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"
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COPYRIGHT (c) 2006 by eXept Software AG
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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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"{ Package: 'stx:libbasic2' }"
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Object subclass:#Singleton
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instanceVariableNames:''
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classVariableNames:'Lock'
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poolDictionaries:''
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category:'System-Support'
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!
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Singleton class instanceVariableNames:'theOnlyInstance'
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"
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No other class instance variables are inherited by this class.
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"
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!
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!Singleton class methodsFor:'documentation'!
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copyright
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"
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COPYRIGHT (c) 2006 by eXept Software AG
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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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documentation
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"
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Subclasses of Singleton have only a single instance.
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The instance creation methods ensure that there is only one instance.
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Singletons that would have inherited from Object could inherit from
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Singleton. For Singletons that do not inherit from Object,
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you have to copy the Singleton's code to your class.
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[author:]
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Stefan Vogel (stefan@zwerg)
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[class instance variables:]
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theOnlyInstance Object The only instance of this class
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[class variables:]
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Lock RecursionLock A global lock to protect agains races during instance creation
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"
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! !
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!Singleton class methodsFor:'initialization'!
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initialize
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Lock := RecursionLock new name:#Singleton
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! !
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!Singleton class methodsFor:'instance creation'!
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basicNew
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"allocate a singleton in a thread-safe way.
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Do lazy locking here"
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theOnlyInstance isNil ifTrue:[
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Lock critical:[
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theOnlyInstance isNil ifTrue:[
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theOnlyInstance := super basicNew.
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].
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]
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].
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^ theOnlyInstance.
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!
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basicNew:anInteger
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"allocate a singleton in a thread-safe way.
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Do lazy locking here"
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theOnlyInstance isNil ifTrue:[
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Lock critical:[
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theOnlyInstance isNil ifTrue:[
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theOnlyInstance := super basicNew:anInteger.
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].
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]
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].
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^ theOnlyInstance.
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! !
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!Singleton class methodsFor:'accessing'!
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singletonLock
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"can be used by other classes that are not subclasses of Singleton"
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^ Lock
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!
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theOnlyInstance
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^ theOnlyInstance
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! !
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!Singleton class methodsFor:'documentation'!
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version
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^ '$Header: /cvs/stx/stx/libbasic2/Singleton.st,v 1.3 2008-01-22 22:31:57 cg Exp $'
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! !
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Singleton initialize!
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