[]layaflash下构造函数需要注意哪些问题？

package 

{

    import flash.display.Sprite;

     

    public class A extends Sprite

    {

        protected var data:String = "layabox";

        public function A()

        {

            super();

        }

    }

}

package 

{

    public class B extends A

    {

        public function B()

        {

            this.data = "layaFlash";//这里的修改无效

            trace("data is " + this.data);

             

            super();

            this.data = "layaFlash";//有效的修改属性代码

            trace("data is " + this.data);

        }

    }

}