| MooseX::Role::Parameterized - roles with composition parameters |
MooseX::Role::Parameterized - roles with composition parameters
version 1.08
package Counter;
use MooseX::Role::Parameterized;
parameter name => (
isa => 'Str',
required => 1,
);
role {
my $p = shift;
my $name = $p->name;
has $name => (
is => 'rw',
isa => 'Int',
default => 0,
);
method "increment_$name" => sub {
my $self = shift;
$self->$name($self->$name + 1);
};
method "reset_$name" => sub {
my $self = shift;
$self->$name(0);
};
};
package MyGame::Weapon;
use Moose;
with Counter => { name => 'enchantment' };
package MyGame::Wand;
use Moose;
with Counter => { name => 'zapped' };
Your parameterized role consists of two new things: parameter declarations
and a role block.
Parameters are declared using the parameter keyword which very much
resembles Moose/has. You can use any option that Moose/has accepts. The
default value for the is option is ro as that's a very common case. Use
is => 'bare' if you want no accessor. These parameters will get their
values when the consuming class (or role) uses Moose/with. A parameter
object will be constructed with these values, and passed to the role block.
The role block then uses the usual the Moose::Role manpage keywords to build up a
role. You can shift off the parameter object to inspect what the consuming
class provided as parameters. You use the parameters to customize your
role however you wish.
There are many possible implementations for parameterized roles (hopefully with a consistent enough API); I believe this to be the easiest and most flexible design. Coincidentally, Pugs originally had an eerily similar design.
See the MooseX::Role::Parameterized::Extending manpage for some tips on how to extend this module.
I've been asked several times ``Why use a parameter object and not just a parameter hashref? That would eliminate the need to explicitly declare your parameters.''
The benefits of using an object are similar to the benefits of using Moose. You get an easy way to specify lazy defaults, type constraint, delegation, and so on. You get to use MooseX modules.
Stop! If you're new here, please read the MooseX::Role::Parameterized::Tutorial manpage for a much gentler introduction.
You also get the usual introspective and intercessory abilities that come standard with the metaobject protocol. Ambitious users should be able to add traits to the parameters metaclass to further customize behavior. Please let me know if you're doing anything viciously complicated with this extension. :)
You must use this syntax to declare methods in the role block:
method NAME => sub { ... };. This is due to a limitation in Perl. In
return though you can use parameters in your methods!
http://sartak.org/2009/01/parametric-roles-in-perl-5.html
http://sartak.org/2009/05/the-design-of-parameterized-roles.html
http://stevan-little.blogspot.com/2009/07/thoughts-on-parameterized-roles.html
http://perldition.org/articles/Parameterized%20Roles%20with%20MooseX::Declare.pod
http://www.modernperlbooks.com/mt/2011/01/the-parametric-role-of-my-mvc-plugin-system.html
http://sartak.org/talks/yapc-asia-2009/(parameterized)-roles/
https://github.com/SamuraiJack/JooseX-Role-Parameterized - this extension ported to JavaScript's Joose
Shawn M Moore <code@sartak.org>
This software is copyright (c) 2008 by Shawn M Moore.
This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.
| MooseX::Role::Parameterized - roles with composition parameters |