8 $VERSION = eval $VERSION;
9 our $AUTHORITY = 'cpan:STEVAN';
11 use Scalar::Util 'blessed';
18 use Moose::Meta::Class;
19 use Moose::Meta::TypeConstraint;
20 use Moose::Meta::TypeCoercion;
21 use Moose::Meta::Attribute;
22 use Moose::Meta::Instance;
26 use Moose::Meta::Role;
27 use Moose::Meta::Role::Composite;
28 use Moose::Meta::Role::Application;
29 use Moose::Meta::Role::Application::RoleSummation;
30 use Moose::Meta::Role::Application::ToClass;
31 use Moose::Meta::Role::Application::ToRole;
32 use Moose::Meta::Role::Application::ToInstance;
34 use Moose::Util::TypeConstraints;
37 use Moose::Meta::Attribute::Native;
48 Moose->throw_error("Must derive at least one class") unless @_;
50 # this checks the metaclass to make sure
51 # it is correct, sometimes it can get out
52 # of sync when the classes are being built
53 $meta->superclasses(@_);
57 Moose::Util::apply_all_roles(shift, @_);
64 Moose->throw_error('Usage: has \'name\' => ( key => value, ... )')
67 my %options = ( definition_context => Moose::Util::_caller_info(), @_ );
68 my $attrs = ( ref($name) eq 'ARRAY' ) ? $name : [ ($name) ];
69 $meta->add_attribute( $_, %options ) for @$attrs;
73 Moose::Util::add_method_modifier(shift, 'before', \@_);
77 Moose::Util::add_method_modifier(shift, 'after', \@_);
81 Moose::Util::add_method_modifier(shift, 'around', \@_);
89 # This check avoids a recursion loop - see
90 # t/100_bugs/020_super_recursion.t
91 return if defined $SUPER_PACKAGE && $SUPER_PACKAGE ne caller();
92 return unless $SUPER_BODY; $SUPER_BODY->(@SUPER_ARGS);
97 my ( $name, $method ) = @_;
98 $meta->add_override_method_modifier( $name => $method );
103 our ( %INNER_BODY, %INNER_ARGS );
105 if ( my $body = $INNER_BODY{$pkg} ) {
106 my @args = @{ $INNER_ARGS{$pkg} };
107 local $INNER_ARGS{$pkg};
108 local $INNER_BODY{$pkg};
109 return $body->(@args);
117 my ( $name, $method ) = @_;
118 $meta->add_augment_method_modifier( $name => $method );
121 Moose::Exporter->setup_import_methods(
123 qw( extends with has before after around override augment )
128 \&Scalar::Util::blessed,
133 # This used to be called as a function. This hack preserves
134 # backwards compatibility.
135 if ( $_[0] ne __PACKAGE__ ) {
136 return __PACKAGE__->init_meta(
146 my $class = $args{for_class}
147 or Moose->throw_error("Cannot call init_meta without specifying a for_class");
148 my $base_class = $args{base_class} || 'Moose::Object';
149 my $metaclass = $args{metaclass} || 'Moose::Meta::Class';
151 Moose->throw_error("The Metaclass $metaclass must be a subclass of Moose::Meta::Class.")
152 unless $metaclass->isa('Moose::Meta::Class');
154 # make a subtype for each Moose class
156 unless find_type_constraint($class);
160 if ( $meta = Class::MOP::get_metaclass_by_name($class) ) {
161 unless ( $meta->isa("Moose::Meta::Class") ) {
162 my $error_message = "$class already has a metaclass, but it does not inherit $metaclass ($meta).";
163 if ( $meta->isa('Moose::Meta::Role') ) {
164 Moose->throw_error($error_message . ' You cannot make the same thing a role and a class. Remove either Moose or Moose::Role.');
166 Moose->throw_error($error_message);
170 # no metaclass, no 'meta' method
172 # now we check whether our ancestors have metaclass, and if so borrow that
173 my ( undef, @isa ) = @{ $class->mro::get_linear_isa };
175 foreach my $ancestor ( @isa ) {
176 my $ancestor_meta = Class::MOP::get_metaclass_by_name($ancestor) || next;
178 my $ancestor_meta_class = ($ancestor_meta->is_immutable
179 ? $ancestor_meta->_get_mutable_metaclass_name
180 : ref($ancestor_meta));
182 # if we have an ancestor metaclass that inherits $metaclass, we use
183 # that. This is like _fix_metaclass_incompatibility, but we can do it now.
