Ruby on Rails

I'm trying to create hotel with some fields, one of the fields is photo, i want to use multiple files upload with carrierwave and nested_form. I found this article and have some result.

When i'm on /hotels/new, filling fields, choosing photos and press submit, gettingActiveRecord::UnknownAttributeError in HotelsController#create unknown attribute: attachable_type. Console

Started POST "/hotels" for 127.0.0.1 at 2013-09-27 17:35:18 +0300  Processing by HotelsController#create as HTML    Parameters: {"utf8"=>"✓", "authenticity_token"=>"+1T2tuygSnj8unOKkXkRWI4L7KvDE  9PPHrqvag7KmIQ=", "hotel"=>{"title"=>"dsa", "address"=>"asd", "star_rating"=>"2"  , "breakfast"=>"Not include", "price_for_room"=>"sadas", "room_description"=>"Gr  eat room", "attachments_attributes"=>{"1380289954031"=>{"file"=>#<ActionDispatch  ::Http::UploadedFile:0xa5d546c @original_filename="11374.jpg", @content_type="im  age/jpeg", @headers="Content-Disposition: form-data; name=\"hotel[attachments_at  tributes][1380289954031][file]\"; filename=\"11374.jpg\"\r\nContent-Type: image/  jpeg\r\n", @tempfile=#<File:/tmp/RackMultipart20130927-7077-50zkol>>, "_destroy"  =>"false"}, "1380289972216"=>{"file"=>#<ActionDispatch::Http::UploadedFile:0xa5d  53a4 @original_filename="357175.jpg", @content_type="image/jpeg", @headers="Cont  ent-Disposition: form-data; name=\"hotel[attachments_attributes][1380289972216][  file]\"; filename=\"357175.jpg\"\r\nContent-Type: image/jpeg\r\n", @tempfile=#<F  ile:/tmp/RackMultipart20130927-7077-dlkmwk>>, "_destroy"=>"false"}}}, "commit"=>  "Done"}  Completed 500 Internal Server Error in 109ms    ActiveRecord::UnknownAttributeError (unknown attribute: attachable_type):    app/controllers/hotels_controller.rb:15:in `new'    app/controllers/hotels_controller.rb:15:in `create'   ...

Model hotel.rb

class Hotel < ActiveRecord::Base    attr_accessible :address, :breakfast, :price_for_room, :room_description,                  :star_rating, :title, :attachments_attributes      has_many :attachments, :as => :attachable    accepts_nested_attributes_for :attachments  end

Model attachment.rb

class Attachment < ActiveRecord::Base    attr_accessible :file      belongs_to :attachable, :polymorphic => true    mount_uploader :file, FileUploader  end

hotels_controller.rb

...        def new          @hotel = Hotel.new        end        def create          @hotel = Hotel.new(params[:hotel])          if @hotel.save            redirect_to hotels_path, notice: "Nice, you added new hotel " + @hotel.title          else            render "new"          end          end

_form.rb

<%= nested_form_for @hotel, :html => {:multipart => true}  do |f| %>    ...    <%= f.fields_for :attachments do |attachment_form|%>          <%= attachment_form.label :file %>      <%= attachment_form.file_field :file %>      <%= attachment_form.link_to_remove "Remove this photo" %>    <% end %>    <%= f.link_to_add "Add photo", :attachments %>    <%= f.submit 'Done', class: 'btn btn-success' %>  <% end %>

Any ideas guys? What am I doing wrong here?