=head1 NAME
-Moose::Intro - What is Moose, and how do I use it?
+Moose::Manual - What is Moose, and how do I use it?
=head1 WHAT IS MOOSE?
-Moose is a I<complete> object system for Perl 5. If you've used a
-modern object-oriented language (which Perl 5 definitely isn't), you
-know they provide keywords for attribute declaration, object
-construction, and inheritance. These keywords are part of the
-language, and you don't care how they are implemented.
+Moose is a I<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 I<declaratively define> your
-class, without needing to know about blessed hashrefs, accessor
-methods, and so on.
+them. More importantly, with Moose, you I<define your class
+declaratively>, without needing to know about blessed hashrefs,
+accessor methods, and so on.
-Moose lets you focus on the I<logical> structure of your classes, so
-you can focus on "what" rather than "how". With Moose, a class
-definition should read like a list of very concise English sentences.
+With Moose, you can concentrate on the I<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 in top of C<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 tedious digging about in the Perl symbol
-table, looking at C<@ISA> vars, and all the other crufty Perl tricks
-we know and love (?).
+API. The MOP abstracts away the symbol table, looking at C<@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
=head1 WHY MOOSE?
Moose makes Perl 5 OO both simpler and more powerful. It encapsulates
-all the tricks of Perl 5 power users in high-level declarative APIs
-which are easy to use, and don't require any special knowledge of how
-Perl works under the hood.
+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.
-Moose makes Perl 5 OO fun, accessible, and powerful. And if you want
-to dig about in the guts, Moose lets you do that too, by using and
-extending its powerful introspection API.
+But if you want to dig about in the guts, Moose lets you do that too,
+by using and extending its powerful introspection API.
=head1 AN EXAMPLE
isa => 'Str',
);
+ no Moose;
+ __PACKAGE__->meta->make_immutable;
+
This is a I<complete and usable> class definition!
package User;
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.
-=head2 Where's the Constructor?
-
-One point of confusion that might come up with Moose is how it handles
-object construction. B<You should not define a C<new()> method for
-your classes!>
-
-Moose will provide one for you. It will accept a hash or hash
-reference of named parameters matching your attributes. This is just
-another way in which Moose keeps you from worrying I<how> classes are
-implemented. Simply define a class and you're ready to start creating
-objects!
-
-=head1 MOOSE CONCEPTS (VS "OLD SCHOOL" Perl)
-
-In the past, you may not have thought too much about the difference
-between packages and classes, attributes and methods, constructors and
-methods, etc. Part of what the MOP provides is well-defined
-introspection features for each of those things, and in turn Moose
-provides I<distinct> sugar for each of them. Moose also introduces
-concepts that are uncommon (or entirely new) like roles, method
-modifiers, and declarative delegation.
-
-Knowing what these concepts mean in Moose-speak, and how they used to
-be done in old school Perl 5 OO is a good way to start learning to use
-Moose.
-
-=head2 Class
-
-When you say "use Moose" in a package, you are defining your package
-as a class. At its simplest, a class will consist simply of attributes
-and/or methods. It can also include roles, method modifiers, and more.
-
-A class I<has> zero or more B<attributes>.
-
-A class I<has> zero or more B<methods>.
-
-A class I<has> zero or more superclasses (aka parent classes). A
-class inherits from its superclass(es).
-
-A class I<has> zero or more B<method modifiers>. These modifiers can
-apply to its own methods or methods that are inherited from its
-ancestors.
-
-A class may I<do> zero or more B<roles>.
-
-A class I<has> a B<constructor> and a B<destructor>. These are
-provided for you "for free" by Moose.
-
-The B<constructor> accepts named parameters corresponding to the
-class's attributes and uses them to initialize an B<object instance>.
-
-A class I<has> a B<metaclass>, which in turn has B<meta-attributes>,
-B<meta-methods>, and B<meta-roles>. This metaclass I<describes> the
-class.
-
-A class is usually analogous to a category of nouns, like "People" or
-"Users".
