8 $VERSION = eval $VERSION;
9 our $AUTHORITY = 'cpan:STEVAN';
11 use Scalar::Util 'blessed';
18 use Moose::Meta::Class;
19 use Moose::Meta::TypeConstraint;
20 use Moose::Meta::TypeCoercion;
21 use Moose::Meta::Attribute;
22 use Moose::Meta::Instance;
26 use Moose::Meta::Role;
27 use Moose::Meta::Role::Composite;
28 use Moose::Meta::Role::Application;
29 use Moose::Meta::Role::Application::RoleSummation;
30 use Moose::Meta::Role::Application::ToClass;
31 use Moose::Meta::Role::Application::ToRole;
32 use Moose::Meta::Role::Application::ToInstance;
34 use Moose::Util::TypeConstraints;
37 use Moose::Meta::Attribute::Native;
48 Moose->throw_error("Must derive at least one class") unless @_;
50 # this checks the metaclass to make sure
51 # it is correct, sometimes it can get out
52 # of sync when the classes are being built
53 Moose::Meta::Class->initialize($class)->superclasses(@_);
58 Moose::Util::apply_all_roles(Class::MOP::Class->initialize($class), @_);
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 Class::MOP::Class->initialize($class)->add_attribute( $_, %options ) for @$attrs;
75 Moose::Util::add_method_modifier($class, 'before', \@_);
80 Moose::Util::add_method_modifier($class, 'after', \@_);
85 Moose::Util::add_method_modifier($class, 'around', \@_);
93 # This check avoids a recursion loop - see
94 # t/100_bugs/020_super_recursion.t
95 return if defined $SUPER_PACKAGE && $SUPER_PACKAGE ne caller();
96 return unless $SUPER_BODY; $SUPER_BODY->(@SUPER_ARGS);
101 my ( $name, $method ) = @_;
102 Class::MOP::Class->initialize($class)->add_override_method_modifier( $name => $method );
107 our ( %INNER_BODY, %INNER_ARGS );
109 if ( my $body = $INNER_BODY{$pkg} ) {
110 my @args = @{ $INNER_ARGS{$pkg} };
111 local $INNER_ARGS{$pkg};
112 local $INNER_BODY{$pkg};
113 return $body->(@args);
121 my ( $name, $method ) = @_;
122 Class::MOP::Class->initialize($class)->add_augment_method_modifier( $name => $method );
125 Moose::Exporter->setup_import_methods(
127 qw( extends with has before after around override augment)
132 \&Scalar::Util::blessed,
137 # This used to be called as a function. This hack preserves
138 # backwards compatibility.
139 if ( $_[0] ne __PACKAGE__ ) {
140 return __PACKAGE__->init_meta(
150 my $class = $args{for_class}
151 or Moose->throw_error("Cannot call init_meta without specifying a for_class");
152 my $base_class = $args{base_class} || 'Moose::Object';
153 my $metaclass = $args{metaclass} || 'Moose::Meta::Class';
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 ( $meta->isa("Moose::Meta::Class") ) {
166 Moose->throw_error("$class already has a metaclass, but it does not inherit $metaclass ($meta)");
169 # no metaclass, no 'meta' method
171 # now we check whether our ancestors have metaclass, and if so borrow that
172 my ( undef, @isa ) = @{ $class->mro::get_linear_isa };
174 foreach my $ancestor ( @isa ) {
175 my $ancestor_meta = Class::MOP::get_metaclass_by_name($ancestor) || next;
177 my $ancestor_meta_class = ($ancestor_meta->is_immutable
178 ? $ancestor_meta->get_mutable_metaclass_name
179 : ref($ancestor_meta));
181 # if we have an ancestor metaclass that inherits $metaclass, we use
182 # that. This is like _fix_metaclass_incompatibility, but we can do it now.
