Yet another OO Meditation...

One of my most and least favorite features of OO in Perl is that method calls are dynamic. Dynamic method calls means you can write code like this: 

  ...
  my $recs = $dbh->selectall_arrayref( $sql );
  my @people;
  foreach my $rec ( @$recs ) {
    my $i = 0;
    my $person = Person->new();
    foreach my $meth ( qw( name hight weight age gender dob ) ) {
       $person->$meth( $rec->[$i++] );
    }
    push @people, $person;
  }

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The other edge of the sword means that you can call methods that don't exist and Perl can't catch them untill run-time. Which is annoying and can be a pain to track down in your code. One technique that helps ease that pain is to define an AUTOLOAD method in the base class to tell you when you've called a method that doesn't exist (possibly due to a typo) as opposed to other run-time errors (such as trying to call a method on an undefined value). 
package Base;
use strict;
use warnings;
our @ISA = qw();
use vars qw( $AUTOLOAD );

sub new
{
  ...
}

sub throw
{
  my $self = shift;
  my($p,$f,$l) = caller();
  die "Exception at: ",$p,"->$f($l)\n  ",join('',@_);
}

# report non-existant methods
sub AUTOLOAD
{
  my($self) = @_;
  $self->throw("Error, unsupported method: $AUTOLOAD\n");
}

1;

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With an AUTOLOAD in the base class, code that calls methods that don't exist, like: 
  $person->shoeSize();

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Will now throw an exception that tells you right where (package, file and line number) the offending code tried to call the non-existant method. This technique has helped reduce the time I spend debugging.

In reply to YAOOM by mortis

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