7 use Scalar::Util 'blessed';
10 use Moose::Deprecated;
15 use Moose::Meta::Class;
16 use Moose::Meta::TypeConstraint;
17 use Moose::Meta::TypeCoercion;
18 use Moose::Meta::Attribute;
19 use Moose::Meta::Instance;
23 use Moose::Meta::Role;
24 use Moose::Meta::Role::Composite;
25 use Moose::Meta::Role::Application;
26 use Moose::Meta::Role::Application::RoleSummation;
27 use Moose::Meta::Role::Application::ToClass;
28 use Moose::Meta::Role::Application::ToRole;
29 use Moose::Meta::Role::Application::ToInstance;
31 use Moose::Util::TypeConstraints;
34 use Moose::Meta::Attribute::Native;
45 Moose->throw_error("Must derive at least one class") unless @_;
47 # this checks the metaclass to make sure
48 # it is correct, sometimes it can get out
49 # of sync when the classes are being built
50 $meta->superclasses(@_);
54 Moose::Util::apply_all_roles(shift, @_);
61 Moose->throw_error('Usage: has \'name\' => ( key => value, ... )')
64 my %options = ( definition_context => Moose::Util::_caller_info(), @_ );
65 my $attrs = ( ref($name) eq 'ARRAY' ) ? $name : [ ($name) ];
66 $meta->add_attribute( $_, %options ) for @$attrs;
70 Moose::Util::add_method_modifier(shift, 'before', \@_);
74 Moose::Util::add_method_modifier(shift, 'after', \@_);
78 Moose::Util::add_method_modifier(shift, 'around', \@_);
86 # This check avoids a recursion loop - see
87 # t/bugs/super_recursion.t
88 return if defined $SUPER_PACKAGE && $SUPER_PACKAGE ne caller();
89 return unless $SUPER_BODY; $SUPER_BODY->(@SUPER_ARGS);
94 my ( $name, $method ) = @_;
95 $meta->add_override_method_modifier( $name => $method );
100 our ( %INNER_BODY, %INNER_ARGS );
102 if ( my $body = $INNER_BODY{$pkg} ) {
103 my @args = @{ $INNER_ARGS{$pkg} };
104 local $INNER_ARGS{$pkg};
105 local $INNER_BODY{$pkg};
106 return $body->(@args);
114 my ( $name, $method ) = @_;
115 $meta->add_augment_method_modifier( $name => $method );
118 Moose::Exporter->setup_import_methods(
120 qw( extends with has before after around override augment )
125 \&Scalar::Util::blessed,
130 # This used to be called as a function. This hack preserves
131 # backwards compatibility.
132 if ( $_[0] ne __PACKAGE__ ) {
133 Moose::Deprecated::deprecated(
134 feature => 'Moose::init_meta',
135 message => 'Calling Moose::init_meta as a function is deprecated.'
136 . ' Doing so will throw an error in Moose 2.0200.'
139 return __PACKAGE__->init_meta(
149 my $class = $args{for_class}
150 or Moose->throw_error("Cannot call init_meta without specifying a for_class");
151 my $base_class = $args{base_class} || 'Moose::Object';
152 my $metaclass = $args{metaclass} || 'Moose::Meta::Class';
153 my $meta_name = exists $args{meta_name} ? $args{meta_name} : 'meta';
155 Moose->throw_error("The Metaclass $metaclass must be a subclass of Moose::Meta::Class.")
156 unless $metaclass->isa('Moose::Meta::Class');
158 # make a subtype for each Moose class
160 unless find_type_constraint($class);
164 if ( $meta = Class::MOP::get_metaclass_by_name($class) ) {
165 unless ( $meta->isa("Moose::Meta::Class") ) {
166 my $error_message = "$class already has a metaclass, but it does not inherit $metaclass ($meta).";
167 if ( $meta->isa('Moose::Meta::Role') ) {
168 Moose->throw_error($error_message . ' You cannot make the same thing a role and a class. Remove either Moose or Moose::Role.');
170 Moose->throw_error($error_message);
176 # now we check whether our ancestors have metaclass, and if so borrow that
177 my ( undef, @isa ) = @{ mro::get_linear_isa($class) };
179 foreach my $ancestor ( @isa ) {
180 my $ancestor_meta = Class::MOP::get_metaclass_by_name($ancestor) || next;
182 my $ancestor_meta_class = $ancestor_meta->_real_ref_name;
184 # if we have an ancestor metaclass that inherits $metaclass, we use
185 # that. This is like _fix_metaclass_incompatibility, but we can do it now.
