Moose::Cookbook::Snack::Keywords

Section: User Contributed Perl Documentation (3)
Updated: 2018-05-16
Page Index

NAME

Moose::Cookbook::Snack::Keywords - Restricted "keywords" in Moose

VERSION

version 2.2011

DESCRIPTION

Moose exports a number of sugar functions in order to emulate Perl built-in keywords. These can cause clashes with other user-defined functions. This document provides a list of those keywords for easy reference.

The 'meta' keyword

"use Moose" adds a method called "meta" to your class. If this conflicts with a method or function you are using, you can rename it, or prevent it from being installed entirely. To do this, pass the "-meta_name" option when you "use Moose". For instance:

  # install it under a different name
  use Moose -meta_name => 'moose_meta';

  # don't install it at all
  use Moose -meta_name => undef;

Moose Keywords

If you are using Moose or Moose::Role it is best to avoid these keywords:

extends
with
has
before
after
around
super
override
inner
augment
confess
blessed
meta

Moose::Util::TypeConstraints Keywords

If you are using Moose::Util::TypeConstraints it is best to avoid these keywords:

type
subtype
class_type
role_type
maybe_type
duck_type
as
where
message
inline_as
coerce
from
via
enum
find_type_constraint
register_type_constraint

Avoiding collisions

Turning off Moose

To remove the sugar functions Moose exports, just add "no Moose" at the bottom of your code:

  package Thing;
  use Moose;

  # code here

  no Moose;

This will unexport the sugar functions that Moose originally exported. The same will also work for Moose::Role and Moose::Util::TypeConstraints.

Sub::Exporter features

Moose, Moose::Role and Moose::Util::TypeConstraints all use Sub::Exporter to handle all their exporting needs. This means that all the features that Sub::Exporter provides are also available to them.

For instance, with Sub::Exporter you can rename keywords, like so:

  package LOL::Cat;
  use Moose 'has' => { -as => 'i_can_haz' };

  i_can_haz 'cheeseburger' => (
      is      => 'rw',
      trigger => sub { print "NOM NOM" }
  );

  LOL::Cat->new->cheeseburger('KTHNXBYE');

See the Sub::Exporter docs for more information.

namespace::autoclean and namespace::clean

You can also use namespace::autoclean to clean up your namespace. This will remove all imported functions from your namespace. Note that if you are importing functions that are intended to be used as methods (this includes overload, due to internal implementation details), it will remove these as well.

Another option is to use namespace::clean directly, but you must be careful not to remove "meta" when doing so:

  package Foo;
  use Moose;
  use namespace::clean -except => 'meta';
  # ...

AUTHORS

•: Stevan Little <stevan.little@iinteractive.com>
•: Dave Rolsky <autarch@urth.org>
•: Jesse Luehrs <doy@tozt.net>
•: Shawn M Moore <code@sartak.org>
•: יובל קוג'מן (Yuval Kogman) <nothingmuch@woobling.org>
•: Karen Etheridge <ether@cpan.org>
•: Florian Ragwitz <rafl@debian.org>
•: Hans Dieter Pearcey <hdp@weftsoar.net>
•: Chris Prather <chris@prather.org>
•: Matt S Trout <mst@shadowcat.co.uk>

COPYRIGHT AND LICENSE

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.