Question

I have a Box, which has many Compartments which contain many Items which belong to a Category. Items are polymorphic (:itemable) as they can belong to Boxes without Compartments – this might be my difficulty.

I can call all Items back for all Boxes in the DB, in the Box controller with:

@category_items = Item.includes(:category).group("categories.name").sum("quantity * value")

but how can I filter these down to those that belong only to the current Box id?

Answer 1

Try

compartment_ids = %(SELECT id FROM compartments WHERE box_id = :box_id)

@category_items = Item.includes(:category).where("(itemable_type = 'box' AND itemable_id = :box_id) OR (itemable_type = 'compartment' AND itemable_id IN (#{compartment_ids}))", :box_id => box_id).group("categories.name").sum("quantity * value")