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131 .IX Title "Moose::Cookbook::Roles::Recipe3 3"
132 .TH Moose::Cookbook::Roles::Recipe3 3 "2009-08-18" "perl v5.8.7" "User Contributed Perl Documentation"
134 Moose::Cookbook::Roles::Recipe3 \- Applying a role to an object instance
136 .IX Header "SYNOPSIS"
138 \& package MyApp::Role::Job::Manager;
142 \& use List::Util qw( first );
150 \& has 'employees' => (
152 \& isa => 'ArrayRef[Employee]',
163 \& my $employee = first { !$_\->has_work } @{ $self\->employees };
167 \& die 'All my employees have work to do!' unless $employee;
171 \& $employee\->work($work);
180 \& my $lisa = Employee\->new( name => 'Lisa' );
181 \& MyApp::Role::Job::Manager\->meta\->apply($lisa);
185 \& my $homer = Employee\->new( name => 'Homer' );
186 \& my $bart = Employee\->new( name => 'Bart' );
187 \& my $marge = Employee\->new( name => 'Marge' );
191 \& $lisa\->employees( [ $homer, $bart, $marge ] );
192 \& $lisa\->assign_work('mow the lawn');
195 .IX Header "DESCRIPTION"
196 In this recipe, we show how a role can be applied to an object. In
197 this specific case, we are giving an employee managerial
200 Applying a role to an object is simple. The Moose::Meta::Role
201 object provides an \f(CW\*(C`apply\*(C'\fR method. This method will do the right
202 thing when given an object instance.
205 \& MyApp::Role::Job::Manager\->meta\->apply($lisa);
208 We could also use the \f(CW\*(C`apply_all_roles\*(C'\fR function from Moose::Util.
211 \& apply_all_roles( $person, MyApp::Role::Job::Manager\->meta );
214 The main advantage of using \f(CW\*(C`apply_all_roles\*(C'\fR is that it can be used
215 to apply more than one role at a time.
217 We could also pass parameters to the role we're applying:
220 \& MyApp::Role::Job::Manager\->meta\->apply(
222 \& \-alias => { assign_work => 'get_off_your_lazy_behind' },
226 We saw examples of how method exclusion and alias working in roles recipe 2.
228 .IX Header "CONCLUSION"
229 Applying a role to an object instance is a useful tool for adding
230 behavior to existing objects. In our example, it is effective used to
233 It can also be useful as a sort of controlled monkey-patching for
234 existing code, particularly non-Moose code. For example, you could
235 create a debugging role and apply it to an object at runtime.
238 Dave Rolsky <autarch@urth.org>
239 .SH "COPYRIGHT AND LICENSE"
240 .IX Header "COPYRIGHT AND LICENSE"
241 Copyright 2006\-2009 by Infinity Interactive, Inc.
243 <http://www.iinteractive.com>
245 This library is free software; you can redistribute it and/or modify
246 it under the same terms as Perl itself.