185 # the case of having an ancestry is not very common, but arises in
187 unless ( $metaclass->isa( $ancestor_meta_class ) ) {
188 if ( $ancestor_meta_class->isa($metaclass) ) {
189 $metaclass = $ancestor_meta_class;
194 $meta = $metaclass->initialize($class);
197 if ( $class->can('meta') ) {
198 # check 'meta' method
200 # it may be inherited
203 # this is the case where the metaclass pragma
204 # was used before the 'use Moose' statement to
205 # override a specific class
206 my $method_meta = $class->meta;
208 ( blessed($method_meta) && $method_meta->isa('Moose::Meta::Class') )
209 || Moose->throw_error("$class already has a &meta function, but it does not return a Moose::Meta::Class ($method_meta)");
211 $meta = $method_meta;
214 unless ( $meta->has_method("meta") ) { # don't overwrite
215 # also check for inherited non moose 'meta' method?
216 # FIXME also skip this if the user requested by passing an option
219 # re-initialize so it inherits properly
220 $metaclass->initialize( ref($_[0]) || $_[0] );
225 # make sure they inherit from Moose::Object
226 $meta->superclasses($base_class)
227 unless $meta->superclasses();
232 # This may be used in some older MooseX extensions.
234 goto &Moose::Exporter::_get_caller;
237 ## make 'em all immutable
240 inline_constructor => 1,
241 constructor_name => "_new",
242 # these are Class::MOP accessors, so they need inlining
243 inline_accessors => 1
244 ) for grep { $_->is_mutable }
247 Moose::Meta::Attribute
249 Moose::Meta::Instance
251 Moose::Meta::TypeCoercion
252 Moose::Meta::TypeCoercion::Union
255 Moose::Meta::Method::Accessor
256 Moose::Meta::Method::Constructor
257 Moose::Meta::Method::Destructor
258 Moose::Meta::Method::Overridden
259 Moose::Meta::Method::Augmented
262 Moose::Meta::Role::Method
263 Moose::Meta::Role::Method::Required
264 Moose::Meta::Role::Method::Conflicting
266 Moose::Meta::Role::Composite
268 Moose::Meta::Role::Application
269 Moose::Meta::Role::Application::RoleSummation
270 Moose::Meta::Role::Application::ToClass
271 Moose::Meta::Role::Application::ToRole
272 Moose::Meta::Role::Application::ToInstance
283 Moose - A postmodern object system for Perl 5
288 use Moose; # automatically turns on strict and warnings
290 has 'x' => (is => 'rw', isa => 'Int');
291 has 'y' => (is => 'rw', isa => 'Int');
304 has 'z' => (is => 'rw', isa => 'Int');
306 after 'clear' => sub {
313 Moose is an extension of the Perl 5 object system.
315 The main goal of Moose is to make Perl 5 Object Oriented programming
316 easier, more consistent and less tedious. With Moose you can to think
317 more about what you want to do and less about the mechanics of OOP.
319 Additionally, Moose is built on top of L<Class::MOP>, which is a
320 metaclass system for Perl 5. This means that Moose not only makes
321 building normal Perl 5 objects better, but it provides the power of
322 metaclass programming as well.
326 If you're new to Moose, the best place to start is the
327 L<Moose::Manual> docs, followed by the L<Moose::Cookbook>. The intro
328 will show you what Moose is, and how it makes Perl 5 OO better.
330 The cookbook recipes on Moose basics will get you up to speed with
331 many of Moose's features quickly. Once you have an idea of what Moose
332 can do, you can use the API documentation to get more detail on
333 features which interest you.
335 =head2 Moose Extensions
337 The C<MooseX::> namespace is the official place to find Moose extensions.
338 These extensions can be found on the CPAN. The easiest way to find them
339 is to search for them (L<http://search.cpan.org/search?query=MooseX::>),
340 or to examine L<Task::Moose> which aims to keep an up-to-date, easily
341 installable list of Moose extensions.
345 Much of the Moose documentation has been translated into other languages.
351 Japanese docs can be found at L<http://perldoc.perlassociation.org/pod/Moose-Doc-JA/index.html>. The source POD files can be found in GitHub: L<http://github.com/jpa/Moose-Doc-JA>
355 =head1 BUILDING CLASSES WITH MOOSE
357 Moose makes every attempt to provide as much convenience as possible during
358 class construction/definition, but still stay out of your way if you want it
359 to. Here are a few items to note when building classes with Moose.
