Forms for complexly nested models

1_models.rb

class Person < ActiveRecord::Base
  has_one :phone
  has_many :dogs
  
  attr_accessible :name
end

class Phone < ActiveRecord::Base
  attr_accessible :phone_number
end

class Dog < ActiveRecord::Base
  has_one :ball

  attr_accessible :name
end

class Ball < ActiveRecord::Base
  attr_accessible :color
end

2_params.rb

{
  :owner_name => "Tom",
  :phone_number => "8885551234",
  :dogs_attributes => 
    {
      "0" => 
        {
          :dog_name => "Buddy",
          :ball_color => "Red",
        },
      "1" => 
        {
          :dog_name => "Max",
          :ball_color => "Blue",
        },
    },
}

3_dog_owner_form.rb

class DogOwnerForm < FreeForm::Form
  form_models :person, :phone
  validate_models

  property :owner_name, :on => :person, :as => :name
  property :phone_number, :on => :phone

  has_many :dogs do
    form_models :dog, :ball
    validate_models

    property :dog_name, :on => :dog, :as => :name
    property :ball_color, :on => :ball, :as => :color
  end

  def dog_initializer
    dog = person.dogs.build
    { :dog => dog, :ball => dog.build_ball }
  end
end