5 Moose::Manual - What is Moose, and how do I use it?
9 Moose is a I<complete> object system for Perl 5. If you've used a
10 modern object-oriented language (which Perl 5 definitely isn't), you
11 know they provide keywords for attribute declaration, object
12 construction, and inheritance. These keywords are part of the
13 language, and you don't care how they are implemented.
15 Moose aims to do the same thing for Perl 5 OO. We can't actually
16 create new keywords, but we do offer "sugar" that looks a lot like
17 them. More importantly, with Moose, you I<declaratively define> your
18 class, without needing to know about blessed hashrefs, accessor
21 Moose helps you define the I<logical> structure of your classes, so
22 you can focus on "what" rather than "how". With Moose, a class
23 definition reads like a list of very concise English sentences.
25 Moose is built in top of C<Class::MOP>, a meta-object protocol (aka
26 MOP). Using the MOP, Moose provides complete introspection for all
27 Moose-using classes. This means you can ask classes about their
28 attributes, parents, children, methods, etc., all using a well-defined
29 API. The MOP abstracts away tedious digging about in the Perl symbol
30 table, looking at C<@ISA> vars, and all the other crufty Perl tricks
33 Moose is based in large part on the Perl 6 object system, as well as
34 drawing on the best ideas from CLOS, Smalltalk, and many other
39 Moose makes Perl 5 OO both simpler and more powerful. It encapsulates
40 all the tricks of Perl 5 power users in high-level declarative APIs
41 which are easy to use, and doesn't require any special knowledge of
42 how Perl works under the hood.
44 If you want to dig about in the guts, Moose lets you do that too, by
45 using and extending its powerful introspection API.
64 __PACKAGE__->meta->make_immutable;
66 This is a I<complete and usable> class definition!
83 handles => { 'date_of_last_login' => 'date' },
90 return 0 if $pw ne $self->password;
92 $self->last_login( DateTime->now() );
98 __PACKAGE__->meta->make_immutable;
100 We'll leave the line-by-line explanation of this code to other
101 documentation, but you can see how Moose reduces common OO idioms to
102 simple declarative constructs.
104 =head2 TABLE OF CONTENTS
106 This manual consists of a number of documents.
110 =item L<Moose::Manual::Concepts>
112 Introduces Moose concepts, and contrasts them against "old school"
115 =item L<Moose::Manual::Classes>
117 How do you make use of Moose in your classes? Now that I'm a Moose,
118 how do I subclass something?
120 =item L<Moose::Manual::Attributes>
122 Attributes are a core part of the Moose OO system. An attribute is a
123 piece of data that an object has. Moose has a lot of attribute-related
126 =item L<Moose::Manual::Construction>
128 Learn how objects are built in Moose, and in particular about the
129 C<BUILD>, C<BUILDARGS> methods. Also covers object destruction
132 =item L<Moose::Manual::MethodModifiers>
134 A method modifier lets you say "before calling method X, do this
135 first", or "wrap method X in this code". Method modifiers are
136 particularly handy in roles and with attribute accessors.
138 =item L<Moose::Manual::Roles>
140 A role is something a class does (like "Debuggable" or
141 "Printable"). Roles provide a way of adding behavior to classes that
142 is orthogonal to inheritance.
144 =item L<Moose::Manual::Types>
146 Moose's type system lets you strictly define what values an attribute
149 =item L<Moose::Manual::Introspection>
151 Moose's introspection system (primarily from C<Class::MOP>) lets you
152 ask classes about their parents, children, methods, attributes, etc.
154 =item L<Moose::Manual::MooseX>
156 This document shows a few of the most useful Moose extensions on CPAN.
162 If you're still still asking yourself "Why do I need this?", then this
167 =item Another object system!?!?
169 Yes, I know there has been an explosion recently of new ways to
170 build objects in Perl 5, most of them based on inside-out objects
171 and other such things. Moose is different because it is not a new
172 object system for Perl 5, but instead an extension of the existing
175 Moose is built on top of L<Class::MOP>, which is a metaclass system
176 for Perl 5. This means that Moose not only makes building normal
177 Perl 5 objects better, but it also provides the power of metaclass
180 =item Is this for real? Or is this just an experiment?
182 Moose is I<based> on the prototypes and experiments Stevan did for the
183 Perl 6 meta-model. However, Moose is B<NOT> an experiment or
184 prototype; it is for B<real>.
186 =item Is this ready for use in production?
190 Moose has been used successfully in production environments by several
191 people and companies. There are Moose applications which have been in
192 production with little or no issue now for well over two years. We
193 consider it highly stable and we are commited to keeping it stable.
195 Of course, in the end, you need to make this call yourself. If you
196 have any questions or concerns, please feel free to email Stevan, the
197 moose@perl.org list, or just stop by irc.perl.org#moose and ask away.
199 =item Is Moose just Perl 6 in Perl 5?
201 No. While Moose is very much inspired by Perl 6, it is not itself Perl
202 6. Instead, it is an OO system for Perl 5. Stevan built Moose because
203 he was tired of writing the same old boring Perl 5 OO code, and
204 drooling over Perl 6 OO. So instead of switching to Ruby, he wrote
207 =item Wait, I<post> modern, I thought it was just I<modern>?
209 Stevan read Larry Wall's talk from the 1999 Linux World entitled
210 "Perl, the first postmodern computer language" in which he talks about
211 how he picked the features for Perl because he thought they were cool
212 and he threw out the ones that he thought sucked. This got him
213 thinking about how we have done the same thing in Moose. For Moose, we
214 have "borrowed" features from Perl 6, CLOS (LISP), Smalltalk, Java,
215 BETA, OCaml, Ruby and more, and the bits we didn't like (cause they
216 sucked) we tossed aside. So for this reason (and a few others) Stevan
217 has re-dubbed Moose a I<postmodern> object system.
225 Dave Rolsky E<lt>autarch@urth.orgE<gt> and Stevan Little
226 E<lt>stevan@iinteractive.comE<gt>
228 =head1 COPYRIGHT AND LICENSE
230 Copyright 2008 by Infinity Interactive, Inc.
232 L<http://www.iinteractive.com>
234 This library is free software; you can redistribute it and/or modify
235 it under the same terms as Perl itself.