如何验证范围的唯一性？

Question

我有：

class Foo
  include Mongoid::Document

  field :year, :type => Integer, :default => Time.now.utc.year
  field :month, :type => Integer, :default => Time.now.utc.month
  field :day, :type => Integer, :default => Time.now.utc.day

  validates :day, :uniqueness => { :scope => [:month,:year] }
end

我做了以下两次：

Foo.create(:day => 24, :year => 2013, :month => 5)

我没有得到验证错误。相反，我有两个相同的记录。我做错了什么？

Answer 1

试

validates_uniqueness_of :day, scope: [:month,:year]