self.up 和 self.down 方法必须在迁移中(db/migrate/20100923101842_create_comic_books.rb)

Methods self.up and self.down must be in the migration(db/migrate/20100923101842_create_comic_books.rb)

CookBook 模型的 Clean 类必须如下所示:

Clean class of the CookBook model must look like this:

class CookBook < ActiveRedord::Base
end