我有几个类实际上不需要任何状态。从组织的角度来看,我想把他们放在层次结构中。
但是我似乎不能为静态类声明继承。
就像这样:
public static class Base
{
}
public static class Inherited : Base
{
}
不会起作用。
为什么语言的设计者们拒绝了这种可能性呢?
我有几个类实际上不需要任何状态。从组织的角度来看,我想把他们放在层次结构中。
但是我似乎不能为静态类声明继承。
就像这样:
public static class Base
{
}
public static class Inherited : Base
{
}
不会起作用。
为什么语言的设计者们拒绝了这种可能性呢?
当前回答
引用本文:
This is actually by design. There seems to be no good reason to inherit a static class. It has public static members that you can always access via the class name itself. The only reasons I have seen for inheriting static stuff have been bad ones, such as saving a couple of characters of typing. There may be reason to consider mechanisms to bring static members directly into scope (and we will in fact consider this after the Orcas product cycle), but static class inheritance is not the way to go: It is the wrong mechanism to use, and works only for static members that happen to reside in a static class. (Mads Torgersen, C# Language PM)
来自9频道的其他观点
Inheritance in .NET works only on instance base. Static methods are defined on the type level not on the instance level. That is why overriding doesn't work with static methods/properties/events... Static methods are only held once in memory. There is no virtual table etc. that is created for them. If you invoke an instance method in .NET, you always give it the current instance. This is hidden by the .NET runtime, but it happens. Each instance method has as first argument a pointer (reference) to the object that the method is run on. This doesn't happen with static methods (as they are defined on type level). How should the compiler decide to select the method to invoke? (littleguru)
作为一个有价值的想法,littleuru对这个问题有一个部分的“变通方案”:单例模式。
其他回答
虽然可以通过继承的类名访问“继承的”静态成员,但静态成员并不是真正继承的。这就是为什么它们不能是虚拟的或抽象的,也不能被覆盖的部分原因。在你的例子中,如果你声明了一个Base.Method(),编译器无论如何都会将对Inherited.Method()的调用映射回Base.Method()。您也可以显式地调用Base.Method()。您可以编写一个小测试,并使用Reflector查看结果。
所以…如果不能继承静态成员,并且静态类只能包含静态成员,那么继承静态类又有什么用呢?
当我试图对第三方库编写IComparer<T>实现时,我遇到了这个问题,其中T是嵌入在类中的enum,如下所示:
public class TheClass
{
public enum EnumOfInterest
{
}
}
但是因为枚举是在第三方库类中定义的,所以我不能编写比较器,因为下面给出了“不能扩展列表”错误:
public class MyComparer : IComparer<TheClass.EnumOfInterest>
{
}
我甚至没有扩展静态类——我只是实现类中定义的枚举的比较器。
嗯…如果你只是用静态方法填充非静态类,情况会有很大不同吗?
引用本文:
This is actually by design. There seems to be no good reason to inherit a static class. It has public static members that you can always access via the class name itself. The only reasons I have seen for inheriting static stuff have been bad ones, such as saving a couple of characters of typing. There may be reason to consider mechanisms to bring static members directly into scope (and we will in fact consider this after the Orcas product cycle), but static class inheritance is not the way to go: It is the wrong mechanism to use, and works only for static members that happen to reside in a static class. (Mads Torgersen, C# Language PM)
来自9频道的其他观点
Inheritance in .NET works only on instance base. Static methods are defined on the type level not on the instance level. That is why overriding doesn't work with static methods/properties/events... Static methods are only held once in memory. There is no virtual table etc. that is created for them. If you invoke an instance method in .NET, you always give it the current instance. This is hidden by the .NET runtime, but it happens. Each instance method has as first argument a pointer (reference) to the object that the method is run on. This doesn't happen with static methods (as they are defined on type level). How should the compiler decide to select the method to invoke? (littleguru)
作为一个有价值的想法,littleuru对这个问题有一个部分的“变通方案”:单例模式。
您希望通过使用类层次结构实现的目标可以通过命名空间实现。因此,支持名称空间的语言(如c#)将无法实现静态类的类层次结构。因为您不能实例化任何类,所以您所需要的只是通过使用名称空间获得的类定义的分层组织