Moose::Cookbook::Extending::DebUsernContrMoose::Cookbook::Extending::Debugging_BaseClassRole(3pm) NAME Moose::Cookbook::Extending::Debugging_BaseClassRole - Providing a role for the base object class VERSION version 2.2200 SYNOPSIS 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; sub BUILD {} 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 "useMooseX::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( 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. sub BUILD {} after BUILD => sub { ... }; Due to the way role composition currently works, if the class that a role is composed into contains a "BUILD" method, then that will override the "BUILD" method in any roles it composes, which is typically not what you want. Using a method modifier on "BUILD" avoids this issue, since method modifiers compose together rather than being overridden. Method modifiers require that a method exists in order to wrap, however, so we also provide a stub method to wrap if no "BUILD" method exists in the class. AUTHORS o Stevan Little <stevan AT cpan.org> o Dave Rolsky <autarch AT urth.org> o Jesse Luehrs <doy AT cpan.org> o Shawn M Moore <sartak AT cpan.org> o ' (Yuval Kogman) <nothingmuch AT woobling.org> o Karen Etheridge <ether AT cpan.org> o Florian Ragwitz <rafl AT debian.org> o Hans Dieter Pearcey <hdp AT cpan.org> o Chris Prather <chris AT prather.org> o Matt S Trout <mstrout AT cpan.org> COPYRIGHT AND LICENSE This software is copyright (c) 2006 by Infinity Interactive, Inc. This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself. perl v5.34.0 Moose::Cookbook::Extending::Debugging_BaseClassRole(3pm)
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