-
- package Person;
-
- use Moose;
- # now it's a Moose class!
-
-=head2 Attribute
-
-An attribute is a property of the class that defines it. It I<always>
-has a name, and it I<may have> a number of other defining
-characteristics.
-
-These characteristics may include a read/write flag, a B<type>,
-accessor method names, B<delegations>, a default value, and more.
-
-Attributes I<are not> methods, but defining them causes various
-accessor methods to be created. At a minimum, a normal attribute will
-always have a reader accessor method. Many attributes have things like
-a writer method, clearer method, and predicate method ("has it been
-set?").
-
-An attribute may also define B<delegation>s, which will create
-additional methods based on the delegation specification.
-
-By default, Moose stores attributes in the object instance, which is a
-hashref, I<but this is invisible to the author of a Moose-base class>!
-It is best to think of Moose attributes as "properties" of the
-I<opaque> B<object instance>. These properties are accessed through
-well-defined accessor methods.
-
-An attribute is usually analogous to a specific feature of something in
-the class's category. For example, People have first and last
-names. Users have passwords and last login datetimes.
-
- has 'first_name' => (
- is => 'rw',
- isa => 'Str',
- );
-
-=head2 Method
-
-A method is very straightforward. Any subroutine you define in your
-class is a method.
-
-Methods correspond to verbs, and are what your objects can do. For
-example, a User can login.
-
- sub login { ... }
-
-=head2 Roles
-
-A role is something that a class I<does>. For example, a Machine class
-might do the Breakable role, and so could a Bone class. A role is
-used to define some concept that cuts across multiple unrelated
-classes, like "breakability", or "has a color".
-
-A role I<has> zero or more B<attributes>.
-
-A role I<has> zero or more B<methods>.
-
-A role I<has> zero or more B<method modifiers>.
-
-A role I<has> zero or more B<required methods>.
-
-A required method is not implemented by the role. Instead, a required
-method says "to use this Role you must implement this method".
-
-Roles are I<composed> into classes (or other roles). When a role is
-composed into a class, its attributes and methods are "flattened" into
-the class. Roles I<do not> show up in the inheritance hierarchy. When
-a role is composed, its attributes and methods appear as if they were
-defined I<in the consuming class>.
-
-Role are somewhat like mixins or interfaces in other OO languages.
-
- package Breakable;
-
- use Moose::Role;
-
- has is_broken => (
- is => 'rw',
- isa => 'Bool',
- );
-
- requires 'break';
-
- before 'break' => {
- my $self = shift;
-
- $self->is_broken(1);
- };
+=head2 TABLE OF CONTENTS
-=head2 Method Modifiers
-
-A method modifier is a way of defining an action to be taken when a
-named method is called. Think of it as a hook on the named method. For
-example, you could say "before calling C<login()>, call this modifier
-first". Modifiers come in different flavors like "before", "after",
-"around", and "augment", and you can apply more than one modifier to
-a single method.
-
-Method modifiers are often used as an alternative to overriding a
-method in a parent class. They are also used in roles as a way of
-modifying methods in the consuming class.
-
-Under the hood, a method modifier is just a plain old Perl subroutine
-that gets called before or after (or around, etc.) some named method.
-
- before 'login' => sub {
- my $self = shift;
- my $pw = shift;
-
- warn "Called login() with $pw\n";
- };
-
-=head2 Type
-
-Moose also comes with a (miniature) type system. This allows you to
-define types for attributes. Moose has a set of built-in types based
-on what Perl provides, such as "Str", "Num", "Bool", "HashRef", etc.
-
-In addition, every class name in your application can also be used as
-a type name. We saw an example using "DateTime" earlier.
-
-Finally, you can define your own types, either as subtypes or entirely
-new types, with their own constraints. For example, you could define a
-type "PosInt", a subtype of "Int" which only allows positive numbers.
