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';
157 Moose->throw_error("The Metaclass $metaclass must be a subclass of Moose::Meta::Class.")
158 unless $metaclass->isa('Moose::Meta::Class');
160 # make a subtype for each Moose class
162 unless find_type_constraint($class);
166 if ( $meta = Class::MOP::get_metaclass_by_name($class) ) {
167 unless ( $meta->isa("Moose::Meta::Class") ) {
168 my $error_message = "$class already has a metaclass, but it does not inherit $metaclass ($meta).";
169 if ( $meta->isa('Moose::Meta::Role') ) {
170 Moose->throw_error($error_message . ' You cannot make the same thing a role and a class. Remove either Moose or Moose::Role.');
172 Moose->throw_error($error_message);
176 # no metaclass, no 'meta' method
178 # now we check whether our ancestors have metaclass, and if so borrow that
179 my ( undef, @isa ) = @{ mro::get_linear_isa($class) };
181 foreach my $ancestor ( @isa ) {
182 my $ancestor_meta = Class::MOP::get_metaclass_by_name($ancestor) || next;
184 my $ancestor_meta_class = ($ancestor_meta->is_immutable
185 ? $ancestor_meta->_get_mutable_metaclass_name
186 : ref($ancestor_meta));
188 # if we have an ancestor metaclass that inherits $metaclass, we use
189 # that. This is like _fix_metaclass_incompatibility, but we can do it now.
191 # the case of having an ancestry is not very common, but arises in
193 unless ( $metaclass->isa( $ancestor_meta_class ) ) {
194 if ( $ancestor_meta_class->isa($metaclass) ) {
195 $metaclass = $ancestor_meta_class;
200 $meta = $metaclass->initialize($class);
203 if ( $class->can('meta') ) {
204 # check 'meta' method
206 # it may be inherited
209 # this is the case where the metaclass pragma
210 # was used before the 'use Moose' statement to
211 # override a specific class
212 my $method_meta = $class->meta;
214 ( blessed($method_meta) && $method_meta->isa('Moose::Meta::Class') )
215 || Moose->throw_error("$class already has a &meta function, but it does not return a Moose::Meta::Class ($method_meta)");
217 $meta = $method_meta;
220 unless ( $meta->has_method("meta") ) { # don't overwrite
221 # also check for inherited non moose 'meta' method?
222 # FIXME also skip this if the user requested by passing an option
225 # re-initialize so it inherits properly
226 $metaclass->initialize( ref($_[0]) || $_[0] );
231 # make sure they inherit from Moose::Object
232 $meta->superclasses($base_class)
233 unless $meta->superclasses();
238 # This may be used in some older MooseX extensions.
240 goto &Moose::Exporter::_get_caller;
243 ## make 'em all immutable
246 inline_constructor => 1,
247 constructor_name => "_new",
248 # these are Class::MOP accessors, so they need inlining
249 inline_accessors => 1
250 ) for grep { $_->is_mutable }
253 Moose::Meta::Attribute
255 Moose::Meta::Instance
257 Moose::Meta::TypeCoercion
258 Moose::Meta::TypeCoercion::Union
261 Moose::Meta::Method::Accessor
262 Moose::Meta::Method::Constructor
263 Moose::Meta::Method::Destructor
264 Moose::Meta::Method::Overridden
265 Moose::Meta::Method::Augmented
268 Moose::Meta::Role::Attribute
269 Moose::Meta::Role::Method
270 Moose::Meta::Role::Method::Required
271 Moose::Meta::Role::Method::Conflicting
273 Moose::Meta::Role::Composite
275 Moose::Meta::Role::Application
276 Moose::Meta::Role::Application::RoleSummation
277 Moose::Meta::Role::Application::ToClass
278 Moose::Meta::Role::Application::ToRole
279 Moose::Meta::Role::Application::ToInstance
282 Moose::Meta::Mixin::AttributeCore->meta->make_immutable(
283 inline_constructor => 0,
284 constructor_name => undef,
295 Moose - A postmodern object system for Perl 5
300 use Moose; # automatically turns on strict and warnings
302 has 'x' => (is => 'rw', isa => 'Int');
303 has 'y' => (is => 'rw', isa => 'Int');
316 has 'z' => (is => 'rw', isa => 'Int');
318 after 'clear' => sub {
325 Moose is an extension of the Perl 5 object system.
327 The main goal of Moose is to make Perl 5 Object Oriented programming
328 easier, more consistent and less tedious. With Moose you can to think
329 more about what you want to do and less about the mechanics of OOP.
