Re: Function-pointers and classes

[Cosmin Halmagi <hcosmin@go.ro>]

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This is for you and the other person who needed help on this.

Function pointers and class member pointers are two different entities in c++ (because class members have to deal with polymorfism, etc...)

So you can't assign to a function pointer the adress of a class member but you can assign it to a class member pointer.

(note: member pointers automaticly deal with polymorfism)

It is defined as: type (classname::*pointername)(parameters);

You can use such a pointer using the ".*" and "->*" operators.

Example:

#include <iostream.h>

class c{
public:
 int(c::*xx)(); /* pointer to member*/
 c();
 int x();
 y();

 };

c::c(){}
int c::x()

{

 return -1;

}
c::y()

{

 xx=&c::x;
 return (this->*xx)();

}

void main()
{

 c cc;
 cout<<cc.y(); /*-1*/

}

 

Unfortunatly this things are often not known.

So c++ is great after all :)

-----Original Message-----
From: Christian Gyrling <d98chgy@stud.hh.se>
To: Game Programmers Mailing List <gameprogrammer@topica.com>
Date: Tuesday, March 06, 2001 12:43 PM
Subject: Function-pointers and classes

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Hello all

 

First of all I give credit to all those who are taking control

of this multi-programmer-game.

 

Next I have a problem similar to that oh Josiha Avery. The thing is

how to use a function-pointer to an instance in a class.

 

int CacheSocket::create()

{

// Locally defined function pointer

// This is how the function-pointer should look to be accepted in the CreateThread

DWORD   (__stdcall *func)(void*);

 

// A function defined in the class we are currently in
func = this->ServerThread;            // THIS IS WHERE THE ERROR OCCURS

ERROR MSG

cannot convert from 'unsigned long (__stdcall CacheSocket::*)(void *)'

to 'unsigned long (__stdcall *)(void *)'

 

// Create the thread

CreateThread( NULL, 0, (LPTHREAD_START_ROUTINE)func, NULL, NULL, &ThreadId );

}

 

DWORD WINAPI CacheSocket::ServerThread( LPVOID lpParameter )

{

}

 

Please help me with this one

 

Christian Gyrling

 

 

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