如何在Rails迁移中安全地使用多态模型？

Question

我知道如果在迁移期间操作模型数据，在迁移中定义模型是一种最佳实践。但是，当我尝试使用多态关联构建时，polymorphic_type属性获取了模型名称空间给我声明的迁移，导致结果数据集没有真正关联。

基本上，我最终将addressable_type设置为“RemoveAddressColumnsFromEmployeesTable :: Employee”而不是“Employee”。

我可以通过明确设置addressable_type和addressable_id来解决这个问题，但这是处理这种封装的唯一方法吗？

class RemoveAddressColumnsFromEmployeesTable < ActiveRecord::Migration 

    class Employee < ActiveRecord::Base 
    has_one :address, :as => :addressable, :inverse_of => :addressable 
    end 

    class Address < ActiveRecord::Base 
    belongs_to :addressable, :polymorphic => true, :inverse_of => :address 
    end 

def up 
    Employee.all.each do |e| 
    address    = e.build_address 
    address.street_address = e.street_address 
    address.apt_num  = e.apt_num 
    address.city   = e.city 
    address.state   = e.state 
    address.zip   = e.zip 
    e.save 
    end 

    remove_column :employees, :street_address 
    remove_column :employees, :apt_num 
    remove_column :employees, :city 
    remove_column :employees, :state 
    remove_column :employees, :zip 
end 

def down 
    add_column :employees, :street_address, :string 
    add_column :employees, :apt_num,  :string 
    add_column :employees, :city,   :string 
    add_column :employees, :state,   :string 
    add_column :employees, :zip,   :string                            

    Employee.all.each do |e| 
    e.street_address = e.address.street_address 
    e.apt_num  = e.address.apt_num 
    e.city   = e.address.city 
    e.state   = e.address.state 
    e.zip   = e.address.zip 
    e.address = nil 
    e.save 
    end 
end 
end 

Answer 1

我找到了安排我的决定。在你的情况下，这意味着替换下一个关联的多态关联：

class Employee < ActiveRecord::Base 
    has_one :address, :foreign_key => :addressable_id, :conditions => {:addressable_type => 'Employee'} 
    end 

    class Address < ActiveRecord::Base 
    belongs_to :addressable, :polymorphic => true 
    end