polymorphic and has_one associations

I am trying to implement a simple acts_as_addressable plugin (using Rails 2.2.2)

it's up and running, but I would like also to give the possibility to define specifics business/billing/private addresses for a defined user.. I read ( http://wiki.rubyonrails.org/rails/pages/UnderstandingPolymorphicAssociations) I should use the following code to place the foreign_key in the owning association :

class Address < ActiveRecord::Base   belongs_to :addressable, :polymorphic => true .. end

class User     has_many :addresses, :as => :addressable     belongs_to :business_address, :foreign_key => 'business_address_id', :class_name => 'Address'     belongs_to :billing_address, :foreign_key => 'billing_address_id', :class_name => 'Address' end

I can run the following : business = Address.new(:street1 => "business1", :city => "city1", :postal_code => "postal_code1") user = User.first user.addresses << business