Question

I am currently trying to create a custom method on a model, where the conditions used are those of a has_many association. The method I have so far is:

class Dealer < ActiveRecord::Base

  has_many :purchases

  def inventory
    inventory = Vehicle.where(:purchases => self.purchases)
    return inventory
  end

end

This is not working, due to the fact that Vehicle has_many :purchases (thus there is no column “purchases” on the vehicle model). How can I use the vehicle.purchases array as a condition in this kind of query?

To complicate matters, the has_many is also polymorphic, so I can not simply use a .join(:purchases) element on the query, as there is no VehiclePurchase model.

EDIT: For clarity, the relevant parts of my purchase model and vehicle models are below:

class Purchase < ActiveRecord::Base
  attr_accessible :dealer_id, :purchase_type_id

  belongs_to :purchase_item_type, :polymorphic => true

end

class Vehicle < ActiveRecord::Base

  has_many :purchases, :as => :purchase_item_type

end

Answer 1

I was able to do this using the :source and :source_type options on the Vehicle model, which allows polymorphic parents to be associated.