How can Derived class inherit a static function from Base class?

Question

struct TimerEvent
{
   event Event;
   timeval TimeOut;
   static void HandleTimer(int Fd, short Event, void *Arg);
};

HandleTimer needs to be stat

Answer 1

To some extent the traits pattern lets you inherit and redefine static methods.

First start with a base class:

struct base {
  static void talk()  { std::cout << "hello" << std::endl; }
  static void shout() { std::cout << "HELLO !!" << std::endl; }
};

Then derive it and redefine some methods:

struct derived: public base {
  static void talk()  { std::cout << "goodbye" << std::endl; }
};

And now call the methods via a traits class:

template < class T >
struct talker_traits {
  static void talk() { T::talk(); }
  static void shout() { T::shout(); }
};

talker_traits::talk()     // prints "hello"
talker_traits::shout()    // prints "HELLO !!"

talker_traits::talk()  // prints "goodbye"
talker_traits::shout() // prints "HELLO !!"

ideone demo

The traits class lets you reuse the static method base::shout while "overriding" base::talk with derived::talk. Still, there are several difference with actual inheritance:

• The function to call is resolved at compile time
• The child method needs not have the same signature as the parent one

It works with static fields and typedefs too, the best example is std::iterator_traits.