361 Unless specified with C<extends>, any class which uses Moose will
362 inherit from L<Moose::Object>.
364 Moose will also manage all attributes (including inherited ones) that are
365 defined with C<has>. And (assuming you call C<new>, which is inherited from
366 L<Moose::Object>) this includes properly initializing all instance slots,
367 setting defaults where appropriate, and performing any type constraint checking
370 =head1 PROVIDED METHODS
372 Moose provides a number of methods to all your classes, mostly through the
373 inheritance of L<Moose::Object>. There is however, one exception.
379 This is a method which provides access to the current class's metaclass.
383 =head1 EXPORTED FUNCTIONS
385 Moose will export a number of functions into the class's namespace which
386 may then be used to set up the class. These functions all work directly
387 on the current class.
391 =item B<extends (@superclasses)>
393 This function will set the superclass(es) for the current class.
395 This approach is recommended instead of C<use base>, because C<use base>
396 actually C<push>es onto the class's C<@ISA>, whereas C<extends> will
397 replace it. This is important to ensure that classes which do not have
398 superclasses still properly inherit from L<Moose::Object>.
400 =item B<with (@roles)>
402 This will apply a given set of C<@roles> to the local class.
404 =item B<has $name|@$names =E<gt> %options>
406 This will install an attribute of a given C<$name> into the current class. If
407 the first parameter is an array reference, it will create an attribute for
408 every C<$name> in the list. The C<%options> are the same as those provided by
409 L<Class::MOP::Attribute>, in addition to the list below which are provided by
410 Moose (L<Moose::Meta::Attribute> to be more specific):
414 =item I<is =E<gt> 'rw'|'ro'>
416 The I<is> option accepts either I<rw> (for read/write) or I<ro> (for read
417 only). These will create either a read/write accessor or a read-only
418 accessor respectively, using the same name as the C<$name> of the attribute.
420 If you need more control over how your accessors are named, you can
421 use the L<reader|Class::MOP::Attribute/reader>,
422 L<writer|Class::MOP::Attribute/writer> and
423 L<accessor|Class::MOP::Attribute/accessor> options inherited from
424 L<Class::MOP::Attribute>, however if you use those, you won't need the
427 =item I<isa =E<gt> $type_name>
429 The I<isa> option uses Moose's type constraint facilities to set up runtime
430 type checking for this attribute. Moose will perform the checks during class
431 construction, and within any accessors. The C<$type_name> argument must be a
432 string. The string may be either a class name or a type defined using
433 Moose's type definition features. (Refer to L<Moose::Util::TypeConstraints>
434 for information on how to define a new type, and how to retrieve type meta-data).
436 =item I<coerce =E<gt> (1|0)>
438 This will attempt to use coercion with the supplied type constraint to change
439 the value passed into any accessors or constructors. You B<must> have supplied
440 a type constraint in order for this to work. See L<Moose::Cookbook::Basics::Recipe5>
443 =item I<does =E<gt> $role_name>
445 This will accept the name of a role which the value stored in this attribute
446 is expected to have consumed.
448 =item I<required =E<gt> (1|0)>
450 This marks the attribute as being required. This means a value must be
451 supplied during class construction, I<or> the attribute must be lazy
452 and have either a default or a builder. Note that c<required> does not
453 say anything about the attribute's value, which can be C<undef>.
455 =item I<weak_ref =E<gt> (1|0)>
457 This will tell the class to store the value of this attribute as a weakened
458 reference. If an attribute is a weakened reference, it B<cannot> also be
461 =item I<lazy =E<gt> (1|0)>
463 This will tell the class to not create this slot until absolutely necessary.
464 If an attribute is marked as lazy it B<must> have a default supplied.
466 =item I<auto_deref =E<gt> (1|0)>
468 This tells the accessor to automatically dereference the value of this
469 attribute when called in list context. The accessor will still return a
470 reference when called in scalar context. This is only legal if your C<isa>
471 option is either C<ArrayRef> or C<HashRef>.
473 =item I<trigger =E<gt> $code>
475 The I<trigger> option is a CODE reference which will be called after
476 the value of the attribute is set. The CODE ref will be passed the
477 instance itself and the updated value. If the attribute already had a
478 value, this will be passed as the third value to the trigger.
