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ACE_Singleton< TYPE, ACE_LOCK > Class Template Reference

A Singleton Adapter uses the Adapter pattern to turn ordinary classes into Singletons optimized with the Double-Checked Locking optimization pattern. More...

#include <Singleton.h>

Inheritance diagram for ACE_Singleton< TYPE, ACE_LOCK >:

[legend]Collaboration diagram for ACE_Singleton< TYPE, ACE_LOCK >:

[legend]List of all members.

Public Methods
virtual void	cleanup (void *param=0)
Static Public Methods
TYPE *	instance (void)
	Global access point to the Singleton.
void	dump (void)
	Dump the state of the object.
Protected Methods
	ACE_Singleton (void)
	Default constructor.
Static Protected Methods
ACE_Singleton< TYPE, ACE_LOCK > *&	instance_i (void)
	Get pointer to the Singleton instance.
Protected Attributes
TYPE	instance_
	Contained instance.
Static Protected Attributes
ACE_Singleton< TYPE, ACE_LOCK > *	singleton_ = 0
	Pointer to the Singleton (ACE_Cleanup) instance.

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Detailed Description

template<class TYPE, class ACE_LOCK>
class ACE_Singleton< TYPE, ACE_LOCK >

A Singleton Adapter uses the Adapter pattern to turn ordinary classes into Singletons optimized with the Double-Checked Locking optimization pattern.

This implementation is a slight variation on the GoF Singleton pattern. In particular, a single <ACE_Singleton<TYPE, ACE_LOCK> > instance is allocated here, not a <TYPE> instance. The reason for this is to allow registration with the ACE_Object_Manager, so that the Singleton can be cleaned up when the process exits. For this scheme to work, a (static) cleanup() function must be provided. ACE_Singleton provides one so that TYPE doesn't need to. If you want to make sure that only the singleton instance of <T> is created, and that users cannot create their own instances of <T>, do the following to class <T>: (a) Make the constructor of <T> private (or protected) (b) Make Singleton a friend of <T> Here is an example:

 * class foo
 * {
 * friend class ACE_Singleton<foo, ACE_Null_Mutex>;
 * private:
 * foo () { cout << "foo constructed" << endl; }
 * ~foo () { cout << "foo destroyed" << endl; }
 * };
 * typedef ACE_Singleton<foo, ACE_Null_Mutex> FOO;
 * 

NOTE: the best types to use for ACE_LOCK are ACE_Recursive_Thread_Mutex and ACE_Null_Mutex. ACE_Recursive_Thread_Mutex should be used in multi-threaded programs in which it is possible for more than one thread to access the <ACE_Singleton<TYPE, ACE_LOCK>> instance. ACE_Null_Mutex can be used otherwise. The reason that these types of locks are best has to do with their allocation by the ACE_Object_Manager. Single ACE_Recursive_Thread_Mutex and ACE_Null_Mutex instances are used for all ACE_Singleton instantiations. However, other types of locks are allocated per ACE_Singleton instantiation.

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Constructor & Destructor Documentation

template<class TYPE, class ACE_LOCK> ACE_INLINE ACE_Singleton< TYPE, ACE_LOCK >::ACE_Singleton (  void    )  [protected]

Default constructor.

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Member Function Documentation

template<class TYPE, class ACE_LOCK> void ACE_Singleton< TYPE, ACE_LOCK >::cleanup (  void *    param = 0 )  [virtual]

Cleanup method, used by <ace_cleanup_destroyer> to destroy the ACE_Singleton. Reimplemented from ACE_Cleanup.

template<class TYPE, class ACE_LOCK> void ACE_Singleton< TYPE, ACE_LOCK >::dump (  void    )  [static]

Dump the state of the object. Reimplemented in ACE_Unmanaged_Singleton< TYPE, ACE_LOCK >.

template<class TYPE, class ACE_LOCK> TYPE * ACE_Singleton< TYPE, ACE_LOCK >::instance (  void    )  [static]

Global access point to the Singleton. Reimplemented in ACE_Unmanaged_Singleton< TYPE, ACE_LOCK >.

template<class TYPE, class ACE_LOCK> ACE_Singleton< TYPE, ACE_LOCK > *& ACE_Singleton< TYPE, ACE_LOCK >::instance_i (  void    )  [static, protected]

Get pointer to the Singleton instance. Reimplemented in ACE_Unmanaged_Singleton< TYPE, ACE_LOCK >.

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Member Data Documentation

template<class TYPE, class ACE_LOCK> TYPE ACE_Singleton< TYPE, ACE_LOCK >::instance_ [protected]

Contained instance.

template<class TYPE, class ACE_LOCK> ACE_Singleton< TYPE, ACE_LOCK > * ACE_Singleton< TYPE, ACE_LOCK >::singleton_ = 0 [static, protected]

Pointer to the Singleton (ACE_Cleanup) instance. Reimplemented in ACE_Unmanaged_Singleton< TYPE, ACE_LOCK >.

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The documentation for this class was generated from the following files:

• Singleton.h
• Singleton.cpp
• Singleton.i

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