Actionscript 3: Force program to wait until event handler is called

I have an AS 3.0 class that loads a JSON file in using a URLRequest.

package {

    import flash.display.MovieClip;
    import flash.display.Loader;
    import flash.net.URLRequest;
    import flash.net.URLLoader;
    import flash.events.Event;

    public class Tiles extends MovieClip {

        private var mapWidth:int,mapHeight:int;
        private var mapFile:String;

        private var mapLoaded:Boolean=false;

        public function Tiles(m:String) {

            init(m);

        }

        private function init(m:String):void {

            // Initiates the map arrays for later use.
            mapFile=m;

            // Load the map file in.
            var loader:URLLoader = new URLLoader();
            loader.addEventListener(Event.COMPLETE, mapHandler);
            loader.load(new URLRequest("maps/" + mapFile));


        }

        private function mapHandler(e:Event):void {

            mapLoaded=true;
            mapWidth=3000;

        }

        public function getMapWidth():int {

            if (mapLoaded) {

                return (mapWidth);

            } else {

                return(-1);
            }

        }

    }

}

When the file is finished loading, the mapHandler event makes changes to the class properties, which i开发者_运维问答n turn are accessed using the getMapWidth function. However, if the getMapwidth function gets called before it finishes loading, the program will fail.

How can I make the class wait to accept function calls until after the file is loaded?

 private function mapHandler(e:Event):void {
              if (mapLoaded) {

                mapLoaded=true;
                 mapWidth=3000;
                return (mapWidth);

             } else {

           getMapWidth()

        }

}

        public function getMapWidth():int 
                return(-1);


        }

This might solve your problem, why are checking it in getMapWidth when there is no need of it.

Okay, so I figured out what I needed to do. The problem was with the code on my main timeline:

trace(bg.getMapWidth());

I forgot that the code only executed once without an event listener on the main timeline, like this

stage.addEventListener(Event.ENTER_FRAME, n);

function n(e:Event):void
{
    trace(bg.getMapWidth());
}

Now the width is returned once per frame, and everything works properly. Thanks for your help ;)