NAME<\/a> Moose::Cookbook::Roles::Restartable_AdvancedComposition \u2212 Advanced Role Composition \u2212 method exclusion and aliasing<\/p>\n version 2.2014<\/p>\n package Restartable; In this example, we demonstrate how to exercise fine-grained control over what methods we consume from a role. We have a “Restartable” role which provides an “is_paused” attribute, and two methods, “stop” and “start”.<\/p>\n Then we have two more roles which implement the same interface, each putting their own spin on the “stop” and “start” methods.<\/p>\n In the “Restartable::ButUnreliable” role, we want to provide a new implementation of “stop” and “start”, but still have access to the original implementation. To do this, we alias the methods from “Restartable” to private methods, and provide wrappers around the originals (1).<\/p>\n Note that aliasing simply adds<\/i> a name, so we also need to exclude the methods with their original names.<\/p>\n with ‘Restartable’ => { In the “Restartable::ButBroken” role, we want to provide an entirely new behavior for “stop” and “start”. We exclude them entirely when composing the “Restartable” role into “Restartable::ButBroken”.<\/p>\n It\u2019s worth noting that the “\u2212excludes” parameter also accepts a single string as an argument if you just want to exclude one method.<\/p>\n with ‘Restartable’ => { \u2212excludes => [ ‘stop’, ‘start’ ] };<\/p>\n Exclusion and renaming are a power tool that can be handy, especially when building roles out of other roles. In this example, all of our roles implement the “Restartable” role. Each role provides same API,<\/small> but each has a different implementation under the hood.<\/p>\n You can also use the method aliasing and excluding features when composing a role into a class.<\/p>\n
VERSION<\/a>
SYNOPSIS<\/a>
DESCRIPTION<\/a>
CONCLUSION<\/a>
FOOTNOTES<\/a>
AUTHORS<\/a>
COPYRIGHT AND LICENSE<\/a> <\/p>\n
\nNAME <\/a> <\/h2>\n
VERSION <\/a> <\/h2>\n
SYNOPSIS <\/a> <\/h2>\n
use Moose::Role;
has ‘is_paused’ => (
is => ‘rw’,
isa => ‘Bool’,
default => 0,
);
requires ‘save_state’, ‘load_state’;
sub stop { 1 }
sub start { 1 }
package Restartable::ButUnreliable;
use Moose::Role;
with ‘Restartable’ => {
\u2212alias => {
stop => ‘_stop’,
start => ‘_start’
},
\u2212excludes => [ ‘stop’, ‘start’ ],
};
sub stop {
my $self = shift;
$self\u2212>explode() if rand(1) > .5;
$self\u2212>_stop();
}
sub start {
my $self = shift;
$self\u2212>explode() if rand(1) > .5;
$self\u2212>_start();
}
package Restartable::ButBroken;
use Moose::Role;
with ‘Restartable’ => { \u2212excludes => [ ‘stop’, ‘start’ ] };
sub stop {
my $self = shift;
$self\u2212>explode();
}
sub start {
my $self = shift;
$self\u2212>explode();
}<\/p>\nDESCRIPTION <\/a> <\/h2>\n
\u2212alias => {
stop => ‘_stop’,
start => ‘_start’
},
\u2212excludes => [ ‘stop’, ‘start’ ],
};<\/p>\nCONCLUSION <\/a> <\/h2>\n
FOOTNOTES <\/a> <\/h2>\n
| <\/td>\n | \n (1)<\/p>\n<\/td>\n | <\/td>\n | \n The mention of wrapper should tell you that we could do the same thing using method modifiers, but for the sake of this example, we don\u2019t.<\/p>\n<\/td>\n<\/tr>\n<\/table>\n AUTHORS <\/a> <\/h2>\n
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