184 # the case of having an ancestry is not very common, but arises in
186 unless ( $metaclass->isa( $ancestor_meta_class ) ) {
187 if ( $ancestor_meta_class->isa($metaclass) ) {
188 $metaclass = $ancestor_meta_class;
193 $meta = $metaclass->initialize($class);
196 if ( $class->can('meta') ) {
197 # check 'meta' method
199 # it may be inherited
202 # this is the case where the metaclass pragma
203 # was used before the 'use Moose' statement to
204 # override a specific class
205 my $method_meta = $class->meta;
207 ( blessed($method_meta) && $method_meta->isa('Moose::Meta::Class') )
208 || Moose->throw_error("$class already has a &meta function, but it does not return a Moose::Meta::Class ($method_meta)");
210 $meta = $method_meta;
213 unless ( $meta->has_method("meta") ) { # don't overwrite
214 # also check for inherited non moose 'meta' method?
215 # FIXME also skip this if the user requested by passing an option
218 # re-initialize so it inherits properly
219 $metaclass->initialize( ref($_[0]) || $_[0] );
224 # make sure they inherit from Moose::Object
225 $meta->superclasses($base_class)
226 unless $meta->superclasses();
231 # This may be used in some older MooseX extensions.
233 goto &Moose::Exporter::_get_caller;
236 ## make 'em all immutable
239 inline_constructor => 1,
240 constructor_name => "_new",
241 # these are Class::MOP accessors, so they need inlining
242 inline_accessors => 1
243 ) for grep { $_->is_mutable }
246 Moose::Meta::Attribute
248 Moose::Meta::Instance
250 Moose::Meta::TypeCoercion
251 Moose::Meta::TypeCoercion::Union
254 Moose::Meta::Method::Accessor
255 Moose::Meta::Method::Constructor
256 Moose::Meta::Method::Destructor
257 Moose::Meta::Method::Overridden
258 Moose::Meta::Method::Augmented
261 Moose::Meta::Role::Method
262 Moose::Meta::Role::Method::Required
263 Moose::Meta::Role::Method::Conflicting
265 Moose::Meta::Role::Composite
267 Moose::Meta::Role::Application
268 Moose::Meta::Role::Application::RoleSummation
269 Moose::Meta::Role::Application::ToClass
270 Moose::Meta::Role::Application::ToRole
271 Moose::Meta::Role::Application::ToInstance
282 Moose - A postmodern object system for Perl 5
287 use Moose; # automatically turns on strict and warnings
289 has 'x' => (is => 'rw', isa => 'Int');
290 has 'y' => (is => 'rw', isa => 'Int');
303 has 'z' => (is => 'rw', isa => 'Int');
305 after 'clear' => sub {
312 Moose is an extension of the Perl 5 object system.
314 The main goal of Moose is to make Perl 5 Object Oriented programming
315 easier, more consistent and less tedious. With Moose you can to think
316 more about what you want to do and less about the mechanics of OOP.
318 Additionally, Moose is built on top of L<Class::MOP>, which is a
319 metaclass system for Perl 5. This means that Moose not only makes
320 building normal Perl 5 objects better, but it provides the power of
321 metaclass programming as well.
325 If you're new to Moose, the best place to start is the
326 L<Moose::Manual> docs, followed by the L<Moose::Cookbook>. The intro
327 will show you what Moose is, and how it makes Perl 5 OO better.
329 The cookbook recipes on Moose basics will get you up to speed with
330 many of Moose's features quickly. Once you have an idea of what Moose
331 can do, you can use the API documentation to get more detail on
332 features which interest you.
334 =head2 Moose Extensions
336 The C<MooseX::> namespace is the official place to find Moose extensions.
337 These extensions can be found on the CPAN. The easiest way to find them
338 is to search for them (L<http://search.cpan.org/search?query=MooseX::>),
339 or to examine L<Task::Moose> which aims to keep an up-to-date, easily
340 installable list of Moose extensions.
342 =head1 BUILDING CLASSES WITH MOOSE
344 Moose makes every attempt to provide as much convenience as possible during
345 class construction/definition, but still stay out of your way if you want it
346 to. Here are a few items to note when building classes with Moose.
348 Unless specified with C<extends>, any class which uses Moose will
349 inherit from L<Moose::Object>.
351 Moose will also manage all attributes (including inherited ones) that are
352 defined with C<has>. And (assuming you call C<new>, which is inherited from
353 L<Moose::Object>) this includes properly initializing all instance slots,
354 setting defaults where appropriate, and performing any type constraint checking
357 =head1 PROVIDED METHODS
359 Moose provides a number of methods to all your classes, mostly through the
360 inheritance of L<Moose::Object>. There is however, one exception.