331 Additionally, Moose is built on top of L<Class::MOP>, which is a
332 metaclass system for Perl 5. This means that Moose not only makes
333 building normal Perl 5 objects better, but it provides the power of
334 metaclass programming as well.
338 If you're new to Moose, the best place to start is the
339 L<Moose::Manual> docs, followed by the L<Moose::Cookbook>. The intro
340 will show you what Moose is, and how it makes Perl 5 OO better.
342 The cookbook recipes on Moose basics will get you up to speed with
343 many of Moose's features quickly. Once you have an idea of what Moose
344 can do, you can use the API documentation to get more detail on
345 features which interest you.
347 =head2 Moose Extensions
349 The C<MooseX::> namespace is the official place to find Moose extensions.
350 These extensions can be found on the CPAN. The easiest way to find them
351 is to search for them (L<http://search.cpan.org/search?query=MooseX::>),
352 or to examine L<Task::Moose> which aims to keep an up-to-date, easily
353 installable list of Moose extensions.
357 Much of the Moose documentation has been translated into other languages.
363 Japanese docs can be found at
364 L<http://perldoc.perlassociation.org/pod/Moose-Doc-JA/index.html>. The
365 source POD files can be found in GitHub:
366 L<http://github.com/jpa/Moose-Doc-JA>
370 =head1 BUILDING CLASSES WITH MOOSE
372 Moose makes every attempt to provide as much convenience as possible during
373 class construction/definition, but still stay out of your way if you want it
374 to. Here are a few items to note when building classes with Moose.
376 When you C<use Moose>, Moose will set the class's parent class to
377 L<Moose::Object>, I<unless> the class using Moose already has a parent
378 class. In addition, specifying a parent with C<extends> will change the parent
381 Moose will also manage all attributes (including inherited ones) that are
382 defined with C<has>. And (assuming you call C<new>, which is inherited from
383 L<Moose::Object>) this includes properly initializing all instance slots,
384 setting defaults where appropriate, and performing any type constraint checking
387 =head1 PROVIDED METHODS
389 Moose provides a number of methods to all your classes, mostly through the
390 inheritance of L<Moose::Object>. There is however, one exception.
396 This is a method which provides access to the current class's metaclass.
400 =head1 EXPORTED FUNCTIONS
402 Moose will export a number of functions into the class's namespace which
403 may then be used to set up the class. These functions all work directly
404 on the current class.
408 =item B<extends (@superclasses)>
410 This function will set the superclass(es) for the current class.
412 This approach is recommended instead of C<use base>, because C<use base>
413 actually C<push>es onto the class's C<@ISA>, whereas C<extends> will
414 replace it. This is important to ensure that classes which do not have
415 superclasses still properly inherit from L<Moose::Object>.
417 Each superclass can be followed by a hash reference with options. Currently,
418 only L<-version|Class::MOP/Class Loading Options> is recognized:
420 extends 'My::Parent' => { -version => 0.01 },
421 'My::OtherParent' => { -version => 0.03 };
423 An exception will be thrown if the version requirements are not
426 =item B<with (@roles)>
428 This will apply a given set of C<@roles> to the local class.
430 Like with C<extends>, each specified role can be followed by a hash
431 reference with a L<-version|Class::MOP/Class Loading Options> option:
433 with 'My::Role' => { -version => 0.32 },
434 'My::Otherrole' => { -version => 0.23 };
436 The specified version requirements must be satisfied, otherwise an
437 exception will be thrown.
439 If your role takes options or arguments, they can be passed along in the
440 hash reference as well.
