_upload.html.erb

<%
  allowed_extensions = [:jpg, :jpeg]
  max_size = 10.megabyte
  allow_multiple_files = true
  button_label = t('uploadify.choose')
  url = url_for(:slideshow_id => slideshow, :action => :create, :controller => :slides)
%>
<%- session_key_name = ActionController::Base.session_options[:key] -%>
<% content_for :header do -%>
<%= javascript_include_tag "swfobject" %>
<%= javascript_include_tag "jquery.uploadify.v2.1.0" %>  
<%= stylesheet_link_tag "uploadify"%>
<% end -%>       

<% form_for(:slide, :id => 'slide_upload', :url => url, :html => { :multipart => true, "data-format" => "json", "data-allow-multiple-files" => allow_multiple_files}) do |f| %>
  <%= hidden_field_tag :session_key_value, (u cookies[session_key_name]) -%>    
  <%= hidden_field_tag :session_key_name, ActionController::Base.session_options[:key] -%>
  <%= f.error_messages %>
  <%= f.file_field :image, "data-allowed-extensions" => allowed_extensions.join(", "), "data-max-file-size" => max_size, "title" => button_label %>
<% end %>

environment.rb

  %w(middleware).each do |dir|
      config.load_paths << "#{RAILS_ROOT}/app/#{dir}"
  end

flash_session_cookie_middleware.rb

# app/middleware/flash_session_cookie_middleware.rb

require 'rack/utils'
 
class FlashSessionCookieMiddleware
  
  def initialize(app, session_key = '_session_id')
    @app = app
    @session_key = session_key
  end
  
  def call(env)
    if env['HTTP_USER_AGENT'] =~ /^(Adobe|Shockwave) Flash/
      req = Rack::Request.new(env)
      env['HTTP_COOKIE'] = "#{@session_key}=#{req.params[@session_key]}".freeze unless req.params[@session_key].nil?
    end
 
    @app.call(env)
  end
  
  
end

session_store.rb

# config/initializer/session_store.rb

# Add this line at the end of the file
ActionController::Dispatcher.middleware.insert_before(ActionController::Session::CookieStore, FlashSessionCookieMiddleware, ActionController::Base.session_options[:key])

show.js.erb

$('#slides').append('<%= escape_javascript(render(:partial => "slides/slide", :object => @slide)) %>').trigger("update");

upload.js

$(document).ready(function(){
  $("form[data-format=json]").has(":file").each(function(){
    
    var val,
      form = $(this),
      input = form.find(":file");
    
    val = function(name){
      return encodeURIComponent(
        form.find("input[name=" + name + "]").val()
      );
    };
    
    scriptData = {
      format: form.attr("data-format"), 
      authenticity_token: encodeURIComponent(val("authenticity_token"))
    };                       
    
    scriptData[val("session_key_name")] = val("session_key_value");
    
    var options = {
       uploader: '/swf/uploadify.swf',
       cancelImg: '/images/cancel.png',

       script: form.attr("action"),
       multi: form.attr("data-allow-multiple-files"),
       
       fileDataName: input.attr("name"),
       buttonText: input.attr("title"),
       fileExt: input.attr("data-allowed-extensions"),
       sizeLimit: input.attr("data-max-file-size"),
       
       scriptData: scriptData,
       
       onComplete: function(event, queue, file, response) {
         var data = eval('(' + response + ')');
         if (data.result == "error"){
           alert(data.error);
         } else {
           $.getScript(data.slide);
         }
       },
       
       onSelectOnce: function(){
         input.uploadifyUpload();
       },
       
       onSelect: function(event, queue, file){
         if (file.size > options.sizeLimit) {
           alert('Das Bild' + file.name + ' ist zu groß.');
           return false;
         }
       }
    };
    
    input.uploadify(options);
  });
});

upload_controller.rb

class UploadController < InheritedResources::Base

    def show
      show! do |format|
        format.js {render :layout => false, :format => :js } 
        format.json { render :json => @slide}    
      end
    end  

    def update
      update! do |format|
        format.json {render :nothing => true }
      end
    end

    def create                         
      create! do |success, failure|
        success.json { render :json => { :result => 'success', :slide => url_for(:slideshow_id => @slideshow, :action => "show", :controller => "slides", :id => @slide, :format => :js) } } 
        failure.json { render :json => { :result => 'error', :error => @slide.errors.full_messages.to_sentence } }
      end    
    end
    
    def destroy
      super do |format|
        format.html { redirect_to url_for(:id => @slideshow, :action => :show, :controller => :slideshows)  }
      end
    end
    
end

uploadify.css

/*
Uploadify v2.1.0
Release Date: August 24, 2009

Copyright (c) 2009 Ronnie Garcia, Travis Nickels

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.
*/
.uploadifyQueueItem {
	font: 11px Verdana, Geneva, sans-serif;
	background-color: #E5E5E5;
	width: 638px;
	margin-bottom: 1px;
	position: relative;
	height: 20px;
}
.uploadifyError {
	border: 2px solid #FBCBBC !important;
	background-color: #FDE5DD !important;
}
.uploadifyQueueItem .cancel {
	position: absolute;
	right: 2px;
	top: 2px;
}

.fileName {
  line-height: 18px;
  margin: 1px 2px 0 4px;
}

.fileName, .percentage {
  position: absolute;
  z-index: 2;
}

.uploadifyProgress {
	top: 0px;
	left: 0px;
	position: absolute;
	width: 616px;
	height: 20px;
}
.uploadifyProgressBar {
	background-color: #0099FF;
	width: 1px;
	height: 20px;
}