Re: Non-static singleton setup to control life time

From:
Kirill_Lykov <lykov.kirill@gmail.com>
Newsgroups:
comp.lang.c++.moderated
Date:
Tue, 15 Dec 2009 10:11:17 CST
Message-ID:
<98e4b985-b70e-481e-98fe-e3b1c657ecf1@e27g2000yqd.googlegroups.com>
On Dec 14, 11:46 pm, Kris Prad <krisp...@yahoo.co.uk> wrote:

I want to setup a singleton, without 'static' initialization. My
motive is to control the life time of the Singleton, bounded by its
scope, something I cannot do with the statics.

Not this way. This uses static:

Single* Get()
{
   Static Single s; // do not want static
   Return &s;

}

Instead, I am doing this (please ignore thread safety issues)
Single* g_Single = NULL; // global singleton ptr
struct Single
{

        Single()
        {
                if (!g_Single)
                {
                        g_Single = this;
                }
                else
                {
                   throw string("Single is a singleton");
                }
        }
        ~Single()
        {
                g_Single = NULL;
        }

};

 Is this ugly or acceptable?

Kris


Well, you should understand the difference between Singleton patterns
and global variable. What you have described is not a singleton.
if you want to control lifetime of you variable you may use Meyers
singleton. Nevertheless, I recommend you to avoid using both
singletons and global variables, for additional details read
"Refactoring to Patterns" by Joshua Kerievsky, chapter 6. Inline
singleton.

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