如何检测具有特定签名的静态成员函数的存在？ [英] How to detect the presence of a static member function with certain signature?

问题描述

我发现了几个问题，关于在处理时（通过SFINAE）检测给定类是否具有特定名称，类型或签名的成员的SO的答案。但是，我找不到一个同样适用于静态公共成员函数的函数（当指向成员的技巧不起作用时）。有任何想法吗？

I found several questions & answers on SO dealing with detecting at compile time (via SFINAE) whether a given class has a member of certain name, type, or signature. However, I couldn't find one that also applies to static public member functions (when pointer-to-member tricks won't work). Any ideas?

推荐答案

以下方法可能会有所帮助：（ https ：//ideone.com/nDlFUE ）

Following may help: (https://ideone.com/nDlFUE)

#include <cstdint>

#define DEFINE_HAS_SIGNATURE(traitsName, funcName, signature)               \
    template <typename U>                                                   \
    class traitsName                                                        \
    {                                                                       \
    private:                                                                \
        template<typename T, T> struct helper;                              \
        template<typename T>                                                \
        static std::uint8_t check(helper<signature, &funcName>*);           \
        template<typename T> static std::uint16_t check(...);               \
    public:                                                                 \
        static                                                              \
        constexpr bool value = sizeof(check<U>(0)) == sizeof(std::uint8_t); \
    }

然后定义一个特征：

DEFINE_HAS_SIGNATURE(has_foo, T::foo, void (*)(void));

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