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 "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(
             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

       •   Stevan Little <stevan@cpan.org>

       •   Dave Rolsky <autarch@urth.org>

       •   Jesse Luehrs <doy@cpan.org>

       •   Shawn M Moore <sartak@cpan.org>

       •   יובל קוג'מן (Yuval Kogman) <nothingmuch@woobling.org>

       •   Karen Etheridge <ether@cpan.org>

       •   Florian Ragwitz <rafl@debian.org>

       •   Hans Dieter Pearcey <hdp@cpan.org>

       •   Chris Prather <chris@prather.org>

       •   Matt S Trout <mstrout@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)