-
-=head2 Delegation
-
-Moose attributes provide declarative syntax for defining
-delegations. A delegation is a method which delegates the real work to
-some attribute of the class.
-
-You saw this in the User example, where we defined a delegation for
-the C<date_of_last_login()> method. Under the hood, this simple calls
-C<date()> on the User object's C<last_login> attribute.
-
-=head2 Constructor
-
-A constructor creates an B<object instance> for the class. In old
-school Perl, this was usually done by defining a method called
-C<new()> which in turn called C<bless> on a reference.
-
-With Moose, this C<new()> method is created for you, and it simply
-does the right thing. You should never need to define your own
-constructor!
-
-Sometimes you want to do something whenever an object is created. In
-those cases, you can provide a C<BUILD()> method in your class. Moose
-will call this for you after creating a new object.
-
-=head2 Destructor
-
-This is a special method called when an object instance goes out of
-scope. You can specialize what your class does in this method if you
-need to, but you usually don't.
-
-With old school Perl 5, this is the C<DESTROY()> method, but with
-Moose it is the C<DEMOLISH()> method.
-
-=head2 Object Instance
-
-An object instance is a specific noun in the class's "category". For
-example, one specific Person or User. An instance is created by the
-class's B<constructor>.
-
-An instance has values for its attributes. For example, a specific
-person has a first and last name.
-
-In old school Perl 5, this is often a blessed hash reference. With
-Moose, you should never need to know what your object instance
-actually is. (ok, it's usually a blessed hashref with Moose too)
-
-=head2 Moose VS Old School Summary
+This manual consists of a number of documents.
=over 4
-=item * Class
-
-A package with no introspection other than mucking about in the symbol
-table.
-
-With Moose, you get well-defined declaration and introspection.
+=item L<Moose::Manual::Concepts>
-=item * Attributes
+Introduces Moose concepts, and contrasts them against "old school"
+Perl 5 OO.
-Hand-written accessor methods, symbol table hackery, or a helper
-module like C<Class::Accessor>.
+=item L<Moose::Manual::Classes>
-With Moose, these are declaratively defined, and distinct from
-methods.
+How do you make use of Moose in your classes? Now that I'm a Moose,
+how do I subclass something?
-=item * Method
+=item L<Moose::Manual::Attributes>
-These are pretty much the same in Moose as in old school Perl.
+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!
-=item * Roles
+=item L<Moose::Manual::Delegation>
-C<Class::Trait> or C<Class::Role>, or maybe C<mixin.pm>.
+Delegation is a powerful way to make use of attribute which are
+themselves objects.
-With Moose, they're part of the core feature set, and are
-introspectable like everything else.
+=item L<Moose::Manual::Construction>
-=item * Method Modifiers
+Learn how objects are built in Moose, and in particular about the
+C<BUILD> and C<BUILDARGS> methods. Also covers object destruction
+with C<DEMOLISH>.
-Could only be done through serious symbol table wizardry, and you
-probably never saw this before (at least in Perl 5).
+=item L<Moose::Manual::MethodModifiers>
-=item * Type
+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.
-Hand-written parameter checking in your C<new()> method and accessors.
+=item L<Moose::Manual::Roles>
-With Moose, you define types declaratively, and then use them by name
-in your attributes.
+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.
-=item * Delegation
+=item L<Moose::Manual::Types>
-C<Class::Delegation> or C<Class::Delegator>, but probably even more
-hand-written code.
+Moose's type system lets you strictly define what values an attribute
+can contain.
-With Moose, this is also declarative.
+=item L<Moose::Manual::MOP>
-=item * Constructor
+Moose's meta API system lets you ask classes about their parents,
+children, methods, attributes, etc.
-A C<new()> method which calls C<bless> on a reference.
+=item L<Moose::Manual::MooseX>
-Comes for free when you define a class with Moose.
+This document shows a few of the most useful Moose extensions on CPAN.
-=item * Destructor
+=item L<Moose::Manual::BestPractices>
-A C<DESTROY()> method.
