ActiveRecord模型子类不显示

Question

这是简单的继承(STI)设置:

class Parent < ActiveRecord::Base
end 

class Daughter < Parent
end

class Son < Parent
end

快速尝试控制台.期待Parent.subclasses返回两个子类,但什么也没得到!

ruby-1.9.2-p0 > Parent.subclasses
 => [] 

还有,打电话

ruby-1.9.2-p0 > Daughter.subclasses
 => [] 

,正确返回没有子节点,使父开始识别子作为子类:

ruby-1.9.2-p0 > Parent.subclasses
 => [Daughter(id: integer, type: string, created_at: datetime, updated_at: datetime)] 

同样适用于另一个子类:

ruby-1.9.2-p0 > Son.subclasses
 => [] 
ruby-1.9.2-p0 > Parent.subclasses
 => [Daughter(id: integer, type: string, created_at: datetime, updated_at: datetime), Son(id: integer, type: string, created_at: datetime, updated_at: datetime)] 

这是rails 3,但在2.3.10上表现出相同的行为

Answer 1

这是一个已知问题

一种解决方法是在基类文件的底部注册子类.

%w(daughter son).each {|r| require_dependency r } if Rails.env.development?