8 $VERSION = eval $VERSION;
9 our $AUTHORITY = 'cpan:STEVAN';
11 use Scalar::Util 'blessed';
14 use Moose::Deprecated;
19 use Moose::Meta::Class;
20 use Moose::Meta::TypeConstraint;
21 use Moose::Meta::TypeCoercion;
22 use Moose::Meta::Attribute;
23 use Moose::Meta::Instance;
27 use Moose::Meta::Role;
28 use Moose::Meta::Role::Composite;
29 use Moose::Meta::Role::Application;
30 use Moose::Meta::Role::Application::RoleSummation;
31 use Moose::Meta::Role::Application::ToClass;
32 use Moose::Meta::Role::Application::ToRole;
33 use Moose::Meta::Role::Application::ToInstance;
35 use Moose::Util::TypeConstraints;
38 use Moose::Meta::Attribute::Native;
49 Moose->throw_error("Must derive at least one class") unless @_;
51 # this checks the metaclass to make sure
52 # it is correct, sometimes it can get out
53 # of sync when the classes are being built
54 $meta->superclasses(@_);
58 Moose::Util::apply_all_roles(shift, @_);
65 Moose->throw_error('Usage: has \'name\' => ( key => value, ... )')
68 my %options = ( definition_context => Moose::Util::_caller_info(), @_ );
69 my $attrs = ( ref($name) eq 'ARRAY' ) ? $name : [ ($name) ];
70 $meta->add_attribute( $_, %options ) for @$attrs;
74 Moose::Util::add_method_modifier(shift, 'before', \@_);
78 Moose::Util::add_method_modifier(shift, 'after', \@_);
82 Moose::Util::add_method_modifier(shift, 'around', \@_);
90 # This check avoids a recursion loop - see
91 # t/100_bugs/020_super_recursion.t
92 return if defined $SUPER_PACKAGE && $SUPER_PACKAGE ne caller();
93 return unless $SUPER_BODY; $SUPER_BODY->(@SUPER_ARGS);
98 my ( $name, $method ) = @_;
99 $meta->add_override_method_modifier( $name => $method );
104 our ( %INNER_BODY, %INNER_ARGS );
106 if ( my $body = $INNER_BODY{$pkg} ) {
107 my @args = @{ $INNER_ARGS{$pkg} };
108 local $INNER_ARGS{$pkg};
109 local $INNER_BODY{$pkg};
110 return $body->(@args);
118 my ( $name, $method ) = @_;
119 $meta->add_augment_method_modifier( $name => $method );
122 Moose::Exporter->setup_import_methods(
124 qw( extends with has before after around override augment )
129 \&Scalar::Util::blessed,
134 # This used to be called as a function. This hack preserves
135 # backwards compatibility.
136 if ( $_[0] ne __PACKAGE__ ) {
137 Moose::Deprecated::deprecated(
138 feature => 'Moose::init_meta',
139 message => 'Calling Moose::init_meta as a function is deprecated',
142 return __PACKAGE__->init_meta(
152 my $class = $args{for_class}
153 or Moose->throw_error("Cannot call init_meta without specifying a for_class");
154 my $base_class = $args{base_class} || 'Moose::Object';
155 my $metaclass = $args{metaclass} || 'Moose::Meta::Class';
156 my $meta_name = exists $args{meta_name} ? $args{meta_name} : 'meta';
158 Moose->throw_error("The Metaclass $metaclass must be a subclass of Moose::Meta::Class.")
159 unless $metaclass->isa('Moose::Meta::Class');
161 # make a subtype for each Moose class
163 unless find_type_constraint($class);
167 if ( $meta = Class::MOP::get_metaclass_by_name($class) ) {
168 unless ( $meta->isa("Moose::Meta::Class") ) {
169 my $error_message = "$class already has a metaclass, but it does not inherit $metaclass ($meta).";
170 if ( $meta->isa('Moose::Meta::Role') ) {
171 Moose->throw_error($error_message . ' You cannot make the same thing a role and a class. Remove either Moose or Moose::Role.');
173 Moose->throw_error($error_message);
179 # now we check whether our ancestors have metaclass, and if so borrow that
180 my ( undef, @isa ) = @{ mro::get_linear_isa($class) };
182 foreach my $ancestor ( @isa ) {
183 my $ancestor_meta = Class::MOP::get_metaclass_by_name($ancestor) || next;
185 my $ancestor_meta_class = $ancestor_meta->_real_ref_name;
187 # if we have an ancestor metaclass that inherits $metaclass, we use
188 # that. This is like _fix_metaclass_incompatibility, but we can do it now.
