Module

myModule.rb

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)
    end
    
  end
end

class User
  include Extensions::Popular
end

myModuleClassMeth.rb

module Extensions
  module ClassEvaluator
    
    def self.included(base)
      base.class_eval do
        # share an association
        belong_to :parent
        
        # share scope
        scope :recent, where(:created_at => 1.day.ago..Time.now)
      end
    end
    
  end
end

myModuleLeaner.rb

module Extensions
  module Popular
    
    def popularity
      1 + (self.points/100)
    end
    
    def self.included(base)
      # base. => defining class methods
      def base.most_popular(limit = 10)
        order('points DESC').limit(limit).all
      end
    end
    
  end
end