[Catalyst] Re: using Plugin::Singleton and testing

[Adam Clarke]

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) => $@\n"; };

     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