我在rails中有一个模型campaign,另一个叫export
class Campaign < ActiveRecord::Base
has_one :export
end
class Export < ActiveRecord::Base
belongs_to :campaign
end
然后我有代码:
if campaign.export.nil?
campaign.create_export(:tag => 'newtag')
end
此代码一次又一次地为导出创建新行,因为campaign.export总是nil.
为什么我创建了导出campaign.create_export(),但campaign.export仍然是nil.