442 =item B<has $name|@$names =E<gt> %options>
444 This will install an attribute of a given C<$name> into the current class. If
445 the first parameter is an array reference, it will create an attribute for
446 every C<$name> in the list. The C<%options> are the same as those provided by
447 L<Class::MOP::Attribute>, in addition to the list below which are provided by
448 Moose (L<Moose::Meta::Attribute> to be more specific):
452 =item I<is =E<gt> 'rw'|'ro'>
454 The I<is> option accepts either I<rw> (for read/write) or I<ro> (for read
455 only). These will create either a read/write accessor or a read-only
456 accessor respectively, using the same name as the C<$name> of the attribute.
458 If you need more control over how your accessors are named, you can
459 use the L<reader|Class::MOP::Attribute/reader>,
460 L<writer|Class::MOP::Attribute/writer> and
461 L<accessor|Class::MOP::Attribute/accessor> options inherited from
462 L<Class::MOP::Attribute>, however if you use those, you won't need the
465 =item I<isa =E<gt> $type_name>
467 The I<isa> option uses Moose's type constraint facilities to set up runtime
468 type checking for this attribute. Moose will perform the checks during class
469 construction, and within any accessors. The C<$type_name> argument must be a
470 string. The string may be either a class name or a type defined using
471 Moose's type definition features. (Refer to L<Moose::Util::TypeConstraints>
472 for information on how to define a new type, and how to retrieve type meta-data).
474 =item I<coerce =E<gt> (1|0)>
476 This will attempt to use coercion with the supplied type constraint to change
477 the value passed into any accessors or constructors. You B<must> supply a type
478 constraint, and that type constraint B<must> define a coercion. See
479 L<Moose::Cookbook::Basics::Recipe5> for an example.
481 =item I<does =E<gt> $role_name>
483 This will accept the name of a role which the value stored in this attribute
484 is expected to have consumed.
486 =item I<required =E<gt> (1|0)>
488 This marks the attribute as being required. This means a value must be
489 supplied during class construction, I<or> the attribute must be lazy
490 and have either a default or a builder. Note that c<required> does not
491 say anything about the attribute's value, which can be C<undef>.
493 =item I<weak_ref =E<gt> (1|0)>
495 This will tell the class to store the value of this attribute as a weakened
496 reference. If an attribute is a weakened reference, it B<cannot> also be
499 =item I<lazy =E<gt> (1|0)>
501 This will tell the class to not create this slot until absolutely necessary.
502 If an attribute is marked as lazy it B<must> have a default supplied.
504 =item I<auto_deref =E<gt> (1|0)>
506 This tells the accessor to automatically dereference the value of this
507 attribute when called in list context. The accessor will still return a
508 reference when called in scalar context. If this behavior isn't desirable,
509 L<Moose::Meta::Attribute::Native::Trait::Array/elements> or
510 L<Moose::Meta::Attribute::Native::Trait::Hash/elements> may be a better
511 choice. The I<auto_deref> option is only legal if your I<isa> option is
512 either C<ArrayRef> or C<HashRef>.
514 =item I<trigger =E<gt> $code>
516 The I<trigger> option is a CODE reference which will be called after
517 the value of the attribute is set. The CODE ref is passed the
518 instance itself, the updated value, and the original value if the
519 attribute was already set.
521 You B<can> have a trigger on a read-only attribute.
523 B<NOTE:> Triggers will only fire when you B<assign> to the attribute,
524 either in the constructor, or using the writer. Default and built values will
525 B<not> cause the trigger to be fired.
527 =item I<handles =E<gt> ARRAY | HASH | REGEXP | ROLE | ROLETYPE | DUCKTYPE | CODE>
529 The I<handles> option provides Moose classes with automated delegation features.
530 This is a pretty complex and powerful option. It accepts many different option
531 formats, each with its own benefits and drawbacks.
533 B<NOTE:> The class being delegated to does not need to be a Moose based class,
534 which is why this feature is especially useful when wrapping non-Moose classes.
536 All I<handles> option formats share the following traits:
538 You cannot override a locally defined method with a delegated method; an
539 exception will be thrown if you try. That is to say, if you define C<foo> in
540 your class, you cannot override it with a delegated C<foo>. This is almost never
541 something you would want to do, and if it is, you should do it by hand and not
544 You cannot override any of the methods found in Moose::Object, or the C<BUILD>
545 and C<DEMOLISH> methods. These will not throw an exception, but will silently
546 move on to the next method in the list. My reasoning for this is that you would
547 almost never want to do this, since it usually breaks your class. As with
548 overriding locally defined methods, if you do want to do this, you should do it
549 manually, not with Moose.
