这段代码中"as"关键字的重要性是什么

Question

package
{
    import flash.display.Sprite;
    import flash.media.Sound;
    import flash.media.SoundChannel;

    public class EmbeddedSoundExample extends Sprite
    {
        [Embed(source="smallSound.mp3")]
        public var soundClass:Class;

        public function EmbeddedSoundExample()
        {
          //WHAT DOES "as" keyword DO IN THE FOLLOWING LINE ??
          //*************************************************

            var smallSound:Sound = new soundClass() as Sound;

            //COULD BE WRITTEN AS : 
            //==>>>> var smallSound:Sound = new soundClass() ???
            // OR
            ////==>>>> var smallSound:Sound = new Sound() ???
         //******************************************************

            smallSound.play();
        }
    }
}

Answer 1

这是在ActionScript 3中引入的转换操作符.与转换as相反(与转换相反Type(object))的区别在于,如果转换失败,结果将是该类型的默认值.更多关于这里