using fields_for & paperclip multiple file update

Question

I 'm trying to upload multiple files to S3 using paperclip gem and referring to this tutorial. I 'm having two issues 1. the upload tag is only rendered once instead of 6 times as specified in the controller. 2. And secondly i get the following error whenever i try to edit the document.

ActiveRecord::UnknownAttributeError in DocumentsController#edit

unknown attribute: document_id

Any suggestions how to fix this?

Models/Document.rb

class Document < ActiveRecord::Base
  attr_accessible :documentId, :name, :notes, :user_id

  belongs_to :user
  has_many :photos, :dependent=>:destroy
  accepts_nested_attributes_for :photos

  acts_as_taggable

  validates :name, :length => {:minimum =>3}
  validates_date :dtReminder, :on_or_after => lambda { Date.current }, :allow_blank => true


  validates_associated :user
  validates_uniqueness_of :name, :scope => :user_id
end

Models/Photo.rb

class Photo < ActiveRecord::Base
  belongs_to :document


  has_attached_file :image, :style =>{:thumb => '150x150#',
          :medium => '300x300>',
          :large => '600x600>'
  }

  validates_attachment_size :photo, :less_than => 500.kilobytes

end

Controller/document_Controller.rb

    def new
        @document = Document.new
        @document.user = current_user
        5.times {@document.photos.build}

        respond_to do |format|
          format.html # new.html.erb
          format.json { render json: @document }
        end
      end

def create
    @document = Document.new(params[:document])
    @document.user = current_user
    5.times {@document.photos.build}

    respond_to do |format|
      if @document.save
        format.html { redirect_to user_documents_path(current_user), notice: 'Document was successfully created.' }
        format.json { render json: @document, status: :created, location: @document }
      else
        format.html { render action: "new" }
        format.json { render json: @document.errors, status: :unprocessable_entity }
      end
    end
  end

Views/documents/_form.html.erb

<%= form_for(document) do |f| %>

        <table>
                <tr>
                        <td><%= f.label :name %></td>
                        <td><%= f.text_field :name %></td>
                </tr>
                <tr>
                        <td><%= f.label :notes  %></td>
                        <td><%= f.text_area :notes %></td>
                </tr>
                <tr>
                                         <td>Photos</td>
                        <td>
                                <%= fields_for :photos do |photo|%>
                                        <%= photo.file_field :image%>
                                <%end%>
                        </td>

                </tr>
                <tr>
                        <td></td>
                        <td><%= f.submit %></td>
                </tr>
        </table>
<% end %>

Answer 1

For multiple image uploading fields, checkout Ryan Bate's screencasts on the a very similar subject.

http://railscasts.com/episodes/73-complex-forms-part-1

http://railscasts.com/episodes/74

http://railscasts.com/episodes/75