Does My Class Have This Member Function?

Checking for a Class Member Function of a Given Signature

Consider the challenge of verifying whether a class possesses a specific member function of a predetermined signature. While related to the concept discussed in Scott Meyers' Effective C Third Edition, this problem requires a distinct solution.

The Problem and Requirement

Unlike Meyers' scenario where ensuring the existence of a member function is crucial for compilation, this situation demands a flexible approach. The objective is to distinguish between classes that implement the desired member function and those that do not, triggering different actions accordingly.

A Template Solution

C 11 provides a template-based solution that effectively detects member functions, even those inherited. The provided implementation relies on the is_same trait to check for return type compatibility:

#include <type_traits>

// Check member function presence and return type correctness
template<typename C, typename Ret, typename... Args>
struct has_serialize {
    static constexpr bool value =
        std::is_same<
            decltype( std::declval<T>().serialize( std::declval<Args>()... ) ),
            Ret
        >::type::value;
};

Usage

To utilize this approach, simply specify the class to check, along with the member function's return type and arguments:

struct X {
     int serialize(const std::string&) { return 42; } 
};

std::cout << has_serialize<Y, int(const std::string&amp;)>::value; // prints 1

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