C#为什么接口不能实现这样的方法？解决我的问题的解决方法是什么？

Question

为什么接口不能实现这样的方法？

public interface ITargetableUnit {
        //Returns whether the object of a class that implements this interface is targetable
     bool unitCanBeTargeted(){
        bool targetable = false;
        if(this is Insect){
            targetable = (this as Insect).isFasterThanLight();
        }
        else if(this is FighterJet){
            targetable = !(this as FighterJet).Flying;
        }
        else if(this is Zombie){
            targetable = !(this as Zombie).Invisible;
        }
        return targetable;
    }
}

Insect 和 Zombie 都已经派生自基类 Creature，而 FighterJet 派生自类 Machine 但是，并非所有 Creature-s 都是可定位的并且不使用 ITargetableUnit 接口。

是否有任何解决方法可以解决我面临的问题？

Answer 1

就像每个人都说你不能为接口定义行为。继承特定类的接口。

public interface ITargetableUnit 
{

     bool unitCanBeTargeted();

}

public class Insect : ITargetableUnit //you can add other interfaces here
{

     public bool unitCanBeTarget()
     {
          return isFasterThanLight();
     }
}

public class Ghost : ITargetableUnit 
{
     public bool unitCanBeTarget()
     {
          return !Flying();
     }
}

public class Zombie : ItargetableUnit
{
     public bool unitCanBeTarget()
     {
          return !Invisible();
     }
}

Answer 2

只是为了记录，您实际上可以这样做（不要！）但这并不是为您有权访问的代码制作扩展方法的好习惯。 Mybirthname's 解决方案是要走的路，这只是为了演示。

public interface ITargetableUnit { }


public static class ITargetableUnitExtension
{

    public static bool unitCanBeTargeted(this ITargetableUnit unit)
    {
        bool targetable = false;
        Insect insect = unit as Insect;
        if(insect != null)
            return insect.isFasterThanLight();
        FighterJet jet = unit as FighterJet;
        if(jet != null)
            return !jet.Flying;
        Zombie zombie = unit as Zombie;
        if(zombie != null)
            return zombie.Invisible;
        return false;
    }
}

Answer 3

也许你想要一个抽象类而不是一个接口？

接口定义了类提供的方法。抽象类也可以做到这一点，但也可以为每个孩子接管一些计算。

请注意，从技术角度来看，Insect 也可以是 Zombie。

编码愉快！

public abstract class TargetableUnit
{
    //Returns whether the object of a class that implements this interface is targetable
    public bool unitCanBeTargeted()
    {
        bool targetable = false;
        if (this is Insect)
        {
            targetable = (this as Insect).isFasterThanLight();
        }
        else if (this is FighterJet)
        {
            targetable = !(this as FighterJet).Flying;
        }
        else if (this is Zombie)
        {
            targetable = !(this as Zombie).Invisible;
        }

        return targetable;
    }
}

public class Insect : TargetableUnit
{
    public bool isFasterThanLight()
    {
        return System.DateTime.UtcNow.Second == 0;
    }
}
public class FighterJet : TargetableUnit
{
    public bool Flying { get; set; }
}
public class Zombie : TargetableUnit
{
    public bool Invisible { get; set; }
}