[Melbourne-pm] overloading 'print'

Joshua Goodall joshua at roughtrade.net
Tue Mar 21 17:23:23 PST 2006

On Wed, Mar 22, 2006 at 11:26:07AM +1100, Mathew Robertson wrote:
> Using IO::Wrap doesn't give that as I would have to change the syntax to:
> use IO::Wrap;
> no warnings;
> sub IO::Wrap::print {
>   my $self = shift;
>   print { $$self } "IO::Wrapped: ", @_;
> }
> use warnings;
> wraphandle(\*STDOUT);
> print "Blah";
> or something similar.  However, this doesn't override 'print' as it 
> produces the output:

man ... why take a nice OO package and shove a pitchfork in its guts? :)
anyway on closer examination IO::Wrap turns out to be the retarded child
of what it might be.

I had something in mind like:

package MyWrap;
use IO::Handle;

sub new {
	my $class = ref($_[0]) || $_[0];
	bless {io => $_[1], class => $class}, $class;

	my $self = shift;
	return if $AUTOLOAD =~ /::DESTROY$/;
	$AUTOLOAD =~ s/^$self->{class}:://;

sub print {
	my $self = shift;
	$self->{io}->print($self->{class}, ": ", @_);

package main;

$stdout = new MyWrap(\*STDOUT);

which is nice for libraries and anything where you shouldn't be relying
on global runtime state (i.e. any code in excess of 4 lines, excepting
perhaps debug code and other meta stuff)

I've used this approach for self-indenting filehandles (which then nests
very nicely). Although it was also finessed with gensym so that they
behaved a little more like IO::Handle objects.


Josh "Koshua" Goodall                      "as modern as tomorrow afternoon"
joshua at roughtrade.net                                       - FW109

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