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Re: Re: AUTOLOAD does not scale

by rir (Vicar)
on May 26, 2004 at 21:48 UTC ( #356739=note: print w/ replies, xml ) Need Help??


in reply to Re: AUTOLOAD does not scale
in thread OO Inheritence

Agreed, but I say playing nicely is a practice that does not scale. If you won't distribute the code there is nothing wrong with using AUTOLOAD.

I am saying that AUTOLOAD does not scale well. Every use of AUTOLOAD in a program should be under the control of one party. If two separate authors use AUTOLOAD in the same program breakage is likely.

Being conservative, I would be suspicious of any program with more than one AUTOLOAD. If two AUTOLOAD routines exist in a hierarchy there is a problem. (Don't forget UNIVERSAL.)

This is a known problem. Consider:

#!/usr/bin/perl use strict; use warnings; # I decide to use a module package Vehicle; use vars '$AUTOLOAD'; sub new { return bless {}, $_[0]; } # handle all "V*" calls sub AUTOLOAD { my ($key) = $AUTOLOAD =~/::(\w+)/; return if $key =~ /^[A-Z]+$/; die "Vehicle::AUTOLOAD can't cope as $key" unless $key =~ /^[vV]/; print "Leaving Vehicle::AUTOLOAD as $key$/"; } # with my program below package Animal; use vars '$AUTOLOAD'; sub new { return bless {}, $_[0]; } # handle all "A*" calls sub AUTOLOAD { my ($key) = $AUTOLOAD =~/::(\w+)/; return if $key =~ /^[A-Z]+$/; die "Animal::AUTOLOAD can't cope as $key" unless $key =~ /^[aA]/; print "Leaving Animal::AUTOLOAD as $key$/"; } package Horse; use vars qw/ @ISA /; @ISA = qw/ Vehicle Animal /; package main; # the two usages cannot work together, I needed to # know that Vehicle used AUTOLOAD so I could avoid it # or rewrite my code to eliminate AUTOLOAD. my $h = Horse->new; $h->Veh(); $h->Ani(); # call intercepted by Vehicle AUTOLOAD
Be well.


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