Path: utzoo!utgpu!jarvis.csri.toronto.edu!cs.utexas.edu!samsung!munnari.oz.au!murtoa.cs.mu.oz.au!charlie!aragorn!rad
From: rad@aragorn.cm.deakin.oz.au (Robert Alan Dew)
Newsgroups: comp.lang.smalltalk
Subject: Re: Data-Hiding?  Really??
Message-ID: <7961@charlie.OZ>
Date: 18 Jan 90 03:38:19 GMT
References: <4811d5e9.20b6d@apollo.HP.COM>
Sender: root@charlie.OZ
Reply-To: rad@aragorn.UUCP (Robert Alan Dew)
Organization: Department of Computing & Mathematics - Deakin University
Lines: 33

In article <4811d5e9.20b6d@apollo.HP.COM> yon@apollo.HP.COM (David Yon) writes:

	[ ... ]

#| apple basket integer anotherApple |
#
#	apple := Apple new.
#	apple setRipeness: 6.
#	basket := AppleBasket new.
#	basket putApple: apple.
#	anotherApple := basket getApple.
#	anotherApple setRipeness: 5
#	basket inspect.
#
#	You'll find that by setting the ripeness factor of the 
#anotherApple variable, it changed the state of the object in the
#AppleBasket.  So the ripeness of the Apple in the AppleBasket will
#have been changed to five.  On the surface, this appears to violate
#the rule that only objects can change their own state.
#
#	Any thoughts on this?

The expression basket getApple returns the Apple instance with ripeness
of 6, not another Apple instance.

Hence the object anotherApple is the object apple.

Robert Dew                             rad@aragorn.cm.deakin.oz.au
Department of Computing and Mathematics
Deakin University
Geelong 
Victoria
Australia 3217