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

NAME
    Moose::Manual - What is Moose, and how do I use it?

VERSION
    version 2.2200

WHAT IS MOOSE?
    Moose is a *complete* object system for Perl 5. Consider any modern object-oriented language
    (which Perl 5 definitely isn't). It provides keywords for attribute declaration, object
    construction, inheritance, and maybe more. These keywords are part of the language, and you
    don't care how they are implemented.

    Moose aims to do the same thing for Perl 5 OO. We can't actually create new keywords, but we do
    offer "sugar" that looks a lot like them. More importantly, with Moose, you *define your class
    declaratively*, without needing to know about blessed hashrefs, accessor methods, and so on.

    With Moose, you can concentrate on the *logical* structure of your classes, focusing on "what"
    rather than "how". A class definition with Moose reads like a list of very concise English
    sentences.

    Moose is built on top of "Class::MOP", a meta-object protocol (aka MOP). Using the MOP, Moose
    provides complete introspection for all Moose-using classes. This means you can ask classes
    about their attributes, parents, children, methods, etc., all using a well-defined API. The MOP
    abstracts away the symbol table, looking at @ISA vars, and all the other crufty Perl tricks we
    know and love(?).

    Moose is based in large part on the Perl 6 object system, as well as drawing on the best ideas
    from CLOS, Smalltalk, and many other languages.

WHY MOOSE?
    Moose makes Perl 5 OO both simpler and more powerful. It encapsulates Perl 5 power tools in
    high-level declarative APIs which are easy to use. Best of all, you don't need to be a wizard to
    use it.

    But if you want to dig about in the guts, Moose lets you do that too, by using and extending its
    powerful introspection API.

AN EXAMPLE
      package Person;

      use Moose;

      has 'first_name' => (
          is  => 'rw',
          isa => 'Str',
      );

      has 'last_name' => (
          is  => 'rw',
          isa => 'Str',
      );

      no Moose;
      __PACKAGE__->meta->make_immutable;

    This is a *complete and usable* class definition!

      package User;

      use DateTime;
      use Moose;

      extends 'Person';

      has 'password' => (
          is  => 'rw',
          isa => 'Str',
      );

      has 'last_login' => (
          is      => 'rw',
          isa     => 'DateTime',
          handles => { 'date_of_last_login' => 'date' },
      );

      sub login {
          my $self = shift;
          my $pw   = shift;

          return 0 if $pw ne $self->password;

          $self->last_login( DateTime->now() );

          return 1;
      }

      no Moose;
      __PACKAGE__->meta->make_immutable;

    When ready to instantiate your class in an application, use it in the "traditional" Perl manner:

      use User;

      my $user = User->new(
        first_name => 'Example',
        last_name  => 'User',
        password   => 'letmein',
      );

      $user->login('letmein');

      say $user->date_of_last_login;

    We'll leave the line-by-line explanation of this code to other documentation, but you can see
    how Moose reduces common OO idioms to simple declarative constructs.

TABLE OF CONTENTS
    This manual consists of a number of documents.

    Moose::Manual::Concepts
        Introduces Moose concepts, and contrasts them against "old school" Perl 5 OO.

    Moose::Manual::Unsweetened
        Shows two example classes, each written first with Moose and then with "plain old Perl 5".

    Moose::Manual::Classes
        How do you make use of Moose in your classes? Now that I'm a Moose, how do I subclass
        something?

    Moose::Manual::Attributes
        Attributes are a core part of the Moose OO system. An attribute is a piece of data that an
        object has. Moose has a lot of attribute-related features!

    Moose::Manual::Delegation
        Delegation is a powerful way to make use of attributes which are themselves objects.

    Moose::Manual::Construction
        Learn how objects are built in Moose, and in particular about the "BUILD" and "BUILDARGS"
        methods. Also covers object destruction with "DEMOLISH".

    Moose::Manual::MethodModifiers
        A method modifier lets you say "before calling method X, do this first", or "wrap method X
        in this code". Method modifiers are particularly handy in roles and with attribute
        accessors.

    Moose::Manual::Roles
        A role is something a class does (like "Debuggable" or "Printable"). Roles provide a way of
        adding behavior to classes that is orthogonal to inheritance.

    Moose::Manual::Types
        Moose's type system lets you strictly define what values an attribute can contain.

    Moose::Manual::MOP
        Moose's meta API system lets you ask classes about their parents, children, methods,
        attributes, etc.

    Moose::Manual::MooseX
        This document describes a few of the most useful Moose extensions on CPAN.

    Moose::Manual::BestPractices
        Moose has a lot of features, and there's definitely more than one way to do it. However, we
        think that picking a subset of these features and using them consistently makes everyone's
        life easier.

    Moose::Manual::FAQ
        Frequently asked questions about Moose.

    Moose::Manual::Resources
        Links to various tutorials, videos, blogs, presentations, interviews, etc...

    Moose::Manual::Contributing
        Interested in hacking on Moose? Read this.

    Moose::Manual::Delta
        This document details backwards-incompatibilities and other major changes to Moose.

JUSTIFICATION
    If you're still asking yourself "Why do I need this?", then this section is for you.

    Another object system!?!?
        Yes, we know there are many, many ways to build objects in Perl 5, many of them based on
        inside-out objects and other such things. Moose is different because it is not a new object
        system for Perl 5, but instead an extension of the existing object system.

        Moose is built on top of Class::MOP, which is a metaclass system for Perl 5. This means that
        Moose not only makes building normal Perl 5 objects better, but it also provides the power
        of metaclass programming.

    Is this for real? Or is this just an experiment?
        Moose is *based* on the prototypes and experiments Stevan did for the Perl 6 meta-model.
        However, Moose is NOT an experiment or prototype; it is for real.

    Is this ready for use in production?
        Yes.

        Moose has been used successfully in production environments by many people and companies.
        There are Moose applications which have been in production with little or no issue now for
        years. We consider it highly stable and we are committed to keeping it stable.

        Of course, in the end, you need to make this call yourself. If you have any questions or
        concerns, please feel free to email Stevan or the moose AT perl.org list, or just stop by
        irc.perl.org#moose and ask away.

    Is Moose just Perl 6 in Perl 5?
        No. While Moose is very much inspired by Perl 6, it is not itself Perl 6. Instead, it is an
        OO system for Perl 5. Stevan built Moose because he was tired of writing the same old boring
        Perl 5 OO code, and drooling over Perl 6 OO. So instead of switching to Ruby, he wrote Moose
        :)

    Wait, *post* modern, I thought it was just *modern*?
        Stevan read Larry Wall's talk from the 1999 Linux World entitled "Perl, the first postmodern
        computer language" in which he talks about how he picked the features for Perl because he
        thought they were cool and he threw out the ones that he thought sucked. This got him
        thinking about how we have done the same thing in Moose. For Moose, we have "borrowed"
        features from Perl 6, CLOS (LISP), Smalltalk, Java, BETA, OCaml, Ruby and more, and the bits
        we didn't like (cause they sucked) we tossed aside. So for this reason (and a few others)
        Stevan has re-dubbed Moose a *postmodern* object system.

        Nuff Said.

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.