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'From Smalltalk/X, Version:2.10.5 on 9-may-1995 at 12:03:02 pm'!
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Model subclass:#ValueModel
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instanceVariableNames:'accepted interrest'
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classVariableNames:''
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poolDictionaries:''
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category:'Interface-Support'
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!
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!ValueModel class methodsFor:'documentation'!
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copyright
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"
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COPYRIGHT (c) 1995 by Claus Gittinger
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All Rights Reserved
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This software is furnished under a license and may be used
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only in accordance with the terms of that license and with the
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inclusion of the above copyright notice. This software may not
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be provided or otherwise made available to, or used by, any
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other person. No title to or ownership of the software is
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hereby transferred.
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"
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!
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version
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"
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$Header: /cvs/stx/stx/libview2/ValueModel.st,v 1.5 1995-05-09 01:53:35 claus Exp $
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"
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!
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documentation
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"
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abstract superclass for ValueHolders and Adaptors.
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It does not itself know how and where the value is stored,
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but knows about interrested objects (which get informed, whenever
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the value changes) and keeps track if the value was ever accepted.
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Notice: this class was implemented using protocol information
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from alpha testers - it may not be complete or compatible to
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the corresponding ST-80 class. If you encounter any incompatibilities,
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please forward a note to the ST/X team.
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subclasses must redefine: #setValue: and #value
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(and optionally redefine #value:)
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"
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! !
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!ValueModel class methodsFor:'instance creation'!
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new
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^ (super new) initialize
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! !
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!ValueModel methodsFor:'change notification'!
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notifyChange:aSymbol
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interrest notNil ifTrue:[
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interrest keysAndValuesDo:[:someone :selector |
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someone perform:selector
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].
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].
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self changed:aSymbol
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! !
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!ValueModel methodsFor:'accessing'!
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value:anObject
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|oldValue|
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oldValue := self value.
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self setValue:anObject.
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anObject ~= oldValue ifTrue:[
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self notifyChange:#value
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]
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!
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accepted
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^ accepted
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!
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accept
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accepted := true
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!
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value
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self subclassResponsibility
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!
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setValue:newValue
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self subclassResponsibility
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! !
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!ValueModel methodsFor:'initialization'!
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initialize
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accepted := false
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! !
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!ValueModel methodsFor:'interrest'!
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retractInterrestFor:someone
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"release interrest i.e. do no longer send changeMsg to changeReceiver
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iff someone is the changeReceiver.
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This can be used to (temporarily) turn off information sends,
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to break endless cycles (if two values change each other)"
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interrest notNil ifTrue:[
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interrest removeKey:someone ifAbsent:nil
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]
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!
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onChangeSend:selector to:someone
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"add an interrest, arranging that
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a message with selector will be sent to someone
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when my value changes."
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interrest isNil ifTrue:[
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interrest := IdentityDictionary new
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].
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interrest at:someone put:selector
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! !
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