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ValueHolder subclass:#BufferedValueHolder
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instanceVariableNames:'subject triggerChannel bufferedValue'
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classVariableNames:'NotYetAssigned'
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poolDictionaries:''
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category:'Interface-Support-Models'
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!
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!BufferedValueHolder 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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72
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$Header: /cvs/stx/stx/libview2/BufferedValueHolder.st,v 1.2 1995-05-12 17:59:39 claus Exp $
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71
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"
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!
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documentation
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"
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a bufferedValueHolder keeps atemporary copy of the realHolders value,
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and only does a real store of the value when triggered.
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Triggering is done by depending on a trigger objects value, which is
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typically a ValueHolder for a boolean, which is set by an ok-button.
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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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"
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!
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examples
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"
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72
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unbuffered (values are changed, even if not accepted,
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iff a field is left with Return or accept is done in a field):
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|firstName lastName dialog|
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firstName := 'foo' asValue.
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lastName := 'bar' asValue.
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dialog := Dialog new.
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(dialog addTextLabel:'Name:') layout:#left.
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dialog addInputFieldOn:firstName.
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dialog addVerticalSpace.
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(dialog addTextLabel:'Address:') layout:#left.
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dialog addInputFieldOn:lastName.
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dialog addAbortButton; addOkButton.
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dialog open.
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Transcript show:firstName value; show:' '; showCr:lastName value
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buffered (values are only stored when accepted; undo reloads old values)
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(use an instance of TriggerValue. If a ValueHolder was used, we had
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to temporarily set its value back to nil, to have the change really be
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forwarded to its dependends)
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|firstName lastName trigger dialog|
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firstName := 'foo' asValue.
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lastName := 'bar' asValue.
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trigger := TriggerValue new.
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dialog := Dialog new.
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(dialog addTextLabel:'Name:') layout:#left.
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dialog addInputFieldOn:(BufferedValueHolder
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subject:firstName
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triggerChannel:trigger).
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dialog addVerticalSpace.
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(dialog addTextLabel:'Address:') layout:#left.
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dialog addInputFieldOn:(BufferedValueHolder
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subject:lastName
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triggerChannel:trigger).
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dialog addAbortButton;
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addButton:(Button new
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label:'undo';
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action:[trigger value:false]);
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addOkButton.
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dialog open.
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dialog accepted ifTrue:[
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trigger value:true
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].
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Transcript show:firstName value; show:' '; showCr:lastName value
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"
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! !
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!BufferedValueHolder class methodsFor:'initialization'!
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intialize
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NotYetAssigned := Object new
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! !
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!BufferedValueHolder class methodsFor:'instance creation'!
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subject:someModel triggerChannel:aTrigger
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"return a new BufferedValueHolder offering a buffered copy of someModels
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value - only updating this value, when aTrigger changes to true."
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^ self new subject:someModel; triggerChannel:aTrigger
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! !
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!BufferedValueHolder methodsFor:'initialization'!
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initialize
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super initialize.
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bufferedValue := NotYetAssigned
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! !
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!BufferedValueHolder methodsFor:'change & update'!
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update:something with:aParameter from:changedObject
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changedObject == triggerChannel ifTrue:[
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triggerChannel value == true ifTrue:[
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"
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now, store the buffered value into the subject
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"
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subject value:bufferedValue.
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^ self
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].
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triggerChannel value == false ifTrue:[
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"
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cancel: flush my buffered value
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"
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bufferedValue := NotYetAssigned.
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].
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self notifyChange:#value.
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^ self
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].
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changedObject == subject ifTrue:[
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bufferedValue := NotYetAssigned.
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self notifyChange:#value.
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^ self
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].
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! !
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!BufferedValueHolder methodsFor:'accessing'!
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subject:someModel
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subject notNil ifTrue:[
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subject removeDependent:self
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].
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subject := someModel.
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subject notNil ifTrue:[
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subject addDependent:self
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]
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!
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triggerChannel:aTrigger
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triggerChannel notNil ifTrue:[
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triggerChannel removeDependent:self
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].
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triggerChannel := aTrigger.
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triggerChannel notNil ifTrue:[
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triggerChannel addDependent:self
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]
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!
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setValue:anObject
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"set my value without notification."
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bufferedValue := anObject.
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!
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value
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"return my value"
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bufferedValue == NotYetAssigned ifTrue:[
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bufferedValue := subject value
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].
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^ bufferedValue
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! !
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