我已经改变了我的模型从我怎么迁移DataMapper的AppEngine上
class Place
include DataMapper::Resource
has n, :trails
property :id, Serial
property :name, String, :length => 140
property :tag, String, :required => true
timestamps :at
end
到
class Place
include DataMapper::Resource
has n, :trails
property :id, Serial
property :name, String, :length => 140
property :tag, String, :required => true
property :trail_count, Integer, :default => 0
timestamps :at
end
我只是说 “属性:trail_count,整型:默认=> 0”
并且我想迁移现有的appengine表,让我有更多的字段“trail_count” 我读过DataMapper.auto_upgrade!应该这样做。
但我得到一个错误“未定义的方法`auto_upgrade!'对于DataMapper:模块“
你能请帮助我如何迁移DM模型?