返回没有关联数据的对象

Question

class Game < Event 
    has_many :statistics, :dependent => :destroy 

    ... 
end 

class Statistic < ActiveRecord::Base 
    belongs_to :game 
end 

我想创建一个仅返回没有统计数据的游戏的命名范围。

感谢

Answer 1

尝试

named_scope :no_statistics, :include => :statistics, :conditions => ['statistics.id IS NULL']