Exploring Flex Proxy class

Proxy is a rather interesting class. It gives you an opportunity to override basic behaviour of some actionscript 3 operators (such as "for each...in", "for...in", "delete", "[]"). You cannot create Proxy instances directly, you must override it and override needed methods.
Proxy is a good class to build enumerable collections. Let's create a custom collection, which overrides Proxy and implements some its basic behaviour.
First I'm going to implement enumeration logic. There are 3 methods in Proxy class, which will help us:

nextNameIndex(index : int) : int
nextName(index : int) : String
nextValue(index : int) : *

nextNameIndex is called within each iteration in "for each...in" and "for...in" loops. It receives index, which is being incremented every iteration by 1 (starting with 0). In this method you're supposed to return an int, which will be next passed to nextValue ("for each...in") or nextName ("for...in"). An important moment here: you return 0 to stop the loop.

There'll be an array as the source of our collection.

flash_proxy override function nextNameIndex(index : int) : int
{
 return index < source.length ? index + 1 : 0;
}
 
flash_proxy override function nextName(index : int) : String
{
 return (index - 1).toString();
}
 
flash_proxy override function nextValue(index : int) : *
{
 return source[index - 1];
}

Pay attention, that all methods are declared in flash_proxy namespace, so don't forget to add  "use namespace flash_proxy" before class declaration.
As you see, we return (index + 1) in  "nextNameIndex", because we cannot return 0 as index. But we use (index - 1) in "nextName" and "nextValue".

To override "[]" operator we should implement "getProperty" and "setProperty" methods.

flash_proxy override function getProperty(name : *) : *
{
 if (name is String && !isNaN(parseInt(name)))
  return source[int(parseInt(name))];
 else
  return undefined;
}
 flash_proxy override function setProperty(name : *, value : *) : void
{
 if (name is String && !isNaN(parseInt(name)))
  source[int(parseInt(name))] = value;
 else
  throw new Error("Illegal index");
}

Using our class:

var col : CustomCollection = new CustomCollection();
for (var i : int = 0; i < 3; i++)
 col[i] = i.toString() + "str";
trace("For each loop:");
for each (var elem : * in col)
 trace(elem);
trace("For loop:");
for (var key : String in col)
 trace("Key: " + key + ", value: " + col[key]);

 More info about Proxy class you can find here.

Creating and applying custom preloader to Flex application (part 2)

In part 1 I created custom preloader for Flex app using Flex API (IPreloaderDisplay). In this post I'm going to apply my preloader through loading Flex compiled SWF. Here I'm using the same SWC with progress bar movieclip as in part 1.

Main steps:

1. Create pure AS3 application.
2. Show custom preloader.
3. Load external SWF with Loader.
4. Catch loading events, update preloader view.
5. Pass flashvars to loaded application.
6. Hide preloader, show application.

Creating and applying custom preloader to Flex application (part 1)

I'm sure, you can find much information on this issue on the internet, but i'll try to explain the process in a detailed way, that it'll be easy to understand. I'm going to show you 2 ways of creating and applying your custom preloader for Flex application.