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From: johnson@p.cs.uiuc.edu
Newsgroups: comp.lang.smalltalk
Subject: Re: super super ?
Message-ID: <80500080@p.cs.uiuc.edu>
Date: 25 Nov 89 17:38:37 GMT
References: <2160@cs-spool.calgary.UUCP>
Lines: 13
Nf-ID: #R:cs-spool.calgary.UUCP:2160:p.cs.uiuc.edu:80500080:000:629
Nf-From: p.cs.uiuc.edu!johnson    Nov 24 22:58:00 1989


Strictly speaking, if Class2 overrides a method defined in its superclass,
Class1, then there is no way that its subclass, Class3, can access the
definition in Class1.  However, this is not a big problem in practice.

For example, Object defines at:, and Set undefines it by providing a
definition that generates an error if executed.  However, Dictionary,
a subclass of Set, needs to access at:.  The standard trick is for
Object to define a basicAt: that is the same thing as at:, and for
no class to redefine basicAt:.  This ensures that any class that
needs to access the basic at: definition will be able to.

Ralph Johnson