551 You do not I<need> to have a reader (or accessor) for the attribute in order
552 to delegate to it. Moose will create a means of accessing the value for you,
553 however this will be several times B<less> efficient then if you had given
554 the attribute a reader (or accessor) to use.
556 Below is the documentation for each option format:
562 This is the most common usage for I<handles>. You basically pass a list of
563 method names to be delegated, and Moose will install a delegation method
568 This is the second most common usage for I<handles>. Instead of a list of
569 method names, you pass a HASH ref where each key is the method name you
570 want installed locally, and its value is the name of the original method
571 in the class being delegated to.
573 This can be very useful for recursive classes like trees. Here is a
574 quick example (soon to be expanded into a Moose::Cookbook recipe):
579 has 'node' => (is => 'rw', isa => 'Any');
584 default => sub { [] }
592 parent_node => 'node',
593 siblings => 'children',
597 In this example, the Tree package gets C<parent_node> and C<siblings> methods,
598 which delegate to the C<node> and C<children> methods (respectively) of the Tree
599 instance stored in the C<parent> slot.
601 You may also use an array reference to curry arguments to the original method.
605 handles => { set_foo => [ set => 'foo' ] },
608 # $self->set_foo(...) calls $self->thing->set('foo', ...)
610 The first element of the array reference is the original method name, and the
611 rest is a list of curried arguments.
615 The regexp option works very similar to the ARRAY option, except that it builds
616 the list of methods for you. It starts by collecting all possible methods of the
617 class being delegated to, then filters that list using the regexp supplied here.
619 B<NOTE:> An I<isa> option is required when using the regexp option format. This
620 is so that we can determine (at compile time) the method list from the class.
621 Without an I<isa> this is just not possible.
623 =item C<ROLE> or C<ROLETYPE>
625 With the role option, you specify the name of a role or a
626 L<role type|Moose::Meta::TypeConstraint::Role> whose "interface" then becomes
627 the list of methods to handle. The "interface" can be defined as; the methods
628 of the role and any required methods of the role. It should be noted that this
629 does B<not> include any method modifiers or generated attribute methods (which
630 is consistent with role composition).
634 With the duck type option, you pass a duck type object whose "interface" then
635 becomes the list of methods to handle. The "interface" can be defined as; the
636 list of methods passed to C<duck_type> to create a duck type object. For more
637 information on C<duck_type> please check
638 L<Moose::Util::TypeConstraints>.
642 This is the option to use when you really want to do something funky. You should
643 only use it if you really know what you are doing, as it involves manual
646 This takes a code reference, which should expect two arguments. The first is the
647 attribute meta-object this I<handles> is attached to. The second is the
648 metaclass of the class being delegated to. It expects you to return a hash (not
649 a HASH ref) of the methods you want mapped.
653 =item I<metaclass =E<gt> $metaclass_name>
655 This tells the class to use a custom attribute metaclass for this particular
656 attribute. Custom attribute metaclasses are useful for extending the
657 capabilities of the I<has> keyword: they are the simplest way to extend the MOP,
658 but they are still a fairly advanced topic and too much to cover here, see
659 L<Moose::Cookbook::Meta::Recipe1> for more information.
661 See L<Metaclass and Trait Name Resolution> for details on how a metaclass name
662 is resolved to a class name.
664 =item I<traits =E<gt> [ @role_names ]>
666 This tells Moose to take the list of C<@role_names> and apply them to the
667 attribute meta-object. This is very similar to the I<metaclass> option, but
668 allows you to use more than one extension at a time.
670 See L<Metaclass and Trait Name Resolution> for details on how a trait name is
671 resolved to a role name.
673 Also see L<Moose::Cookbook::Meta::Recipe3> for a metaclass trait
676 =item I<builder> => Str
678 The value of this key is the name of the method that will be called to
679 obtain the value used to initialize the attribute. See the L<builder
680 option docs in Class::MOP::Attribute|Class::MOP::Attribute/builder>
681 and/or L<Moose::Cookbook::Basics::Recipe8> for more information.
