Pointer to function in C++

[Cgangster]

Hi,
Can anyone help me how to creat a pointer function in C++?

class Mailbox
{
    public:
       Mailbox();
       Mailbox(int add, string mess);
       void setMessage(string mess);
       void setAddress(int add); 
       char * getMessage();
       void (*fun)(int callback); 

       ~Mailbox();
};
How to implement and pass the pointer function in a class?
Thank you.

[Prelude]

>How to implement and pass the pointer function in a class?
It depends on what you're trying to do with this function pointer, in most cases I would have the address of the function be passed either to the constructor as an explicit argument, or assigned with a member function to a private function pointer which the class can then use:

#include <iostream>

typedef std::ostream& (*pf)( std::ostream&, const char * );

class test
{
public:
  explicit test ( pf func ) : display ( func ) {}

  void print_console ( const char *mess ) { display ( std::cout, mess ); }
private:
  pf display;
};

std::ostream& display_mess ( std::ostream& out, const char *mess )
{
  return out<< mess;
}

int main()
{
  test t ( display_mess );

  t.print_console ( "This is a test" );

  std::cin.get();
}

-Prelude

[Cgangster]

Thanks a lot! Prelude.
If you dont mind, can you illustrate a less complicate example with
not involved with C++ buildin objects like ostream.
Again, thanks for your help
Cgangster

[Prelude]

>If you dont mind, can you illustrate a less complicate example
No problem, I wasn't sure of your experience level. This is simplified a bit and commented liberally with details I thought may not make sense at first, let me know if you would like me to explain something that is unclear.

#include <iostream>

typedef void (*pf)( const char * );
// Now pointers to functions of this type can be declared as
//   pf <variable>
//
//   instead of the ugly and confusing
//
//   void (*<variable>)( const char * );

class test
{
public:
  explicit test ( pf func ) { display = func; }
  // Declaring a single argument constructor as explicit means
  // that it can only be called as constr <object> ( <argument> );
  // and not as constr <object> = <argument>;

  void print_console ( const char *mess ) { display ( mess ); }
private:
  pf display; // Pointer to function
};

void display_mess ( const char *mess )
{
  std::cout<< mess;
}

int main()
{
  test t ( display_mess );
  // You can pass the address of a function as either <name> or &<name>.
  // Both forms are equivalent since any operation performed on a function
  // is either calling it or taking its address. Since you obviously aren't
  // calling it, then you must be taking its address.

  t.print_console ( "This is a test" );

  std::cin.get();
}

-Prelude