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package Moose::Cookbook::Roles::Recipe3;
=pod
=begin testing-SETUP
{
# Not in the recipe, but needed for writing tests.
package Employee;
use Moose;
has 'name' => (
is => 'ro',
isa => 'Str',
required => 1,
);
has 'work' => (
is => 'rw',
isa => 'Str',
predicate => 'has_work',
);
}
=end testing-SETUP
=head1 NAME
Moose::Cookbook::Roles::Recipe3 - Applying a role to an object instance
=head1 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 ] );
$lisa->assign_work('mow the lawn');
=head1 DESCRIPTION
In this recipe, we show how a role can be applied to an object. In
this specific case, we are giving an employee managerial
responsibilities.
Applying a role to an object is simple. The L<Moose::Meta::Role>
object provides an C<apply> method. This method will do the right
thing when given an object instance.
MyApp::Role::Job::Manager->meta->apply($lisa);
We could also use the C<apply_all_roles> function from L<Moose::Util>.
apply_all_roles( $person, MyApp::Role::Job::Manager->meta );
The main advantage of using C<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 L<roles
recipe 2|Moose::Cookbook::Roles::Recipe2>.
=head1 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.
=head1 AUTHOR
Dave Rolsky E<lt>autarch@urth.orgE<gt>
=head1 COPYRIGHT AND LICENSE
Copyright 2006-2010 by Infinity Interactive, Inc.
L<http://www.iinteractive.com>
This library is free software; you can redistribute it and/or modify
it under the same terms as Perl itself.
=begin testing
{
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');
ok( $lisa->does('MyApp::Role::Job::Manager'),
'lisa now does the manager role' );
is( $homer->work, 'mow the lawn',
'homer was assigned a task by lisa' );
}
=end testing
=cut
|
