How to override static method of template class in derived class

Question

I'm having a little issue with overriding static methods of base clases, but the whole question is very complicated and too long (generalization of resource management in game engine), so here's a simplified version:

template<class T> class base {     static void bar()     { printf("bar"); } public:     static void foo()     { bar(); } };  class derived : public base<int> {     static void bar()     { printf("baz"); } };  int main() { derived::foo(); } 

The code above outputs "bar" in my case, insted I want it to output "baz". How can I go about that? It seems that no matter what I attempt, base::foo() always calls base::bar(). I might have an issue with the design. I've never came across this problem - how can I resolve it?

Answer 1

What you're trying to do is not achievable with simple class inheritance; a method cannot be both static and virtual.

You need a static method to be able to call a function without an object (an instance); and you need bar to be virtual so that bar<int>::foo() calls derived::bar() when called from a derived instance.

Those two traits are mutually exclusive. But the Curiously Recursive Template Pattern (CRTP) may be a solution here:

#include <iostream>  template<class T> struct base {     static void foo()     {         T::bar();     } };  struct derived : public base<derived> {     static void bar()     {         std::cout << "derived" << std::endl;     } };  int main() {     derived::foo(); } 

Live example