[ActionScript 3.0] 如何获得实例对象的类名及类

package
{
    import flash.display.DisplayObject;
    import flash.display.MovieClip;
    import flash.display.Sprite;
    import flash.events.Event;
    import flash.events.MouseEvent;
    import flash.utils.getDefinitionByName;
    import flash.utils.getQualifiedClassName;
    
    public class QualifiedClass extends Sprite
    {
        private var _mc:MovieClip;
        
        public function QualifiedClass()
        {
            this.graphics.beginFill(0x000000);
            this.graphics.drawRect(0,0,500,500);
            this.graphics.endFill();
            _mc = new MovieClip();
            _mc.graphics.beginFill(0x00ff00);
            _mc.graphics.drawRect(0,0,50,50);
            this.addChild(_mc);
            stage.addEventListener(MouseEvent.CLICK,onClick);
            _mc.addEventListener(MouseEvent.CLICK,onClick);
        }
        private function onClick(e:MouseEvent):void
        {
            //1.获得某个实例对象的类名：getQualifiedClassName (实例名字符串表达式);
            trace("click");
            trace(e.target.name); //返回instance**之类的
            trace(getQualifiedClassName(e.target)); //返回元件名
            
            //2.获得某个实例对象的类：constructor
            trace(A.prototype.constructor);      // [class A] 
            trace(A.prototype.constructor == A); // true 
            var myA:A = new A(); 
            trace(myA.constructor == A);         // true 
            
            //3.根据类名获得类： getDefinitionByName(类名);
            var ClassReference:Class = getDefinitionByName("flash.display.Sprite") as Class; 
            var instance:Object = new ClassReference(); 
            instance.graphics.beginFill(0xff0000); 
            instance.graphics.drawRect(50, 50, 50, 50); 
            instance.graphics.endFill(); 
            addChild(DisplayObject(instance)); 
        }
        
    }
}
dynamic class A {}