Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!shadooby!accuvax.nwu.edu!nucsrl!gore!jacob
From: jacob@gore.com (Jacob Gore)
Newsgroups: comp.sys.next
Subject: Deferred methods and strong typing
Message-ID: <130007@gore.com>
Date: 5 Jul 89 08:41:34 GMT
Reply-To: jacob@gore.com (Jacob Gore)
Organization: Gore Enterprises
Lines: 39

Consider a class that has a deferred method:

  A.h:
	#import <objc/Object.h>
	@interface A:Object {...}
	- (A*)someMethod;
	...
	@end
  A.m:
	#import "A.h"
	- (A*)someMethod { return [self subclassResponsibility]; }

and a subclass that implements that method:

  B.h:
	#import "A.h"
	@interface B:A {...}
	- (B*)someMethod;
	...
	@end
  B.m:
	#import "B.h"
	- (B*)someMethod { ... actual implementation ... }

Now, consider the use of someMethod:

  C.m:
	#import "B.h"
	...
	[anInstanceOfB someMethod];

Intuition tells me that B's someMethod is to be used.  But the compiler in
0.9 gives a "multiple declarations for method `someMethod'" warning, and
then uses A's someMethod.

What's the scoop?

--
Jacob Gore	Jacob@Gore.Com		{nucsrl,boulder}!gore!jacob