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From: terry@cs.tamu.edu (Terry Escamilla)
Newsgroups: comp.lang.smalltalk
Subject: Help with perplexing Smalltalk question
Message-ID: <11770@helios.TAMU.EDU>
Date: 4 Feb 91 17:23:13 GMT
Sender: usenet@helios.TAMU.EDU
Distribution: usa
Organization: Computer Science Department, Texas A&M University
Lines: 62


Hello.  I ran into a few problems with ST v/286 while working
at home last night.

(1) How do you get rid of Global Variables?  I created a
    global var as an instance of a class.  When I tried
    to modify the class, ST claimed I couldn't because my
    class had instances.  I tried a series of mistakes
    as indicated below.

(2) First I tried 'Smalltalk at: #VarName put: nil'.  
    But that didn't solve the problem.  I think it
    removed the relationship link from VarName to the
    class, but not vice versa.  So my class still thought
    it had some instances.

(3) Then I tried 'Smalltalk removeKey: #VarName' which
    screwed up everything.  I had to reload the system
    and fileIn all of the classes I had written.     

(4) By accident, I removed the name of one of my subclasses
    from the Smalltalk system dictionary.  However, in
    the ClassBrowser, the parent class still was linked to
    that subclass.  Clicking on the subclass name in the 
    ClassBrowser resulted in an error message telling me
    that the subclass did not exist (even though it shows
    in the Browser list for the parent class).  So, there's
    no way to stop the subclass from showing up in the
    Browser.  Any way to fix this?

I've decided to avoid global variables all together because I
could never figure out a way to disassociate a global variable
from the class it was created from.  Here are a few other 
questions.

(5) Is there any way to find out the names of all the global
    variables the system knows?  I apparently forgot
    some (and had already compressed the change log), so it
    was impossible for me to remove them because I didn't
    know their names.

(6) Back to (1) above, even if you know the name of a global
    var, how do you delete it?

(7) Is there any way to delete the instances which a class
    has?  I tried a bunch of different ways to inspect the
    class, but could never get a useful list of current
    instances for that class.  If I'd found the instances
    list and modified it, would that have caused some
    dangling pointers anywhere?

(8) If there are some instances of a class, and you want to
    change the class, the instances must somehow be deallocated.
    If they are global variables, is there a way to
    de-reference them from the class without removing them from
    the system dictionary?

Thanks for any insight on this murky matter.

Terry Escamilla
terry@cs.tamu.edu