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From: jmaloney@cs.washington.edu (John Maloney)
Newsgroups: comp.lang.smalltalk
Subject: Re: recognizing instances in Smalltalk/V
Message-ID: <12955@june.cs.washington.edu>
Date: 5 Sep 90 00:07:48 GMT
Organization: U of Washington, Computer Science, Seattle
Lines: 31

Suppose object A has the method "webster" defined as:

    webster
        ^webster

Then "A perform: 'webster' asSymbol" should do the trick. If it
didn't work for then perhaps you are sending the "perform:" message
to the wrong object (in your example you sent it to "self" but
maybe "self" wasn't the object that had "webster" defined? Just a
guess.)

The other thing you can do is:
	A instVarAt: index

where "index" is the index of the instance variable "webster" in object A.
You can find the proper index using:

	index := (A class allInstVarNames) indexOf: 'webster'

Using "instVarAt:" does not even require you to have defined the
method for "webster". What you are doing is intentionally breaking
the object encapsulation of Smalltalk. There are times when this is
justified--for example, the debugger and inspector tools use this trick--
but you should be really sure that this is the only way to do what
you want to do. Why not simply keep a dictionary of name->value
bindings in your object and implement a "getValueOf: aName" message
to look up the values?

This info is for Smalltalk-80; ST/V might differ. Good luck.

	-- John