use strict; use warnings; package Moose; # git description: 2.2014-5-g83ef6774c our $ The I<is> option accepts either I<rw> (for read/write) or I<ro> (for read only). These will create either a read/write accessor or a read-only accessor respectively, using the same name as the C<$name> of the attribute. If you need more control over how your accessors are named, you can use the L<reader|Class::MOP::Attribute/reader>, L<writer|Class::MOP::Attribute/writer> and L<accessor|Class::MOP::Attribute/accessor> options inherited from L<Class::MOP::Attribute>, however if you use those, you won't need the I<is> option. =item I<isa =E<gt> $type_name> The I<isa> option uses Moose's type constraint facilities to set up runtime type checking for this attribute. Moose will perform the checks during class construction, and within any accessors. The C<$type_name> argument must be a string. The string may be either a class name or a type defined using Moose's type definition features. (Refer to L<Moose::Util::TypeConstraints> for information on how to define a new type, and how to retrieve type meta-data). =item I<coerce =E<gt> (1|0)> This will attempt to use coercion with the supplied type constraint to change the value passed into any accessors or constructors. You B<must> supply a type constraint, and that type constraint B<must> define a coercion. See L<Moose::Cookbook::Basics::HTTP_SubtypesAndCoercion> for an example. =item I<does =E<gt> $role_name> This will accept the name of a role which the value stored in this attribute is expected to have consumed. =item I<required =E<gt> (1|0)> This marks the attribute as being required. This means a value must be supplied during class construction, I<or> the attribute must be lazy and have either a default or a builder. Note that C<required> does not say anything about the attribute's value, which can be C<undef>. =item I<weak_ref =E<gt> (1|0)> This will tell the class to store the value of this attribute as a weakened reference. If an attribute is a weakened reference, it B<cannot> also be coerced. Note that when a weak ref expires, the attribute's value becomes undefined, and is still considered to be set for purposes of predicate, default, etc. =item I<lazy =E<gt> (1|0)> This will tell the class to not create this slot until absolutely necessary. If an attribute is marked as lazy it B<must> have a default or builder supplied. =item I<trigger =E<gt> $code> The I<trigger> option is a CODE reference which will be called after the value of the attribute is set. The CODE ref is passed the instance itself, the updated value, and the original value if the attribute was already set. You B<can> have a trigger on a read-only attribute. B<NOTE:> Triggers will only fire when you B<assign> to the attribute, either in the constructor, or using the writer. Default and built values will B<not> cause the trigger to be fired. =item I<handles =E<gt> ARRAY | HASH | REGEXP | ROLE | ROLETYPE | DUCKTYPE | CODE> The I<handles> option provides Moose classes with automated delegation features. This is a pretty complex and powerful option. It accepts many different option formats, each with its own benefits and drawbacks. B<NOTE:> The class being delegated to does not need to be a Moose based class, which is why this feature is especially useful when wrapping non-Moose classes. All I<handles> option formats share the following traits: You cannot override a locally defined method with a delegated method; an exception will be thrown if you try. That is to say, if you define C<foo> in your class, you cannot override it with a delegated C<foo>. This is almost never something you would want to do, and if it is, you should do it by hand and not use Moose. You cannot override any of the methods found in Moose::Object, or the C<BUILD> and I<need> to have a reader (or accessor) for the attribute in order to delegate to it. Moose will create a means of accessing the value for you, however this will be several times B<less> efficient then if you had given the attribute a reader (or accessor) to use. Below is the documentation for each option format: =over 4 =item C<ARRAY> This is the most common usage for I<handles>. You basically pass a list of method names to be delegated, and Moose will install a delegation method for each one. =item C<HASH> This is the