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Moose::Manual(3)                     User Contributed Perl Documentation                    Moose::Manual(3)



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

VERSION
       version 2.0205

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 highlevel
       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;

       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::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 insideout
           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@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.

AUTHOR
       Stevan Little <stevan@iinteractive.com>

COPYRIGHT AND LICENSE
       This software is copyright (c) 2011 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 v5.12.5                                     2011-09-06                                 Moose::Manual(3)