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From: pbiron@weber.ucsd.edu (Paul Biron)
Newsgroups: comp.sys.next,comp.lang.objective-c
Subject: Re:  probate
Summary: how to keep a sub-class from inheriting from its super-class?
Keywords: doesNotRecognize:(SEL)aSelector
Message-ID: <3874@network.ucsd.edu>
Date: 16 Oct 90 17:07:44 GMT
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Reply-To: pbiron@weber.ucsd.edu (Paul Biron)
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In <3861@network.ucsd.edu>, pbiron@weber.ucsd.edu (Paul Biron) writes:
	>I'm trying to figure out an "elegent" way to keep a sub-class
	>from inheriting methods from its super-class.

	[feable attempt deleted]

	>In other words, just give the same kind of message that the
	>Obj-C runtime mechanism gives when you send an unknown message
	>to an object.

	>Is there a "better" way?  Is there anything in the specs for
	>Obj-C which say how this should be handled (I couldn't find
	                                             ^^^^^^^^^^^^^^
	                                             see below

Thanx to those who responded to my posting.

Here is the answer.  The Object class defines a method

	-doesNotRecognize:(SEL)aSelector

which does just what I want.  So to prevent a sub-class from
inheriting a method from its super-class just re-define it as:

- someMethod:arg
{
	[self doesNotRecognize:@(someMethod:)] ;
	return (self) ;
}

The reason for my not being able to find this in the NeXT on-line
manuals is that the description given for this method says (Chap 22, p 31):

	- doesNotRecognize:(SEL)aSelector
		Prints an error message.  The Objective-C run-time system
		sends doesNotRecognize: messages whenever an object
		recieves an _aSelector_ message that it can't respond
		to.  You generally wouldn't send them in the code you write.

Again, I have to bitch about NeXT documentation (or maybe this
Spec Sheet comes straight from StepStone, even though it does
have NeXT specific things in it?).  Upon first purusal of the
Spec Sheet, I read "the run-time system sends" and "you wouldn't
send", so I just skipped over it, thinking that it didn't apply.
Not only that, but it doesn't mention that a SIGIOT is generated!

Thanx again to those who pointed me at this.

Paul Biron      pbiron@ucsd.edu        (619) 534-5758
Central University Library, Mail Code C-075-R
Social Sciences DataBase Project
University of California, San Diego, La Jolla, Ca. 92093