Moose::Cookbook::Extending::Recipe2 - Providing a role for the base object class
package MooseX::Debugging; use Moose::Exporter; Moose::Exporter->setup_import_methods( base_class_roles => ['MooseX::Debugging::Role::Object'], ); package MooseX::Debugging::Role::Object; use Moose::Role; after 'BUILDALL' => sub { my $self = shift; warn "Made a new " . ( ref $self ) . " object\n"; };
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.
use MooseX::Debugging
There are a few pieces of code worth looking at more closely.
Moose::Exporter->setup_import_methods( base_class_roles => ['MooseX::Debugging::Role::Object'], );
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 related to exports, but we need to have an import method to ensure that our init_meta method is called. The init_meta is created by setup_import_methods for us, since we passed the base_class_roles parameter. The generated init_meta will in turn call Moose::Util::MetaRole::apply_base_class_roles.
import
MooseX::Debugging
setup_import_methods
init_meta
base_class_roles
Dave Rolsky <autarch@urth.org>
Copyright 2009 by Infinity Interactive, Inc.
http://www.iinteractive.com
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