    def self.included(base)
      def base.most_popular(limit=10)
        order('points desc').limit(limit).all
      end
    end
  end
end