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From: tenny@ootool.dec.com (Dave Tenny)
Newsgroups: comp.sys.next
Subject: How do make Objective-C handle circular class references, HELP!
Message-ID: <1991Feb19.012656.2785@engage.enet.dec.com>
Date: 19 Feb 91 01:21:35 GMT
Sender: news@engage.enet.dec.com (USENET News System)
Organization: Digital Equipment Corporation
Lines: 39


I've read all my NeXT Objc docs, including the more useful and no
longer present with V2.0 Chapter 3 from NexT 1.0 docs on Objc.

If there isn't a solution I have to "undo" a class and inline it as a struct,
doubling the complexity of the class inlining it.  Yuck. (It's a lot
of QuadTree code).

Basically, I have this

... in file X.h ...			... in file Y.h ...

#import "Y.h"				#import "X.h"

@interface X				@interface Y
{					{
  Y *d ;				  X *e ;
 }					}

There's more in the classes of course, but the jist is they are 
cooperating object classes.  But I can't figure any way to get Objective
C to handle these circular references, since it lacks the equivalent of
C++ "Class X" forward declaration construct, and the interfaces aren't the same
as C structure tags.

The only solution I have so far is to make all occurances of
one instance of circular reference (say Y in class X) be
of type "id".  But then they'll all incur extra method lookup, and lose
the static type checking.  Speed is crucial in theses particular objects,
and I like to keep static checking when I can get it.

I tried some macro tricks, but nothing worked satisfactorily.
If you know the solution, please let me know.  This is "real" code, I'm
not just trying to come up with yet-another-complaint about 
yet-another-compiler.  

Many thanks for help...

Dave