366 This is a method which provides access to the current class's metaclass.
370 =head1 EXPORTED FUNCTIONS
372 Moose will export a number of functions into the class's namespace which
373 may then be used to set up the class. These functions all work directly
374 on the current class.
378 =item B<extends (@superclasses)>
380 This function will set the superclass(es) for the current class.
382 This approach is recommended instead of C<use base>, because C<use base>
383 actually C<push>es onto the class's C<@ISA>, whereas C<extends> will
384 replace it. This is important to ensure that classes which do not have
385 superclasses still properly inherit from L<Moose::Object>.
387 =item B<with (@roles)>
389 This will apply a given set of C<@roles> to the local class.
391 =item B<has $name|@$names =E<gt> %options>
393 This will install an attribute of a given C<$name> into the current class. If
394 the first parameter is an array reference, it will create an attribute for
395 every C<$name> in the list. The C<%options> are the same as those provided by
396 L<Class::MOP::Attribute>, in addition to the list below which are provided by
397 Moose (L<Moose::Meta::Attribute> to be more specific):
401 =item I<is =E<gt> 'rw'|'ro'>
403 The I<is> option accepts either I<rw> (for read/write) or I<ro> (for read
404 only). These will create either a read/write accessor or a read-only
405 accessor respectively, using the same name as the C<$name> of the attribute.
407 If you need more control over how your accessors are named, you can
408 use the L<reader|Class::MOP::Attribute/reader>,
409 L<writer|Class::MOP::Attribute/writer> and
410 L<accessor|Class::MOP::Attribute/accessor> options inherited from
411 L<Class::MOP::Attribute>, however if you use those, you won't need the
414 =item I<isa =E<gt> $type_name>
416 The I<isa> option uses Moose's type constraint facilities to set up runtime
417 type checking for this attribute. Moose will perform the checks during class
418 construction, and within any accessors. The C<$type_name> argument must be a
419 string. The string may be either a class name or a type defined using
420 Moose's type definition features. (Refer to L<Moose::Util::TypeConstraints>
421 for information on how to define a new type, and how to retrieve type meta-data).
423 =item I<coerce =E<gt> (1|0)>
425 This will attempt to use coercion with the supplied type constraint to change
426 the value passed into any accessors or constructors. You B<must> have supplied
427 a type constraint in order for this to work. See L<Moose::Cookbook::Basics::Recipe5>
430 =item I<does =E<gt> $role_name>
432 This will accept the name of a role which the value stored in this attribute
433 is expected to have consumed.
435 =item I<required =E<gt> (1|0)>
437 This marks the attribute as being required. This means a value must be
438 supplied during class construction, I<or> the attribute must be lazy
439 and have either a default or a builder. Note that c<required> does not
440 say anything about the attribute's value, which can be C<undef>.
442 =item I<weak_ref =E<gt> (1|0)>
444 This will tell the class to store the value of this attribute as a weakened
445 reference. If an attribute is a weakened reference, it B<cannot> also be
448 =item I<lazy =E<gt> (1|0)>
450 This will tell the class to not create this slot until absolutely necessary.
451 If an attribute is marked as lazy it B<must> have a default supplied.
453 =item I<auto_deref =E<gt> (1|0)>
455 This tells the accessor whether to automatically dereference the value returned.
456 This is only legal if your C<isa> option is either C<ArrayRef> or C<HashRef>.
458 =item I<trigger =E<gt> $code>
460 The I<trigger> option is a CODE reference which will be called after
461 the value of the attribute is set. The CODE ref will be passed the
462 instance itself and the updated value. If the attribute already had a
463 value, this will be passed as the third value to the trigger.
465 You B<can> have a trigger on a read-only attribute.
467 B<NOTE:> Triggers will only fire when you B<assign> to the attribute,
468 either in the constructor, or using the writer. Default and built values will
469 B<not> cause the trigger to be fired.
471 =item I<handles =E<gt> ARRAY | HASH | REGEXP | ROLE | DUCKTYPE | CODE>
473 The I<handles> option provides Moose classes with automated delegation features.
474 This is a pretty complex and powerful option. It accepts many different option
475 formats, each with its own benefits and drawbacks.
477 B<NOTE:> The class being delegated to does not need to be a Moose based class,
478 which is why this feature is especially useful when wrapping non-Moose classes.
