class Class def attr_accessor_with_h istory attr_name attr_name attr_n

    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 bar_history getter  
      
          # write our setter code below  
          class_eval %Q(  
                      def #{attr_name}=(attr_name)  
                         @#{attr_name} = attr_name  
      
                         unless @#{attr_name + "_history"}  
                            @#{attr_name + "_history"} = []  
                            @#{attr_name + "_history"} << nil  
                         end  
      
                         @#{attr_name + "_history"} << attr_name  
      
                       end  
                     )  
       end  
    end