Path: utzoo!attcan!uunet!tektronix!tekcrl!tekgvs!jans
From: jans@tekgvs.GVS.TEK.COM (Jan Steinman)
Newsgroups: comp.lang.smalltalk
Subject: Re: Unwanted Instances
Message-ID: <4179@tekgvs.GVS.TEK.COM>
Date: 1 Nov 88 00:03:50 GMT
Distribution: na
Organization: Tektronix Inc., Beaverton, Or.
Lines: 42

<<jans@tekgvs.GVS.TEK.COM (Jan Steinman)>>
<obrien@anpiel.aero.org (Mike O'Brien)>

<<Any object that is potentially circular... should implement "release"...  
I've implemented a number of methods for... carrying on a dialog with a 
sender...>>

<..."release" is a good first level of defense..., (but doesn't) always work.. 
(for) those cases where an execution error interrupts the normal flow of 
control and prevents various "release" methods from ever being sent...  The 
only thing I can think of to do is to implement a special case of your 
"dialog":>

(N.B.:  The following is for Tek Smalltalk, your mileage may vary.  I just 
wrote it on the spot to illustrate the point, and it should not be considered a 
fully debugged solution!)

As a starting point, here is a method that will execute a block for each sender 
in the context.  When things break, DO NOT throw away the debugger, instead, 
execute within the debugger:

	thisContext sendersDo: [:sender |
		(#(TroublesomeClass1 TroublesomeClass2) includes: sender class)
			ifTrue: [sender release]]

Note that simply putting "sender release" in the block will probably 
irrepairably damage your image, as things like ControlManager get released!

{!ContextPart methodsFor: 'testing'!

sendersDo: aBlock
	"Cause each sender receiver to execute <aBlock> with itself as the argument."

	| ctx |
	ctx _ self.
		[true] whileTrue:
			[aBlock value: ctx receiver.
			(ctx _ ctx sender) == nil ifTrue: [^self]]! !}

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