Question

我一直在做一些测试并遇到了一些奇怪的事情。说我有这个界面

interface IRobot
    {
         int Fuel { get; }
    }

如您所见，它是只读的。所以现在我要创建一个实现它的类

 class FighterBot : IRobot
    {

        public int Fuel { get; set; }
    }

现在您可以阅读并设置它。所以让我们做一些测试：

        FighterBot fighterBot;
        IRobot robot;
        IRobot robot2;
        int Fuel;
public Form1()
        {
            InitializeComponent();
            fighterBot = new FighterBot();
            robot = new FighterBot();
        }

首先我这样做了：

 Fuel = fighterBot.Fuel;// Can get it
            fighterBot.Fuel = 10; //Can set it

这是可以预料的，然后我这样做了：

 Fuel = robot.Fuel; //Can get it
            robot.Fuel = 10; //Doesn't work, is read only

同样值得期待。但是当我这样做时：

robot2 = robot as FighterBot;
            Fuel = robot2.Fuel; //Can get it
            robot2.Fuel = 10;//Doesn't work, is read only

为什么不起作用？是不是将robot2视为FighterBot？因此，它不应该能够设置燃料吗？

Answer 1

即使您通过“as”语句将robot强制转换为FighterBot，您也会将结果存储在IRobot类型的变量中，因此仍会读取Fuel仅

您需要将转化结果存储在FighterBot类型的变量中：

var robot3 = robot as FighterBot;

然后它会起作用。

Answer 2

interface IRobot
{
     int Fuel { get; }
}

robot2 = robot as FighterBot;
Fuel = robot2.Fuel;

// robot2 is STILL stored as IRobot, so the interface allowed 
// to communicate with this object will be restricted by 
// IRobot, no matter what object you put in (as long as it implements IRobot)
robot2.Fuel = 10; // evidently, won't compile.

更多背景信息：

IRobot r = new FighterBot();
// you can only call method // properties that are described in IRobot

如果要与对象进行交互并设置属性，请使用为其设计的界面。

FigherBot r = new FighterBot();
r.Fuel = 10;

`as`关键字是否会带回该类的所有成员？

2 个答案: