Path: utzoo!utgpu!news-server.csri.toronto.edu!mailrus!uunet!tcs!nujoizey!gwu
From: gwu@nujoizey.tcs.com (George Wu)
Newsgroups: comp.lang.c++
Subject: Re: What are pointers-to-members good for?
Keywords: member pointers
Message-ID: <1007@tcs.tcs.com>
Date: 11 Sep 90 03:44:17 GMT
References: <1990Sep4.225920.14917@agate.berkeley.edu>
Sender: usenet@tcs.com
Reply-To: gwu@nujoizey.tcs.com (George Wu)
Organization: Teknekron Communications Systems
Lines: 39

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.

     We use such pointers for generic menu item and button classes.  For
instance, we have a generic button which, when pressed, will call the
previously defined function:

class Caller {
	// . . .
};

class CbButton {
	CbButton(const char *label, Caller *object, (Caller::*funcPtr)());

	Press()
};

where Press() looks something like:

CbButton::Press()
{
	(object->*funcPtr)();
}

     We actually use a generic type for CbButton in order to get the type
checking correct.  And we use such code in all sorts of places.  Sure, it's
simple, but it's effective.

							George

----
George J Wu                           | gwu@tcs.com or ucbcad!tcs!gwu
Software Engineer                     | 2121 Allston Way, Berkeley, CA, 94704
Teknekron Communications Systems, Inc.| (415) 649-3752