Promises and Services (old). Please see: http://github.com/darscan/robotlegs-extensions-Oil

JsonRemoteService.as

package org.robotlegs.utilities.remote
{
	import com.adobe.serializers.json.JSONDecoder;
	
	import mx.collections.ArrayCollection;
	
	public class JsonRemoteService extends RemoteServiceBase
	{
		public function JsonRemoteService(rootURL:String = "")
		{
			super(rootURL);
		}
		
		override protected function generateObject(data:*):Object
		{
			// Hack:
			if (data == "[]")
				return new ArrayCollection();
			return new JSONDecoder().decode(String(data));
		}
	}
}

Promise.as

package org.robotlegs.utilities.remote
{
	
	public class Promise
	{
		public static var PENDING:String = "pending";
		public static var COMPLETE:String = "complete";
		public static var FAILED:String = "failed";
		public static var CANCELLED:String = "cancelled";
		
		protected var resultHandlers:Array;
		protected var faultHandlers:Array;
		
		[Bindable]
		public var status:String;
		
		[Bindable]
		public var result:*;
		
		[Bindable]
		public var fault:*;
		
		public function Promise()
		{
			status = PENDING;
			resetHandlers();
		}
		
		public function addResultHandler(handler:Function):Promise
		{
			if (status == COMPLETE)
			{
				handler(this);
			}
			else if (status == PENDING && resultHandlers.indexOf(handler) == -1)
			{
				resultHandlers.push(handler);
			}
			return this;
		}
		
		public function addFaultHandler(handler:Function):Promise
		{
			if (status == FAILED)
			{
				handler(this);
			}
			else if (status == PENDING && faultHandlers.indexOf(handler) == -1)
			{
				faultHandlers.push(handler);
			}
			return this;
		}
		
		public function handleResult(obj:Object):void
		{
			status = COMPLETE;
			result = obj;
			var len:int = resultHandlers.length;
			for (var i:int = 0; i < len; i++)
			{
				var handler:Function = resultHandlers[i];
				handler(this);
			}
			resetHandlers();
		}
		
		public function handleFault(obj:Object):void
		{
			status = FAILED;
			fault = obj;
			var len:int = faultHandlers.length;
			for (var i:int = 0; i < len; i++)
			{
				var handler:Function = faultHandlers[i];
				handler(this);
			}
			resetHandlers();
		}
		
		public function cancel():void
		{
			status = CANCELLED;
			resetHandlers();
		}
		
		protected function resetHandlers():void
		{
			resultHandlers = [];
			faultHandlers = [];
		}
	}
}

RemoteService.as

package org.robotlegs.utilities.remote
{
	
	public interface RemoteService
	{
		function get(url:String):Promise;
		function post(url:String, params:Object = null):Promise;
	}
}

RemoteServiceBase.as

package org.robotlegs.utilities.remote
{
	import flash.events.Event;
	import flash.events.IOErrorEvent;
	import flash.events.ProgressEvent;
	import flash.events.SecurityErrorEvent;
	import flash.net.URLLoader;
	import flash.net.URLRequest;
	import flash.net.URLRequestMethod;
	import flash.net.URLVariables;
	import flash.utils.Dictionary;
	
	public class RemoteServiceBase implements RemoteService
	{
		protected var loaders:Dictionary;
		protected var promises:Array;
		protected var rootURL:String;
		
		public function RemoteServiceBase(rootURL:String = "")
		{
			this.loaders = new Dictionary();
			this.promises = new Array();
			this.rootURL = rootURL;
		}
		
		public function get(url:String):Promise
		{
			var req:URLRequest = new URLRequest(fullUrl(url));
			return request(req);
		}
		
		public function post(url:String, params:Object = null):Promise
		{
			var req:URLRequest = new URLRequest(fullUrl(url));
			var vars:URLVariables = new URLVariables();
			// Flash Player seems to perform a GET if no params are passed
			params ||= {forcePost:true};
			for (var prop:String in params)
				vars[prop] = params[prop];
			req.data = vars;
			req.method = URLRequestMethod.POST;
			return request(req);
		}
		
		protected function request(req:URLRequest):Promise
		{
			var promise:Promise = new Promise();
			var loader:URLLoader = new URLLoader();
			loader.addEventListener(Event.COMPLETE, createHandler(handleComplete, promise));
			loader.addEventListener(IOErrorEvent.IO_ERROR, createHandler(handleIoError, promise));
			loader.addEventListener(ProgressEvent.PROGRESS, createHandler(handleProgress, promise));
			loader.addEventListener(SecurityErrorEvent.SECURITY_ERROR, createHandler(handleSecurity, promise));
			promises.push(promise);
			loaders[promise] = loader;
			loader.load(req);
			return promise;
		}
		
		protected function releasePromise(promise:Promise):void
		{
			var index:int = promises.indexOf(promise);
			if (index != -1)
			{
				promises.splice(index, 1);
				delete loaders[promise];
			}
		}
		
		protected function createHandler(listener:Function, promise:Promise):Function
		{
			return function(event:Event):void
			{
				listener(event, promise);
			}
		}
		
		protected function handleSecurity(e:SecurityErrorEvent, promise:Promise):void
		{
			releasePromise(promise);
			promise.handleFault({error: "Security Error", message: e.text});
		}
		
		protected function handleProgress(e:ProgressEvent, promise:Promise):void
		{
			// promise.handleProgress({bytesTotal: e.bytesTotal, bytesLoaded: e.bytesLoaded});
		}
		
		protected function handleIoError(e:IOErrorEvent, promise:Promise):void
		{
			releasePromise(promise);
			promise.handleFault({error: "IO Error", message: e.text});
		}
		
		protected function handleComplete(e:Event, promise:Promise):void
		{
			releasePromise(promise);
			promise.handleResult(generateObject(e.target.data));
		}
		
		protected function fullUrl(url:String):String
		{
			if (url == null || url.length == 0)
				return null;
			
			return url.indexOf("://") > -1 ? url : rootURL + url;
		}
		
		protected function generateObject(data:*):Object
		{
			return Object(data);
		}
	}
}

Promise is not the right name for this. Operation might be better.

Nice mate, could you provide an implementation suitable for AMF?

@quantuminformation You can check it out on my forked version: http://gist.github.com/643492

@darscan Could you check if there's everything good about proper adding event handlers for NetConnection object?

@wrobel221 I've moved this stuff into a new RL extension called Oil: http://github.com/darscan/robotlegs-extensions-Oil