class Class
  def attr_accessor_with_history(attr_name)
    attr_name = attr_name.to_s
    attr_reader attr_name
    attr_reader attr_name+"_history"
    class_eval %Q{ @#{attr_name}_history = [nil] }
    class_eval %Q{ def #{attr_name}=(new_value)
                     @#{attr_name}_history << @#{attr_name} = new_value
                   end }
  end
end

class SomeOtherClass
  attr_accessor_with_history :bar
  attr_accessor_with_history :foo
end