[Wolsh]

	public class OnlineData extends EventDispatcher
	{
		public const DATA_LOADED:String = "dataLoaded";
		private var _polyWidth:int;
		private var _polyHeight:int;
		private var myLoader:URLLoader;
 
		public function OnlineData()
		{
		}
		public function load():void
		{
			var json_URL:String = "http://***";			
			var myJSONURL:URLRequest = new URLRequest(json_URL); 			
			myLoader = new URLLoader(myJSONURL); 
			myLoader.addEventListener(Event.COMPLETE, jsonLoaded, false, 0, true); 
		}
		public function get polyWidth():int
		{
			return _polyWidth;
		}
		public function get polyHeight():int
		{
			return _polyHeight;
		}
 
		private function jsonLoaded(event:Event):void 
		{
			myLoader.removeEventListener(Event.COMPLETE, jsonLoaded);			
			var myJSON:String = String(myLoader.data); 
			trace (myJSON);
			var json_data:Object=com.adobe.serialization.json.JSON.decode(myJSON);	
			//проверка, есть ли такие свойства
			if (json_data.hasOwnProperty("width") && json_data.hasOwnProperty("height"))
			{					
				_polyWidth = int(json_data["width"]);
				_polyHeight = int(json_data["height"]);	
				trace (_polyWidth);
 				dispatchEvent(new Event(DATA_LOADED));
			}				
		}
	}

В "другом классе" (пример использования):

private var _onlineData:OnlineData = new OnlineData();
_onlineData.addEventListener(OnlineData.DATA_LOADED, onDataLoaded);
_onlineData.load();
//...
private function onDataLoaded(event:Event):void
{
	trace("- - - - - - - - - - - - - - -");
	trace(_onlineData.polyWidth);
	trace(_onlineData.polyHeight);
}