683 =item I<default> => SCALAR | CODE
685 The value of this key is the default value which will initialize the attribute.
687 NOTE: If the value is a simple scalar (string or number), then it can
688 be just passed as is. However, if you wish to initialize it with a
689 HASH or ARRAY ref, then you need to wrap that inside a CODE reference.
690 See the L<default option docs in
691 Class::MOP::Attribute|Class::MOP::Attribute/default> for more
694 =item I<clearer> => Str
696 Creates a method allowing you to clear the value, see the L<clearer option
697 docs in Class::MOP::Attribute|Class::MOP::Attribute/clearer> for more
700 =item I<predicate> => Str
702 Creates a method to perform a basic test to see if a value has been set in the
703 attribute, see the L<predicate option docs in
704 Class::MOP::Attribute|Class::MOP::Attribute/predicate> for more information.
706 =item I<lazy_build> => (0|1)
708 Automatically define lazy => 1 as well as builder => "_build_$attr", clearer =>
709 "clear_$attr', predicate => 'has_$attr' unless they are already defined.
711 =item I<initializer> => Str
713 This may be a method name (referring to a method on the class with
714 this attribute) or a CODE ref. The initializer is used to set the
715 attribute value on an instance when the attribute is set during
716 instance initialization (but not when the value is being assigned
717 to). See the L<initializer option docs in
718 Class::MOP::Attribute|Class::MOP::Attribute/initializer> for more
721 =item I<documentation> => $string
723 An arbitrary string that can be retrieved later by calling C<<
724 $attr->documentation >>.
730 =item B<has +$name =E<gt> %options>
732 This is variation on the normal attribute creator C<has> which allows you to
733 clone and extend an attribute from a superclass or from a role. Here is an
734 example of the superclass usage:
742 default => 'Hello, I am a Foo'
750 has '+message' => (default => 'Hello I am My::Foo');
752 What is happening here is that B<My::Foo> is cloning the C<message> attribute
753 from its parent class B<Foo>, retaining the C<is =E<gt> 'rw'> and C<isa =E<gt>
754 'Str'> characteristics, but changing the value in C<default>.
756 Here is another example, but within the context of a role:
764 default => 'Hello, I am a Foo'
772 has '+message' => (default => 'Hello I am My::Foo');
774 In this case, we are basically taking the attribute which the role supplied
775 and altering it within the bounds of this feature.
777 Note that you can only extend an attribute from either a superclass or a role,
778 you cannot extend an attribute in a role that composes over an attribute from
781 Aside from where the attributes come from (one from superclass, the other
782 from a role), this feature works exactly the same. This feature is restricted
783 somewhat, so as to try and force at least I<some> sanity into it. You are only
784 allowed to change the following attributes:
790 Change the default value of an attribute.
794 Change whether the attribute attempts to coerce a value passed to it.
798 Change if the attribute is required to have a value.
800 =item I<documentation>
802 Change the documentation string associated with the attribute.
806 Change if the attribute lazily initializes the slot.
810 You I<are> allowed to change the type without restriction.
812 It is recommended that you use this freedom with caution. We used to
813 only allow for extension only if the type was a subtype of the parent's
814 type, but we felt that was too restrictive and is better left as a
819 You are allowed to B<add> a new C<handles> definition, but you are B<not>
820 allowed to I<change> one.
824 You are allowed to B<add> a new C<builder> definition, but you are B<not>
825 allowed to I<change> one.
829 You are allowed to B<add> a new C<metaclass> definition, but you are
830 B<not> allowed to I<change> one.
834 You are allowed to B<add> additional traits to the C<traits> definition.
835 These traits will be composed into the attribute, but preexisting traits
836 B<are not> overridden, or removed.
840 =item B<before $name|@names|\@names|qr/.../ =E<gt> sub { ... }>
842 =item B<after $name|@names|\@names|qr/.../ =E<gt> sub { ... }>
844 =item B<around $name|@names|\@names|qr/.../ =E<gt> sub { ... }>
846 These three items are syntactic sugar for the before, after, and around method
847 modifier features that L<Class::MOP> provides. More information on these may be
848 found in L<Moose::Manual::MethodModifiers> and the
849 L<Class::MOP::Class documentation|Class::MOP::Class/"Method Modifiers">.
853 The keyword C<super> is a no-op when called outside of an C<override> method. In
854 the context of an C<override> method, it will call the next most appropriate
855 superclass method with the same arguments as the original method.
