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Moose::Cookbook::Extending::Recipe2.3pm
Langue: en
Version: 2009-03-09 (fedora - 05/07/09)
Section: 3 (Bibliothèques de fonctions)
NAME
Moose::Cookbook::Extending::Recipe2 - Providing a role for the base object classSYNOPSIS
package MooseX::Debugging; use strict; use warnings; use Moose (); use Moose::Exporter; use Moose::Util::MetaRole; Moose::Exporter->setup_import_methods; sub init_meta { shift; my %options = @_; Moose->init_meta(%options); Moose::Util::MetaRole::apply_base_class_roles( for_class => $options{for_class}, roles => ['MooseX::Debugging::Role::Object'], ); } package MooseX::Debugging::Role::Object; use Moose::Role; after 'BUILD' => sub { my $self = shift; warn "Made a new " . ref $self . " object\n"; };
DESCRIPTION
In this example, we provide a role for the base object class that adds some simple debugging output. Every time an object is created, it spits out a warning saying what type of object it was.Obviously, a real debugging role would do something more interesting, but this recipe is all about how we apply that role.
In this case, with the combination of Moose::Exporter and Moose::Util::MetaRole, we ensure that when a module does "use MooseX::Debugging", it automatically gets the debugging role applied to its base object class.
There are a few pieces of code worth looking at more closely.
Moose::Exporter->setup_import_methods;
This creates an "import" method in the "MooseX::Debugging" package. Since we are not actually exporting anything, we do not pass "setup_import_methods" any parameters. However, we need to have an "import" method to ensure that our "init_meta" method is called.
Then in our "init_meta" method we have this line:
Moose->init_meta(%options);
This is a bit of boilerplate that almost every extension will use. This ensures that the caller has a normal Moose metaclass before we go and add traits to it.
The "Moose->init_meta" method does ensures that the caller has a sane metaclass, and we don't want to replicate that logic in our extension. If the "Moose->init_meta" was already called (because the caller did "use Moose" before using our extension), then calling "Moose->init_meta" again is effectively a no-op.
AUTHOR
Dave Rolsky <autarch@urth.org>COPYRIGHT AND LICENSE
Copyright 2009 by Infinity Interactive, Inc.<http://www.iinteractive.com>
This library is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
Contenus ©2006-2024 Benjamin Poulain
Design ©2006-2024 Maxime Vantorre