NAME

       Moose::Cookbook::Roles::ApplicationToInstance - Applying a role to an object instance

VERSION

       version 2.2009

SYNOPSIS

         package MyApp::Role::Job::Manager;

         use List::Util qw( first );

         use Moose::Role;

         has 'employees' => (
             is  => 'rw',
             isa => 'ArrayRef[Employee]',
         );

         sub assign_work {
             my $self = shift;
             my $work = shift;

             my $employee = first { !$_->has_work } @{ $self->employees };

             die 'All my employees have work to do!' unless $employee;

             $employee->work($work);
         }

         package main;

         my $lisa = Employee->new( name => 'Lisa' );
         MyApp::Role::Job::Manager->meta->apply($lisa);

         my $homer = Employee->new( name => 'Homer' );
         my $bart  = Employee->new( name => 'Bart' );
         my $marge = Employee->new( name => 'Marge' );

         $lisa->employees( [ $homer, $bart, $marge ] );
         $lisa->assign_work('mow the lawn');

DESCRIPTION

       In this recipe, we show how a role can be applied to an object. In this specific case, we
       are giving an employee managerial responsibilities.

       Applying a role to an object is simple. The Moose::Meta::Role object provides an "apply"
       method. This method will do the right thing when given an object instance.

         MyApp::Role::Job::Manager->meta->apply($lisa);

       We could also use the "apply_all_roles" function from Moose::Util.

         apply_all_roles( $person, MyApp::Role::Job::Manager->meta );

       The main advantage of using "apply_all_roles" is that it can be used to apply more than
       one role at a time.

       We could also pass parameters to the role we're applying:

         MyApp::Role::Job::Manager->meta->apply(
             $lisa,
             -alias => { assign_work => 'get_off_your_lazy_behind' },
         );

       We saw examples of how method exclusion and alias working in
       Moose::Cookbook::Roles::Restartable_AdvancedComposition.

CONCLUSION

       Applying a role to an object instance is a useful tool for adding behavior to existing
       objects. In our example, it is effective used to model a promotion.

       It can also be useful as a sort of controlled monkey-patching for existing code,
       particularly non-Moose code. For example, you could create a debugging role and apply it
       to an object at runtime.

AUTHORS

       •   Stevan Little <stevan.little@iinteractive.com>

       •   Dave Rolsky <autarch@urth.org>

       •   Jesse Luehrs <doy@tozt.net>

       •   Shawn M Moore <code@sartak.org>

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

       •   Karen Etheridge <ether@cpan.org>

       •   Florian Ragwitz <rafl@debian.org>

       •   Hans Dieter Pearcey <hdp@weftsoar.net>

       •   Chris Prather <chris@prather.org>

       •   Matt S Trout <mst@shadowcat.co.uk>

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 v5.26.1                                201Moose::Cookbook::Roles::ApplicationToInstance(3pm)