480 All I<handles> option formats share the following traits:
482 You cannot override a locally defined method with a delegated method; an
483 exception will be thrown if you try. That is to say, if you define C<foo> in
484 your class, you cannot override it with a delegated C<foo>. This is almost never
485 something you would want to do, and if it is, you should do it by hand and not
488 You cannot override any of the methods found in Moose::Object, or the C<BUILD>
489 and C<DEMOLISH> methods. These will not throw an exception, but will silently
490 move on to the next method in the list. My reasoning for this is that you would
491 almost never want to do this, since it usually breaks your class. As with
492 overriding locally defined methods, if you do want to do this, you should do it
493 manually, not with Moose.
495 You do not I<need> to have a reader (or accessor) for the attribute in order
496 to delegate to it. Moose will create a means of accessing the value for you,
497 however this will be several times B<less> efficient then if you had given
498 the attribute a reader (or accessor) to use.
500 Below is the documentation for each option format:
506 This is the most common usage for I<handles>. You basically pass a list of
507 method names to be delegated, and Moose will install a delegation method
512 This is the second most common usage for I<handles>. Instead of a list of
513 method names, you pass a HASH ref where each key is the method name you
514 want installed locally, and its value is the name of the original method
515 in the class being delegated to.
517 This can be very useful for recursive classes like trees. Here is a
518 quick example (soon to be expanded into a Moose::Cookbook recipe):
523 has 'node' => (is => 'rw', isa => 'Any');
528 default => sub { [] }
536 parent_node => 'node',
537 siblings => 'children',
541 In this example, the Tree package gets C<parent_node> and C<siblings> methods,
542 which delegate to the C<node> and C<children> methods (respectively) of the Tree
543 instance stored in the C<parent> slot.
545 You may also use an array reference to curry arguments to the original method.
549 handles => { set_foo => [ set => 'foo' ] },
552 # $self->set_foo(...) calls $self->thing->set('foo', ...)
554 The first element of the array reference is the original method name, and the
555 rest is a list of curried arguments.
559 The regexp option works very similar to the ARRAY option, except that it builds
560 the list of methods for you. It starts by collecting all possible methods of the
561 class being delegated to, then filters that list using the regexp supplied here.
563 B<NOTE:> An I<isa> option is required when using the regexp option format. This
564 is so that we can determine (at compile time) the method list from the class.
565 Without an I<isa> this is just not possible.
569 With the role option, you specify the name of a role whose "interface" then
570 becomes the list of methods to handle. The "interface" can be defined as; the
571 methods of the role and any required methods of the role. It should be noted
572 that this does B<not> include any method modifiers or generated attribute
573 methods (which is consistent with role composition).
577 With the duck type option, you pass a duck type object whose "interface" then
578 becomes the list of methods to handle. The "interface" can be defined as; the
579 list of methods passed to C<duck_type> to create a duck type object. For more
580 information on C<duck_type> please check
581 L<Moose::Util::TypeConstraints>.
585 This is the option to use when you really want to do something funky. You should
586 only use it if you really know what you are doing, as it involves manual
589 This takes a code reference, which should expect two arguments. The first is the
590 attribute meta-object this I<handles> is attached to. The second is the
591 metaclass of the class being delegated to. It expects you to return a hash (not
592 a HASH ref) of the methods you want mapped.
596 =item I<metaclass =E<gt> $metaclass_name>
598 This tells the class to use a custom attribute metaclass for this particular
599 attribute. Custom attribute metaclasses are useful for extending the
600 capabilities of the I<has> keyword: they are the simplest way to extend the MOP,
601 but they are still a fairly advanced topic and too much to cover here, see
602 L<Moose::Cookbook::Meta::Recipe1> for more information.
604 See L<Metaclass and Trait Name Resolution> for details on how a metaclass name
605 is resolved to a class name.
607 =item I<traits =E<gt> [ @role_names ]>
609 This tells Moose to take the list of C<@role_names> and apply them to the
610 attribute meta-object. This is very similar to the I<metaclass> option, but
611 allows you to use more than one extension at a time.
613 See L<Metaclass and Trait Name Resolution> for details on how a trait name is
614 resolved to a role name.
