在 C++ 中扩展枚举?
C++ 有没有办法扩展/继承"枚举?
Is there a way in C++ to extend/"inherit" enums?
即:
enum Enum {A,B,C};
enum EnumEx : public Enum {D,E,F};
或者至少定义它们之间的转换?
or at least define a conversion between them?
推荐答案
不，没有.
enum 在 C++ 中真的很糟糕，这当然是不幸的.
enum are really the poor thing in C++, and that's unfortunate of course.
即使是 C++0x 中引入的 class enum 也没有解决这个可扩展性问题(尽管它们至少为类型安全做了一些事情).
Even the class enum introduced in C++0x does not address this extensibility issue (though they do some things for type safety at least).
enum 的唯一优点是它们不存在:它们提供了一些类型安全性，同时不会强加任何运行时开销，因为它们被编译器直接替换.
The only advantage of enum is that they do not exist: they offer some type safety while not imposing any runtime overhead as they are substituted by the compiler directly.
如果你想要这样的野兽，你必须自己努力:
If you want such a beast, you'll have to work yourself:
- 创建一个类
MyEnum，其中包含一个 int(基本上) - 为每个有趣的值创建命名构造函数
- create a class
MyEnum, that contains an int (basically) - create named constructors for each of the interesting values
您现在可以随意扩展您的类(添加命名构造函数)...
you may now extend your class (adding named constructors) at will...
虽然这是一种解决方法，但我从未找到一种令人满意的处理枚举的方法......
That's a workaround though, I have never found a satistifying way of dealing with an enumeration...
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