Moose::Cookbook::Extending::Debugging_BaseClassRole - phpMan

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 AT cpan.org>

    *   Dave Rolsky <autarch AT urth.org>

    *   Jesse Luehrs <doy AT cpan.org>

    *   Shawn M Moore <sartak AT cpan.org>

    *   יובל קוג'מן (Yuval Kogman) <nothingmuch AT woobling.org>

    *   Karen Etheridge <ether AT cpan.org>

    *   Florian Ragwitz <rafl AT debian.org>

    *   Hans Dieter Pearcey <hdp AT cpan.org>

    *   Chris Prather <chris AT prather.org>

    *   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.