616 Also see L<Moose::Cookbook::Meta::Recipe3> for a metaclass trait
619 =item I<builder> => Str
621 The value of this key is the name of the method that will be called to
622 obtain the value used to initialize the attribute. See the L<builder
623 option docs in Class::MOP::Attribute|Class::MOP::Attribute/builder>
624 and/or L<Moose::Cookbook::Basics::Recipe8> for more information.
626 =item I<default> => SCALAR | CODE
628 The value of this key is the default value which will initialize the attribute.
630 NOTE: If the value is a simple scalar (string or number), then it can
631 be just passed as is. However, if you wish to initialize it with a
632 HASH or ARRAY ref, then you need to wrap that inside a CODE reference.
633 See the L<default option docs in
634 Class::MOP::Attribute|Class::MOP::Attribute/default> for more
637 =item I<clearer> => Str
639 Creates a method allowing you to clear the value, see the L<clearer option
640 docs in Class::MOP::Attribute|Class::MOP::Attribute/clearer> for more
643 =item I<predicate> => Str
645 Creates a method to perform a basic test to see if a value has been set in the
646 attribute, see the L<predicate option docs in
647 Class::MOP::Attribute|Class::MOP::Attribute/predicate> for more information.
649 =item I<lazy_build> => (0|1)
651 Automatically define lazy => 1 as well as builder => "_build_$attr", clearer =>
652 "clear_$attr', predicate => 'has_$attr' unless they are already defined.
654 =item I<initializer> => Str
656 This may be a method name (referring to a method on the class with
657 this attribute) or a CODE ref. The initializer is used to set the
658 attribute value on an instance when the attribute is set during
659 instance initialization (but not when the value is being assigned
660 to). See the L<initializer option docs in
661 Class::MOP::Attribute|Class::MOP::Attribute/initializer> for more
664 =item I<documentation> => $string
666 An arbitrary string that can be retrieved later by calling C<<
667 $attr->documentation >>.
673 =item B<has +$name =E<gt> %options>
675 This is variation on the normal attribute creator C<has> which allows you to
676 clone and extend an attribute from a superclass or from a role. Here is an
677 example of the superclass usage:
685 default => 'Hello, I am a Foo'
693 has '+message' => (default => 'Hello I am My::Foo');
695 What is happening here is that B<My::Foo> is cloning the C<message> attribute
696 from its parent class B<Foo>, retaining the C<is =E<gt> 'rw'> and C<isa =E<gt>
697 'Str'> characteristics, but changing the value in C<default>.
699 Here is another example, but within the context of a role:
707 default => 'Hello, I am a Foo'
715 has '+message' => (default => 'Hello I am My::Foo');
717 In this case, we are basically taking the attribute which the role supplied
718 and altering it within the bounds of this feature.
720 Note that you can only extend an attribute from either a superclass or a role,
721 you cannot extend an attribute in a role that composes over an attribute from
724 Aside from where the attributes come from (one from superclass, the other
725 from a role), this feature works exactly the same. This feature is restricted
726 somewhat, so as to try and force at least I<some> sanity into it. You are only
727 allowed to change the following attributes:
733 Change the default value of an attribute.
737 Change whether the attribute attempts to coerce a value passed to it.
741 Change if the attribute is required to have a value.
743 =item I<documentation>
745 Change the documentation string associated with the attribute.
749 Change if the attribute lazily initializes the slot.
753 You I<are> allowed to change the type without restriction.
755 It is recommended that you use this freedom with caution. We used to
756 only allow for extension only if the type was a subtype of the parent's
757 type, but we felt that was too restrictive and is better left as a
762 You are allowed to B<add> a new C<handles> definition, but you are B<not>
763 allowed to I<change> one.
767 You are allowed to B<add> a new C<builder> definition, but you are B<not>
768 allowed to I<change> one.
