Polymorphic Autosave Associations with Paperclip

_form.html.haml

= f.error_messages
%div{:style=>"padding-bottom:20px"}
  %div
    = f.label :name, 'Nombre del producto'
    %br
    = f.text_field :name, :size => 70
#clientdesc
  %div
    = f.label :excerpt, 'Resumen del producto'
    %br
    = f.textile_editor :excerpt, :cols => 70 ,:rows => 8
  %br
  
  %div
    = f.label :description, 'Descripción del producto'
    %br
    = f.textile_editor :description, :cols => 70 ,:rows => 30
  %br
  .image
    Imagen del producto
    %br
    - f.fields_for :image do |image_form|
      = image_form.file_field :data

image.rb

class Image < ActiveRecord::Base
  belongs_to :imageable, :polymorphic  => true
  
  has_attached_file :data, :styles => {
    :small => ">150x150>",
    :medium  => "350x350>",
    :gallery => "700x438"
  }
  
  validates_attachment_presence :data, :message => "Se necesita subir una imagen"
  
  validates_attachment_content_type :data, { 
    :content_type => ['image/jpg', 'image/jpeg', 'image/gif', 'image/png'] 
  }
  
  def self.destroy_pics(imageable, images)
    Image.find(images, :conditions => imageable).each(&:destroy)
  end  
end

new.html.haml

#content
  = javascript_include_tag 'textile-editor'
  .inside
    %h2 Agregar un nuevo producto
    - form_for(@product, :html => {:multipart => true}) do |f|
      = render :partial => 'form', :locals => {:f => f}
      %p{:style=>"padding-top:20px"}= f.submit 'Crear Producto', :class => "button"
    = textile_editor_initialize
    = link_to 'Atras', products_path

product.rb

class Product < ActiveRecord::Base
  has_one :image, :as  => :imageable, :autosave => true, :dependent => :destroy
  
  acts_as_textiled :description, :excerpt

  validates_presence_of :name, :description, :excerpt
  
  accepts_nested_attributes_for :image, :allow_destroy => :true
end

products_controller.rb

class ProductsController < ApplicationController
  
  # GET /products/new
  # GET /products/new.xml
  def new
    @product = Product.new
    @product.image = Image.new
    respond_to do |format|
      format.html # new.html.erb
      format.xml  { render :xml => @product }
    end
  end

  # POST /products
  # POST /products.xml
    def create
    params[:product][:image_attributes] ||= {}
    
    @product = Product.new(params[:product])
    
    respond_to do |format|
      if @product.save
        flash[:notice] = 'El producto se ha creado exitosamente'
        format.html { redirect_to(@product) }
        format.xml  { render :xml => @product, :status => :created, 
          :location => @product }
      else
        format.html { render :action => "new" }
        format.xml  { render :xml => @product.errors, 
          :status => :unprocessable_entity }
      end
    end
  end

end