Path: utzoo!attcan!uunet!husc6!bbn!rochester!pt.cs.cmu.edu!andrew.cmu.edu!sa1z+
From: sa1z+@andrew.cmu.edu (Sudheer Apte)
Newsgroups: comp.lang.smalltalk
Subject: Message dispatch on argument class
Message-ID: <AXRDuKt78k-04Ce11X@andrew.cmu.edu>
Date: 7 Nov 88 01:38:30 GMT
Organization: Carnegie Mellon
Lines: 20

Suppose I want the same selector to behave differently depending upon the class
of the argument. In Smalltalk (I run ParcPlace V2.2 on a Sun 3/50) I have to
write the method thus:

add: anObject

(anObject class == Class1) ifTrue:
     [^self privateAdd1: anObject]
ifFalse:
     ["Code dealing with all other valid classes"]

I have to make this decision within the method because I have no way
in Smalltalk to specify different methods to be invoked by the same message
selector depending upon the class of the argument. It seems this problem has
been well researched, and some kind of solution has been found which does not
sacrifice speed. Anyone know anything about this?

Thanks,
Sudheer.
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