480 You B<can> have a trigger on a read-only attribute.
482 B<NOTE:> Triggers will only fire when you B<assign> to the attribute,
483 either in the constructor, or using the writer. Default and built values will
484 B<not> cause the trigger to be fired.
486 =item I<handles =E<gt> ARRAY | HASH | REGEXP | ROLE | DUCKTYPE | CODE>
488 The I<handles> option provides Moose classes with automated delegation features.
489 This is a pretty complex and powerful option. It accepts many different option
490 formats, each with its own benefits and drawbacks.
492 B<NOTE:> The class being delegated to does not need to be a Moose based class,
493 which is why this feature is especially useful when wrapping non-Moose classes.
495 All I<handles> option formats share the following traits:
497 You cannot override a locally defined method with a delegated method; an
498 exception will be thrown if you try. That is to say, if you define C<foo> in
499 your class, you cannot override it with a delegated C<foo>. This is almost never
500 something you would want to do, and if it is, you should do it by hand and not
503 You cannot override any of the methods found in Moose::Object, or the C<BUILD>
504 and C<DEMOLISH> methods. These will not throw an exception, but will silently
505 move on to the next method in the list. My reasoning for this is that you would
506 almost never want to do this, since it usually breaks your class. As with
507 overriding locally defined methods, if you do want to do this, you should do it
508 manually, not with Moose.
510 You do not I<need> to have a reader (or accessor) for the attribute in order
511 to delegate to it. Moose will create a means of accessing the value for you,
512 however this will be several times B<less> efficient then if you had given
513 the attribute a reader (or accessor) to use.
515 Below is the documentation for each option format:
521 This is the most common usage for I<handles>. You basically pass a list of
522 method names to be delegated, and Moose will install a delegation method
527 This is the second most common usage for I<handles>. Instead of a list of
528 method names, you pass a HASH ref where each key is the method name you
529 want installed locally, and its value is the name of the original method
530 in the class being delegated to.
532 This can be very useful for recursive classes like trees. Here is a
533 quick example (soon to be expanded into a Moose::Cookbook recipe):
538 has 'node' => (is => 'rw', isa => 'Any');
543 default => sub { [] }
551 parent_node => 'node',
552 siblings => 'children',
556 In this example, the Tree package gets C<parent_node> and C<siblings> methods,
557 which delegate to the C<node> and C<children> methods (respectively) of the Tree
558 instance stored in the C<parent> slot.
560 You may also use an array reference to curry arguments to the original method.
564 handles => { set_foo => [ set => 'foo' ] },
567 # $self->set_foo(...) calls $self->thing->set('foo', ...)
569 The first element of the array reference is the original method name, and the
570 rest is a list of curried arguments.
574 The regexp option works very similar to the ARRAY option, except that it builds
575 the list of methods for you. It starts by collecting all possible methods of the
576 class being delegated to, then filters that list using the regexp supplied here.
578 B<NOTE:> An I<isa> option is required when using the regexp option format. This
579 is so that we can determine (at compile time) the method list from the class.
580 Without an I<isa> this is just not possible.
584 With the role option, you specify the name of a role whose "interface" then
585 becomes the list of methods to handle. The "interface" can be defined as; the
586 methods of the role and any required methods of the role. It should be noted
587 that this does B<not> include any method modifiers or generated attribute
588 methods (which is consistent with role composition).
592 With the duck type option, you pass a duck type object whose "interface" then
593 becomes the list of methods to handle. The "interface" can be defined as; the
594 list of methods passed to C<duck_type> to create a duck type object. For more
595 information on C<duck_type> please check
596 L<Moose::Util::TypeConstraints>.
600 This is the option to use when you really want to do something funky. You should
601 only use it if you really know what you are doing, as it involves manual
604 This takes a code reference, which should expect two arguments. The first is the
605 attribute meta-object this I<handles> is attached to. The second is the
606 metaclass of the class being delegated to. It expects you to return a hash (not
607 a HASH ref) of the methods you want mapped.
611 =item I<metaclass =E<gt> $metaclass_name>
613 This tells the class to use a custom attribute metaclass for this particular
614 attribute. Custom attribute metaclasses are useful for extending the
615 capabilities of the I<has> keyword: they are the simplest way to extend the MOP,
616 but they are still a fairly advanced topic and too much to cover here, see
617 L<Moose::Cookbook::Meta::Recipe1> for more information.
619 See L<Metaclass and Trait Name Resolution> for details on how a metaclass name
620 is resolved to a class name.
