From:	hhkraemer AT web DOT de (Horst Kraemer)
Newsgroups:	comp.os.msdos.djgpp
Subject:	Re: How would I build a pointer to a method of my class
Date:	Sun, 08 Apr 2001 10:38:43 GMT
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On Sun, 8 Apr 2001 11:16:25 +0200, "Wormy" <wormy AT technologist DOT com>
wrote:

> Hello all!
> 
> In simple C, I would do something like this:
> 
> 
> -------------------------------------------
> typedef void (My_func)(short parameter);
> 
> My_func Pointer_to_My_func;
> -------------------------------------------
> 
> and then, later in my code (DOTHIS_func and DOTHAT_func are declared and
> defined somewhere)
> 
> -------------------------------------------
> if (i == 0)
>     Pointer_to_My_func = DOTHIS_func;
> else
>     Pointer_to_My_func = DOTHAT_func;
> 
> (*Pointer_to_My_func)(parameter_to_pass);
> ----------------------------------------------
> 
> OK.... but now, how am I doing it in C++ if I'm fumbling around with a
> class?
> 
> ------------
> class CMy_class
> {
>     void DOTHIS_method(short parameter);
>     void DOTHAT_method(short parameter);
> 
>     void ANOTHER_method();
> };
> 
> CMy_class My_class;
> --------------------------------
> 
> And, in the method ANOTHER_method() I would like to set the pointer to one
> of the two methods above (as I did it in C)... BUT I DON'T HAVE ANY IDEA
> HOW! I wrote down a simple pseudocode below.
> (NOTE: DOTHIS_method and DOTHAT_method are all methods of the same class)
> 
> -------------------------------
> void ANOTHER_method()
> {
> .
> .
> .
> 
>     if (i == 1)
>         pointer should point to DOTHIS_method;
>      else
>         pointer should point to DOTHAT_method;
> 
>     and now call the method my pointer is pointing to
> 
> .
> .
> .
> }
> -----------------------------
> 
> Can someone please give me a hint? BTW I am using VISUAL C++ 6.0 if this
> problem couldn't be solved in "ANSI" C++


class CMy_class
{
   void DOTHIS_method(short parameter);
   void DOTHAT_method(short parameter);
   typedef void (CMy_class::*PMF) (short);
public: 
   void ANOTHER_method();
};

void CMy_class::ANOTHER_method(short)
{
  PMF pmf;

  pmf = &CMy_class::DOTHIS_method;

  (this->*pmf)(42);
}

This is ANSI C++ and supported by MSVC++ (and gcc of course).

 
Regards
Horst

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