This drives me crazy !!!

[Foo Bar]

Singleton.pm:
=============
package Singleton;
my $instance = undef;
sub new
{
if (!defined $instance) {
$instance->{count} = 0;
bless($instance, 'Singleton');
}
return $instance;
}
1;

Obj.pm:
=======
package Obj;
use Singleton;
@Obj::ISA = qw(Singleton);
sub count {
my $self = shift;
return $self->{count}++;
}
1;

test.pl:
========
#!/usr/bin/perl -w
use Obj;
my $obj = new Obj;
print $obj->count, "\n";

Friggin' error:
===============
Can't locate object method "count" via package "Singleton" at test.pl line 60.

Even I tried to throw in Singleton as follow and it didn't help:
BEGIN
{
use Exporter ();
@Singleton::ISA = qw(Exporter);
}

Dang...I'm too tired to figure out what goes wrong!!!!

 

[Tassilo v. Parseval]

Also sprach Foo Bar:

Singleton.pm:
=============
package Singleton;
my $instance = undef;
sub new
{
if (!defined $instance) {
$instance->{count} = 0;
bless($instance, 'Singleton');

This will bless the object into the hard-coded class
'Singleton'.

}
return $instance;
}
1;

Obj.pm:
=======
package Obj;
use Singleton;
@Obj::ISA = qw(Singleton);
sub count {
my $self = shift;
return $self->{count}++;
}
1;

test.pl:
========
#!/usr/bin/perl -w
use Obj;
my $obj = new Obj;

Here you want to create an object that is an instance of the class Obj.
Obj inherits new() from Singleton which always blesses the created
object into 'Singleton'. However, you want it to bless into 'Obj'.

So change the inherited new():

sub new {
my $class = shift;
if (!defined $instance) {
$instance->{count} = 0;
return bless $instance => $class;
}
}

Tassilo

 

[Foo Bar]

This will bless the object into the hard-coded class
'Singleton'.

Arrrrggggg!!! Staying up late sure has its effect! Thanks, Tassilo.