622 =item I<traits =E<gt> [ @role_names ]>
624 This tells Moose to take the list of C<@role_names> and apply them to the
625 attribute meta-object. This is very similar to the I<metaclass> option, but
626 allows you to use more than one extension at a time.
628 See L<Metaclass and Trait Name Resolution> for details on how a trait name is
629 resolved to a role name.
631 Also see L<Moose::Cookbook::Meta::Recipe3> for a metaclass trait
634 =item I<builder> => Str
636 The value of this key is the name of the method that will be called to
637 obtain the value used to initialize the attribute. See the L<builder
638 option docs in Class::MOP::Attribute|Class::MOP::Attribute/builder>
639 and/or L<Moose::Cookbook::Basics::Recipe8> for more information.
641 =item I<default> => SCALAR | CODE
643 The value of this key is the default value which will initialize the attribute.
645 NOTE: If the value is a simple scalar (string or number), then it can
646 be just passed as is. However, if you wish to initialize it with a
647 HASH or ARRAY ref, then you need to wrap that inside a CODE reference.
648 See the L<default option docs in
649 Class::MOP::Attribute|Class::MOP::Attribute/default> for more
652 =item I<clearer> => Str
654 Creates a method allowing you to clear the value, see the L<clearer option
655 docs in Class::MOP::Attribute|Class::MOP::Attribute/clearer> for more
658 =item I<predicate> => Str
660 Creates a method to perform a basic test to see if a value has been set in the
661 attribute, see the L<predicate option docs in
662 Class::MOP::Attribute|Class::MOP::Attribute/predicate> for more information.
664 =item I<lazy_build> => (0|1)
666 Automatically define lazy => 1 as well as builder => "_build_$attr", clearer =>
667 "clear_$attr', predicate => 'has_$attr' unless they are already defined.
669 =item I<initializer> => Str
671 This may be a method name (referring to a method on the class with
672 this attribute) or a CODE ref. The initializer is used to set the
673 attribute value on an instance when the attribute is set during
674 instance initialization (but not when the value is being assigned
675 to). See the L<initializer option docs in
676 Class::MOP::Attribute|Class::MOP::Attribute/initializer> for more
679 =item I<documentation> => $string
681 An arbitrary string that can be retrieved later by calling C<<
682 $attr->documentation >>.
688 =item B<has +$name =E<gt> %options>
690 This is variation on the normal attribute creator C<has> which allows you to
691 clone and extend an attribute from a superclass or from a role. Here is an
692 example of the superclass usage:
700 default => 'Hello, I am a Foo'
708 has '+message' => (default => 'Hello I am My::Foo');
710 What is happening here is that B<My::Foo> is cloning the C<message> attribute
711 from its parent class B<Foo>, retaining the C<is =E<gt> 'rw'> and C<isa =E<gt>
712 'Str'> characteristics, but changing the value in C<default>.
714 Here is another example, but within the context of a role:
722 default => 'Hello, I am a Foo'
730 has '+message' => (default => 'Hello I am My::Foo');
732 In this case, we are basically taking the attribute which the role supplied
733 and altering it within the bounds of this feature.
735 Note that you can only extend an attribute from either a superclass or a role,
736 you cannot extend an attribute in a role that composes over an attribute from
739 Aside from where the attributes come from (one from superclass, the other
740 from a role), this feature works exactly the same. This feature is restricted
741 somewhat, so as to try and force at least I<some> sanity into it. You are only
742 allowed to change the following attributes:
748 Change the default value of an attribute.
752 Change whether the attribute attempts to coerce a value passed to it.
756 Change if the attribute is required to have a value.
758 =item I<documentation>
760 Change the documentation string associated with the attribute.
764 Change if the attribute lazily initializes the slot.
768 You I<are> allowed to change the type without restriction.
770 It is recommended that you use this freedom with caution. We used to
771 only allow for extension only if the type was a subtype of the parent's
772 type, but we felt that was too restrictive and is better left as a
777 You are allowed to B<add> a new C<handles> definition, but you are B<not>
778 allowed to I<change> one.
782 You are allowed to B<add> a new C<builder> definition, but you are B<not>
783 allowed to I<change> one.