second most common usage for I C<parent_node> and C<siblings> methods, which delegate to the C<node> and C<children> methods (respectively) of the Tree instance stored in the C<parent> slot.. =item C<REGEXP> The regexp option works very similar to the ARRAY option, except that it builds the list of methods for you. It starts by collecting all possible methods of the class being delegated to, then filters that list using the regexp supplied here. B<NOTE:> An I<isa> option is required when using the regexp option format. This is so that we can determine (at compile time) the method list from the class. Without an I<isa> this is just not possible. =item C<ROLE> or C<ROLETYPE> With the role option, you specify the name of a role or a L<role type|Moose::Meta::TypeConstraint::Role> whose "interface" then becomes the list of methods to handle. The "interface" can be defined as; the methods of the role and any required methods of the role. It should be noted that this does B<not> include any method modifiers or generated attribute methods (which is consistent with role composition). =item C<DUCKTYPE> With the duck type option, you pass a duck type object whose "interface" then becomes the list of methods to handle. The "interface" can be defined as the list of methods passed to C<duck_type> to create a duck type object. For more information on C<duck_type> please check L<Moose::Util::TypeConstraints>. =item C I<handles> is attached to. The second is the metaclass of the class being delegated to. It expects you to return a hash (not a HASH ref) of the methods you want mapped. =back =item I<traits =E<gt> [ @role_names ]> This tells Moose to take the list of C<@role_names> and apply them to the attribute meta-object. Custom attribute metaclass traits are useful for extending the capabilities of the I<has> keyword: they are the simplest way to extend the MOP, but they are still a fairly advanced topic and too much to cover here. See L<Metaclass and Trait Name Resolution> for details on how a trait name is resolved to a role name. Also see L<Moose::Cookbook::Meta::Labeled_AttributeTrait> for a metaclass trait example. =item I<builder> => Str The value of this key is the name of the method that will be called to obtain the value used to initialize the attribute. See the L<builder option docs in Class::MOP::Attribute|Class::MOP::Attribute/builder> and/or L<Moose::Cookbook::Basics::BinaryTree_BuilderAndLazyBuild> for more information. =item L<default option docs in Class::MOP::Attribute|Class::MOP::Attribute/default> for more information. =item I<clearer> => Str Creates a method allowing you to clear the value. See the L<clearer option docs in Class::MOP::Attribute|Class::MOP::Attribute/clearer> for more information. =item I<predicate> => Str Creates a method to perform a basic test to see if a value has been set in the attribute. See the L<predicate option docs in Class::MOP::Attribute|Class::MOP::Attribute/predicate> for more information. Note that the predicate will return true even for a C<weak_ref> attribute whose value has expired. =item I<documentation> => $string An arbitrary string that can be retrieved later by calling C<< $attr->documentation >>. =back =head2 has +$name =E<gt> %options This is variation on the normal attribute creator C B<My::Foo> is cloning the C<message> attribute from its parent class B<Foo>, retaining the C<is =E<gt> 'rw'> and C<isa =E<gt> 'Str'> characteristics, but changing the value in I<some> sanity into it. Most options work the same, but there are some exceptions: =over 4 =item I<reader> =item I<writer> =item I<accessor> =item I<clearer> =item I<predicate> These options can be added, but cannot override a superclass definition. =item I<traits> You are allowed to B<add> additional traits to the C<traits> definition. These traits will be composed into the attribute, but preexisting traits B<are not> overridden, or removed. =back =head2 before $name|@names|\@names|qr/.../ =E<gt> sub { ... } =head2 after $name|@names|\@names|qr/.../ =E<gt> sub { ... } =head2 around $name|@names|\@names|qr/.../ =E<gt> sub { ... } These three items are syntactic sugar for the before, after, and around method modifier features that L<Class::MOP> provides. More information on these may be found in L<Moose::Manual::MethodModifiers> and the L<Class::MOP::Class