Solved

pointer to member functions

Posted on 2000-02-25
2
274 Views
Last Modified: 2010-04-02
#include <stdio.h>
class a
{
public:
 void      funca();
};
class b
{
public:
void   funcb();
};

void a::funca() { printf("aaaaaaaaaaaaaa\n");};
void b::funcb() { printf("bbbbbbbbbbbbbb\n");};

class c:public a,public b
{
public:
      typedef void (c::*FUNC)();

      c(int aint){if (aint==0)
                  funcc=&c::funca;
                  else
                  funcc=&c::funcb;
                  
      };
      ~c(){};
public:
      void stubfunc(){(this->*funcc)();};//why need this-> ?
public:
   
      FUNC funcc;
};

void main()
{
      c ac(0),bc(1);
      (ac.*ac.funcc)();// why not be ac.*funcc()? more details will
                         // be appreciated.
      (ac.*bc.funcc)();// it's right! why?
      (bc.*ac.funcc)();
      (bc.*bc.funcc)();
      ac.stubfunc();
      bc.stubfunc();

}
0
Comment
Question by:anonexperts
[X]
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions
2 Comments
 
LVL 5

Expert Comment

by:Wyn
ID: 2560206
hi,anonexperts:

one trival hint:

All non-static functions need a specific valid class instance to work with.

one friendly advice:

Here many experts on this field ,but you'd better give more points(at least 50pt).That will interst them to answer you and you will get more help.It's worthy.

Regards
W.Yinan

0
 
LVL 10

Accepted Solution

by:
RONSLOW earned 5 total points
ID: 2560767
>void stubfunc(){(this->*funcc)();};//why need this-> ?

->* is required to dereference the function pointer.

funcc() would not be enough.

You alwas need a LHS for the ->* (or .*) member-function pointer.  And in this case, it is a member of ourself (ie. this) that we want to call.

>(ac.*ac.funcc)();// why not be ac.*funcc()? more details will
>                         // be appreciated.

ac.*funcc would mean there is a local var called funcc that is a pointer-to-memeber-function.  In this case, the pointer to memeber function is a member of ac, so you need ac.*ac.func

>(ac.*bc.funcc)();// it's right! why?

yes .. this looks at bc to see which memeber function bc.funcc is pointing to, and then invokes that function for object ac.

0

Featured Post

Free Tool: IP Lookup

Get more info about an IP address or domain name, such as organization, abuse contacts and geolocation.

One of a set of tools we are providing to everyone as a way of saying thank you for being a part of the community.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Suggested Solutions

Title # Comments Views Activity
FMX enumerated colours 2 153
C++ help/ Toy problem 19 69
Need some help with mailto 16 41
Winapi.Windows.hpp problem 7 40
Written by John Humphreys C++ Threading and the POSIX Library This article will cover the basic information that you need to know in order to make use of the POSIX threading library available for C and C++ on UNIX and most Linux systems.   [s…
Introduction This article is the first in a series of articles about the C/C++ Visual Studio Express debugger.  It provides a quick start guide in using the debugger. Part 2 focuses on additional topics in breakpoints.  Lastly, Part 3 focuses on th…
The viewer will learn how to pass data into a function in C++. This is one step further in using functions. Instead of only printing text onto the console, the function will be able to perform calculations with argumentents given by the user.
The viewer will learn additional member functions of the vector class. Specifically, the capacity and swap member functions will be introduced.

737 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question