Paperclip updating database with NULLS for filename, filesize, etc in Rails3

I'm attempting to implement Paperclip in my Rails3 app and using Emerson Lackey's railscast (http://www.emersonlackey.com/article/paperclip-with-rails-3) as a model as its very similar to what 开发者_运维百科I am looking to do (have multiple photos for a particular model). However, I'm not getting any of the children objects to save anything other than NULLS about the images.

Here is the parent model, cars, which have multiple car photos:

class Car < ActiveRecord::Base
attr_accessible  :model_year, :admin_model_name_id, :chassis_number, :location, :description, :for_sale, :sale_contact_info_visible_to_all, :sale_contact_number, :car_photos_attributes
has_many :car_photos, :dependent => :destroy
accepts_nested_attributes_for :car_photos, :allow_destroy => true

And then the model for the car photo:

class CarPhoto < ActiveRecord::Base
  belongs_to :car
  has_attached_file :car_photo, :styles => { :large => "640x480", :medium => "300x300>",   :thumb => "100x100>" }
  attr_accessible :file_name, :content_type, :file_size, :car_id
end

Upon saving a new car, the Car saves fine as before but the CarPhotos do not. Here is the output from webrick:

AREL (0.2ms)  INSERT INTO `car_photos` (`file_name`, `content_type`, `file_size`, `car_id`, `created_at`, `updated_at`) VALUES (NULL, NULL, NULL, 38, '2011-03-10 17:15:52', '2011-03-10 17:15:52')
[paperclip] Saving attachments.
[paperclip] Saving attachments.
  SQL (5.8ms)  COMMIT
Redirected to http://127.0.0.1:3000/cars/38
Completed 302 Found in 144ms

I expect that this has something to do with the attr_accessible macros in the two models but I have not been able to determine exactly what it is. Emerson's source code has no changes from the scaffolding for the create method so not sure if I need to update mine to get the children to save the values from the form. I do have the :html => { :multipart => true } in my form_for @car in my view. Clues? Thanks in advance.

here's code I used earlier this week on Rails3 - in my model

has_attached_file :image1

No attr_accessible

and then my up migration to add the fields to the model look like

add_column :offers, :image1_file_name, :string
add_column :offers, :image1_content_type, :string
add_column :offers, :image1_file_size, :integer
add_column :offers, :image1_updated_at, :datetime

hope that helps and provides some insight? Looking like you might be missing the image name from your field names?