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Re: How Are Attributes Useful?

by eric256 (Parson)
on Mar 23, 2007 at 21:36 UTC ( [id://606352]=note: print w/replies, xml ) Need Help??


in reply to How Are Attributes Useful?

I didn't realize till after compiling an example that this was a rather old post, but I'll post it anyway. Here is an example of using attributes to added debug information to a sub (printing out its @_ before and after execution) as well as a way to wrap some errors/warnings around methods. Both of these use Hook::LexWrap to warp extra code around the function being attributed...attributized, attributated?</code>

use strict; use warnings; { package tools; use Data::Dumper; use Hook::LexWrap; use Attribute::Handlers; sub UNIVERSAL::Debug :ATTR(CODE) { wrap $_[1], pre => sub { pop; print Dumper({'Pre' => \@_ + })}, post => sub { pop; print Dumper({'Post' => \@_ + })}, } sub UNIVERSAL::Method :ATTR(CODE) { my ($package, $symbol, $referent, $attr, $data, $phase) = +@_; wrap $_[1], pre => sub { my $self = shift; die "Must be used as a method" +unless ref($self) eq $package; }; } } { package Test; sub method_test :Method { print "This should be called on a reference\n"; } } package main; sub foo : Debug { print "This is the end!\n"; return 123;}; foo(1,2,3); my $x = bless {}, 'Test'; $x->method_test(); Test::method_test('hello'); __DATA__ $VAR1 = { 'Pre' => [ 1, 2, 3 ] }; This is the end! $VAR1 = { 'Post' => [ 1, 2, 3 ] }; This should be called on a reference Must be used as a method at attributes.pl line 16.


___________
Eric Hodges

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