787 You are allowed to B<add> a new C<metaclass> definition, but you are
788 B<not> allowed to I<change> one.
792 You are allowed to B<add> additional traits to the C<traits> definition.
793 These traits will be composed into the attribute, but preexisting traits
794 B<are not> overridden, or removed.
798 =item B<before $name|@names =E<gt> sub { ... }>
800 =item B<after $name|@names =E<gt> sub { ... }>
802 =item B<around $name|@names =E<gt> sub { ... }>
804 These three items are syntactic sugar for the before, after, and around method
805 modifier features that L<Class::MOP> provides. More information on these may be
806 found in L<Moose::Manual::MethodModifiers> and the
807 L<Class::MOP::Class documentation|Class::MOP::Class/"Method Modifiers">.
811 The keyword C<super> is a no-op when called outside of an C<override> method. In
812 the context of an C<override> method, it will call the next most appropriate
813 superclass method with the same arguments as the original method.
815 =item B<override ($name, &sub)>
817 An C<override> method is a way of explicitly saying "I am overriding this
818 method from my superclass". You can call C<super> within this method, and
819 it will work as expected. The same thing I<can> be accomplished with a normal
820 method call and the C<SUPER::> pseudo-package; it is really your choice.
824 The keyword C<inner>, much like C<super>, is a no-op outside of the context of
825 an C<augment> method. You can think of C<inner> as being the inverse of
826 C<super>; the details of how C<inner> and C<augment> work is best described in
827 the L<Moose::Cookbook::Basics::Recipe6>.
829 =item B<augment ($name, &sub)>
831 An C<augment> method, is a way of explicitly saying "I am augmenting this
832 method from my superclass". Once again, the details of how C<inner> and
833 C<augment> work is best described in the L<Moose::Cookbook::Basics::Recipe6>.
837 This is the C<Carp::confess> function, and exported here because I use it
842 This is the C<Scalar::Util::blessed> function, it is exported here because I
843 use it all the time. It is highly recommended that this is used instead of
844 C<ref> anywhere you need to test for an object's class name.
850 When you use Moose, you can specify which metaclass to use:
852 use Moose -metaclass => 'My::Meta::Class';
854 You can also specify traits which will be applied to your metaclass:
856 use Moose -traits => 'My::Trait';
858 This is very similar to the attribute traits feature. When you do
859 this, your class's C<meta> object will have the specified traits
860 applied to it. See L<Metaclass and Trait Name Resolution> for more
863 =head2 Metaclass and Trait Name Resolution
865 By default, when given a trait name, Moose simply tries to load a
866 class of the same name. If such a class does not exist, it then looks
867 for for a class matching
868 B<Moose::Meta::$type::Custom::Trait::$trait_name>. The C<$type>
869 variable here will be one of B<Attribute> or B<Class>, depending on
870 what the trait is being applied to.
872 If a class with this long name exists, Moose checks to see if it has
873 the method C<register_implementation>. This method is expected to
874 return the I<real> class name of the trait. If there is no
875 C<register_implementation> method, it will fall back to using
876 B<Moose::Meta::$type::Custom::Trait::$trait> as the trait name.
878 The lookup method for metaclasses is the same, except that it looks
879 for a class matching B<Moose::Meta::$type::Custom::$metaclass_name>.
881 If all this is confusing, take a look at
882 L<Moose::Cookbook::Meta::Recipe3>, which demonstrates how to create an
885 =head1 UNIMPORTING FUNCTIONS
889 Moose offers a way to remove the keywords it exports, through the C<unimport>
890 method. You simply have to say C<no Moose> at the bottom of your code for this
891 to work. Here is an example:
896 has 'first_name' => (is => 'rw', isa => 'Str');
897 has 'last_name' => (is => 'rw', isa => 'Str');
901 $self->first_name . ' ' . $self->last_name
904 no Moose; # keywords are removed from the Person package
906 =head1 EXTENDING AND EMBEDDING MOOSE
908 To learn more about extending Moose, we recommend checking out the
909 "Extending" recipes in the L<Moose::Cookbook>, starting with
910 L<Moose::Cookbook::Extending::Recipe1>, which provides an overview of
911 all the different ways you might extend Moose.
913 =head2 B<< Moose->init_meta(for_class => $class, base_class => $baseclass, metaclass => $metaclass) >>
915 The C<init_meta> method sets up the metaclass object for the class
916 specified by C<for_class>. This method injects a a C<meta> accessor
917 into the class so you can get at this object. It also sets the class's
918 superclass to C<base_class>, with L<Moose::Object> as the default.