190 # the case of having an ancestry is not very common, but arises in
192 unless ( $metaclass->isa( $ancestor_meta_class ) ) {
193 if ( $ancestor_meta_class->isa($metaclass) ) {
194 $metaclass = $ancestor_meta_class;
199 $meta = $metaclass->initialize($class);
202 if (defined $meta_name) {
203 # also check for inherited non moose 'meta' method?
204 my $existing = $meta->get_method($meta_name);
205 if ($existing && !$existing->isa('Class::MOP::Method::Meta')) {
206 Carp::cluck "Moose is overwriting an existing method named "
207 . "$meta_name in class $class with a method "
208 . "which returns the class's metaclass. If this is "
209 . "actually what you want, you should remove the "
210 . "existing method, otherwise, you should rename or "
211 . "disable this generated method using the "
212 . "'-meta_name' option to 'use Moose'.";
214 $meta->_add_meta_method($meta_name);
217 # make sure they inherit from Moose::Object
218 $meta->superclasses($base_class)
219 unless $meta->superclasses();
224 # This may be used in some older MooseX extensions.
226 goto &Moose::Exporter::_get_caller;
229 ## make 'em all immutable
232 inline_constructor => 1,
233 constructor_name => "_new",
234 # these are Class::MOP accessors, so they need inlining
235 inline_accessors => 1
236 ) for grep { $_->is_mutable }
239 Moose::Meta::Attribute
241 Moose::Meta::Instance
243 Moose::Meta::TypeCoercion
244 Moose::Meta::TypeCoercion::Union
247 Moose::Meta::Method::Accessor
248 Moose::Meta::Method::Constructor
249 Moose::Meta::Method::Destructor
250 Moose::Meta::Method::Overridden
251 Moose::Meta::Method::Augmented
254 Moose::Meta::Role::Attribute
255 Moose::Meta::Role::Method
256 Moose::Meta::Role::Method::Required
257 Moose::Meta::Role::Method::Conflicting
259 Moose::Meta::Role::Composite
261 Moose::Meta::Role::Application
262 Moose::Meta::Role::Application::RoleSummation
263 Moose::Meta::Role::Application::ToClass
264 Moose::Meta::Role::Application::ToRole
265 Moose::Meta::Role::Application::ToInstance
268 Moose::Meta::Mixin::AttributeCore->meta->make_immutable(
269 inline_constructor => 0,
270 constructor_name => undef,
281 Moose - A postmodern object system for Perl 5
286 use Moose; # automatically turns on strict and warnings
288 has 'x' => (is => 'rw', isa => 'Int');
289 has 'y' => (is => 'rw', isa => 'Int');
302 has 'z' => (is => 'rw', isa => 'Int');
304 after 'clear' => sub {
311 Moose is an extension of the Perl 5 object system.
313 The main goal of Moose is to make Perl 5 Object Oriented programming
314 easier, more consistent and less tedious. With Moose you can to think
315 more about what you want to do and less about the mechanics of OOP.
317 Additionally, Moose is built on top of L<Class::MOP>, which is a
318 metaclass system for Perl 5. This means that Moose not only makes
319 building normal Perl 5 objects better, but it provides the power of
320 metaclass programming as well.
324 If you're new to Moose, the best place to start is the
325 L<Moose::Manual> docs, followed by the L<Moose::Cookbook>. The intro
326 will show you what Moose is, and how it makes Perl 5 OO better.
328 The cookbook recipes on Moose basics will get you up to speed with
329 many of Moose's features quickly. Once you have an idea of what Moose
330 can do, you can use the API documentation to get more detail on
331 features which interest you.
333 =head2 Moose Extensions
335 The C<MooseX::> namespace is the official place to find Moose extensions.
336 These extensions can be found on the CPAN. The easiest way to find them
337 is to search for them (L<http://search.cpan.org/search?query=MooseX::>),
338 or to examine L<Task::Moose> which aims to keep an up-to-date, easily
339 installable list of Moose extensions.
343 Much of the Moose documentation has been translated into other languages.
349 Japanese docs can be found at
350 L<http://perldoc.perlassociation.org/pod/Moose-Doc-JA/index.html>. The
351 source POD files can be found in GitHub:
352 L<http://github.com/jpa/Moose-Doc-JA>
356 =head1 BUILDING CLASSES WITH MOOSE
358 Moose makes every attempt to provide as much convenience as possible during
359 class construction/definition, but still stay out of your way if you want it
360 to. Here are a few items to note when building classes with Moose.
