Rails Multi Table Inheritance and Polymorphic Associations

Question

I'm currently developing an application using Rails 3.2 and have run into a bit of a problem. I know this has been asked hundreds of times before but I couldn't find an answer that solved it. Here is a similar ER: http://i.stack.imgur.com/x5V0G.png

Fairly obvious what i'm trying to do. I'm hoping for the association to read like the following:

Supplier.first.theatres.first.events.first.orders
TourEvent.first.orders
Tour.first.orders

Now it would be nice to be able to define my models like so:

class Event < ActiveRecord::Base
  has_many :orders
  belongs_to :eventable, polymorphic: true

  # id, eventable_id, eventable_type, title, date, price
end

class TourEvent < Event
  belongs_to :tour

  # id, tour_id, rendezvous, guide_name
end

class Tour < ActiveRecord::Base
   has_many :events, class_name: 'TourEvent'

  # id, name, venue, duration
end

But I understand that's reserved for "STI" rather than "MTI". Any ideas how to get my solution working without the need for complicated mixins or plugins? Or is it just not possible?

Answer 1

I think you can make something like this:

suppliers 
has_many :events

events
belongs_to :suppliers
belongs_to :institutions
has_many :orders
# id, supplier_id, institution_id, ...

institutions
# id, type, title, ...
types: theatre, club, tour

orders
belongs_to :events
# id, event_id

Then, you can access to event orders:

Supplier.first.events.first.orders