Path: utzoo!attcan!uunet!tut.cis.ohio-state.edu!att!dptg!ulysses!andante!alice!garry
From: garry@alice.UUCP (garry hodgson)
Newsgroups: comp.lang.c++
Subject: Re: What are pointers-to-members good for?
Keywords: member pointers
Message-ID: <11329@alice.UUCP>
Date: 13 Sep 90 19:17:52 GMT
References: <1990Sep4.225920.14917@agate.berkeley.edu>
Organization: AT&T Bell Laboratories, Murray Hill NJ
Lines: 29

In article <1990Sep4.225920.14917@agate.berkeley.edu>, holub@violet.berkeley.edu writes:
> Can anyone give me a realistic example of what pointers to class members
> are good for? I understand how they work and what they do, but all of the
> books I've seen give examples that are too trivial to be useful, and
> every time I try to use them I come up against some structural problem that
> eventually makes me take a different approach.

Here are 2 small but useful examples that I use.

I use a Generic list class, called a Bunch, which has an Invoke() member
function which invokes the specified member function on each of its
elements.

Thus, for example, in the Bunchimplement macro in my Bunch.h, I might have

	void
	Bunch(type)::Print()
	{
		Invoke( &type::Print );
	}

You could use this same approach to build mapping functions like those in Lisp.

In InterViews applications, I have a generic Popup menu class.
Associated with each menu entry is a callback procedure, which is
a member function of the class which owns the menu, and thus has
access to whatever it needs to implement the function.

garry hodgson