SFINAE test for specific member function using C++11

member_function_reflection.cpp

#include <iostream>
#include <type_traits>

class Foo {
public:
    int ToString();
};

class Bar {
public:
    char ToString;
};

class Nil {
};

// possible implementatino of std::is_member_function_pointer
// ref. http://en.cppreference.com/w/cpp/types/is_member_function_pointer
// 
// struct is_member_function_pointer_helper : std::false_type {};
// template< class T, class U> 
// struct is_member_function_pointer_helper<T U::*> : std::is_function<T> {};
// template< class T >
// struct is_member_function_pointer : is_member_function_pointer_helper<typename std::remove_cv<T>::type> {};

// test whether T has "ToString" method
template <typename T>
struct has_to_string {
    typedef char Yes[1];
    typedef char No[2];
    template <typename U> static Yes& test(typename std::enable_if<std::is_member_function_pointer<decltype(&U::ToString)>::value,bool>::type=0);
    template <typename U> static No& test(...);
    static bool const value = sizeof(test<typename std::remove_cv<T>::type>(0)) == sizeof(Yes&);
};

int main() {
    std::cout << has_to_string<Foo>::value << std::endl;
    std::cout << has_to_string<Bar>::value << std::endl;
    std::cout << has_to_string<Nil>::value << std::endl;
    std::cout << has_to_string<int>::value << std::endl;
    return 0;
}