adding singleton methods to objects

[andal]

Description:

This piece of code may serve as the base class for objects that need singleton methods (methods specific for this object and not for whole class). One can use it directly

my $obj = DynObject->new(id => 'MyObj', action => sub{print "hi\n";});

print $obj->id, "\n";
$obj->action();

or as base class

$obj = MyDyn->new(id => 'MyObj');
print $obj->id, "\n";
$obj->action();

package MyDyn;
use base 'DynObject';
sub action
{
   print "hi\n";
}

use strict;
package DynObject;
use Carp;

my $counter = 0;

sub new
{
    my $class = shift;
    croak("The number of parameters must be even") unless @_ % 2 == 0;

    no strict 'refs';
    my $type = ref $class;
    my $code;
    if(!$type)
    {
        $type = __PACKAGE__;
        $type .= "::obj@{[$counter++]}";
        *{"${type}::ISA"} = [$class];
    }
    for(my $i = 0; $i < @_; $i+=2)
    {
        croak("The method name '$_[$i]' is not a word")
            unless $_[$i] =~ /^\w+$/ && $_[$i] !~ /^\d+$/;
        if(ref $_[$i+1] eq 'CODE')
        {
            *{"${type}::$_[$i]"} = $_[$i+1];
        }
        elsif(defined $_[$i+1] && !ref $_[$i+1])
        {
            my $str = $_[$i+1];
            *{"${type}::$_[$i]"} = sub{$str};
        }
        else
        {
            delete ${"${type}::"}{$_[$i]};
        }
    }
    return ref $class ? $class : bless [], $type;
}

sub DESTROY
{
    my $obj = shift;
    my $type = ref $obj;
    $type =~ s/(\w+)$//;
    my $name = $1 . "::";
    no strict 'refs';
    delete ${$type}{$name};
}

1;

[merlyn]

Or, just look at Class::Prototyped, a full-featured, mature (used in production) solution of this. There are likely also some MooseX:: modules that implement prototype-based behavior as well.