documentation|Class::MOP::Class/"Method Modifiers">. =head2 override ($name, &sub) An C<override> method is a way of explicitly saying "I am overriding this method from my superclass". You can call C<super> within this method, and it will work as expected. The same thing I<can> be accomplished with a normal method call and the C<SUPER::> pseudo-package; it is really your choice. =head2 super The keyword C<super> is a no-op when called outside of an C<override> method. In the context of an C<override> method, it will call the next most appropriate superclass method with the same arguments as the original method. =head2 augment ($name, &sub) An C<augment> method, is a way of explicitly saying "I am augmenting this method from my superclass". Once again, the details of how C<inner> and C<augment> work is best described in the L<Moose::Cookbook::Basics::Document_AugmentAndInner>. =head2 inner The keyword C<inner>, much like C<super>, is a no-op outside of the context of an C<augment> method. You can think of C<inner> as being the inverse of C<super>; the details of how C<inner> and C<augment> work is best described in the L<Moose::Cookbook::Basics::Document_AugmentAndInner>. =head2 blessed This is the C<Scalar::Util::blessed> function. It is highly recommended that this is used instead of C<ref> anywhere you need to test for an object's class name. =head2 confess This is the C<Carp::confess> function, and exported here for historical reasons. =head1 METACLASS When you use Moose, you can specify traits which will be applied to your metaclass: use Moose -traits => 'My::Trait'; This is very similar to the attribute traits feature. When you do this, your class's C<meta> object will have the specified traits applied to it. =head2 Metaclass and Trait Name Resolution By default, when given a trait name, Moose simply tries to load a class of the same name. If such a class does not exist, it then looks for a class matching B<Moose::Meta::$type::Custom::Trait::$trait_name>. The C<$type> variable here will be one of B<Attribute> or B<Class>, depending on what the trait is being applied to. If a class with this long name exists, Moose checks to see if it has the method C<register_implementation>. This method is expected to return the I<real> class name of the trait. If there is no C<register_implementation> method, it will fall back to using B<Moose::Meta::$type::Custom::Trait::$trait> as the trait name. The lookup method for metaclasses is the same, except that it looks for a class matching B<Moose::Meta::$type::Custom::$metaclass_name>. If all this is confusing, take a look at L<Moose::Cookbook::Meta::Labeled_AttributeTrait>, which demonstrates how to create an attribute trait. =head1 UNIMPORTING FUNCTIONS =head2 B<unimport> Moose offers a way to remove the keywords it exports, through the C<unimport> method. You simply have to say C =head1 EXTENDING AND EMBEDDING MOOSE To learn more about extending Moose, we recommend checking out the "Extending" recipes in the L<Moose::Cookbook>, starting with L<Moose::Cookbook::Extending::ExtensionOverview>, which provides an overview of all the different ways you might extend Moose. L<Moose::Exporter> and L<Moose::Util::MetaRole> are the modules which provide the majority of the extension functionality, so reading their documentation should also be helpful. =head2 The MooseX:: namespace Generally if you're writing an extension I<for> Moose itself you'll want to put your extension in the C<MooseX::> namespace. This namespace is specifically for extensions that make Moose better or different in some fundamental way. It is traditionally B<not> for a package that just happens to use Moose. This namespace follows from the examples of the C<LWPx::> and C<DBIx::> namespaces that perform the same function for C<LWP> and C<DBI> respectively. =head1 METACLASS COMPATIBILITY AND MOOSE Metaclass compatibility is a thorny subject. You should start by reading the "About Metaclass compatibility" section in the L<Class::MOP> docs. Moose will attempt to resolve a few cases of metaclass incompatibility when you set the superclasses for a class, in addition to the cases that C. =head1 CAVEATS It should be noted that C<super> and C<inner> B<cannot> be used in the same method. However, they may be combined within the same class hierarchy; see