Path: utzoo!attcan!uunet!tut.cis.ohio-state.edu!zaphod.mps.ohio-state.edu!sdd.hp.com!ucsd!ucbvax!pasteur!agate!shelby!daemon
From: shiffman@sumex-aim.stanford.edu (Smadar Shiffman)
Newsgroups: comp.sys.next
Subject: re: Null Selector (was Re: Question about Objective-C's @selector)
Message-ID: <2225@shelby.Stanford.EDU>
Date: 18 Jul 90 15:23:22 GMT
Sender: daemon@shelby.Stanford.EDU
Lines: 20


In his posting from Jul 18 neveu@fugitive.berkeley.edu writes

>I have a question about SEL variables. How do you initialize a SEL variable
>to have an invalid, or null, value.  That is, I have a SEL variable that I
>want to initialize to a value that is invalid; some part of the program will
>set the value to a valid selector; another part of the program will check
>the value to determine whether it is valid and if it is, send that message
>to an object.
>So what do I initialize the variable to? 0? -1? (int) NULL?

SEL is defined in /usr/include/objc/objc.h :
typedef unsigned int		SEL;

As far as I know 0 is not used for any selector (you can see that by
requesting 'info selector' when running gdb with some application). I would
try using 0 as an 'invalid' selector.

	Smadar
-------