772 You are allowed to B<add> a new C<metaclass> definition, but you are
773 B<not> allowed to I<change> one.
777 You are allowed to B<add> additional traits to the C<traits> definition.
778 These traits will be composed into the attribute, but preexisting traits
779 B<are not> overridden, or removed.
783 =item B<before $name|@names =E<gt> sub { ... }>
785 =item B<after $name|@names =E<gt> sub { ... }>
787 =item B<around $name|@names =E<gt> sub { ... }>
789 These three items are syntactic sugar for the before, after, and around method
790 modifier features that L<Class::MOP> provides. More information on these may be
791 found in L<Moose::Manual::MethodModifiers> and the
792 L<Class::MOP::Class documentation|Class::MOP::Class/"Method Modifiers">.
796 The keyword C<super> is a no-op when called outside of an C<override> method. In
797 the context of an C<override> method, it will call the next most appropriate
798 superclass method with the same arguments as the original method.
800 =item B<override ($name, &sub)>
802 An C<override> method is a way of explicitly saying "I am overriding this
803 method from my superclass". You can call C<super> within this method, and
804 it will work as expected. The same thing I<can> be accomplished with a normal
805 method call and the C<SUPER::> pseudo-package; it is really your choice.
809 The keyword C<inner>, much like C<super>, is a no-op outside of the context of
810 an C<augment> method. You can think of C<inner> as being the inverse of
811 C<super>; the details of how C<inner> and C<augment> work is best described in
812 the L<Moose::Cookbook::Basics::Recipe6>.
814 =item B<augment ($name, &sub)>
816 An C<augment> method, is a way of explicitly saying "I am augmenting this
817 method from my superclass". Once again, the details of how C<inner> and
818 C<augment> work is best described in the L<Moose::Cookbook::Basics::Recipe6>.
822 This is the C<Carp::confess> function, and exported here because I use it
827 This is the C<Scalar::Util::blessed> function, it is exported here because I
828 use it all the time. It is highly recommended that this is used instead of
829 C<ref> anywhere you need to test for an object's class name.
835 When you use Moose, you can specify which metaclass to use:
837 use Moose -metaclass => 'My::Meta::Class';
839 You can also specify traits which will be applied to your metaclass:
841 use Moose -traits => 'My::Trait';
843 This is very similar to the attribute traits feature. When you do
844 this, your class's C<meta> object will have the specified traits
845 applied to it. See L<Metaclass and Trait Name Resolution> for more
848 =head2 Metaclass and Trait Name Resolution
850 By default, when given a trait name, Moose simply tries to load a
851 class of the same name. If such a class does not exist, it then looks
852 for for a class matching
853 B<Moose::Meta::$type::Custom::Trait::$trait_name>. The C<$type>
854 variable here will be one of B<Attribute> or B<Class>, depending on
855 what the trait is being applied to.
857 If a class with this long name exists, Moose checks to see if it has
858 the method C<register_implementation>. This method is expected to
859 return the I<real> class name of the trait. If there is no
860 C<register_implementation> method, it will fall back to using
861 B<Moose::Meta::$type::Custom::Trait::$trait> as the trait name.
863 The lookup method for metaclasses is the same, except that it looks
864 for a class matching B<Moose::Meta::$type::Custom::$metaclass_name>.
866 If all this is confusing, take a look at
867 L<Moose::Cookbook::Meta::Recipe3>, which demonstrates how to create an
870 =head1 UNIMPORTING FUNCTIONS
874 Moose offers a way to remove the keywords it exports, through the C<unimport>
875 method. You simply have to say C<no Moose> at the bottom of your code for this
876 to work. Here is an example:
881 has 'first_name' => (is => 'rw', isa => 'Str');
882 has 'last_name' => (is => 'rw', isa => 'Str');
886 $self->first_name . ' ' . $self->last_name
889 no Moose; # keywords are removed from the Person package
891 =head1 EXTENDING AND EMBEDDING MOOSE
893 To learn more about extending Moose, we recommend checking out the
894 "Extending" recipes in the L<Moose::Cookbook>, starting with
895 L<Moose::Cookbook::Extending::Recipe1>, which provides an overview of
896 all the different ways you might extend Moose.
898 =head2 B<< Moose->init_meta(for_class => $class, base_class => $baseclass, metaclass => $metaclass) >>
900 The C<init_meta> method sets up the metaclass object for the class
901 specified by C<for_class>. This method injects a a C<meta> accessor
902 into the class so you can get at this object. It also sets the class's
903 superclass to C<base_class>, with L<Moose::Object> as the default.
