Re: StateFull vs Stateless Singleton

From:

James Kanze <james.kanze@gmail.com>

Newsgroups:

comp.lang.c++

Date:

Mon, 5 Jul 2010 07:38:30 -0700 (PDT)

Message-ID:

<a1daab4a-3b0e-495d-9530-03dd817b100c@z10g2000yqb.googlegroups.com>

On Jul 5, 12:31 am, =D6=F6 Tiib <oot...@hot.ee> wrote:

On 4 juuli, 23:58, sebastian <sebastianga...@gmail.com> wrote:

[...]

Looks as beautiful like any other reinvented square wheel. The
requirements seem to be that such code must work:

int main( void )
{
     {
         foo a;
         foo::instance( ).bar( );
     }
     foo c; // Second singleton and *NO* Whoops
     foo::instance( ).bar( );
}

Not sure why someone needs to have global state? Typical
example of singletons is a logger. Huh? So ... OK. What if
i need to have separate logs from different modules? I will
then need new class for each log to have separate singleton
logger for each module? Nonsense.

So your log manager is a singleton. Somewhere, there must be
a single bit of code which reads the configuration file for the
log.

Similarly, the configuration manager is a singleton. As is the
code which captures the command line and its options. In
a multithreaded application, the thread manager (which ensures
e.g. a clean shutdown) must be a singleton.

What if i need to have separate logs from different threads?
Then that Logger::instance() should give me "different"
singletons based on thread ID? Huh? Why it can't just be
debugging::log() and where it logs is its internal business,
no global state no nothing?

Huh? What is debugging::log()? (The syntax suggests a static
class member. A class instance function, in sum. So that its
data is a "singleton".)

--
James Kanze