使用枚举进行类型检查

使用枚举进行类型检查 - 如何正确定位范围(Using enums for type checking — how to scope properly)

我有一个C ++类的混合，其中一些存储状态变量0..9作为整数，其他使用'0'...'9'。 目前我这样做：

enum { kOne = '1' }; class StoresValueAsInt { static int value; // contains 0 ... 9 }; class StoresValueAsChar { static char value; // contains '0' ... '9' }; class StoresValueAsChar { static char value; }; template <typename X> isOne() { return X::value == kOne; }

这允许我编写错误的代码isOne<StoresValueAsInt::value>() 。 相反，我想让编译器抱怨这种不正确的用法。 我尝试了以下方法：

enum ValueInt { kOne = 1 }; enum ValueChar { kOne = '1' }; class StoresValueAsInt { static ValueInt value; }; class StoresValueAsChar { static ValueChar value; }; class StoresValueAsChar2 { static ValueChar value; };

但是，这不起作用，因为kOne在命名空间级别是可见的，因此它具有冲突的kOne声明。

有没有办法不在命名空间中声明枚举？ 或者更好的方法吗？

更新：添加了我目前所做的事情; 希望澄清我的用例。

I have a mixture of C++ classes, some of which store a state variable 0..9 as integer, others use '0' ... '9'. Currently I do:

enum { kOne = '1' }; class StoresValueAsInt { static int value; // contains 0 ... 9 }; class StoresValueAsChar { static char value; // contains '0' ... '9' }; class StoresValueAsChar { static char value; }; template <typename X> isOne() { return X::value == kOne; }

This allows me to write the buggy code isOne<StoresValueAsInt::value>(). Instead, I would like to have the compiler complain about this incorrect usage. I tried the following:

enum ValueInt { kOne = 1 }; enum ValueChar { kOne = '1' }; class StoresValueAsInt { static ValueInt value; }; class StoresValueAsChar { static ValueChar value; }; class StoresValueAsChar2 { static ValueChar value; };

However, this does not work, because kOne is visible at the namespace level, and thus it has conflicting declarations of kOne.

Is there a way to not have the enums declared in the namespace? Or a better approach here?

updated: Added what I currently do; hoping to clarify my use case.

最满意答案

就最佳实践而言，我真的不确定你要在这里完成什么，所以我不能指出你正确的方向。

但是，要直接回答您的问题：将枚举放在单独的命名空间中可以解决您的问题：

namespace IntVals { enum ValueInt { kOne = 1 }; } namespace CharVals { enum ValueChar { kOne = '1' }; } class StoresValueAsInt { static ValueInt value; }; class StoresValueAsChar { static ValueChar value; };

然后你应该能够使用以下内容：

StoresValueAsInt::value == CharVals::kOne

虽然这很丑陋，但我希望我能更好地理解你的目标，提供比这更优雅的解决方案。

As far as best practice, I'm really not sure what you are trying to accomplish here so I can't point you in the right direction.

However, to answer your question directly: Placing the enums in seperate namespaces would solve your issue:

namespace IntVals { enum ValueInt { kOne = 1 }; } namespace CharVals { enum ValueChar { kOne = '1' }; } class StoresValueAsInt { static ValueInt value; }; class StoresValueAsChar { static ValueChar value; };

Then you should be able to use the following:

StoresValueAsInt::value == CharVals::kOne

Though this is ugly, and I wish I understood better what you were going for to offer a more elegant solution than this.