187 # the case of having an ancestry is not very common, but arises in
189 unless ( $metaclass->isa( $ancestor_meta_class ) ) {
190 if ( $ancestor_meta_class->isa($metaclass) ) {
191 $metaclass = $ancestor_meta_class;
196 $meta = $metaclass->initialize($class);
199 if (defined $meta_name) {
200 # also check for inherited non moose 'meta' method?
201 my $existing = $meta->get_method($meta_name);
202 if ($existing && !$existing->isa('Class::MOP::Method::Meta')) {
203 Carp::cluck "Moose is overwriting an existing method named "
204 . "$meta_name in class $class with a method "
205 . "which returns the class's metaclass. If this is "
206 . "actually what you want, you should remove the "
207 . "existing method, otherwise, you should rename or "
208 . "disable this generated method using the "
209 . "'-meta_name' option to 'use Moose'.";
211 $meta->_add_meta_method($meta_name);
214 # make sure they inherit from Moose::Object
215 $meta->superclasses($base_class)
216 unless $meta->superclasses();
221 # This may be used in some older MooseX extensions.
223 goto &Moose::Exporter::_get_caller;
226 ## make 'em all immutable
229 inline_constructor => 1,
230 constructor_name => "_new",
231 # these are Class::MOP accessors, so they need inlining
232 inline_accessors => 1
233 ) for grep { $_->is_mutable }
236 Moose::Meta::Attribute
238 Moose::Meta::Instance
240 Moose::Meta::TypeCoercion
241 Moose::Meta::TypeCoercion::Union
244 Moose::Meta::Method::Accessor
245 Moose::Meta::Method::Constructor
246 Moose::Meta::Method::Destructor
247 Moose::Meta::Method::Overridden
248 Moose::Meta::Method::Augmented
251 Moose::Meta::Role::Attribute
252 Moose::Meta::Role::Method
253 Moose::Meta::Role::Method::Required
254 Moose::Meta::Role::Method::Conflicting
256 Moose::Meta::Role::Composite
258 Moose::Meta::Role::Application
259 Moose::Meta::Role::Application::RoleSummation
260 Moose::Meta::Role::Application::ToClass
261 Moose::Meta::Role::Application::ToRole
262 Moose::Meta::Role::Application::ToInstance
265 Moose::Meta::Mixin::AttributeCore->meta->make_immutable(
266 inline_constructor => 0,
267 constructor_name => undef,
272 # ABSTRACT: A postmodern object system for Perl 5
281 use Moose; # automatically turns on strict and warnings
283 has 'x' => (is => 'rw', isa => 'Int');
284 has 'y' => (is => 'rw', isa => 'Int');
297 has 'z' => (is => 'rw', isa => 'Int');
299 after 'clear' => sub {
306 Moose is an extension of the Perl 5 object system.
308 The main goal of Moose is to make Perl 5 Object Oriented programming
309 easier, more consistent, and less tedious. With Moose you can think
310 more about what you want to do and less about the mechanics of OOP.
312 Additionally, Moose is built on top of L<Class::MOP>, which is a
313 metaclass system for Perl 5. This means that Moose not only makes
314 building normal Perl 5 objects better, but it provides the power of
315 metaclass programming as well.
319 If you're new to Moose, the best place to start is the
320 L<Moose::Manual> docs, followed by the L<Moose::Cookbook>. The intro
321 will show you what Moose is, and how it makes Perl 5 OO better.
323 The cookbook recipes on Moose basics will get you up to speed with
324 many of Moose's features quickly. Once you have an idea of what Moose
325 can do, you can use the API documentation to get more detail on
326 features which interest you.
328 =head2 Moose Extensions
330 The C<MooseX::> namespace is the official place to find Moose extensions.
331 These extensions can be found on the CPAN. The easiest way to find them
332 is to search for them (L<http://search.cpan.org/search?query=MooseX::>),
333 or to examine L<Task::Moose> which aims to keep an up-to-date, easily
334 installable list of Moose extensions.
338 Much of the Moose documentation has been translated into other languages.
344 Japanese docs can be found at
345 L<http://perldoc.perlassociation.org/pod/Moose-Doc-JA/index.html>. The
346 source POD files can be found in GitHub:
347 L<http://github.com/jpa/Moose-Doc-JA>
351 =head1 BUILDING CLASSES WITH MOOSE
353 Moose makes every attempt to provide as much convenience as possible during
354 class construction/definition, but still stay out of your way if you want it
355 to. Here are a few items to note when building classes with Moose.
357 When you C<use Moose>, Moose will set the class's parent class to
358 L<Moose::Object>, I<unless> the class using Moose already has a parent
359 class. In addition, specifying a parent with C<extends> will change the parent
362 Moose will also manage all attributes (including inherited ones) that are
363 defined with C<has>. And (assuming you call C<new>, which is inherited from
364 L<Moose::Object>) this includes properly initializing all instance slots,
365 setting defaults where appropriate, and performing any type constraint checking
368 =head1 PROVIDED METHODS
370 Moose provides a number of methods to all your classes, mostly through the
371 inheritance of L<Moose::Object>. There is however, one exception.
377 This is a method which provides access to the current class's metaclass.
381 =head1 EXPORTED FUNCTIONS
383 Moose will export a number of functions into the class's namespace which
384 may then be used to set up the class. These functions all work directly
385 on the current class.
389 =item B<extends (@superclasses)>
391 This function will set the superclass(es) for the current class.
393 This approach is recommended instead of C<use base>, because C<use base>
394 actually C<push>es onto the class's C<@ISA>, whereas C<extends> will
395 replace it. This is important to ensure that classes which do not have
396 superclasses still properly inherit from L<Moose::Object>.
398 Each superclass can be followed by a hash reference with options. Currently,
399 only L<-version|Class::MOP/Class Loading Options> is recognized:
401 extends 'My::Parent' => { -version => 0.01 },
402 'My::OtherParent' => { -version => 0.03 };
404 An exception will be thrown if the version requirements are not
407 =item B<with (@roles)>
409 This will apply a given set of C<@roles> to the local class.
411 Like with C<extends>, each specified role can be followed by a hash
412 reference with a L<-version|Class::MOP/Class Loading Options> option:
414 with 'My::Role' => { -version => 0.32 },
415 'My::Otherrole' => { -version => 0.23 };
417 The specified version requirements must be satisfied, otherwise an
418 exception will be thrown.
420 If your role takes options or arguments, they can be passed along in the
421 hash reference as well.
423 =item B<has $name|@$names =E<gt> %options>
425 This will install an attribute of a given C<$name> into the current class. If
426 the first parameter is an array reference, it will create an attribute for
427 every C<$name> in the list. The C<%options> are the same as those provided by
428 L<Class::MOP::Attribute>, in addition to the list below which are provided by
429 Moose (L<Moose::Meta::Attribute> to be more specific):
433 =item I<is =E<gt> 'rw'|'ro'>
435 The I<is> option accepts either I<rw> (for read/write) or I<ro> (for read
436 only). These will create either a read/write accessor or a read-only
437 accessor respectively, using the same name as the C<$name> of the attribute.
439 If you need more control over how your accessors are named, you can
440 use the L<reader|Class::MOP::Attribute/reader>,
441 L<writer|Class::MOP::Attribute/writer> and
442 L<accessor|Class::MOP::Attribute/accessor> options inherited from
443 L<Class::MOP::Attribute>, however if you use those, you won't need the
446 =item I<isa =E<gt> $type_name>
448 The I<isa> option uses Moose's type constraint facilities to set up runtime
449 type checking for this attribute. Moose will perform the checks during class
450 construction, and within any accessors. The C<$type_name> argument must be a
451 string. The string may be either a class name or a type defined using
452 Moose's type definition features. (Refer to L<Moose::Util::TypeConstraints>
453 for information on how to define a new type, and how to retrieve type meta-data).
455 =item I<coerce =E<gt> (1|0)>
457 This will attempt to use coercion with the supplied type constraint to change
458 the value passed into any accessors or constructors. You B<must> supply a type
459 constraint, and that type constraint B<must> define a coercion. See
460 L<Moose::Cookbook::Basics::Recipe5> for an example.
462 =item I<does =E<gt> $role_name>
464 This will accept the name of a role which the value stored in this attribute
465 is expected to have consumed.
467 =item I<required =E<gt> (1|0)>
469 This marks the attribute as being required. This means a value must be
470 supplied during class construction, I<or> the attribute must be lazy
471 and have either a default or a builder. Note that c<required> does not
472 say anything about the attribute's value, which can be C<undef>.
474 =item I<weak_ref =E<gt> (1|0)>
476 This will tell the class to store the value of this attribute as a weakened
477 reference. If an attribute is a weakened reference, it B<cannot> also be
478 coerced. Note that when a weak ref expires, the attribute's value becomes
479 undefined, and is still considered to be set for purposes of predicate,
482 =item I<lazy =E<gt> (1|0)>
484 This will tell the class to not create this slot until absolutely necessary.
485 If an attribute is marked as lazy it B<must> have a default or builder
488 =item I<trigger =E<gt> $code>
490 The I<trigger> option is a CODE reference which will be called after
491 the value of the attribute is set. The CODE ref is passed the
492 instance itself, the updated value, and the original value if the
493 attribute was already set.
495 You B<can> have a trigger on a read-only attribute.
497 B<NOTE:> Triggers will only fire when you B<assign> to the attribute,
498 either in the constructor, or using the writer. Default and built values will
499 B<not> cause the trigger to be fired.
501 =item I<handles =E<gt> ARRAY | HASH | REGEXP | ROLE | ROLETYPE | DUCKTYPE | CODE>
503 The I<handles> option provides Moose classes with automated delegation features.
504 This is a pretty complex and powerful option. It accepts many different option
505 formats, each with its own benefits and drawbacks.
507 B<NOTE:> The class being delegated to does not need to be a Moose based class,
508 which is why this feature is especially useful when wrapping non-Moose classes.
510 All I<handles> option formats share the following traits:
512 You cannot override a locally defined method with a delegated method; an
513 exception will be thrown if you try. That is to say, if you define C<foo> in
514 your class, you cannot override it with a delegated C<foo>. This is almost never
515 something you would want to do, and if it is, you should do it by hand and not
518 You cannot override any of the methods found in Moose::Object, or the C<BUILD>
519 and C<DEMOLISH> methods. These will not throw an exception, but will silently
520 move on to the next method in the list. My reasoning for this is that you would
521 almost never want to do this, since it usually breaks your class. As with
522 overriding locally defined methods, if you do want to do this, you should do it
523 manually, not with Moose.
525 You do not I<need> to have a reader (or accessor) for the attribute in order
526 to delegate to it. Moose will create a means of accessing the value for you,
527 however this will be several times B<less> efficient then if you had given
528 the attribute a reader (or accessor) to use.
530 Below is the documentation for each option format:
536 This is the most common usage for I<handles>. You basically pass a list of
537 method names to be delegated, and Moose will install a delegation method
542 This is the second most common usage for I<handles>. Instead of a list of
543 method names, you pass a HASH ref where each key is the method name you
544 want installed locally, and its value is the name of the original method
545 in the class being delegated to.
547 This can be very useful for recursive classes like trees. Here is a
548 quick example (soon to be expanded into a Moose::Cookbook recipe):
553 has 'node' => (is => 'rw', isa => 'Any');
558 default => sub { [] }
566 parent_node => 'node',
567 siblings => 'children',
571 In this example, the Tree package gets C<parent_node> and C<siblings> methods,
572 which delegate to the C<node> and C<children> methods (respectively) of the Tree
573 instance stored in the C<parent> slot.
575 You may also use an array reference to curry arguments to the original method.
579 handles => { set_foo => [ set => 'foo' ] },
582 # $self->set_foo(...) calls $self->thing->set('foo', ...)
584 The first element of the array reference is the original method name, and the
585 rest is a list of curried arguments.
589 The regexp option works very similar to the ARRAY option, except that it builds
590 the list of methods for you. It starts by collecting all possible methods of the
591 class being delegated to, then filters that list using the regexp supplied here.
593 B<NOTE:> An I<isa> option is required when using the regexp option format. This
594 is so that we can determine (at compile time) the method list from the class.
595 Without an I<isa> this is just not possible.
597 =item C<ROLE> or C<ROLETYPE>
599 With the role option, you specify the name of a role or a
600 L<role type|Moose::Meta::TypeConstraint::Role> whose "interface" then becomes
601 the list of methods to handle. The "interface" can be defined as; the methods
602 of the role and any required methods of the role. It should be noted that this
603 does B<not> include any method modifiers or generated attribute methods (which
604 is consistent with role composition).
608 With the duck type option, you pass a duck type object whose "interface" then
609 becomes the list of methods to handle. The "interface" can be defined as the
610 list of methods passed to C<duck_type> to create a duck type object. For more
611 information on C<duck_type> please check
612 L<Moose::Util::TypeConstraints>.
616 This is the option to use when you really want to do something funky. You should
617 only use it if you really know what you are doing, as it involves manual
620 This takes a code reference, which should expect two arguments. The first is the
621 attribute meta-object this I<handles> is attached to. The second is the
622 metaclass of the class being delegated to. It expects you to return a hash (not
623 a HASH ref) of the methods you want mapped.
627 =item I<metaclass =E<gt> $metaclass_name>
629 This tells the class to use a custom attribute metaclass for this particular
630 attribute. Custom attribute metaclasses are useful for extending the
631 capabilities of the I<has> keyword: they are the simplest way to extend the MOP,
632 but they are still a fairly advanced topic and too much to cover here. See
633 L<Moose::Cookbook::Meta::Recipe1> for more information.
635 See L<Metaclass and Trait Name Resolution> for details on how a metaclass name
636 is resolved to a class name.
638 =item I<traits =E<gt> [ @role_names ]>
640 This tells Moose to take the list of C<@role_names> and apply them to the
641 attribute meta-object. This is very similar to the I<metaclass> option, but
642 allows you to use more than one extension at a time.
644 See L<Metaclass and Trait Name Resolution> for details on how a trait name is
645 resolved to a role name.
647 Also see L<Moose::Cookbook::Meta::Recipe3> for a metaclass trait
650 =item I<builder> => Str
652 The value of this key is the name of the method that will be called to
653 obtain the value used to initialize the attribute. See the L<builder
654 option docs in Class::MOP::Attribute|Class::MOP::Attribute/builder>
655 and/or L<Moose::Cookbook::Basics::Recipe8> for more information.
657 =item I<default> => SCALAR | CODE
659 The value of this key is the default value which will initialize the attribute.
661 NOTE: If the value is a simple scalar (string or number), then it can
662 be just passed as is. However, if you wish to initialize it with a
663 HASH or ARRAY ref, then you need to wrap that inside a CODE reference.
664 See the L<default option docs in
665 Class::MOP::Attribute|Class::MOP::Attribute/default> for more
668 =item I<clearer> => Str
670 Creates a method allowing you to clear the value. See the L<clearer option
671 docs in Class::MOP::Attribute|Class::MOP::Attribute/clearer> for more
674 =item I<predicate> => Str
676 Creates a method to perform a basic test to see if a value has been set in the
677 attribute. See the L<predicate option docs in
678 Class::MOP::Attribute|Class::MOP::Attribute/predicate> for more information.
680 Note that the predicate will return true even for a C<weak_ref> attribute
681 whose value has expired.
683 =item I<lazy_build> => (0|1)
685 Automatically define lazy => 1 as well as builder => "_build_$attr", clearer =>
686 "clear_$attr', predicate => 'has_$attr' unless they are already defined.
688 =item I<initializer> => Str
690 This may be a method name (referring to a method on the class with
691 this attribute) or a CODE ref. The initializer is used to set the
692 attribute value on an instance when the attribute is set during
693 instance initialization (but not when the value is being assigned
694 to). See the L<initializer option docs in
695 Class::MOP::Attribute|Class::MOP::Attribute/initializer> for more
698 =item I<documentation> => $string
700 An arbitrary string that can be retrieved later by calling C<<
701 $attr->documentation >>.
707 =item B<has +$name =E<gt> %options>
709 This is variation on the normal attribute creator C<has> which allows you to
710 clone and extend an attribute from a superclass or from a role. Here is an
711 example of the superclass usage:
719 default => 'Hello, I am a Foo'
727 has '+message' => (default => 'Hello I am My::Foo');
729 What is happening here is that B<My::Foo> is cloning the C<message> attribute
730 from its parent class B<Foo>, retaining the C<is =E<gt> 'rw'> and C<isa =E<gt>
731 'Str'> characteristics, but changing the value in C<default>.
733 Here is another example, but within the context of a role:
741 default => 'Hello, I am a Foo'
749 has '+message' => (default => 'Hello I am My::Foo');
751 In this case, we are basically taking the attribute which the role supplied
752 and altering it within the bounds of this feature.
754 Note that you can only extend an attribute from either a superclass or a role,
755 you cannot extend an attribute in a role that composes over an attribute from
758 Aside from where the attributes come from (one from superclass, the other
759 from a role), this feature works exactly the same. This feature is restricted
760 somewhat, so as to try and force at least I<some> sanity into it. You are only
761 allowed to change the following attributes:
767 Change the default value of an attribute.
771 Change whether the attribute attempts to coerce a value passed to it.
775 Change if the attribute is required to have a value.
777 =item I<documentation>
779 Change the documentation string associated with the attribute.
783 Change if the attribute lazily initializes the slot.
787 You I<are> allowed to change the type without restriction.
789 It is recommended that you use this freedom with caution. We used to
790 only allow for extension only if the type was a subtype of the parent's
791 type, but we felt that was too restrictive and is better left as a
796 You are allowed to B<add> a new C<handles> definition, but you are B<not>
797 allowed to I<change> one.
801 You are allowed to B<add> a new C<builder> definition, but you are B<not>
802 allowed to I<change> one.
806 You are allowed to B<add> a new C<metaclass> definition, but you are
807 B<not> allowed to I<change> one.
811 You are allowed to B<add> additional traits to the C<traits> definition.
812 These traits will be composed into the attribute, but preexisting traits
813 B<are not> overridden, or removed.
817 =item B<before $name|@names|\@names|qr/.../ =E<gt> sub { ... }>
819 =item B<after $name|@names|\@names|qr/.../ =E<gt> sub { ... }>
821 =item B<around $name|@names|\@names|qr/.../ =E<gt> sub { ... }>
823 These three items are syntactic sugar for the before, after, and around method
824 modifier features that L<Class::MOP> provides. More information on these may be
825 found in L<Moose::Manual::MethodModifiers> and the
826 L<Class::MOP::Class documentation|Class::MOP::Class/"Method Modifiers">.
830 The keyword C<super> is a no-op when called outside of an C<override> method. In
831 the context of an C<override> method, it will call the next most appropriate
832 superclass method with the same arguments as the original method.
834 =item B<override ($name, &sub)>
836 An C<override> method is a way of explicitly saying "I am overriding this
837 method from my superclass". You can call C<super> within this method, and
838 it will work as expected. The same thing I<can> be accomplished with a normal
839 method call and the C<SUPER::> pseudo-package; it is really your choice.
843 The keyword C<inner>, much like C<super>, is a no-op outside of the context of
844 an C<augment> method. You can think of C<inner> as being the inverse of
845 C<super>; the details of how C<inner> and C<augment> work is best described in
846 the L<Moose::Cookbook::Basics::Recipe6>.
848 =item B<augment ($name, &sub)>
850 An C<augment> method, is a way of explicitly saying "I am augmenting this
851 method from my superclass". Once again, the details of how C<inner> and
852 C<augment> work is best described in the L<Moose::Cookbook::Basics::Recipe6>.
856 This is the C<Carp::confess> function, and exported here because I use it
861 This is the C<Scalar::Util::blessed> function. It is exported here because I
862 use it all the time. It is highly recommended that this is used instead of
863 C<ref> anywhere you need to test for an object's class name.
869 When you use Moose, you can specify which metaclass to use:
871 use Moose -metaclass => 'My::Meta::Class';
873 You can also specify traits which will be applied to your metaclass:
875 use Moose -traits => 'My::Trait';
877 This is very similar to the attribute traits feature. When you do
878 this, your class's C<meta> object will have the specified traits
879 applied to it. See L<Metaclass and Trait Name Resolution> for more
882 =head2 Metaclass and Trait Name Resolution
884 By default, when given a trait name, Moose simply tries to load a
885 class of the same name. If such a class does not exist, it then looks
886 for for a class matching
887 B<Moose::Meta::$type::Custom::Trait::$trait_name>. The C<$type>
888 variable here will be one of B<Attribute> or B<Class>, depending on
889 what the trait is being applied to.
891 If a class with this long name exists, Moose checks to see if it has
892 the method C<register_implementation>. This method is expected to
893 return the I<real> class name of the trait. If there is no
894 C<register_implementation> method, it will fall back to using
895 B<Moose::Meta::$type::Custom::Trait::$trait> as the trait name.
897 The lookup method for metaclasses is the same, except that it looks
898 for a class matching B<Moose::Meta::$type::Custom::$metaclass_name>.
900 If all this is confusing, take a look at
901 L<Moose::Cookbook::Meta::Recipe3>, which demonstrates how to create an
904 =head1 UNIMPORTING FUNCTIONS
908 Moose offers a way to remove the keywords it exports, through the C<unimport>
909 method. You simply have to say C<no Moose> at the bottom of your code for this
910 to work. Here is an example:
915 has 'first_name' => (is => 'rw', isa => 'Str');
916 has 'last_name' => (is => 'rw', isa => 'Str');
920 $self->first_name . ' ' . $self->last_name
923 no Moose; # keywords are removed from the Person package
925 =head1 EXTENDING AND EMBEDDING MOOSE
927 To learn more about extending Moose, we recommend checking out the
928 "Extending" recipes in the L<Moose::Cookbook>, starting with
929 L<Moose::Cookbook::Extending::Recipe1>, which provides an overview of
930 all the different ways you might extend Moose.
932 =head2 B<< Moose->init_meta(for_class => $class, base_class => $baseclass, metaclass => $metaclass) >>
934 The C<init_meta> method sets up the metaclass object for the class
935 specified by C<for_class>. This method injects a a C<meta> accessor
936 into the class so you can get at this object. It also sets the class's
937 superclass to C<base_class>, with L<Moose::Object> as the default.
939 C<init_meta> returns the metaclass object for C<$class>.
941 You can specify an alternate metaclass with the C<metaclass> option.
943 For more detail on this topic, see L<Moose::Cookbook::Extending::Recipe2>.
945 This method used to be documented as a function which accepted
946 positional parameters. This calling style will still work for
947 backwards compatibility, but is deprecated.
951 Moose's C<import> method supports the L<Sub::Exporter> form of C<{into =E<gt> $pkg}>
952 and C<{into_level =E<gt> 1}>.
954 B<NOTE>: Doing this is more or less deprecated. Use L<Moose::Exporter>
955 instead, which lets you stack multiple C<Moose.pm>-alike modules
956 sanely. It handles getting the exported functions into the right place
959 =head2 B<throw_error>
961 An alias for C<confess>, used internally by Moose.
963 =head2 The MooseX:: namespace
965 Generally if you're writing an extension I<for> Moose itself you'll want
966 to put your extension in the C<MooseX::> namespace. This namespace is
967 specifically for extensions that make Moose better or different in some
968 fundamental way. It is traditionally B<not> for a package that just happens
969 to use Moose. This namespace follows from the examples of the C<LWPx::>
970 and C<DBIx::> namespaces that perform the same function for C<LWP> and C<DBI>
973 =head1 METACLASS COMPATIBILITY AND MOOSE
975 Metaclass compatibility is a thorny subject. You should start by
976 reading the "About Metaclass compatibility" section in the
979 Moose will attempt to resolve a few cases of metaclass incompatibility
980 when you set the superclasses for a class, in addition to the cases that
981 C<Class::MOP> handles.
983 Moose tries to determine if the metaclasses only "differ by roles". This
984 means that the parent and child's metaclass share a common ancestor in
985 their respective hierarchies, and that the subclasses under the common
986 ancestor are only different because of role applications. This case is
987 actually fairly common when you mix and match various C<MooseX::*>
988 modules, many of which apply roles to the metaclass.
990 If the parent and child do differ by roles, Moose replaces the
991 metaclass in the child with a newly created metaclass. This metaclass
992 is a subclass of the parent's metaclass which does all of the roles that
993 the child's metaclass did before being replaced. Effectively, this
994 means the new metaclass does all of the roles done by both the
995 parent's and child's original metaclasses.
997 Ultimately, this is all transparent to you except in the case of an
998 unresolvable conflict.
1006 It should be noted that C<super> and C<inner> B<cannot> be used in the same
1007 method. However, they may be combined within the same class hierarchy; see
1008 F<t/basics/override_augment_inner_super.t> for an example.
1010 The reason for this is that C<super> is only valid within a method
1011 with the C<override> modifier, and C<inner> will never be valid within an
1012 C<override> method. In fact, C<augment> will skip over any C<override> methods
1013 when searching for its appropriate C<inner>.
1015 This might seem like a restriction, but I am of the opinion that keeping these
1016 two features separate (yet interoperable) actually makes them easy to use, since
1017 their behavior is then easier to predict. Time will tell whether I am right or
1018 not (UPDATE: so far so good).
1024 We offer both a mailing list and a very active IRC channel.
1026 The mailing list is L<moose@perl.org>. You must be subscribed to send
1027 a message. To subscribe, send an empty message to
1028 L<moose-subscribe@perl.org>
1030 You can also visit us at C<#moose> on L<irc://irc.perl.org/#moose>
1031 This channel is quite active, and questions at all levels (on Moose-related
1032 topics ;) are welcome.
1034 =head1 ACKNOWLEDGEMENTS
1038 =item I blame Sam Vilain for introducing me to the insanity that is meta-models.
1040 =item I blame Audrey Tang for then encouraging my meta-model habit in #perl6.
1042 =item Without Yuval "nothingmuch" Kogman this module would not be possible,
1043 and it certainly wouldn't have this name ;P
1045 =item The basis of the TypeContraints module was Rob Kinyon's idea
1046 originally, I just ran with it.
1048 =item Thanks to mst & chansen and the whole #moose posse for all the
1049 early ideas/feature-requests/encouragement/bug-finding.
1051 =item Thanks to David "Theory" Wheeler for meta-discussions and spelling fixes.
1059 =item L<http://www.iinteractive.com/moose>
1061 This is the official web home of Moose, it contains links to our public git repository
1062 as well as links to a number of talks and articles on Moose and Moose related
1065 =item The Moose is flying, a tutorial by Randal Schwartz
1067 Part 1 - L<http://www.stonehenge.com/merlyn/LinuxMag/col94.html>
1069 Part 2 - L<http://www.stonehenge.com/merlyn/LinuxMag/col95.html>
1071 =item Several Moose extension modules in the C<MooseX::> namespace.
1073 See L<http://search.cpan.org/search?query=MooseX::> for extensions.
1075 =item Moose stats on ohloh.net - L<http://www.ohloh.net/projects/moose>
1083 =item The Art of the MetaObject Protocol
1085 I mention this in the L<Class::MOP> docs too, as this book was critical in
1086 the development of both modules and is highly recommended.
1094 =item L<http://www.cs.utah.edu/plt/publications/oopsla04-gff.pdf>
1096 This paper (suggested by lbr on #moose) was what lead to the implementation
1097 of the C<super>/C<override> and C<inner>/C<augment> features. If you really
1098 want to understand them, I suggest you read this.
1104 All complex software has bugs lurking in it, and this module is no
1107 Please report any bugs to C<bug-moose@rt.cpan.org>, or through the web
1108 interface at L<http://rt.cpan.org>.
1110 You can also discuss feature requests or possible bugs on the Moose mailing
1111 list (moose@perl.org) or on IRC at L<irc://irc.perl.org/#moose>.
1113 =head1 FEATURE REQUESTS
1115 We are very strict about what features we add to the Moose core, especially
1116 the user-visible features. Instead we have made sure that the underlying
1117 meta-system of Moose is as extensible as possible so that you can add your
1118 own features easily.
1120 That said, occasionally there is a feature needed in the meta-system
1121 to support your planned extension, in which case you should either
1122 email the mailing list (moose@perl.org) or join us on IRC at
1123 L<irc://irc.perl.org/#moose> to discuss. The
1124 L<Moose::Manual::Contributing> has more detail about how and when you
1129 There are only a few people with the rights to release a new version
1130 of Moose. The Moose Cabal are the people to go to with questions regarding
1131 the wider purview of Moose. They help maintain not just the code
1132 but the community as well.
1134 Stevan (stevan) Little E<lt>stevan@iinteractive.comE<gt>
1136 Jesse (doy) Luehrs E<lt>doy at tozt dot netE<gt>
1138 Yuval (nothingmuch) Kogman
1140 Shawn (sartak) Moore E<lt>sartak@bestpractical.comE<gt>
1142 Hans Dieter (confound) Pearcey E<lt>hdp@pobox.comE<gt>
1144 Chris (perigrin) Prather
1146 Florian Ragwitz E<lt>rafl@debian.orgE<gt>
1148 Dave (autarch) Rolsky E<lt>autarch@urth.orgE<gt>
1154 Adam (Alias) Kennedy
1156 Anders (Debolaz) Nor Berle
1158 Chris (perigrin) Prather
1160 Christian (chansen) Hansen
1164 Dylan Hardison (doc fixes)
1166 Eric (ewilhelm) Wilhelm
1170 Florian (rafl) Ragwitz
1172 Guillermo (groditi) Roditi
1178 Jess (castaway) Robinson
1180 Jonathan (jrockway) Rockway
1184 Nathan (kolibrie) Gray
1186 Paul (frodwith) Driver
1188 Piotr (dexter) Roszatycki
1192 Robert (phaylon) Sedlacek
1196 Sam (mugwump) Vilain
1198 Scott (konobi) McWhirter
1200 Shawn (Sartak) Moore
1202 Shlomi (rindolf) Fish
1206 Wallace (wreis) Reis
1208 ... and many other #moose folks