Moose::Cookbook::RolesUserpConMoose::Cookbook::Roles::ApplicationToInstance(3)NAMEMoose::Cookbook::Roles::ApplicationToInstance - Applying a role to an
object instance
VERSION
version 2.1005
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.
AUTHOR
Moose is maintained by the Moose Cabal, along with the help of many
contributors. See "CABAL" in Moose and "CONTRIBUTORS" in Moose for
details.
COPYRIGHT AND LICENSE
This software is copyright (c) 2013 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 v5.18.1Moose::Cookbook::Roles::ApplicationToInstance(3)