905 C<init_meta> returns the metaclass object for C<$class>.
907 You can specify an alternate metaclass with the C<metaclass> option.
909 For more detail on this topic, see L<Moose::Cookbook::Extending::Recipe2>.
911 This method used to be documented as a function which accepted
912 positional parameters. This calling style will still work for
913 backwards compatibility, but is deprecated.
917 Moose's C<import> method supports the L<Sub::Exporter> form of C<{into =E<gt> $pkg}>
918 and C<{into_level =E<gt> 1}>.
920 B<NOTE>: Doing this is more or less deprecated. Use L<Moose::Exporter>
921 instead, which lets you stack multiple C<Moose.pm>-alike modules
922 sanely. It handles getting the exported functions into the right place
925 =head2 B<throw_error>
927 An alias for C<confess>, used by internally by Moose.
929 =head1 METACLASS COMPATIBILITY AND MOOSE
931 Metaclass compatibility is a thorny subject. You should start by
932 reading the "About Metaclass compatibility" section in the
935 Moose will attempt to resolve a few cases of metaclass incompatibility
936 when you set the superclasses for a class, unlike C<Class::MOP>, which
937 simply dies if the metaclasses are incompatible.
939 In actuality, Moose fixes incompatibility for I<all> of a class's
940 metaclasses, not just the class metaclass. That includes the instance
941 metaclass, attribute metaclass, as well as its constructor class and
942 destructor class. However, for simplicity this discussion will just
943 refer to "metaclass", meaning the class metaclass, most of the time.
945 Moose has two algorithms for fixing metaclass incompatibility.
947 The first algorithm is very simple. If all the metaclass for the
948 parent is a I<subclass> of the child's metaclass, then we simply
949 replace the child's metaclass with the parent's.
951 The second algorithm is more complicated. It tries to determine if the
952 metaclasses only "differ by roles". This means that the parent and
953 child's metaclass share a common ancestor in their respective
954 hierarchies, and that the subclasses under the common ancestor are
955 only different because of role applications. This case is actually
956 fairly common when you mix and match various C<MooseX::*> modules,
957 many of which apply roles to the metaclass.
959 If the parent and child do differ by roles, Moose replaces the
960 metaclass in the child with a newly created metaclass. This metaclass
961 is a subclass of the parent's metaclass, does all of the roles that
962 the child's metaclass did before being replaced. Effectively, this
963 means the new metaclass does all of the roles done by both the
964 parent's and child's original metaclasses.
966 Ultimately, this is all transparent to you except in the case of an
967 unresolvable conflict.
969 =head2 The MooseX:: namespace
971 Generally if you're writing an extension I<for> Moose itself you'll want
972 to put your extension in the C<MooseX::> namespace. This namespace is
973 specifically for extensions that make Moose better or different in some
974 fundamental way. It is traditionally B<not> for a package that just happens
975 to use Moose. This namespace follows from the examples of the C<LWPx::>
976 and C<DBIx::> namespaces that perform the same function for C<LWP> and C<DBI>
985 It should be noted that C<super> and C<inner> B<cannot> be used in the same
986 method. However, they may be combined within the same class hierarchy; see
987 F<t/014_override_augment_inner_super.t> for an example.
989 The reason for this is that C<super> is only valid within a method
990 with the C<override> modifier, and C<inner> will never be valid within an
991 C<override> method. In fact, C<augment> will skip over any C<override> methods
992 when searching for its appropriate C<inner>.
994 This might seem like a restriction, but I am of the opinion that keeping these
995 two features separate (yet interoperable) actually makes them easy to use, since
996 their behavior is then easier to predict. Time will tell whether I am right or
997 not (UPDATE: so far so good).
1003 We offer both a mailing list and a very active IRC channel.
1005 The mailing list is L<moose@perl.org>. You must be subscribed to send
1006 a message. To subscribe, send an empty message to
1007 L<moose-subscribe@perl.org>
1009 You can also visit us at L<#moose on
1010 irc.perl.org|irc://irc.perl.org/#moose>. This channel is quite active,
1011 and questions at all levels (on Moose-related topics ;) are welcome.
1013 =head1 ACKNOWLEDGEMENTS
1017 =item I blame Sam Vilain for introducing me to the insanity that is meta-models.
1019 =item I blame Audrey Tang for then encouraging my meta-model habit in #perl6.