362 When you C<use Moose>, Moose will set the class's parent class to
363 L<Moose::Object>, I<unless> the class using Moose already has a parent
364 class. In addition, specifying a parent with C<extends> will change the parent
367 Moose will also manage all attributes (including inherited ones) that are
368 defined with C<has>. And (assuming you call C<new>, which is inherited from
369 L<Moose::Object>) this includes properly initializing all instance slots,
370 setting defaults where appropriate, and performing any type constraint checking
373 =head1 PROVIDED METHODS
375 Moose provides a number of methods to all your classes, mostly through the
376 inheritance of L<Moose::Object>. There is however, one exception.
382 This is a method which provides access to the current class's metaclass.
386 =head1 EXPORTED FUNCTIONS
388 Moose will export a number of functions into the class's namespace which
389 may then be used to set up the class. These functions all work directly
390 on the current class.
394 =item B<extends (@superclasses)>
396 This function will set the superclass(es) for the current class.
398 This approach is recommended instead of C<use base>, because C<use base>
399 actually C<push>es onto the class's C<@ISA>, whereas C<extends> will
400 replace it. This is important to ensure that classes which do not have
401 superclasses still properly inherit from L<Moose::Object>.
403 Each superclass can be followed by a hash reference with options. Currently,
404 only L<-version|Class::MOP/Class Loading Options> is recognized:
406 extends 'My::Parent' => { -version => 0.01 },
407 'My::OtherParent' => { -version => 0.03 };
409 An exception will be thrown if the version requirements are not
412 =item B<with (@roles)>
414 This will apply a given set of C<@roles> to the local class.
416 Like with C<extends>, each specified role can be followed by a hash
417 reference with a L<-version|Class::MOP/Class Loading Options> option:
419 with 'My::Role' => { -version => 0.32 },
420 'My::Otherrole' => { -version => 0.23 };
422 The specified version requirements must be satisfied, otherwise an
423 exception will be thrown.
425 If your role takes options or arguments, they can be passed along in the
426 hash reference as well.
428 =item B<has $name|@$names =E<gt> %options>
430 This will install an attribute of a given C<$name> into the current class. If
431 the first parameter is an array reference, it will create an attribute for
432 every C<$name> in the list. The C<%options> are the same as those provided by
433 L<Class::MOP::Attribute>, in addition to the list below which are provided by
434 Moose (L<Moose::Meta::Attribute> to be more specific):
438 =item I<is =E<gt> 'rw'|'ro'>
440 The I<is> option accepts either I<rw> (for read/write) or I<ro> (for read
441 only). These will create either a read/write accessor or a read-only
442 accessor respectively, using the same name as the C<$name> of the attribute.
444 If you need more control over how your accessors are named, you can
445 use the L<reader|Class::MOP::Attribute/reader>,
446 L<writer|Class::MOP::Attribute/writer> and
447 L<accessor|Class::MOP::Attribute/accessor> options inherited from
448 L<Class::MOP::Attribute>, however if you use those, you won't need the
451 =item I<isa =E<gt> $type_name>
453 The I<isa> option uses Moose's type constraint facilities to set up runtime
454 type checking for this attribute. Moose will perform the checks during class
455 construction, and within any accessors. The C<$type_name> argument must be a
456 string. The string may be either a class name or a type defined using
457 Moose's type definition features. (Refer to L<Moose::Util::TypeConstraints>
458 for information on how to define a new type, and how to retrieve type meta-data).
460 =item I<coerce =E<gt> (1|0)>
462 This will attempt to use coercion with the supplied type constraint to change
463 the value passed into any accessors or constructors. You B<must> supply a type
464 constraint, and that type constraint B<must> define a coercion. See
465 L<Moose::Cookbook::Basics::Recipe5> for an example.
467 =item I<does =E<gt> $role_name>
469 This will accept the name of a role which the value stored in this attribute
470 is expected to have consumed.
472 =item I<required =E<gt> (1|0)>
474 This marks the attribute as being required. This means a value must be
475 supplied during class construction, I<or> the attribute must be lazy
476 and have either a default or a builder. Note that c<required> does not
477 say anything about the attribute's value, which can be C<undef>.
