:clear_after_save => trueを指定すると、save後はmodified?がtrueじゃなくなる。 person = Person.find(:first) person.age # 100 person.age = 10 person.age_modified? # true person.original_age # 100 person.modified_attributes # {:age => 100} # restore person.restore_attributes :only => :age person.age # 100 # clear person.clear_original_attributes :only => :age # dbと比較 person.modified?(:reload) # true