6 Moose::Cookbook::Roles::Recipe2 - Advanced Role Composition - method exclusion and aliasing
19 requires 'save_state', 'load_state';
25 package Restartable::ButUnreliable;
28 with 'Restartable' => {
38 $self->explode() if rand(1) > .5;
46 $self->explode() if rand(1) > .5;
51 package Restartable::ButBroken;
54 with 'Restartable' => { excludes => [ 'stop', 'start' ] };
70 Sometimes when you include a role in a class, you may want to leave
71 out some of its methods. In this example, we have a role C<Restartable>
72 which provides an C<is_paused> attribute, and two methods, C<stop> and
73 C<start>. The implementation of those two methods is irrelevant.
75 Then we have two more roles which also implement the same interface,
76 each putting their own spin on the C<stop> and C<start> method.
78 In the C<Restartable::ButUnreliable> role, we want to provide a new
79 implementation of C<stop> and C<start>, but still have access to the
80 original implementation. To do this, we alias the methods from
81 C<Restartable> to private methods, and provide wrappers around the
84 In the C<Restartable::ButBroken> role, we want to provide an entirely
85 new behavior for C<stop> and C<start>, so we exclude them when
86 composing the C<Restartable> role into C<Restartable::ButBroken>.
88 It's worth noting that the C<excludes> parameter also accepts a single
89 string as an argument if you just want to exclude one method.
93 Method exclusion and renaming can come in handy, especially when
94 building roles out of other roles. In this example, all of our roles
95 implement the C<Restartable> role. Each role provides same API, but
96 each has a different implementation under the hood.
98 You can also use the method aliasing and excluding features when
99 composing a role into a class.
107 The mention of wrapper should tell you that we could do the same thing
108 using method modifiers, but for the sake of this example, we don't.
114 Dave Rolsky E<lt>autarch@urth.orgE<gt>
116 =head1 COPYRIGHT AND LICENSE
118 Copyright 2006-2009 by Infinity Interactive, Inc.
120 L<http://www.iinteractive.com>
122 This library is free software; you can redistribute it and/or modify
123 it under the same terms as Perl itself.