479 =item I<weak_ref =E<gt> (1|0)>
481 This will tell the class to store the value of this attribute as a weakened
482 reference. If an attribute is a weakened reference, it B<cannot> also be
485 =item I<lazy =E<gt> (1|0)>
487 This will tell the class to not create this slot until absolutely necessary.
488 If an attribute is marked as lazy it B<must> have a default supplied.
490 =item I<auto_deref =E<gt> (1|0)>
492 This tells the accessor to automatically dereference the value of this
493 attribute when called in list context. The accessor will still return a
494 reference when called in scalar context. If this behavior isn't desirable,
495 L<Moose::Meta::Attribute::Native::Trait::Array/elements> or
496 L<Moose::Meta::Attribute::Native::Trait::Hash/elements> may be a better
497 choice. The I<auto_deref> option is only legal if your I<isa> option is
498 either C<ArrayRef> or C<HashRef>.
500 =item I<trigger =E<gt> $code>
502 The I<trigger> option is a CODE reference which will be called after
503 the value of the attribute is set. The CODE ref is passed the
504 instance itself, the updated value, and the original value if the
505 attribute was already set.
507 You B<can> have a trigger on a read-only attribute.
509 B<NOTE:> Triggers will only fire when you B<assign> to the attribute,
510 either in the constructor, or using the writer. Default and built values will
511 B<not> cause the trigger to be fired.
513 =item I<handles =E<gt> ARRAY | HASH | REGEXP | ROLE | ROLETYPE | DUCKTYPE | CODE>
515 The I<handles> option provides Moose classes with automated delegation features.
516 This is a pretty complex and powerful option. It accepts many different option
517 formats, each with its own benefits and drawbacks.
519 B<NOTE:> The class being delegated to does not need to be a Moose based class,
520 which is why this feature is especially useful when wrapping non-Moose classes.
522 All I<handles> option formats share the following traits:
524 You cannot override a locally defined method with a delegated method; an
525 exception will be thrown if you try. That is to say, if you define C<foo> in
526 your class, you cannot override it with a delegated C<foo>. This is almost never
527 something you would want to do, and if it is, you should do it by hand and not
530 You cannot override any of the methods found in Moose::Object, or the C<BUILD>
531 and C<DEMOLISH> methods. These will not throw an exception, but will silently
532 move on to the next method in the list. My reasoning for this is that you would
533 almost never want to do this, since it usually breaks your class. As with
534 overriding locally defined methods, if you do want to do this, you should do it
535 manually, not with Moose.
537 You do not I<need> to have a reader (or accessor) for the attribute in order
538 to delegate to it. Moose will create a means of accessing the value for you,
539 however this will be several times B<less> efficient then if you had given
540 the attribute a reader (or accessor) to use.
542 Below is the documentation for each option format:
548 This is the most common usage for I<handles>. You basically pass a list of
549 method names to be delegated, and Moose will install a delegation method
554 This is the second most common usage for I<handles>. Instead of a list of
555 method names, you pass a HASH ref where each key is the method name you
556 want installed locally, and its value is the name of the original method
557 in the class being delegated to.
559 This can be very useful for recursive classes like trees. Here is a
560 quick example (soon to be expanded into a Moose::Cookbook recipe):
565 has 'node' => (is => 'rw', isa => 'Any');
570 default => sub { [] }
578 parent_node => 'node',
579 siblings => 'children',
583 In this example, the Tree package gets C<parent_node> and C<siblings> methods,
584 which delegate to the C<node> and C<children> methods (respectively) of the Tree
585 instance stored in the C<parent> slot.
587 You may also use an array reference to curry arguments to the original method.
591 handles => { set_foo => [ set => 'foo' ] },
594 # $self->set_foo(...) calls $self->thing->set('foo', ...)
596 The first element of the array reference is the original method name, and the
597 rest is a list of curried arguments.
601 The regexp option works very similar to the ARRAY option, except that it builds
602 the list of methods for you. It starts by collecting all possible methods of the
603 class being delegated to, then filters that list using the regexp supplied here.
605 B<NOTE:> An I<isa> option is required when using the regexp option format. This
606 is so that we can determine (at compile time) the method list from the class.
607 Without an I<isa> this is just not possible.
609 =item C<ROLE> or C<ROLETYPE>
611 With the role option, you specify the name of a role or a
612 L<role type|Moose::Meta::TypeConstraint::Role> whose "interface" then becomes
613 the list of methods to handle. The "interface" can be defined as; the methods
614 of the role and any required methods of the role. It should be noted that this
615 does B<not> include any method modifiers or generated attribute methods (which
616 is consistent with role composition).