920 C<init_meta> returns the metaclass object for C<$class>.
922 You can specify an alternate metaclass with the C<metaclass> option.
924 For more detail on this topic, see L<Moose::Cookbook::Extending::Recipe2>.
926 This method used to be documented as a function which accepted
927 positional parameters. This calling style will still work for
928 backwards compatibility, but is deprecated.
932 Moose's C<import> method supports the L<Sub::Exporter> form of C<{into =E<gt> $pkg}>
933 and C<{into_level =E<gt> 1}>.
935 B<NOTE>: Doing this is more or less deprecated. Use L<Moose::Exporter>
936 instead, which lets you stack multiple C<Moose.pm>-alike modules
937 sanely. It handles getting the exported functions into the right place
940 =head2 B<throw_error>
942 An alias for C<confess>, used by internally by Moose.
944 =head1 METACLASS COMPATIBILITY AND MOOSE
946 Metaclass compatibility is a thorny subject. You should start by
947 reading the "About Metaclass compatibility" section in the
950 Moose will attempt to resolve a few cases of metaclass incompatibility
951 when you set the superclasses for a class, unlike C<Class::MOP>, which
952 simply dies if the metaclasses are incompatible.
954 In actuality, Moose fixes incompatibility for I<all> of a class's
955 metaclasses, not just the class metaclass. That includes the instance
956 metaclass, attribute metaclass, as well as its constructor class and
957 destructor class. However, for simplicity this discussion will just
958 refer to "metaclass", meaning the class metaclass, most of the time.
960 Moose has two algorithms for fixing metaclass incompatibility.
962 The first algorithm is very simple. If all the metaclass for the
963 parent is a I<subclass> of the child's metaclass, then we simply
964 replace the child's metaclass with the parent's.
966 The second algorithm is more complicated. It tries to determine if the
967 metaclasses only "differ by roles". This means that the parent and
968 child's metaclass share a common ancestor in their respective
969 hierarchies, and that the subclasses under the common ancestor are
970 only different because of role applications. This case is actually
971 fairly common when you mix and match various C<MooseX::*> modules,
972 many of which apply roles to the metaclass.
974 If the parent and child do differ by roles, Moose replaces the
975 metaclass in the child with a newly created metaclass. This metaclass
976 is a subclass of the parent's metaclass, does all of the roles that
977 the child's metaclass did before being replaced. Effectively, this
978 means the new metaclass does all of the roles done by both the
979 parent's and child's original metaclasses.
981 Ultimately, this is all transparent to you except in the case of an
982 unresolvable conflict.
984 =head2 The MooseX:: namespace
986 Generally if you're writing an extension I<for> Moose itself you'll want
987 to put your extension in the C<MooseX::> namespace. This namespace is
988 specifically for extensions that make Moose better or different in some
989 fundamental way. It is traditionally B<not> for a package that just happens
990 to use Moose. This namespace follows from the examples of the C<LWPx::>
991 and C<DBIx::> namespaces that perform the same function for C<LWP> and C<DBI>
1000 It should be noted that C<super> and C<inner> B<cannot> be used in the same
1001 method. However, they may be combined within the same class hierarchy; see
1002 F<t/014_override_augment_inner_super.t> for an example.
1004 The reason for this is that C<super> is only valid within a method
1005 with the C<override> modifier, and C<inner> will never be valid within an
1006 C<override> method. In fact, C<augment> will skip over any C<override> methods
1007 when searching for its appropriate C<inner>.
1009 This might seem like a restriction, but I am of the opinion that keeping these
1010 two features separate (yet interoperable) actually makes them easy to use, since
1011 their behavior is then easier to predict. Time will tell whether I am right or
1012 not (UPDATE: so far so good).
1018 We offer both a mailing list and a very active IRC channel.
1020 The mailing list is L<moose@perl.org>. You must be subscribed to send
1021 a message. To subscribe, send an empty message to
1022 L<moose-subscribe@perl.org>
1024 You can also visit us at C<#moose> on C<< irc://irc.perl.org/#moose >>
1025 This channel is quite active, and questions at all levels (on Moose-related
1026 topics ;) are welcome.
1028 =head1 ACKNOWLEDGEMENTS
1032 =item I blame Sam Vilain for introducing me to the insanity that is meta-models.
1034 =item I blame Audrey Tang for then encouraging my meta-model habit in #perl6.
