A global is something that is in the global namespace. A singleton
isn't, any more than other class is. You have to import the class to
which it belongs to use it.
Noone mentioned making the *stream* a singleton. I'd expect to find
teh *stream* at OS level. It's just that an audio *player* is a better
example of something that you might want to be assured that there can
only be one *instance* of.
Until someone actually presents a solid reason why you should *never*
have a class which can only have a single instance, the argument is
going nowhere, as far as I can see.
(apologies for polluting the list with this rather OT stuff ...)
On 11/17/06, Adam Clarke <[EMAIL PROTECTED]> wrote:
On 17/11/2006, at 4:37 PM, Jonathan Rockway wrote:
> On Thursday 16 November 2006 20:08, A. Pagaltzis wrote:
>> A singleton is nothing but a global variable, except the
>> identifier comes from the class namespace rather than the
>> variable namespace. Put it in a global variable already.
>
> Not entirely true. Try this:
>
> $global = "Oops, accidentally overwrote the instance with garbage.";
>
> vs.
>
> Singleton->get_instance() = "Oops, accidentally overwrote the
> instance.";
Not really, because ...
use Readonly;
Readonly my $global => "Warming";
print "Before => $global\n\n";
eval {
$global = "Oops, accidentally overwrote the instance with
garbage.";
};
if ($@) { print "Error (would have died if uneval'd) => [EMAIL
PROTECTED]"; };
print "After => $global\n";
produces ...
Before => Warming
Error (would have died if uneval'd) => Modification of a read-
only value attempted at t.pl line 8
After => Warming
No matter what my prime minister says.
Cheers
--
Adam Clarke
www.strategicdata.com.au
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--
Daniel McBrearty
email : danielmcbrearty at gmail.com
www.engoi.com : the multi - language vocab trainer
BTW : 0873928131
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