NAME¶
MooseX::Role::Parameterized - roles with composition parameters
VERSION¶
version 1.08
SYNOPSIS¶
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' };
DESCRIPTION¶
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 "has" in Moose. You can use any option that
"has" in Moose 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 "with" in Moose. A parameter
object will be constructed with these values, and passed to the
"role" block.
The "role" block then uses the usual Moose::Role 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 MooseX::Role::Parameterized::Extending for some tips on how to extend this
module.
Why a parameters object?¶
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.
MooseX::Role::Parameterized::Tutorial¶
Stop! If you're new here, please read
MooseX::Role::Parameterized::Tutorial 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. :)
CAVEATS¶
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!
SEE ALSO¶
<
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://jjnapiorkowski.typepad.com/modern-perl/2010/08/parameterized-roles-and-method-traits-redo.html>
<
http://sartak.org/talks/yapc-asia-2009/(parameterized)-roles/>
<
https://github.com/SamuraiJack/JooseX-Role-Parameterized> - this
extension ported to JavaScript's Joose
AUTHOR¶
Shawn M Moore <code@sartak.org>
COPYRIGHT AND LICENSE¶
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.
CONTRIBUTORS¶
- •
- Karen Etheridge <ether@cpan.org>
- •
- Dave Rolsky <autarch@urth.org>
- •
- Oliver Charles <oliver.g.charles@googlemail.com>
- •
- Jesse Luehrs <doy@tozt.net>
- •
- Yuval Kogman <nothingmuch@woobling.org>
- •
- Florian Ragwitz <rafl@debian.org>
- •
- Robert 'phaylon' Sedlacek <rs@474.at>
- •
- Chris Weyl <cweyl@alumni.drew.edu>
- •
- Csson <erik.carlsson@live.com>
- •
- Todd Hepler <thepler@employees.org>
- •
- Ricardo Signes <rjbs@cpan.org>