Moose::Manual(3pm) User Contributed Perl Documentation Moose::Manual(3pm)
NAME
Moose::Manual - What is Moose, and how do I use it?
VERSION
version 2.2203
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@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@cpan.org>
• Dave Rolsky <autarch@urth.org>
• Jesse Luehrs <doy@cpan.org>
• Shawn M Moore <sartak@cpan.org>
• יובל קוג'מן (Yuval Kogman) <nothingmuch@woobling.org>
• Karen Etheridge <ether@cpan.org>
• Florian Ragwitz <rafl@debian.org>
• Hans Dieter Pearcey <hdp@cpan.org>
• Chris Prather <chris@prather.org>
• Matt S Trout <mstrout@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.
perl v5.36.0 2023-01-30 Moose::Manual(3pm)
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