Member function call on shared_ptr through member function pointer in template

Question

This is a template function that takes a pointer (or a pointer like object) and a member function:

template <typename Ptr, typename MemberFunctor> int example(Ptr ptr, MemberFunctor func ) {     return (ptr->*func)(); } 

If works when used with ordinary pointer:

struct C {     int getId() const { return 1; } };  C* c = new C; example(c, &C::getId);    // Works fine 

But it does not work with smart pointers:

std::shared_ptr<C> c2(new C); example(c2, &C::getId); 

Error message:

error: C2296: '->*' : illegal, left operand has type 'std::shared_ptr<C>' 

Why? and How to make something that works with both?

Answer 1

std::shared_ptr doesn't support pointer-to-member access operator (i.e. ->* and .*). So we can't invoke member function pointers with ->* on it directly. You can change the invoking syntax to use operator* and operator.*, which works for both raw pointers and smart pointers.

template <typename Ptr, typename MemberFunctor> int example(Ptr ptr, MemberFunctor func ) {     return ((*ptr).*func)(); } 

LIVE