620 With the duck type option, you pass a duck type object whose "interface" then
621 becomes the list of methods to handle. The "interface" can be defined as; the
622 list of methods passed to C<duck_type> to create a duck type object. For more
623 information on C<duck_type> please check
624 L<Moose::Util::TypeConstraints>.
628 This is the option to use when you really want to do something funky. You should
629 only use it if you really know what you are doing, as it involves manual
632 This takes a code reference, which should expect two arguments. The first is the
633 attribute meta-object this I<handles> is attached to. The second is the
634 metaclass of the class being delegated to. It expects you to return a hash (not
635 a HASH ref) of the methods you want mapped.
639 =item I<metaclass =E<gt> $metaclass_name>
641 This tells the class to use a custom attribute metaclass for this particular
642 attribute. Custom attribute metaclasses are useful for extending the
643 capabilities of the I<has> keyword: they are the simplest way to extend the MOP,
644 but they are still a fairly advanced topic and too much to cover here, see
645 L<Moose::Cookbook::Meta::Recipe1> for more information.
647 See L<Metaclass and Trait Name Resolution> for details on how a metaclass name
648 is resolved to a class name.
650 =item I<traits =E<gt> [ @role_names ]>
652 This tells Moose to take the list of C<@role_names> and apply them to the
653 attribute meta-object. This is very similar to the I<metaclass> option, but
654 allows you to use more than one extension at a time.
656 See L<Metaclass and Trait Name Resolution> for details on how a trait name is
657 resolved to a role name.
659 Also see L<Moose::Cookbook::Meta::Recipe3> for a metaclass trait
662 =item I<builder> => Str
664 The value of this key is the name of the method that will be called to
665 obtain the value used to initialize the attribute. See the L<builder
666 option docs in Class::MOP::Attribute|Class::MOP::Attribute/builder>
667 and/or L<Moose::Cookbook::Basics::Recipe8> for more information.
669 =item I<default> => SCALAR | CODE
671 The value of this key is the default value which will initialize the attribute.
673 NOTE: If the value is a simple scalar (string or number), then it can
674 be just passed as is. However, if you wish to initialize it with a
675 HASH or ARRAY ref, then you need to wrap that inside a CODE reference.
676 See the L<default option docs in
677 Class::MOP::Attribute|Class::MOP::Attribute/default> for more
680 =item I<clearer> => Str
682 Creates a method allowing you to clear the value, see the L<clearer option
683 docs in Class::MOP::Attribute|Class::MOP::Attribute/clearer> for more
686 =item I<predicate> => Str
688 Creates a method to perform a basic test to see if a value has been set in the
689 attribute, see the L<predicate option docs in
690 Class::MOP::Attribute|Class::MOP::Attribute/predicate> for more information.
692 =item I<lazy_build> => (0|1)
694 Automatically define lazy => 1 as well as builder => "_build_$attr", clearer =>
695 "clear_$attr', predicate => 'has_$attr' unless they are already defined.
697 =item I<initializer> => Str
699 This may be a method name (referring to a method on the class with
700 this attribute) or a CODE ref. The initializer is used to set the
701 attribute value on an instance when the attribute is set during
702 instance initialization (but not when the value is being assigned
703 to). See the L<initializer option docs in
704 Class::MOP::Attribute|Class::MOP::Attribute/initializer> for more
707 =item I<documentation> => $string
709 An arbitrary string that can be retrieved later by calling C<<
710 $attr->documentation >>.
716 =item B<has +$name =E<gt> %options>
718 This is variation on the normal attribute creator C<has> which allows you to
719 clone and extend an attribute from a superclass or from a role. Here is an
720 example of the superclass usage:
728 default => 'Hello, I am a Foo'
736 has '+message' => (default => 'Hello I am My::Foo');
738 What is happening here is that B<My::Foo> is cloning the C<message> attribute
739 from its parent class B<Foo>, retaining the C<is =E<gt> 'rw'> and C<isa =E<gt>
740 'Str'> characteristics, but changing the value in C<default>.
742 Here is another example, but within the context of a role:
750 default => 'Hello, I am a Foo'
758 has '+message' => (default => 'Hello I am My::Foo');
760 In this case, we are basically taking the attribute which the role supplied
761 and altering it within the bounds of this feature.
763 Note that you can only extend an attribute from either a superclass or a role,
764 you cannot extend an attribute in a role that composes over an attribute from
767 Aside from where the attributes come from (one from superclass, the other
768 from a role), this feature works exactly the same. This feature is restricted
769 somewhat, so as to try and force at least I<some> sanity into it. You are only
770 allowed to change the following attributes:
776 Change the default value of an attribute.
780 Change whether the attribute attempts to coerce a value passed to it.
784 Change if the attribute is required to have a value.
786 =item I<documentation>
788 Change the documentation string associated with the attribute.
792 Change if the attribute lazily initializes the slot.
796 You I<are> allowed to change the type without restriction.
798 It is recommended that you use this freedom with caution. We used to
799 only allow for extension only if the type was a subtype of the parent's
800 type, but we felt that was too restrictive and is better left as a
805 You are allowed to B<add> a new C<handles> definition, but you are B<not>
806 allowed to I<change> one.
