Re: [boost] pure virtual singleton

From: Jason Hise (chaos_at_[hidden])
Date: 2005-03-29 10:44:57

Rob Stewart wrote:

>IOW, if basic_singleton requires that the Creator template
>argument derive from creator_base, and creator_base uses a
>noninstantiable technique, then the client cannot create a
>Creator instance, so the only way to create an instance of type T
>is if T permits it.
>  
>
Exactly.

>Provided that using basic_singleton<T> places no contrary burdens
>on T such that basic_singleton<T> controls (a) common, Singleton
>instance(s), yet other T's can be instantiated directly, it
>sounds good.  Unfortunately, the functionality you described was
>provided by singleton_base suggests that this isn't the case.
>
>Am I missing something still?
>
The functionality is provided in terms of a member class, called 
pointer.  If T derives from singleton < T >, client code can use 
T::pointer instances to get at the singleton instance.  If T does not 
derive from singleton < T >, client code must use singleton < T 
 >::pointer instances to refer to the singleton instance.

-Jason