857 =item B<override ($name, &sub)>
859 An C<override> method is a way of explicitly saying "I am overriding this
860 method from my superclass". You can call C<super> within this method, and
861 it will work as expected. The same thing I<can> be accomplished with a normal
862 method call and the C<SUPER::> pseudo-package; it is really your choice.
866 The keyword C<inner>, much like C<super>, is a no-op outside of the context of
867 an C<augment> method. You can think of C<inner> as being the inverse of
868 C<super>; the details of how C<inner> and C<augment> work is best described in
869 the L<Moose::Cookbook::Basics::Recipe6>.
871 =item B<augment ($name, &sub)>
873 An C<augment> method, is a way of explicitly saying "I am augmenting this
874 method from my superclass". Once again, the details of how C<inner> and
875 C<augment> work is best described in the L<Moose::Cookbook::Basics::Recipe6>.
879 This is the C<Carp::confess> function, and exported here because I use it
884 This is the C<Scalar::Util::blessed> function, it is exported here because I
885 use it all the time. It is highly recommended that this is used instead of
886 C<ref> anywhere you need to test for an object's class name.
892 When you use Moose, you can specify which metaclass to use:
894 use Moose -metaclass => 'My::Meta::Class';
896 You can also specify traits which will be applied to your metaclass:
898 use Moose -traits => 'My::Trait';
900 This is very similar to the attribute traits feature. When you do
901 this, your class's C<meta> object will have the specified traits
902 applied to it. See L<Metaclass and Trait Name Resolution> for more
905 =head2 Metaclass and Trait Name Resolution
907 By default, when given a trait name, Moose simply tries to load a
908 class of the same name. If such a class does not exist, it then looks
909 for for a class matching
910 B<Moose::Meta::$type::Custom::Trait::$trait_name>. The C<$type>
911 variable here will be one of B<Attribute> or B<Class>, depending on
912 what the trait is being applied to.
914 If a class with this long name exists, Moose checks to see if it has
915 the method C<register_implementation>. This method is expected to
916 return the I<real> class name of the trait. If there is no
917 C<register_implementation> method, it will fall back to using
918 B<Moose::Meta::$type::Custom::Trait::$trait> as the trait name.
920 The lookup method for metaclasses is the same, except that it looks
921 for a class matching B<Moose::Meta::$type::Custom::$metaclass_name>.
923 If all this is confusing, take a look at
924 L<Moose::Cookbook::Meta::Recipe3>, which demonstrates how to create an
927 =head1 UNIMPORTING FUNCTIONS
931 Moose offers a way to remove the keywords it exports, through the C<unimport>
932 method. You simply have to say C<no Moose> at the bottom of your code for this
933 to work. Here is an example:
938 has 'first_name' => (is => 'rw', isa => 'Str');
939 has 'last_name' => (is => 'rw', isa => 'Str');
943 $self->first_name . ' ' . $self->last_name
946 no Moose; # keywords are removed from the Person package
948 =head1 EXTENDING AND EMBEDDING MOOSE
950 To learn more about extending Moose, we recommend checking out the
951 "Extending" recipes in the L<Moose::Cookbook>, starting with
952 L<Moose::Cookbook::Extending::Recipe1>, which provides an overview of
953 all the different ways you might extend Moose.
955 =head2 B<< Moose->init_meta(for_class => $class, base_class => $baseclass, metaclass => $metaclass) >>
957 The C<init_meta> method sets up the metaclass object for the class
958 specified by C<for_class>. This method injects a a C<meta> accessor
959 into the class so you can get at this object. It also sets the class's
960 superclass to C<base_class>, with L<Moose::Object> as the default.