810 You are allowed to B<add> a new C<builder> definition, but you are B<not>
811 allowed to I<change> one.
815 You are allowed to B<add> a new C<metaclass> definition, but you are
816 B<not> allowed to I<change> one.
820 You are allowed to B<add> additional traits to the C<traits> definition.
821 These traits will be composed into the attribute, but preexisting traits
822 B<are not> overridden, or removed.
826 =item B<before $name|@names|\@names|qr/.../ =E<gt> sub { ... }>
828 =item B<after $name|@names|\@names|qr/.../ =E<gt> sub { ... }>
830 =item B<around $name|@names|\@names|qr/.../ =E<gt> sub { ... }>
832 These three items are syntactic sugar for the before, after, and around method
833 modifier features that L<Class::MOP> provides. More information on these may be
834 found in L<Moose::Manual::MethodModifiers> and the
835 L<Class::MOP::Class documentation|Class::MOP::Class/"Method Modifiers">.
839 The keyword C<super> is a no-op when called outside of an C<override> method. In
840 the context of an C<override> method, it will call the next most appropriate
841 superclass method with the same arguments as the original method.
843 =item B<override ($name, &sub)>
845 An C<override> method is a way of explicitly saying "I am overriding this
846 method from my superclass". You can call C<super> within this method, and
847 it will work as expected. The same thing I<can> be accomplished with a normal
848 method call and the C<SUPER::> pseudo-package; it is really your choice.
852 The keyword C<inner>, much like C<super>, is a no-op outside of the context of
853 an C<augment> method. You can think of C<inner> as being the inverse of
854 C<super>; the details of how C<inner> and C<augment> work is best described in
855 the L<Moose::Cookbook::Basics::Recipe6>.
857 =item B<augment ($name, &sub)>
859 An C<augment> method, is a way of explicitly saying "I am augmenting this
860 method from my superclass". Once again, the details of how C<inner> and
861 C<augment> work is best described in the L<Moose::Cookbook::Basics::Recipe6>.
865 This is the C<Carp::confess> function, and exported here because I use it
870 This is the C<Scalar::Util::blessed> function, it is exported here because I
871 use it all the time. It is highly recommended that this is used instead of
872 C<ref> anywhere you need to test for an object's class name.
878 When you use Moose, you can specify which metaclass to use:
880 use Moose -metaclass => 'My::Meta::Class';
882 You can also specify traits which will be applied to your metaclass:
884 use Moose -traits => 'My::Trait';
886 This is very similar to the attribute traits feature. When you do
887 this, your class's C<meta> object will have the specified traits
888 applied to it. See L<Metaclass and Trait Name Resolution> for more
891 =head2 Metaclass and Trait Name Resolution
893 By default, when given a trait name, Moose simply tries to load a
894 class of the same name. If such a class does not exist, it then looks
895 for for a class matching
896 B<Moose::Meta::$type::Custom::Trait::$trait_name>. The C<$type>
897 variable here will be one of B<Attribute> or B<Class>, depending on
898 what the trait is being applied to.
900 If a class with this long name exists, Moose checks to see if it has
901 the method C<register_implementation>. This method is expected to
902 return the I<real> class name of the trait. If there is no
903 C<register_implementation> method, it will fall back to using
904 B<Moose::Meta::$type::Custom::Trait::$trait> as the trait name.
906 The lookup method for metaclasses is the same, except that it looks
907 for a class matching B<Moose::Meta::$type::Custom::$metaclass_name>.
909 If all this is confusing, take a look at
910 L<Moose::Cookbook::Meta::Recipe3>, which demonstrates how to create an
913 =head1 UNIMPORTING FUNCTIONS
917 Moose offers a way to remove the keywords it exports, through the C<unimport>
918 method. You simply have to say C<no Moose> at the bottom of your code for this
919 to work. Here is an example:
924 has 'first_name' => (is => 'rw', isa => 'Str');
925 has 'last_name' => (is => 'rw', isa => 'Str');
929 $self->first_name . ' ' . $self->last_name
932 no Moose; # keywords are removed from the Person package
934 =head1 EXTENDING AND EMBEDDING MOOSE
936 To learn more about extending Moose, we recommend checking out the
937 "Extending" recipes in the L<Moose::Cookbook>, starting with
938 L<Moose::Cookbook::Extending::Recipe1>, which provides an overview of
939 all the different ways you might extend Moose.
