single table inheritance

rubyonrails-talk
1

hi,

I have the models:

order_item.rb: class OrderItem < ActiveRecord::Base end

foreign_item.rb: class ForeignItem < OrderItem   has_many :purchased_items end

retailler1_item.rb class Retailer1Item < ForeignItem end

retailler2_item.rb class Retailer2Item < ForeignItem end

purchased_item.rb: class PurchasedItem < ActiveRecord::Base   belongs_to :foreign_item end

Now I have an instance of PurchasedItem and would like to get its foreign_item:

foreign_item = purchased_item.foreign_item (purchased_item.foreign_item_id == 100, and the related foreign_item has type == 'Retailer1Item' or type == 'Retailer2Item')

The sql-query should look like: "SELECT FROM order_items WHERE order_items.id = 100 AND (order_items.type = 'ForeignItem' OR order_items.type = 'Retailer1Item' OR order_items.type = 'Retailer2Item')"

but this is executed:

  [4;36;1mForeignItem Columns (0.007000) [0m [0;1mSHOW FIELDS FROM `order_items` [0m   [4;35;1mForeignItem Load (0.001000) [0m [0mSELECT * FROM `order_items` WHERE (`order_items`.`id` = 100) AND ( (`order_items`.`type` = 'ForeignItem' ) ) [0m

Thus, the foreign_item cannot be found. The same when I explicitly use ForeignItem.find

What can I do?

Luma

2

Now I have an instance of PurchasedItem and would like to get its foreign_item:

foreign_item = purchased_item.foreign_item (purchased_item.foreign_item_id == 100, and the related foreign_item has type == 'Retailer1Item' or type == 'Retailer2Item')

The sql-query should look like: "SELECT FROM order_items WHERE order_items.id = 100 AND (order_items.type = 'ForeignItem' OR order_items.type = 'Retailer1Item' OR order_items.type = 'Retailer2Item')"

but this is executed:

[4;36;1mForeignItem Columns (0.007000) [0m [0;1mSHOW FIELDS FROM `order_items` [0m [4;35;1mForeignItem Load (0.001000) [0m [0mSELECT * FROM `order_items` WHERE (`order_items`.`id` = 100) AND ( (`order_items`.`type` = 'ForeignItem' ) ) [0m

Thus, the foreign_item cannot be found. The same when I explicitly use ForeignItem.find

This is STI magic. At this point the classes Retailer1Item and
Retailer2Item item have not been loaded and Active Record is not aware
of their existence. if you require them explicitly with
require_dependency (eg at the bottom of foreign_item.rb) then it
should do the right thing.

Fred