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Linux Dream Job - Achieved
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Moose::Cookbook::Roles::Recipe3(3) User Contributed Perl Documentation Moose::Cookbook::Roles::Recipe3(3) NAME
Moose::Cookbook::Roles::Recipe3 - Applying a role to an object instance VERSION
version 2.0205 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 roles recipe 2. 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. AUTHOR
Stevan Little <stevan@iinteractive.com> COPYRIGHT AND LICENSE
This software is copyright (c) 2011 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 v5.12.5 2011-09-06 Moose::Cookbook::Roles::Recipe3(3)
