所有文件在一个dir，linux中(All files in one dir, linux)

 这让人联想起经典的友谊模特问题。 多态联想不仅仅是重点。 
 
 Rails版本不可知解决方案： 
 
class User < ActiveRecord::Base
  has_many :instigator_actions, :class_name => "Action", :as => :instigator
  has_many :victim_actions, :class_name => "Action", :as => :victim
  has_many :actions, :finder_sql => '
       SELECT a.* 
       FROM   actions a
       WHERE  (a.instigator_type = "User" AND instigator_id = #{id}) OR 
              (a.victim_type     = "User" AND victim_id     = #{id})'
end
 
 创建Actions时，使用前两个关联之一创建它们。 
 
u1.instigator_actions.create(:victim => u2)
 
 要么 
 
u1.victim_actions.create(:instigator => u2)
 
 同时，您可以使用操作关联获取与用户关联的操作列表。 
 
u1.actions

This reminds of classic Friendship model problem. Polymorphic association is besides the point.
 
Rails version agnostic solution:
 
class User < ActiveRecord::Base
  has_many :instigator_actions, :class_name => "Action", :as => :instigator
  has_many :victim_actions, :class_name => "Action", :as => :victim
  has_many :actions, :finder_sql => '
       SELECT a.* 
       FROM   actions a
       WHERE  (a.instigator_type = "User" AND instigator_id = #{id}) OR 
              (a.victim_type     = "User" AND victim_id     = #{id})'
end
 
While creating the Actions create them using one of the first two associations.
 
u1.instigator_actions.create(:victim => u2)
 
OR
 
u1.victim_actions.create(:instigator => u2)
 
At the same time you can get a list of actions associated with an user using the actions association.
 
u1.actions