Class: Singleton

• Inheritance
• Description
• Class protocol
  • accessing
  • initialization
  • instance creation

Inheritance:

   Object
   |
   +--Singleton
      |
      +--Dolphin::DeafObject

Package:

stx:libbasic2

Category:

System-Support

Version:

rev: 1.10 date: 2021/03/09 09:40:10

user: cg

file: Singleton.st directory: libbasic2

module: stx stc-classLibrary: libbasic2

Description:

Subclasses of Singleton have only a single instance.
The instance creation methods ensure that there is only one instance.

Singletons that would have inherited from Object could inherit from
Singleton. For Singletons that do not inherit from Object, 
you have to copy the Singleton's code to your class.


[class instance variables:]
    theOnlyInstance     Object          The only instance of this class

[class variables:]
    Lock                RecursionLock   A global lock to protect against races during instance creation

copyright
COPYRIGHT (c) 2006 by eXept Software AG
             All Rights Reserved

This software is furnished under a license and may be used
only in accordance with the terms of that license and with the
inclusion of the above copyright notice.   This software may not
be provided or otherwise made available to, or used by, any
other person.  No title to or ownership of the software is
hereby transferred.

Class protocol:

 singletonLock

can be used by other classes that are not subclasses of Singleton

 theOnlyInstance

must check again because of possible raise

 initialize

(comment from inherited method)
called only once - initialize signals

 basicNew

allocate a singleton in a thread-safe way.
Do lazy locking here

 basicNew: anInteger

allocate a singleton in a thread-safe way.
Do lazy locking here

 new

allocate a singleton in a thread-safe way.
Do lazy locking here

 new: count

allocate a singleton in a thread-safe way.
Do lazy locking here

 releaseInstance

release the singleton's instance.
Use only for debugging!