class Class

  def attr_accessor_with_history(attr_name)
    attr_name = attr_name.to_s       #make sure it's a string
    attr_reader attr_name            #create the attribute's getter
    attr_reader attr_name+"_history" #create the bar_history getter

    class_eval %Q{
      def #{attr_name}=(val)
        @#{attr_name} = val
        @#{attr_name}_history = (@#{attr_name}_history || []) << val
      end
    } #when you set the attribute, you set it and save it to an array
  end
end