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A cacheing tied hash base class

by rdw (Curate)
on Sep 13, 2000 at 05:17 UTC ( [id://32233]=CUFP: print w/replies, xml ) Need Help??

After a long and helpful discussion in the Chatterbox, I hacked this together. It's a base class which lets you build a hash that fills itself 'on demand'.
#! /usr/bin/perl -w package Tie::AutoCache; use strict; use vars qw(@ISA); use Tie::Hash; @ISA = qw(Tie::StdHash); sub TIEHASH { my($class) = shift; my($self) = { }; bless $self, $class; } sub FETCH { my($self, $key) = @_; unless (exists $self->{$key}) { if ($self->can($key)) { $self->{$key} = $self->$key(); } else { warn "No method for '$key'"; $self->{$key} = undef; } } return $self->{$key}; } 1; ######################################################### package Thingy; use vars qw(@ISA); @ISA = qw(Tie::AutoCache); sub new { my($class) = shift; my(%hash); tie %hash, $class; return \%hash; } sub foo { my($self) = @_; $self->{bar} = "this is bar\n"; return "this is foo\n"; } 1; ######################################################### package main; my($thingy) = new Thingy(); print $thingy->{foo}; print $thingy->{bar}; print $thingy->{not};

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RE: A cacheing tied hash base class
by merlyn (Sage) on Sep 13, 2000 at 05:46 UTC
    Very cool! But you can save the double lookup easily:
    sub FETCH { my($self, $key) = @_; unless (exists $self->{$key}) { if (my $meth = $self->can($key)) { $self->{$key} = $meth->($self); } else { warn "No method for '$key'"; $self->{$key} = undef; } } return $self->{$key}; }
    That's because $obj->can('meth') returns the coderef to execute!

    -- Randal L. Schwartz, Perl hacker

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