Re: [boost] Re: Re: Singleton

From: Thomas Beckmann (beckmann.bremen_at_[hidden])
Date: 2005-01-09 14:25:17

At 16:56 09.01.2005 +0100, you wrote:
> > Actually, that try block exists for only the specific case when the
> > constructor throws... I'm not sure how it could be implemented via RAII,
> > as dependencies should only be decremented upon failure.  The dtor itself,
> > and thus ReleaseDependency, should not be called if new or the ctor
> > throws.
> >
>
>struct undoer_t {
>    int* value;
>   undoer_t(int* val) value(val) {}
>   ~undoer_t() { if (value) --*value; }
>   void dismiss() { value = 0; }
>} undoer(&dependents);
>
>..... possibly throwing operation
>
>undoer.dismiss();

Wouldn't it be easier to change AddDependency to something like the following:

static void AddDependency ( )
{
         static bool first = true;

         if ( first ) {
                 s_inst = static_cast < T * > ( A :: Create ( ) );
                 dependents = 0;
                 first = false;
         }
         ++dependents;
}

Thomas Beckmann