Question

当我有一个继承的类时，我在执行反向多态关联时遇到了麻烦。有谁知道发生了什么事？

ruby-1.9.2-rc2 > Label.first
 => #<Label id: 1, owner_id: 1, owner_type: "Student", name: "Lorem", created_at: "2011-01-23 05:02:29", updated_at: "2011-01-23 05:02:29"> 
ruby-1.9.2-rc2 > Label.first.owner
 => #<Student id: 1, email: "alice1@example.com", ...,  avatar_updated_at: nil> 
ruby-1.9.2-rc2 > Label.first.owner.labels
 => [] 

class Student < User
  has_many :labels, :as => :owner


class Label < ActiveRecord::Base
  belongs_to :owner, :polymorphic => true

注意：只是为了好的措施（不是这应该是不同的，但以防万一......）

User.find(1).labels
 => []

另外

l = Label.find(4)
 => #<Label id: 4, owner_id: 2, owner_type: "Student", name: "sit", created_at: "2011-01-23 05:02:29", updated_at: "2011-01-23 05:02:29"> 
ruby-1.9.2-rc2 > l.owner_type = "User"
 => "User" 
ruby-1.9.2-rc2 > l.save
 => true 
ruby-1.9.2-rc2 > Student.find(2).labels
 => [#<Label id: 4, owner_id: 2, owner_type: "User", name: "sit", created_at: "2011-01-23 05:02:29", updated_at: "2011-01-23 07:13:37">]

Answer 1

仍然不确定为什么会失败（好吧，我可以猜测，考虑到学生/用户的二分法），但为了将来的参考，这个黑客有效：

has_many :labels, :conditions => ["owner_type = ?", "Student"], 
                          :foreign_key => "owner_id"

多态rails关联在继承类上失败？

1 个答案: