My recipe was Migrating Serialization Changes in AIR. Thanks to anyone who voted for it.

I have a follow-up recipe I haven’t gotten to write up yet, but I’ll try to get it up in the next week. It will provide a solution to add the marker which is required for this serialization to work to the front of your structures if you already have files being serialized in an existing AIR application and you want to start taking advantage of this migration technique.

I started by creating a module that opens up the will_paginate collection class and includes ActiveResource and alias method chain the to_xml method to include these values. Example code below.

#enviroment.rb
...
require 'to_xml_extensions'

#lib/to_xml_extensions.rb
module WillPaginateHelpers
  include ActiveSupport::CoreExtensions::Array::Conversions
  def to_xml_with_collection_type(options = {})
        serializeable_collection.to_xml_without_collection_type(options) do |xml|
          xml.tag!(:current_page, {:type => ActiveSupport::CoreExtensions::Hash::Conversions::XML_TYPE_NAMES[current_page.class.name]}, current_page)
          xml.tag!(:per_page, {:type => ActiveSupport::CoreExtensions::Hash::Conversions::XML_TYPE_NAMES[per_page.class.name]}, per_page)
          xml.tag!(:total_entries, {:type => ActiveSupport::CoreExtensions::Hash::Conversions::XML_TYPE_NAMES[total_entries.class.name]}, total_entries)
        end.sub(%{type="array"}, %{type="collection"})
      end
      alias_method_chain :to_xml, :collection_type
 
      def serializeable_collection #:nodoc:
        # Ugly hack because to_xml will not yield the XML Builder object when empty?
        empty? ? returning(self.clone) { |c| c.instance_eval {|i| def empty?; false; end } } : self
      end
end
 
WillPaginate::Collection.send(:include, WillPaginateHelpers)

This now gives me the proper xml when I call to_xml

<?xml version="1.0" encoding="UTF-8"?>
<time-cards type="collection">
  <current_page type="integer">1</current_page>
  <per_page type="integer">25</per_page>
  <total_entries type="integer">108</total_entries>
  <time_card>
    <approved type="boolean">false</approved>
    <billable type="boolean">false</billable>
    <created_at type="datetime">2008-10-10T14:04:13-04:00</created_at>
    <date type="datetime">2008-10-10T14:04:13-04:00</date>
    <has_been_billed type="boolean">false</has_been_billed>
    <has_been_paid type="boolean">true</has_been_paid>
    <hours type="float">2.0</hours>
    <id type="integer">98</id>
    <is_overtime type="boolean">false</is_overtime>
    <task_id type="integer">6</task_id>
    <updated_at type="datetime">2008-10-10T14:04:13-04:00</updated_at>
    <user_id type="integer">1</user_id>
  </time_card>
  ...
</timecards>

It solves the problem of having your AIR application store an IExternalizable class on disk but then later adding more fields to that class. How would you read the old version of the class without encountering a runtime error if you tried to read the new field that wasn’t present in the older serialization?

Go check it out the cookbook entry to find out how to do this and please rate the article!

I’m trying to read all of the bytes in the readExternal() function of a class implementing IExternalizable, so that I may use the position property to move back in stream in case I need to do so. The problem only seems to occur if I am trying to de-serialize an Array of anonymous objects. If I put plain old Strings in the Array it will work fine. I find this odd since I would expect

public function readExternal(input:IDataInput):void {
  var arr:Array = input.readObject() as Array;
}

to have the exact same behavior as:

public function readExternal(input:IDataInput):void {
  var ba:ByteArray = new ByteArray(); 
  var inputBytes:uint = input.bytesAvailable;
  input.readBytes(ba);
  var baBytes:uint = ba.bytesAvailable;
  var arr:Array = ba.readObject() as Array;
  trace("inputBytes == baBytes ?= " + (inputBytes == baBytes)); // traces "inputBytes == baBytes ?= true
}

AIR installer and code attached below…

The classes I’m trying to serialize are simple as I’m only trying to serialize an Array in this test application. (Excuse the poor code of assuming the items in the Array are Objects in the toString()

io/WorkingSerializer.as

package io {
 
	import flash.utils.IExternalizable;
	import flash.utils.IDataInput;
	import flash.utils.IDataOutput;
 
	public class WorkingSerializer implements IExternalizable {
 
		public var arr:Array;
 
		public function WorkingSerializer(a:Array=null) {
			arr = a ? a : [];
		}
 
		public function readExternal(input:IDataInput):void {
			arr = input.readObject() as Array;
		}
 
		public function writeExternal(output:IDataOutput):void {
			output.writeObject(arr);
		}
 
		public function toString():String {
			var s:String = "";
			for each(var obj:Object in arr) {
				s += "\n\t{ ";
				for(var p:String in obj)
					s += p + ": " + obj[p] + ",";
				s += " }\n";
			}
			return "[WorkingSerializer]\n arr: [ " + s + "]";
		}
 
	}
}

io/ProblemSerializer.as

package io {
 
	import flash.utils.ByteArray;
	import flash.utils.IExternalizable;
	import flash.utils.IDataInput;
	import flash.utils.IDataOutput;
 
	public class ProblemSerializer implements IExternalizable {
 
		public var arr:Array;
 
		public function ProblemSerializer(a:Array=null) {
			arr = a ? a : [];
		}
 
		public function readExternal(input:IDataInput):void {
			var ba:ByteArray = new ByteArray();
			input.readBytes(ba);
			arr = ba.readObject() as Array;
		}
 
		public function writeExternal(output:IDataOutput):void {
			output.writeObject(arr);
		}
 
		public function toString():String {
			var s:String = "";
			for each(var obj:Object in arr) {
				s += "\n\t{ ";
				for(var p:String in obj)
					s += p + ": " + obj[p] + ",";
				s += " }\n";
			}
			return "[ProblemSerializer]\n arr: [ " + s + "]";
		}
 
	}
}

And here is the main application file. I wrote it as an AIR application so install AIR first if you don't have it.

SerializationIssue.mxml

<?xml version="1.0" encoding="utf-8"?>
<mx:WindowedApplication xmlns:mx="http://www.adobe.com/2006/mxml" creationComplete="init()"
						layout="vertical" horizontalAlign="center" width="500" height="500">
 
	<mx:Script>
		<![CDATA[
			import io.*;
 
			private const WORKING:String = "workingfile_v1";
			private const PROBLEM:String = "problemfile_v1";
 
			private function init():void {
				registerClassAlias("io.WorkingSerializer", io.WorkingSerializer);
				registerClassAlias("io.ProblemSerializer", io.ProblemSerializer);
 
				var wo:WorkingSerializer = new WorkingSerializer([{obj: "some"}, {obj: "items"}, {obj: "are"}, {obj: "here"}]);
				var s:FileStream = new FileStream();
				s.open(getFile(WORKING), FileMode.WRITE);
				s.writeObject(wo);
				s.close();
 
				var po:ProblemSerializer = new ProblemSerializer([{obj: "items"}, {obj: "in"}, {obj: "problem"}, {obj: "serializer"}]);
				s.open(getFile(PROBLEM), FileMode.WRITE);
				s.writeObject(po);
				s.close();
			}
 
			private function getFile(filename:String):File { return File.applicationStorageDirectory.resolvePath(filename); }
 
			private function readObj(readWorking:Boolean=false):void {
				var s:FileStream = new FileStream();
				s.open(getFile(readWorking ? WORKING : PROBLEM), FileMode.READ);
 
				if(readWorking) {
					var wo:WorkingSerializer = s.readObject() as WorkingSerializer;
					logger.text += wo + "\n\n";
					trace(wo);
				}
				else {
					var po:ProblemSerializer = s.readObject() as ProblemSerializer;
					logger.text += po + "\n\n";
					trace(po);
				}
				s.close();
			}
		]]>
	</mx:Script>
 
	<mx:HBox>
		<mx:Button label="Read Working Serializer" click="readObj(true)" />
		<mx:Button label="Read Problem Serializer" click="readObj()" />
	</mx:HBox>
 
	<mx:Panel title="Logging" width="100%" height="100%">
		<mx:TextArea id="logger" width="100%" height="100%" editable="false" wordWrap="true"
					 updateComplete="logger.verticalScrollPosition=logger.maxVerticalScrollPosition" />
	</mx:Panel>
 
</mx:WindowedApplication>

To test this out without having to compile it yourself, I've compiled it as an AIR installer: Serialization Issue AIR Application. And the source: Serialization Issue Source.

When I run the code below and click on the "Read Working Serializer" button I correctly see:

[WorkingSerializer]
 arr: [ 
	{ obj: some, }
 
	{ obj: items, }
 
	{ obj: are, }
 
	{ obj: here, }
]

get output to the console. But, if I click on the "Read Problem Serializer" button I get the following RangeError:

RangeError: Error #2006: The supplied index is out of bounds. 
at flash.utils::ByteArray/readObject() 
at io::ProblemSerializer/readExternal()[<path to environment>/SerializationIssue/src/io/ProblemSerializer.as:19] 
at flash.filesystem::FileStream/readObject() 
at SerializationIssue/readObj()[<path to environment>/SerializationIssue/src/SerializationIssue.mxml:40] 
at SerializationIssue/___SerializationIssue_Button2_click()[<path to environment>/SerializationIssue/src/SerializationIssue.mxml:51]

In the meantime I'll find a workaround for this, but has anyone encountered anything similar to this or know why this isn't working?

Ryan Stewart

Ryan Stewart kicked off the keynote giving an introduction and overview to Adobe AIR. After briefly going over the background/web-history of the Flash player and the motivations behind the development of Adobe AIR, Ryan showcased some AIR applications:

• Finetune
• A task app that was made in 24 hours w/ straight CSS & JavaScript by the creator of the Ext framework
• Buzzword
• Adobe Media Player (not publicly released yet)

He also highlighted that with the newly announced update to Flash Player 9 (codenamed “Moviestar”), Flash SWFs will be able to support H.264 video and HE-AAC audio. This will allow Quicktime movies to be played through SWFs and the Adobe Media Player.

Ryan then mentioned that the second public beta drop of AIR will be released during the MAX 2007 conference. Also, we were reminded of the AIR Developer Derby: a contest to see who can make the best AIR application. The grand prize is essentially a $100,000 travel coupon. There will also be five category winners that will win “The Ultimate Desktop Environment”, which is pretty much a bunch of beast hardware.

Mike Chambers

Next up was Mike Chambers demo’ing how to write a HelloWorld Flex-based AIR application. Pretty standard, but he went on to highlight the install experience for end-users that will be using AIR applications we developers will be creating. End-users will need the AIR runtime in order to install an AIR app, but developers will be able to place a Flash Badge on their website which will allow users without the AIR runtime to install both the runtime and their AIR application with only 4 clicks.

Mike finished off with pointing any developers that are starting to play around with AIR to the onAIR Bus APIs which have a ton of live data that can be used in an AIR app.

Kevin Hoyt

Kevin Hoyt was next to demo how to build an HTML-based AIR Application.

Kevin emphasized that Flex Builder is not necessary to create AIR applications. The Flex 3 SDK (which is freely downloadable) contains the AIR SDK as well, so you can compile and debug your AIR applications from the command line. Dreamweaver CS3 also has an AIR extension so if you’re a web developer that’s afraid of the command line you can go ahead and develop your HTML page in Dreamweaver and debug the application or package it as an AIR file directly within the comfort of Dreamweaver.

Script Bridging

Kevin next demo’d the script bridging capabilities of AIR, which lets JavaScript reach into the ActionScript world and invoke any methods in the Flash API (anything in the flash.* namespace). The reverse is also true (ActionScript reaching into the JavaScript world). This means you can have a purely HTML-based AIR application that can call methods in the Flash API by simply doing things like:

<script>
  var airFile = window.runtime.flash.filesystem.File;
  var desktop = airFile.desktopDirectory;
  var myFileInJS = new airFile(desktop.resolve("file_on_the_desktop.txt");
</script>

Here, myFileInJS is a JavaScript variable that references an ActionScript 3 class from the AIR SDK.

So “window.runtime.flash.* can let you directly use any Flash class from JavaScript. IMO the coolest thing Kevin covered is the ability augment the Flash packages you can use by simply script including a library.swf from any SWC to access those AS classes:

<script src="library.swf"></script>
<script>
  var encoder = runtime.com.adobe.images.PNGEncoder;
  encoder.encode( bitmapData )
</script>

In this example, encoder is the PNGEncoder from the as3corelib project, but the encoding is being done in JavaScript using AS classes! Very cool stuff. (FYI: a SWC is stored in a ZIP format, so you can just unzip a SWC file to access the library.swf inside of it)

Chafic Kazoun: Windowing in AIR

Windowing concepts Chafic covered/demo’d:

• utility window
• standard window
• custom chrome transparent window
• custom chrome where background is embedded in a SWF
• custom window dispatching events and being listened to by another window

Ben Forta: AIR + ColdFusion

Highlights from Ben’s talk:

• 50% of existing ColdFusion customers have upgraded to ColdFusion 8.
• ColdFusion/Flex Extensions for Eclipse available at Adobe’s ColdFusion page.

Can generate a ColdFusion-backed Flex web app w/ literally no front-end coding; the extension has Master/Detail/Master_Detail and DB wizards to configure everything which then generates the CFCs, MXML components, and CSS stylesheets using all best practices.

This was possible before in ColdFusion 7, but now ColdFusion 8 can generate a ColdFusion-backed AJAX/HTML/CSS web app in the same manner.

From AIR you can load an HTML page from a ColdFusion backend and it will properly renders this AJAX/HTML/CSS generated content.