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From: dingelde@viktoria.grz (Dennis Dingeldein)
Newsgroups: comp.lang.c++
Subject: Again: Pointer to methods ?
Keywords: Pointers to methods
Message-ID: <2292@zgdvda.zgdvda.uucp>
Date: 10 Aug 90 08:48:33 GMT
Sender: news@zgdvda.zgdvda.uucp
Organization: ZGDV Darmstadt, FRG
Lines: 60

Hello!

I scanned our old articles of "comp.lang.c++" but couldn`t find a *real*
solution to the following problem. 
I`m sorry if that problem was already solved last year :-)

Problem:

1. The method of my class needs to accept a pointer to a method of another
class.
	MyClass::SetPointer( <Method of another class> )

2. At compile time of my class I don`t know anything about the other class.

3. SetPointer must be a *method* (of my class), no C function.

4. A solution like "Use a third class with virtual method "SetPointer" and
derive from that class "SetPointer" methods with the appreciated parameters"
is not the one I like to use. This seems to me like "programming around the 
problem because I couldn`t solve it".

I`ll give a simple example, what I wan`t to do with that method

// ----- start of example

// class Menu provides a pulldown functionality
class Menu {

public:
	SetPointer( ???? ); // the method ???? will be called if any
			    // Menu Entry is selected (not senseful, I know)
	Start(); // display and start the interaction with the menu
	...
};

// class Circle is unknown class, here only for the example visible
// it provides the output behaviour of a circle.
class Circle {

public:
	Draw(); // displays the circle
};

// main shows a menu and draws the circle on selection
main() {
	Menu MyMenu( "Draw Circle" );
	Circle MyCircle( ... );

	MyMenu.SetPointer( MyCircle::Draw( ... ) );

	// If the User selects an entry , the circle is drawn!
	Menu.Start();
}

Who know's what to do ? What`s the prototype of Method "SetPointer" ?

Dennis Dingeldein	ZGDV Zentrum fuer Graphische Datenverarbeitung
(dingelde@zgdvda.uucp)	Wilhelminenstr. 7
			D-6100 Darmstadt, West Germany
			Phone: +49/6151/155-121