941 =head2 B<< Moose->init_meta(for_class => $class, base_class => $baseclass, metaclass => $metaclass) >>
943 The C<init_meta> method sets up the metaclass object for the class
944 specified by C<for_class>. This method injects a a C<meta> accessor
945 into the class so you can get at this object. It also sets the class's
946 superclass to C<base_class>, with L<Moose::Object> as the default.
948 C<init_meta> returns the metaclass object for C<$class>.
950 You can specify an alternate metaclass with the C<metaclass> option.
952 For more detail on this topic, see L<Moose::Cookbook::Extending::Recipe2>.
954 This method used to be documented as a function which accepted
955 positional parameters. This calling style will still work for
956 backwards compatibility, but is deprecated.
960 Moose's C<import> method supports the L<Sub::Exporter> form of C<{into =E<gt> $pkg}>
961 and C<{into_level =E<gt> 1}>.
963 B<NOTE>: Doing this is more or less deprecated. Use L<Moose::Exporter>
964 instead, which lets you stack multiple C<Moose.pm>-alike modules
965 sanely. It handles getting the exported functions into the right place
968 =head2 B<throw_error>
970 An alias for C<confess>, used by internally by Moose.
972 =head2 The MooseX:: namespace
974 Generally if you're writing an extension I<for> Moose itself you'll want
975 to put your extension in the C<MooseX::> namespace. This namespace is
976 specifically for extensions that make Moose better or different in some
977 fundamental way. It is traditionally B<not> for a package that just happens
978 to use Moose. This namespace follows from the examples of the C<LWPx::>
979 and C<DBIx::> namespaces that perform the same function for C<LWP> and C<DBI>
982 =head1 METACLASS COMPATIBILITY AND MOOSE
984 Metaclass compatibility is a thorny subject. You should start by
985 reading the "About Metaclass compatibility" section in the
988 Moose will attempt to resolve a few cases of metaclass incompatibility
989 when you set the superclasses for a class, in addition to the cases that
990 C<Class::MOP> handles.
992 Moose tries to determine if the metaclasses only "differ by roles". This
993 means that the parent and child's metaclass share a common ancestor in
994 their respective hierarchies, and that the subclasses under the common
995 ancestor are only different because of role applications. This case is
996 actually fairly common when you mix and match various C<MooseX::*>
997 modules, many of which apply roles to the metaclass.
999 If the parent and child do differ by roles, Moose replaces the
1000 metaclass in the child with a newly created metaclass. This metaclass
1001 is a subclass of the parent's metaclass, does all of the roles that
1002 the child's metaclass did before being replaced. Effectively, this
1003 means the new metaclass does all of the roles done by both the
1004 parent's and child's original metaclasses.
1006 Ultimately, this is all transparent to you except in the case of an
1007 unresolvable conflict.
1015 It should be noted that C<super> and C<inner> B<cannot> be used in the same
1016 method. However, they may be combined within the same class hierarchy; see
1017 F<t/014_override_augment_inner_super.t> for an example.
1019 The reason for this is that C<super> is only valid within a method
1020 with the C<override> modifier, and C<inner> will never be valid within an
1021 C<override> method. In fact, C<augment> will skip over any C<override> methods
1022 when searching for its appropriate C<inner>.
1024 This might seem like a restriction, but I am of the opinion that keeping these
1025 two features separate (yet interoperable) actually makes them easy to use, since
1026 their behavior is then easier to predict. Time will tell whether I am right or
1027 not (UPDATE: so far so good).
1033 We offer both a mailing list and a very active IRC channel.
1035 The mailing list is L<moose@perl.org>. You must be subscribed to send
1036 a message. To subscribe, send an empty message to
1037 L<moose-subscribe@perl.org>
1039 You can also visit us at C<#moose> on L<irc://irc.perl.org/#moose>
1040 This channel is quite active, and questions at all levels (on Moose-related
1041 topics ;) are welcome.
1043 =head1 ACKNOWLEDGEMENTS
1047 =item I blame Sam Vilain for introducing me to the insanity that is meta-models.
1049 =item I blame Audrey Tang for then encouraging my meta-model habit in #perl6.
1051 =item Without Yuval "nothingmuch" Kogman this module would not be possible,
1052 and it certainly wouldn't have this name ;P
1054 =item The basis of the TypeContraints module was Rob Kinyon's idea
1055 originally, I just ran with it.