F<t/basics/override_augment_inner_super.t> for an example. The reason for this is that C<super> is only valid within a method with the C<override> modifier, and C<inner> will never be valid within an C<override> method. In fact, C<augment> will skip over any C<override> methods when searching for its appropriate C). =head1 GETTING HELP We offer both a mailing list and a very active IRC channel. The mailing list is L<mailto:moose@perl.org>. You must be subscribed to send a message. To subscribe, send an empty message to L<mailto:moose-subscribe@perl.org> You can also visit us at C<#moose> on L<irc://irc.perl.org/#moose> This channel is quite active, and questions at all levels (on Moose-related topics ;) are welcome. =head1 WHAT DOES MOOSE STAND FOR? Moose doesn't stand for one thing in particular, however, if you want, here are a few of our favorites. Feel free to contribute more! =over 4 =item * Make Other Object Systems Envious =item * Makes Object Orientation So Easy =item * Makes Object Orientation Spiffy- Er (sorry ingy) =item * Most Other Object Systems Emasculate =item * Moose Often Ovulate Sorta Early =item * Moose Offers Often Super Extensions =item * Meta Object Obligates Salivary Excitation =item * Meta Object Orientation Syntax Extensions =item * Moo, Only Overengineered, Slow, and Execrable (blame rjbs!) =item * Massive Object-Oriented Stacktrace Emitter =back =head1 ACKNOWLEDGEMENTS =over 4 =item I blame Sam Vilain for introducing me to the insanity that is meta-models. =item I blame Audrey Tang for then encouraging my meta-model habit in #perl6. =item Without Yuval "nothingmuch" Kogman this module would not be possible, and it certainly wouldn't have this name ;P =item The basis of the TypeContraints module was Rob Kinyon's idea originally, I just ran with it. =item Thanks to mst & chansen and the whole #moose posse for all the early ideas/feature-requests/encouragement/bug-finding. =item Thanks to David "Theory" Wheeler for meta-discussions and spelling fixes. =back =head1 SEE ALSO =over 4 =item L<> This is the official web home of Moose. It contains links to our public git repository, as well as links to a number of talks and articles on Moose and Moose related technologies. =item the L<Moose manual|Moose::Manual> This is an introduction to Moose which covers most of the basics. =item Modern Perl, by chromatic This is an introduction to modern Perl programming, which includes a section on Moose. It is available in print and as a free download from L<>. =item The Moose is flying, a tutorial by Randal Schwartz Part 1 - L<> Part 2 - L<> =item Several Moose extension modules in the C<MooseX::> namespace. See L<::> for extensions. =back =head2 Books =over 4 =item The Art of the MetaObject Protocol I mention this in the L<Class::MOP> docs too, as this book was critical in the development of both modules and is highly recommended. =back =head2 Papers =over 4 =item L<> This paper (suggested by lbr on #moose) was what lead to the implementation of the C<super>/C<override> and C<inner>/C<augment> features. If you really want to understand them, I suggest you read this. =back =head1 BUGS All complex software has bugs lurking in it, and this module is no exception. Please report any bugs to C<bug-moose@rt.cpan.org>, or through the web interface at L<>. You can also submit a C<TODO> test as a pull request at L<>. You can also discuss feature requests or possible bugs on the Moose mailing list (moose@perl.org) or on IRC at L<irc://irc.perl.org/#moose>. =head1 L<irc://irc.perl.org/#moose> to discuss. The L<Moose::Manual::Contributing> has more detail about how and when you can contribute. =head1. See the list below under L</AUTHORS>. =head1 CONTRIBUTORS Moose is a community project, and as such, involves the work of many, many members of the community beyond just the members in the cabal. In particular: Dave (autarch) Rolsky wrote most of the documentation in L<Moose::Manual>. John (jgoulah) Goulah wrote L<Moose::Cookbook::Snack::Keywords>. Jess (castaway) Robinson wrote L<Moose::Cookbook::Snack::Types>. Aran (bluefeet) Clary Deltac wrote L<Moose::Cookbook::Basics::Genome_OverloadingSubtypesAndCoercion>. Anders (Debolaz) Nor Berle contributed L<Test::Moose> and L<Moose::Util>. Also, the code in L<Moose::Meta::Attribute::Native> is based on code from the 