-
-With Moose, this is called C<DEMOLISH()>.
-
-=item * Object Instance
-
-A blessed reference, usually a hash reference.
-
-With Moose, this is an opaque thing which has a bunch of attributes
-and methods, as defined by its class.
-
-=item * Immutabilization
-
-Moose comes with a feature called "immutabilization". When you make
-your class immutable, it means you're done adding methods, attributes,
-roles, etc. This lets Moose optimize your class with a bunch of
-extremely dirty in-place code generation tricks that speed up things
-like object construction and so on.
+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.
=back
-=head1 META WHAT?
-
-A metaclass is a class that describes classes. With Moose, every class
-you define gets a C<meta()> method. It returns a L<Moose::Meta::Class>
-object, which has an introspection API that can tell you about the
-class it represents.
-
- my $meta = User->meta();
-
- for my $attribute ( $meta->compute_all_applicable_attributes ) {
- print $attribute->name(), "\n";
-
- if ( $attribute->has_type_constraint ) {
- print " type: ", $attribute->type_constraint->name, "\n";
- }
- }
-
- for my $method ( $meta->compute_all_applicable_methods ) {
- print $method->name, "\n";
- }
-
-Almost every concept we defined earlier has a meta class, so we have
-L<Moose::Meta::Class>, L<Moose::Meta::Attribute>,
-L<Moose::Meta::Method>, L<Moose::Meta::Role>,
-L<Moose::Meta::TypeConstraint>, L<Moose::Meta::Instance>, and so on.
-
-=head1 BUT I NEED TO DO IT MY WAY!
-
-One of the great things about Moose is that if you dig down and find
-that it does something the "wrong way", you can change it by extending
-a metaclass. For example, you can have arrayref based objects, you can
-make your constructors strict (no unknown params allowed!), you can
-define a naming scheme for attribute accessors, you can make a class a
-Singleton, and much, much more.
-
-Many of these extensions require surprisingly small amounts of code,
-and once you've done it once, you'll never have to hand-code "your way
-of doing things" again. Instead you'll just load your favorite
-extensions.
-
- package MyWay::User;
-
- use Moose;
- use MooseX::StrictConstructor
- use MooseX::MyWay;
-
- has ...;
-
-
=head1 JUSTIFICATION
If you're still still asking yourself "Why do I need this?", then this
=item Another object system!?!?
-Yes, I know there has been an explosion recently of new ways to
-build objects in Perl 5, most 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.
+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 L<Class::MOP>, which is a metaclass system
for Perl 5. This means that Moose not only makes building normal
Yes.
-Moose has been used successfully in production environments by several
+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 well over two years. We
-consider it highly stable and we are commited to keeping it stable.
+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, the
=item 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
+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 :)
=back
-=head1 WHAT NEXT?
-
-So you're sold on Moose. Time to learn how to really use it.
-
-We recommend that you start with the L<Moose::Cookbook>. If you work
-your way through all the recipes under the basics section, you should
-have a pretty good sense of how Moose works, and all of its basic OO
-features.
-
-After that, check out the Role recipes. If you're really curious, go
-on and read the Meta and Extending recipes, but those are mostly there
-for people who want to be Moose wizards and change how Moose works.
-
-If you want to see how Moose would translate directly old school Perl
-5 OO code, check out L<Moose::Unsweetened>.
+=head1 AUTHORS
-=head1 AUTHOR
+Dave Rolsky E<lt>autarch@urth.orgE<gt>
-Dave Rolsky E<lt>autarch@urth.orgE<gt> and Stevan Little
-E<lt>stevan@iinteractive.comE<gt>
+Stevan Little E<lt>stevan@iinteractive.comE<gt>
=head1 COPYRIGHT AND LICENSE
-Copyright 2008 by Infinity Interactive, Inc.
+Copyright 2008-2009 by Infinity Interactive, Inc.
L<http://www.iinteractive.com>
projects / gitmo/Moose.git / blobdiff