phpman > perldoc > Moose::Manual::Classes(3pm)

NAME
    Moose::Manual::Classes - Making your classes use Moose (and subclassing)

VERSION
    version 2.2200

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 AT cpan.org>

    *   Dave Rolsky <autarch AT urth.org>

    *   Jesse Luehrs <doy AT cpan.org>

    *   Shawn M Moore <sartak AT cpan.org>

    *   יובל קוג'מן (Yuval Kogman) <nothingmuch AT woobling.org>

    *   Karen Etheridge <ether AT cpan.org>

    *   Florian Ragwitz <rafl AT debian.org>

    *   Hans Dieter Pearcey <hdp AT cpan.org>

    *   Chris Prather <chris AT prather.org>

    *   Matt S Trout <mstrout AT cpan.org>

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.