回形针不显示错误消息

Question

我正在使用rails 3.2.6。我在我的模型文件中添加了这个：

 has_one :avatar, :as => :imageable, :dependent => :destroy
 validates_presence_of :avatar, :message => "can't be empty"

但如果字段留空，我没有收到任何错误消息。我只在页面顶部显示Please review the problems below:。任何人都可以提出任何建议吗？

has_one :avatar, :as => :imageable, :dependent => :destroy
  has_many :attachments, :as => :attachable, :dependent => :destroy

  accepts_nested_attributes_for :avatar, :reject_if => :all_blank

实际上如何在嵌套属性中给出错误信息？