1021 =item Without Yuval "nothingmuch" Kogman this module would not be possible,
1022 and it certainly wouldn't have this name ;P
1024 =item The basis of the TypeContraints module was Rob Kinyon's idea
1025 originally, I just ran with it.
1027 =item Thanks to mst & chansen and the whole #moose posse for all the
1028 early ideas/feature-requests/encouragement/bug-finding.
1030 =item Thanks to David "Theory" Wheeler for meta-discussions and spelling fixes.
1038 =item L<http://www.iinteractive.com/moose>
1040 This is the official web home of Moose, it contains links to our public SVN repository
1041 as well as links to a number of talks and articles on Moose and Moose related
1044 =item The Moose is flying, a tutorial by Randal Schwartz
1046 Part 1 - L<http://www.stonehenge.com/merlyn/LinuxMag/col94.html>
1048 Part 2 - L<http://www.stonehenge.com/merlyn/LinuxMag/col95.html>
1050 =item Several Moose extension modules in the C<MooseX::> namespace.
1052 See L<http://search.cpan.org/search?query=MooseX::> for extensions.
1054 =item Moose stats on ohloh.net - L<http://www.ohloh.net/projects/moose>
1062 =item The Art of the MetaObject Protocol
1064 I mention this in the L<Class::MOP> docs too, this book was critical in
1065 the development of both modules and is highly recommended.
1073 =item L<http://www.cs.utah.edu/plt/publications/oopsla04-gff.pdf>
1075 This paper (suggested by lbr on #moose) was what lead to the implementation
1076 of the C<super>/C<override> and C<inner>/C<augment> features. If you really
1077 want to understand them, I suggest you read this.
1083 All complex software has bugs lurking in it, and this module is no
1086 Please report any bugs to C<bug-moose@rt.cpan.org>, or through the web
1087 interface at L<http://rt.cpan.org>.
1089 =head1 FEATURE REQUESTS
1091 We are very strict about what features we add to the Moose core, especially
1092 the user-visible features. Instead we have made sure that the underlying
1093 meta-system of Moose is as extensible as possible so that you can add your
1094 own features easily.
1096 That said, occasionally there is a feature needed in the meta-system
1097 to support your planned extension, in which case you should either
1098 email the mailing list (moose@perl.org) or join us on IRC at
1099 L<irc://irc.perl.org/#moose> to discuss. The
1100 L<Moose::Manual::Contributing> has more detail about how and when you
1105 Moose is an open project, there are at this point dozens of people who have
1106 contributed, and can contribute. If you have added anything to the Moose
1107 project you have a commit bit on this file and can add your name to the list.
1111 However there are only a few people with the rights to release a new version
1112 of Moose. The Moose Cabal are the people to go to with questions regarding
1113 the wider purview of Moose, and help out maintaining not just the code
1114 but the community as well.
1116 Stevan (stevan) Little E<lt>stevan@iinteractive.comE<gt>
1118 Yuval (nothingmuch) Kogman
1120 Shawn (sartak) Moore E<lt>sartak@bestpractical.comE<gt>
1122 Dave (autarch) Rolsky E<lt>autarch@urth.orgE<gt>
1124 =head2 OTHER CONTRIBUTORS
1128 Adam (Alias) Kennedy
1130 Anders (Debolaz) Nor Berle
1132 Nathan (kolibrie) Gray
1134 Christian (chansen) Hansen
1136 Hans Dieter (confound) Pearcey
1138 Eric (ewilhelm) Wilhelm
1140 Guillermo (groditi) Roditi
1142 Jess (castaway) Robinson
1146 Robert (phaylon) Sedlacek
1150 Scott (konobi) McWhirter
1152 Shlomi (rindolf) Fish
1154 Chris (perigrin) Prather
1156 Wallace (wreis) Reis
1158 Jonathan (jrockway) Rockway
1160 Piotr (dexter) Roszatycki
1162 Sam (mugwump) Vilain
1166 Dylan Hardison (doc fixes)
1168 ... and many other #moose folks
1170 =head1 COPYRIGHT AND LICENSE
1172 Copyright 2006-2009 by Infinity Interactive, Inc.
1174 L<http://www.iinteractive.com>
1176 This library is free software; you can redistribute it and/or modify
1177 it under the same terms as Perl itself.