1057 =item Thanks to mst & chansen and the whole #moose posse for all the
1058 early ideas/feature-requests/encouragement/bug-finding.
1060 =item Thanks to David "Theory" Wheeler for meta-discussions and spelling fixes.
1068 =item L<http://www.iinteractive.com/moose>
1070 This is the official web home of Moose, it contains links to our public git repository
1071 as well as links to a number of talks and articles on Moose and Moose related
1074 =item The Moose is flying, a tutorial by Randal Schwartz
1076 Part 1 - L<http://www.stonehenge.com/merlyn/LinuxMag/col94.html>
1078 Part 2 - L<http://www.stonehenge.com/merlyn/LinuxMag/col95.html>
1080 =item Several Moose extension modules in the C<MooseX::> namespace.
1082 See L<http://search.cpan.org/search?query=MooseX::> for extensions.
1084 =item Moose stats on ohloh.net - L<http://www.ohloh.net/projects/moose>
1092 =item The Art of the MetaObject Protocol
1094 I mention this in the L<Class::MOP> docs too, this book was critical in
1095 the development of both modules and is highly recommended.
1103 =item L<http://www.cs.utah.edu/plt/publications/oopsla04-gff.pdf>
1105 This paper (suggested by lbr on #moose) was what lead to the implementation
1106 of the C<super>/C<override> and C<inner>/C<augment> features. If you really
1107 want to understand them, I suggest you read this.
1113 All complex software has bugs lurking in it, and this module is no
1116 Please report any bugs to C<bug-moose@rt.cpan.org>, or through the web
1117 interface at L<http://rt.cpan.org>.
1119 You can also discuss feature requests or possible bugs on the Moose mailing
1120 list (moose@perl.org) or on IRC at L<irc://irc.perl.org/#moose>.
1122 =head1 FEATURE REQUESTS
1124 We are very strict about what features we add to the Moose core, especially
1125 the user-visible features. Instead we have made sure that the underlying
1126 meta-system of Moose is as extensible as possible so that you can add your
1127 own features easily.
1129 That said, occasionally there is a feature needed in the meta-system
1130 to support your planned extension, in which case you should either
1131 email the mailing list (moose@perl.org) or join us on IRC at
1132 L<irc://irc.perl.org/#moose> to discuss. The
1133 L<Moose::Manual::Contributing> has more detail about how and when you
1138 Moose is an open project, there are at this point dozens of people who have
1139 contributed, and can contribute. If you have added anything to the Moose
1140 project you have a commit bit on this file and can add your name to the list.
1144 However there are only a few people with the rights to release a new version
1145 of Moose. The Moose Cabal are the people to go to with questions regarding
1146 the wider purview of Moose, and help out maintaining not just the code
1147 but the community as well.
1149 Stevan (stevan) Little E<lt>stevan@iinteractive.comE<gt>
1151 Jesse (doy) Luehrs E<lt>doy at tozt dot netE<gt>
1153 Yuval (nothingmuch) Kogman
1155 Shawn (sartak) Moore E<lt>sartak@bestpractical.comE<gt>
1157 Hans Dieter (confound) Pearcey E<lt>hdp@pobox.comE<gt>
1159 Chris (perigrin) Prather
1161 Florian Ragwitz E<lt>rafl@debian.orgE<gt>
1163 Dave (autarch) Rolsky E<lt>autarch@urth.orgE<gt>
1165 =head2 OTHER CONTRIBUTORS
1169 Adam (Alias) Kennedy
1171 Anders (Debolaz) Nor Berle
1173 Nathan (kolibrie) Gray
1175 Christian (chansen) Hansen
1177 Eric (ewilhelm) Wilhelm
1179 Guillermo (groditi) Roditi
1181 Jess (castaway) Robinson
1185 Robert (phaylon) Sedlacek
1189 Scott (konobi) McWhirter
1191 Shlomi (rindolf) Fish
1193 Wallace (wreis) Reis
1195 Jonathan (jrockway) Rockway
1197 Piotr (dexter) Roszatycki
1199 Sam (mugwump) Vilain
1203 Dylan Hardison (doc fixes)
1205 ... and many other #moose folks
1207 =head1 COPYRIGHT AND LICENSE
1209 Copyright 2006-2010 by Infinity Interactive, Inc.
1211 L<http://www.iinteractive.com>
1213 This library is free software; you can redistribute it and/or modify
1214 it under the same terms as Perl itself.