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moose::cookbook::roles::recipe3(3) [osx man page]

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)

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Moose::Cookbook::Meta::Recipe5(3)			User Contributed Perl Documentation			 Moose::Cookbook::Meta::Recipe5(3)

NAME
Moose::Cookbook::Meta::Recipe5 - The "table" attribute as a metaclass trait VERSION
version 2.0205 SYNOPSIS
package MyApp::Meta::Class::Trait::HasTable; use Moose::Role; has table => ( is => 'rw', isa => 'Str', ); package Moose::Meta::Class::Custom::Trait::HasTable; sub register_implementation { 'MyApp::Meta::Class::Trait::HasTable' } package MyApp::User; use Moose -traits => 'HasTable'; __PACKAGE__->meta->table('User'); DESCRIPTION
This recipe takes the metaclass table attribute from Moose::Cookbook::Meta::Recipe4 and implements it as a metaclass trait. Traits are just roles, as we saw in Moose::Cookbook::Meta::Recipe3. The advantage of using traits is that it's easy to combine multiple traits, whereas combining multiple metaclass subclasses requires creating yet another subclass. With traits, Moose takes care of applying them to your metaclass. Using this Metaclass Trait in Practice Once this trait has been applied to a metaclass, it looks exactly like the example we saw in Moose::Cookbook::Meta::Recipe4: my $table = MyApp::User->meta->table; # the safe version $table = MyApp::User->meta->table if MyApp::User->meta->meta->can('does') and MyApp::User->meta->meta->does('MyApp::Meta::Class'); The safe version is a little complicated. We have to check that the metaclass object's metaclass has a "does" method, in which case we can ask if the the metaclass does a given role. It's simpler to just write: $table = MyApp::User->meta->table if MyApp::User->meta->can('table'); In theory, this is a little less correct, since the metaclass might be getting its "table" method from a different role. In practice, you are unlikely to encounter this sort of problem. SEE ALSO
Moose::Cookbook::Meta::Recipe3 - Labels implemented via attribute traits Moose::Cookbook::Meta::Recipe4 - Adding a "table" attribute to the metaclass 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::Meta::Recipe5(3)
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