Foreign key in has_one instead of belongs_to

Hi all,

Is it possible to have the foreign key in the table where its model have has_one instead of belongs_to? Let me explain. I have a lot of tables that use the table Addresses, like Customer, Billing, etc, but I don't want all that foreign keys in the Address table (customer_id, billing_id and so on).

Switching has_one and belongs_to its not the ideal solution I guess, because it would not be possible to save address automatically when saving Customer, or set Address as dependent of Customer (:dependent => delete). Whats the best solution here?

Thanks for any help!