962 C<init_meta> returns the metaclass object for C<$class>.
964 You can specify an alternate metaclass with the C<metaclass> option.
966 For more detail on this topic, see L<Moose::Cookbook::Extending::Recipe2>.
968 This method used to be documented as a function which accepted
969 positional parameters. This calling style will still work for
970 backwards compatibility, but is deprecated.
974 Moose's C<import> method supports the L<Sub::Exporter> form of C<{into =E<gt> $pkg}>
975 and C<{into_level =E<gt> 1}>.
977 B<NOTE>: Doing this is more or less deprecated. Use L<Moose::Exporter>
978 instead, which lets you stack multiple C<Moose.pm>-alike modules
979 sanely. It handles getting the exported functions into the right place
982 =head2 B<throw_error>
984 An alias for C<confess>, used by internally by Moose.
986 =head2 The MooseX:: namespace
988 Generally if you're writing an extension I<for> Moose itself you'll want
989 to put your extension in the C<MooseX::> namespace. This namespace is
990 specifically for extensions that make Moose better or different in some
991 fundamental way. It is traditionally B<not> for a package that just happens
992 to use Moose. This namespace follows from the examples of the C<LWPx::>
993 and C<DBIx::> namespaces that perform the same function for C<LWP> and C<DBI>
996 =head1 METACLASS COMPATIBILITY AND MOOSE
998 Metaclass compatibility is a thorny subject. You should start by
999 reading the "About Metaclass compatibility" section in the
1002 Moose will attempt to resolve a few cases of metaclass incompatibility
1003 when you set the superclasses for a class, in addition to the cases that
1004 C<Class::MOP> handles.
1006 Moose tries to determine if the metaclasses only "differ by roles". This
1007 means that the parent and child's metaclass share a common ancestor in
1008 their respective hierarchies, and that the subclasses under the common
1009 ancestor are only different because of role applications. This case is
1010 actually fairly common when you mix and match various C<MooseX::*>
1011 modules, many of which apply roles to the metaclass.
1013 If the parent and child do differ by roles, Moose replaces the
1014 metaclass in the child with a newly created metaclass. This metaclass
1015 is a subclass of the parent's metaclass, does all of the roles that
1016 the child's metaclass did before being replaced. Effectively, this
1017 means the new metaclass does all of the roles done by both the
1018 parent's and child's original metaclasses.
1020 Ultimately, this is all transparent to you except in the case of an
1021 unresolvable conflict.
1029 It should be noted that C<super> and C<inner> B<cannot> be used in the same
1030 method. However, they may be combined within the same class hierarchy; see
1031 F<t/014_override_augment_inner_super.t> for an example.
1033 The reason for this is that C<super> is only valid within a method
1034 with the C<override> modifier, and C<inner> will never be valid within an
1035 C<override> method. In fact, C<augment> will skip over any C<override> methods
1036 when searching for its appropriate C<inner>.
1038 This might seem like a restriction, but I am of the opinion that keeping these
1039 two features separate (yet interoperable) actually makes them easy to use, since
1040 their behavior is then easier to predict. Time will tell whether I am right or
1041 not (UPDATE: so far so good).
1047 We offer both a mailing list and a very active IRC channel.
1049 The mailing list is L<moose@perl.org>. You must be subscribed to send
1050 a message. To subscribe, send an empty message to
1051 L<moose-subscribe@perl.org>
1053 You can also visit us at C<#moose> on L<irc://irc.perl.org/#moose>
1054 This channel is quite active, and questions at all levels (on Moose-related
1055 topics ;) are welcome.
1057 =head1 ACKNOWLEDGEMENTS
1061 =item I blame Sam Vilain for introducing me to the insanity that is meta-models.
1063 =item I blame Audrey Tang for then encouraging my meta-model habit in #perl6.
1065 =item Without Yuval "nothingmuch" Kogman this module would not be possible,
1066 and it certainly wouldn't have this name ;P
1068 =item The basis of the TypeContraints module was Rob Kinyon's idea
1069 originally, I just ran with it.
1071 =item Thanks to mst & chansen and the whole #moose posse for all the
1072 early ideas/feature-requests/encouragement/bug-finding.
1074 =item Thanks to David "Theory" Wheeler for meta-discussions and spelling fixes.
