active_record_model_rewrite.rb

#A typical ActiveRecord Model would need to extends ActiveRecord::Base, like so:

class Person < ActiveRecord::Base
end

#And now we have access to class & instance level methods like find & save
p = Person.find 1
p.save

#A non-inheritance based re-write of the above code - i.e. one that does not require
#model objects to inherit from ActiveRecord::Base but rather mixin functionality would look like

module Persistable
  def save
    $stdout.write "in save"
  end

  module ClassMethods
    def find(num)
      $stdout.write "in find"
      #find has to return an instance of the receiver class - the *new* class method can be used for now
      new
    end
  end
end

#And now - here is how the Person class would mixin the Persistable functionality
class Person
  include Persistable
  extend Persistable::ClassMethods
end

#We can reduce the restriction on model objects to remember to both include Persistable and extend
#Persistable::ClassMethods by the hook-method included 

module Persistable
  def save
    $stdout.write "in save"
  end

  #The hook-method: When this module is included - extend the ClassMethods module to provide
  #class methods functionality
  def self.included(cls)
    cls.extend(ClassMethods)
  end

  module ClassMethods
    def find(num)
      $stdout.write "in find"
      #find has to return an instance of the receiver class - the *new* class method can be used for now
      new
    end
  end
end

#Now the Person class does not need to also extends
class Person
  include Persistable
end