gistfile1.rb

module AuditingExtensions   
  def self.included( recipient )
    recipient.extend( ModelClassMethods )
    recipient.class_eval do
      include ModelInstanceMethods
    end
  end

  module ModelClassMethods
    def audit_me
      audit :when => :before_update,
            :if => lambda{|m| m.changed?},
            :with_message => :audit_message
    end    
  end # class methods
  
  module ModelInstanceMethods
    def audit_message
      columns = changed - ['updated_at']
      columns.map{|a| 
        was = self.send("#{a}_was")
        is = self.send(a)
        if is != was
          "*#{a}*: #{was} => #{is}"
        else
          nil
        end
      }.compact.join(",\n ")
    end    
  end # instance methods
end