package Factory;

use strict;
use DBI;

my $dbh = DBI->connect(
   qw(DBI:vendor:database:host user pass),
   { RaiseError => 1}
);

sub instantiate { 
   my ($self,$package,$id) = @_; 

   my $sth = $dbh->selectall_arrayref('
      select title,artist,year
      from songs
      where id = ?
   ',undef,$id)->[0];

   my $obj = eval { $package->new($id,@$sth) };
   return $@ ? undef : $obj;
}

package My::User;

use strict;

sub new {
   my ($class,$id,$title,$artist,$year) = @_;
   my $self = {
      id     => $id,
      title  => $title,
      artist => $artist,
      year   => $year,
   };
   return bless $self,$class;
}

# this will be discussed later ...
sub foo { 'foo' }

1;