Moose::Manual::ClassesUser)Contributed Perl DocumenMoose::Manual::Classes(3pm)NAMEMoose::Manual::Classes - Making your classes use Moose (and
subclassing)
VERSION
version 2.2009
USING MOOSE
Using Moose is very simple, you just "use Moose":
package Person;
use Moose;
That's it, you've made a class with Moose!
There's actually a lot going on here under the hood, so let's step
through it.
When you load Moose, a bunch of sugar functions are exported into your
class, such as "extends", "has", "with", and more. These functions are
what you use to define your class. For example, you might define an
attribute ...
package Person;
use Moose;
has 'ssn' => ( is => 'rw' );
Attributes are described in the Moose::Manual::Attributes
documentation.
Loading Moose also enables the "strict" and "warnings" pragmas in your
class.
When you load Moose, your class will become a subclass of
Moose::Object. The Moose::Object class provides a default constructor
and destructor, as well as object construction helper methods. You can
read more about this in the Moose::Manual::Construction document.
As a convenience, Moose creates a new class type for your class. See
the Moose::Manual::Types document to learn more about types.
It also creates a Moose::Meta::Class object for your class. This
metaclass object is now available by calling a "meta" method on your
class, for example "Person->meta".
The metaclass object provides an introspection API for your class. It
is also used by Moose itself under the hood to add attributes, define
parent classes, and so on. In fact, all of Moose's sugar does the real
work by calling methods on this metaclass object (and other meta API
objects).
SUBCLASSING
Moose provides a simple sugar function for declaring your parent
classes, "extends":
package User;
use Moose;
extends 'Person';
has 'username' => ( is => 'rw' );
Note that each call to "extends" will reset your parents. For multiple
inheritance you must provide all the parents at once, "extends 'Foo',
'Bar'".
When you call "extends" Moose will try to load any classes you pass.
You can use Moose to extend a non-Moose parent. However, when you do
this, you will inherit the parent class's constructor (assuming it is
also called "new"). In that case, you will have to take care of
initializing attributes manually, either in the parent's constructor,
or in your subclass, and you will lose a lot of Moose magic.
See the MooseX::NonMoose module on CPAN if you're interested in
extending non-Moose parent classes with Moose child classes.
CLEANING UP MOOSE DROPPINGS
Moose exports a number of functions into your class. It's a good idea
to remove these sugar functions from your class's namespace, so that
"Person->can('has')" will no longer return true.
There are several ways to do this. We recommend using
namespace::autoclean, a CPAN module. Not only will it remove Moose
exports, it will also remove any other exports.
package Person;
use namespace::autoclean;
use Moose;
If you absolutely can't use a CPAN module (but can use Moose?), you can
write "no Moose" at the end of your class. This will remove any Moose
exports in your class.
package Person;
use Moose;
has 'ssn' => ( is => 'rw' );
no Moose;
MAKING IT FASTER
Moose has a feature called "immutabilization" that you can use to
greatly speed up your classes at runtime. However, using it incurs a
cost when your class is first being loaded. When you make your class
immutable you tell Moose that you will not be changing it in the
future. You will not be adding any more attributes, methods, roles,
etc.
This allows Moose to generate code specific to your class. In
particular, it creates an "inline" constructor, making object
construction much faster.
To make your class immutable you simply call "make_immutable" on your
class's metaclass object.
__PACKAGE__->meta->make_immutable;
Immutabilization and "new()"
If you override "new()" in your class, then the immutabilization code
will not be able to provide an optimized constructor for your class.
Instead, you should use a "BUILD()" method, which will be called from
the inlined constructor.
Alternately, if you really need to provide a different "new()", you can
also provide your own immutabilization method. Doing so requires
extending the Moose metaclasses, and is well beyond the scope of this
manual.
INSTANTIATING CLASSES
When you're ready to use Moose classes in an application, reference
them in your code in the regular Perl OO way by including a "use"
directive at the top of the file where the objects should be created.
use Person;
my $person = Person->new(
# attribute values at instantiation
# go here
ssn => '123456789',
);
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 software is copyright (c) 2006 by Infinity Interactive, Inc.
This is free software; you can redistribute it and/or modify it under
the same terms as the Perl 5 programming language system itself.
perl v5.26.1 2017-12-21 Moose::Manual::Classes(3pm)
