Hi Cory, I was thinking along the following lines where a ‘Purchase’ is really an ‘Order’:
User has_many Order Order belongs_to User Order has_many Products Product belongs_to Order
Next, I would associate a timestamp to an Order for simplicity because everytime you make a purchase that has 1 or more Products one creates an Order which has an Order id and time of purchase. Well, I must go and I wish that this helps.
Peace,
-Conrad