Polymorphic form

I have two partials to deal with contact information. The Contact
information uses single-table polymorphism. I want to be able to use
save on Contact and set 'type' manually, based on the type of form the
user is filling in. This is saved as the value on a hidden field.

class Contact
  belongs_to :person
  acts_as_list :scope => :person
  validates_presence_of :type
  validates_inclusion_of :type, :in => TYPES.map {|disp, val| val}
  validates_presence_of :label
end

class PhoneNumber < Contact