“作为"有什么意义?此代码中的关键字 [英] What's the significance of "as" keyword in this code

问题描述

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();
        }
    }
}

推荐答案

这是 ActionScript 3 中引入的强制转换运算符.与 as 的区别(相对于 Type(object)casting) 是如果转换失败，结果将是类型的默认值.更多关于这个这里

This is a casting operator introduced in ActionScript 3. The difference with as (as opposed to Type(object) casting) is that if the cast fails, the result will be the default value for the type. More on this here

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