Following the article written in here:
I came across this code (shortened and changed for clarity):
template <class T> struct hasSerialize
{
// This helper struct permits us to check that serialize is truly a method.
// The second argument must be of the type of the first.
// For instance reallyHas<int, 10> would be substituted by reallyHas<int, int 10> and works!
// reallyHas<int, &C::serialize> would be substituted by reallyHas<int, int &C::serialize> and fail!
// Note: It only works with integral constants and pointers (so function pointers work).
// In our case we check that &C::serialize has the same signature as the first argument!
// reallyHas<std::string (C::*)(), &C::serialize> should be substituted by
// reallyHas<std::string (C::*)(), std::string (C::*)() &C::serialize> and work!
template <typename U, U u> struct reallyHas;
// We accept a pointer to our helper struct, in order to avoid to instantiate a real instance of this type.
// std::string (C::*)() is function pointer declaration.
template <typename C>
static char&
test(reallyHas<std::string (C::*)(), &C::serialize>* /*unused*/) { }
};
So this
std::string (C::*)()
caught my attention.
Can anyone explain me the C::* part? That is a function pointer that returns std::string but what more?