1036 =item Without Yuval "nothingmuch" Kogman this module would not be possible,
1037 and it certainly wouldn't have this name ;P
1039 =item The basis of the TypeContraints module was Rob Kinyon's idea
1040 originally, I just ran with it.
1042 =item Thanks to mst & chansen and the whole #moose posse for all the
1043 early ideas/feature-requests/encouragement/bug-finding.
1045 =item Thanks to David "Theory" Wheeler for meta-discussions and spelling fixes.
1053 =item L<http://www.iinteractive.com/moose>
1055 This is the official web home of Moose, it contains links to our public SVN repository
1056 as well as links to a number of talks and articles on Moose and Moose related
1059 =item The Moose is flying, a tutorial by Randal Schwartz
1061 Part 1 - L<http://www.stonehenge.com/merlyn/LinuxMag/col94.html>
1063 Part 2 - L<http://www.stonehenge.com/merlyn/LinuxMag/col95.html>
1065 =item Several Moose extension modules in the C<MooseX::> namespace.
1067 See L<http://search.cpan.org/search?query=MooseX::> for extensions.
1069 =item Moose stats on ohloh.net - L<http://www.ohloh.net/projects/moose>
1077 =item The Art of the MetaObject Protocol
1079 I mention this in the L<Class::MOP> docs too, this book was critical in
1080 the development of both modules and is highly recommended.
1088 =item L<http://www.cs.utah.edu/plt/publications/oopsla04-gff.pdf>
1090 This paper (suggested by lbr on #moose) was what lead to the implementation
1091 of the C<super>/C<override> and C<inner>/C<augment> features. If you really
1092 want to understand them, I suggest you read this.
1098 All complex software has bugs lurking in it, and this module is no
1101 Please report any bugs to C<bug-moose@rt.cpan.org>, or through the web
1102 interface at L<http://rt.cpan.org>.
1104 =head1 FEATURE REQUESTS
1106 We are very strict about what features we add to the Moose core, especially
1107 the user-visible features. Instead we have made sure that the underlying
1108 meta-system of Moose is as extensible as possible so that you can add your
1109 own features easily.
1111 That said, occasionally there is a feature needed in the meta-system
1112 to support your planned extension, in which case you should either
1113 email the mailing list (moose@perl.org) or join us on IRC at
1114 L<irc://irc.perl.org/#moose> to discuss. The
1115 L<Moose::Manual::Contributing> has more detail about how and when you
1120 Moose is an open project, there are at this point dozens of people who have
1121 contributed, and can contribute. If you have added anything to the Moose
1122 project you have a commit bit on this file and can add your name to the list.
1126 However there are only a few people with the rights to release a new version
1127 of Moose. The Moose Cabal are the people to go to with questions regarding
1128 the wider purview of Moose, and help out maintaining not just the code
1129 but the community as well.
1131 Stevan (stevan) Little E<lt>stevan@iinteractive.comE<gt>
1133 Yuval (nothingmuch) Kogman
1135 Shawn (sartak) Moore E<lt>sartak@bestpractical.comE<gt>
1137 Dave (autarch) Rolsky E<lt>autarch@urth.orgE<gt>
1139 Jesse (doy) Luehrs E<lt>doy at tozt dot netE<gt>
1141 Hans Dieter (confound) Pearcey E<lt>hdp@pobox.comE<gt>
1143 Chris (perigrin) Prather
1145 Florian Ragwitz E<lt>rafl@debian.orgE<gt>
1147 =head2 OTHER CONTRIBUTORS
1151 Adam (Alias) Kennedy
1153 Anders (Debolaz) Nor Berle
1155 Nathan (kolibrie) Gray
1157 Christian (chansen) Hansen
1159 Eric (ewilhelm) Wilhelm
1161 Guillermo (groditi) Roditi
1163 Jess (castaway) Robinson
1167 Robert (phaylon) Sedlacek
1171 Scott (konobi) McWhirter
1173 Shlomi (rindolf) Fish
1175 Wallace (wreis) Reis
1177 Jonathan (jrockway) Rockway
1179 Piotr (dexter) Roszatycki
1181 Sam (mugwump) Vilain
1185 Dylan Hardison (doc fixes)
1187 ... and many other #moose folks
1189 =head1 COPYRIGHT AND LICENSE
1191 Copyright 2006-2009 by Infinity Interactive, Inc.
1193 L<http://www.iinteractive.com>
1195 This library is free software; you can redistribute it and/or modify
1196 it under the same terms as Perl itself.