Rails Mongoid Buyer, Item, Purchase model associations

Question

I'm using Rails 3.2 and Mongoid and I need to set up a simple purchases association. Current I have:

class Item
has_many :purchases

class Buyer
has_many :purchases

class Purchase
has_one :buyer
has_one :item

I'd like to be able to call all the items purchased by a given buyer which I current achieve with: def purchased_by(buyer_id) items = [] ids = Buyer.find(buyer_id).purchase_ids Item.each do |i| items << i if (i.purchase_ids & ids).length > 0 end items end

But this seems horribly inefficient. Any thoughts?

Answer 1

Try this:

class Buyer
  def items_purchased
    purchases.collect(&:item)
  end
end

Then given an object buyer, you can get what you want by calling:

buyer.items_purchased