1082 =item L<http://www.iinteractive.com/moose>
1084 This is the official web home of Moose, it contains links to our public git repository
1085 as well as links to a number of talks and articles on Moose and Moose related
1088 =item The Moose is flying, a tutorial by Randal Schwartz
1090 Part 1 - L<http://www.stonehenge.com/merlyn/LinuxMag/col94.html>
1092 Part 2 - L<http://www.stonehenge.com/merlyn/LinuxMag/col95.html>
1094 =item Several Moose extension modules in the C<MooseX::> namespace.
1096 See L<http://search.cpan.org/search?query=MooseX::> for extensions.
1098 =item Moose stats on ohloh.net - L<http://www.ohloh.net/projects/moose>
1106 =item The Art of the MetaObject Protocol
1108 I mention this in the L<Class::MOP> docs too, this book was critical in
1109 the development of both modules and is highly recommended.
1117 =item L<http://www.cs.utah.edu/plt/publications/oopsla04-gff.pdf>
1119 This paper (suggested by lbr on #moose) was what lead to the implementation
1120 of the C<super>/C<override> and C<inner>/C<augment> features. If you really
1121 want to understand them, I suggest you read this.
1127 All complex software has bugs lurking in it, and this module is no
1130 Please report any bugs to C<bug-moose@rt.cpan.org>, or through the web
1131 interface at L<http://rt.cpan.org>.
1133 You can also discuss feature requests or possible bugs on the Moose mailing
1134 list (moose@perl.org) or on IRC at L<irc://irc.perl.org/#moose>.
1136 =head1 FEATURE REQUESTS
1138 We are very strict about what features we add to the Moose core, especially
1139 the user-visible features. Instead we have made sure that the underlying
1140 meta-system of Moose is as extensible as possible so that you can add your
1141 own features easily.
1143 That said, occasionally there is a feature needed in the meta-system
1144 to support your planned extension, in which case you should either
1145 email the mailing list (moose@perl.org) or join us on IRC at
1146 L<irc://irc.perl.org/#moose> to discuss. The
1147 L<Moose::Manual::Contributing> has more detail about how and when you
1152 Moose is an open project, there are at this point dozens of people who have
1153 contributed, and can contribute. If you have added anything to the Moose
1154 project you have a commit bit on this file and can add your name to the list.
1158 However there are only a few people with the rights to release a new version
1159 of Moose. The Moose Cabal are the people to go to with questions regarding
1160 the wider purview of Moose, and help out maintaining not just the code
1161 but the community as well.
1163 Stevan (stevan) Little E<lt>stevan@iinteractive.comE<gt>
1165 Jesse (doy) Luehrs E<lt>doy at tozt dot netE<gt>
1167 Yuval (nothingmuch) Kogman
1169 Shawn (sartak) Moore E<lt>sartak@bestpractical.comE<gt>
1171 Hans Dieter (confound) Pearcey E<lt>hdp@pobox.comE<gt>
1173 Chris (perigrin) Prather
1175 Florian Ragwitz E<lt>rafl@debian.orgE<gt>
1177 Dave (autarch) Rolsky E<lt>autarch@urth.orgE<gt>
1179 =head2 OTHER CONTRIBUTORS
1183 Adam (Alias) Kennedy
1185 Anders (Debolaz) Nor Berle
1187 Nathan (kolibrie) Gray
1189 Christian (chansen) Hansen
1191 Eric (ewilhelm) Wilhelm
1193 Guillermo (groditi) Roditi
1195 Jess (castaway) Robinson
1199 Robert (phaylon) Sedlacek
1203 Scott (konobi) McWhirter
1205 Shlomi (rindolf) Fish
1207 Wallace (wreis) Reis
1209 Jonathan (jrockway) Rockway
1211 Piotr (dexter) Roszatycki
1213 Sam (mugwump) Vilain
1217 Dylan Hardison (doc fixes)
1219 ... and many other #moose folks
1221 =head1 COPYRIGHT AND LICENSE
1223 Copyright 2006-2010 by Infinity Interactive, Inc.
1225 L<http://www.iinteractive.com>
1227 This library is free software; you can redistribute it and/or modify
1228 it under the same terms as Perl itself.