A complete sample of how to perform nested polymorphic uploads in rails using carrierwave

_form.html.haml

=semantic_form_for [:admin, @dog], validate: true, html: {multipart: true} do |f|
  =f.inputs do
    =f.input :name
    =f.input :kennel_name  
    =f.input :birthdate   
    =f.input :gender,    as: :radio,  collection: {'Tik' => 'F', 'Hane' => 'M'}
    =f.input :father_id, as: :select, collection: @dogs
    =f.input :mother_id, as: :select, collection: @bitches
    
    =f.semantic_fields_for :pictures do |pic|
      =pic.inputs do 
        =pic.hidden_field :id
        =pic.hidden_field :attachable_id
        =pic.hidden_field :attachable_type    
        =pic.file_field :image  
                            
  =f.buttons

dog.rb

class Dog < ActiveRecord::Base
  attr_accessible :name, :kennel_name, :mother_id, :father_id, :birthdate, :gender, :pictures_attributes, :pictures
  attr_accessor :image, :file
  belongs_to :father, class_name: "Dog", foreign_key: "father_id"
  belongs_to :mother, class_name: "Dog", foreign_key: "mother_id"
  
  has_many :pictures, as: :attachable
  accepts_nested_attributes_for :pictures
  
  validates :gender, inclusion: ['F', 'M']
  
  def gender_name
    return 'Tik' if self.gender == 'F'
    return 'Hane' if self.gender == 'M'
  end
                                                                                   
  def self.with_parents
    includes(:father).includes(:mother) 
  end   
  
  def self.with_pictures
     includes(:pictures)
  end
end

dogs_controller.rb

class DogsController < ApplicationController         
  before_filter :login_required
  def index
    @dogs = Dog.with_parents
  end

  def show
    @dog = Dog.with_parents.with_pictures.find(params[:id]) 
    @puppies = Dog.where('father_id = ? OR mother_id = ?', params[:id], params[:id]) 
  end

  def new
    @dog = Dog.new 
    @dog.pictures.build         
    @bitches = Dog.where('gender = ?', 'F')
    @dogs = Dog.where('gender = ?', 'M')
  end

  def create
    @dog = Dog.new(params[:dog])      
    if @dog.save
      redirect_to [:admin, @dog], :notice => "Successfully created dog."
    else
      render :action => 'new'
    end
  end

  def edit
    @dog = Dog.find(params[:id])      
    @dog.pictures.build if @dog.pictures.empty?
    @bitches = Dog.where('id != ?', params[:id]).where('gender = ?', 'F')
    @dogs = Dog.where('id != ?', params[:id]).where('gender = ?', 'M')
  end

  def update
    @dog = Dog.find(params[:id])           
    if @dog.update_attributes(params[:dog])
      redirect_to [:admin, @dog], :notice  => "Successfully updated dog."
    else
      render :action => 'edit'
    end
  end

  def destroy
    @dog = Dog.find(params[:id])
    @dog.destroy
    redirect_to admin_dogs_url, :notice => "Successfully destroyed dog."
  end
end

edit.html.haml

- title "Edit Dog"

= render 'form'

%p
  = link_to "Show", @dog
  |
  = link_to "View All", admin_dogs_path

image_uploader.rb

# encoding: utf-8

class ImageUploader < CarrierWave::Uploader::Base
  include CarrierWave::MiniMagick

  storage :file

  def store_dir
    "uploads/#{model.class.to_s.underscore}/#{mounted_as}/#{model.id}"
  end

  process convert: 'png', :resize_to_fit => [1024, 1024]

  version :medium do
    process resize_to_fit: [300, 300]
    process convert: 'png'
  end

  version :thumb do
    process resize_to_fit: [100, 100]
    process convert: 'png'
  end

  def extension_white_list
    %w(jpg jpeg gif png)
  end

end

new.html.haml

- title "New Dog"

= render 'form'

%p= link_to "Back to List", dogs_path

picture.rb

class Picture < ActiveRecord::Base  
  belongs_to :attachable, polymorphic: true    
  attr_accessible :image, :attachable_id, :attachable_type
  mount_uploader :image, ImageUploader 
  
end

schema.rb

ActiveRecord::Schema.define(:version => 20110508171542) do

  create_table "dogs", :force => true do |t|
    t.string   "name"
    t.string   "kennel_name"
    t.integer  "mother_id"
    t.integer  "father_id"
    t.date     "birthdate"
    t.string   "gender",      :default => "F"
    t.datetime "created_at"
    t.datetime "updated_at"
  end

  create_table "pictures", :force => true do |t|
    t.datetime "created_at"
    t.datetime "updated_at"
    t.string   "image"
    t.integer  "attachable_id"
    t.string   "attachable_type"
  end

end