How to define a function pointer to a member function of an object

Pointer to non-static member function.

As the member functions depend on object, the point of a non-static function is actually an offset.

   1:  class A

   2:  {

   3:      int _val;

   4:      int val();

   5:  };

   6:   

   7:  int (A::*p_val) = &A::_val;

   8:  int ( A::*p_func )() = &A::val；

Pointer to static member function. As static function of a class does not depend on any object of that class, the pointer is the same as the one in C.

   1:  class A

   2:  {

   3:      static int _val;

   4:      static int val();

   5:  };

   6:   

   7:  int *p_val = &A::_val;

   8:  int (*p_func) = &A::val;

Advantages: 1. easy to call; 2. callback function

A complete example:

   1:  #include <iostream>

   2:  #include <string>

   3:  using namespace std;

   4:   

   5:  typedef void (*funchandler)();

   6:   

   7:  void register_func(funchandler f)

   8:  {

   9:      cout << "register_func" << endl;

  10:      (*f)();

  11:  }

  12:   

  13:  class A

  14:  {

  15:  public:

  16:      A() : _val( 0 ) { cout << "create A..." << endl; }

  17:      void test() { cout << "test..." << endl; }

  18:      void test1() { cout << "test1..." << endl; }

  19:      void test2() { cout << "test2..." << endl; }

  20:      int val() { return _val; }

  21:      static void test3() { cout << "test3..." << endl; }

  22:      int _val;

  23:  private:

  24:  };

  25:   

  26:  int main()

  27:  {

  28:      A a;

  29:      int ( A::*p_val ) = 0;

  30:      p_val = &A::_val;

  31:      cout << "a.*p_val: " << a.*p_val << endl;

  32:     

  33:      void (A::*p_func)();

  34:      p_func = &A::test;

  35:     

  36:      a.test();

  37:      (a.*p_func)();

  38:     

  39:      p_func = &A::test1;

  40:      ( a.*p_func )();

  41:      p_func = &A::test2;

  42:      ( a.*p_func )();

  43:     

  44:      void (* pp_func)();

  45:      pp_func = &A::test3;

  46:      (*pp_func)();

  47:     

  48:      register_func( pp_func );

  49:      return 0;

  50:  }