8 $VERSION = eval $VERSION;
9 our $AUTHORITY = 'cpan:STEVAN';
11 use Scalar::Util 'blessed';
18 use Moose::Meta::Class;
19 use Moose::Meta::TypeConstraint;
20 use Moose::Meta::TypeCoercion;
21 use Moose::Meta::Attribute;
22 use Moose::Meta::Instance;
26 use Moose::Meta::Role;
27 use Moose::Meta::Role::Composite;
28 use Moose::Meta::Role::Application;
29 use Moose::Meta::Role::Application::RoleSummation;
30 use Moose::Meta::Role::Application::ToClass;
31 use Moose::Meta::Role::Application::ToRole;
32 use Moose::Meta::Role::Application::ToInstance;
34 use Moose::Util::TypeConstraints;
46 Moose->throw_error("Must derive at least one class") unless @_;
48 # this checks the metaclass to make sure
49 # it is correct, sometimes it can get out
50 # of sync when the classes are being built
51 Moose::Meta::Class->initialize($class)->superclasses(@_);
56 Moose::Util::apply_all_roles(Class::MOP::Class->initialize($class), @_);
63 Moose->throw_error('Usage: has \'name\' => ( key => value, ... )')
66 my %options = ( definition_context => Moose::Util::_caller_info(), @_ );
67 my $attrs = ( ref($name) eq 'ARRAY' ) ? $name : [ ($name) ];
68 Class::MOP::Class->initialize($class)->add_attribute( $_, %options ) for @$attrs;
73 Moose::Util::add_method_modifier($class, 'before', \@_);
78 Moose::Util::add_method_modifier($class, 'after', \@_);
83 Moose::Util::add_method_modifier($class, 'around', \@_);
91 # This check avoids a recursion loop - see
92 # t/100_bugs/020_super_recursion.t
93 return if defined $SUPER_PACKAGE && $SUPER_PACKAGE ne caller();
94 return unless $SUPER_BODY; $SUPER_BODY->(@SUPER_ARGS);
99 my ( $name, $method ) = @_;
100 Class::MOP::Class->initialize($class)->add_override_method_modifier( $name => $method );
105 our ( %INNER_BODY, %INNER_ARGS );
107 if ( my $body = $INNER_BODY{$pkg} ) {
108 my @args = @{ $INNER_ARGS{$pkg} };
109 local $INNER_ARGS{$pkg};
110 local $INNER_BODY{$pkg};
111 return $body->(@args);
119 my ( $name, $method ) = @_;
120 Class::MOP::Class->initialize($class)->add_augment_method_modifier( $name => $method );
123 Moose::Exporter->setup_import_methods(
125 qw( extends with has before after around override augment)
130 \&Scalar::Util::blessed,
135 # This used to be called as a function. This hack preserves
136 # backwards compatibility.
137 if ( $_[0] ne __PACKAGE__ ) {
138 return __PACKAGE__->init_meta(
148 my $class = $args{for_class}
149 or Moose->throw_error("Cannot call init_meta without specifying a for_class");
150 my $base_class = $args{base_class} || 'Moose::Object';
151 my $metaclass = $args{metaclass} || 'Moose::Meta::Class';
153 Moose->throw_error("The Metaclass $metaclass must be a subclass of Moose::Meta::Class.")
154 unless $metaclass->isa('Moose::Meta::Class');
156 # make a subtype for each Moose class
158 unless find_type_constraint($class);
162 if ( $meta = Class::MOP::get_metaclass_by_name($class) ) {
163 unless ( $meta->isa("Moose::Meta::Class") ) {
164 Moose->throw_error("$class already has a metaclass, but it does not inherit $metaclass ($meta)");
167 # no metaclass, no 'meta' method
169 # now we check whether our ancestors have metaclass, and if so borrow that
170 my ( undef, @isa ) = @{ $class->mro::get_linear_isa };
172 foreach my $ancestor ( @isa ) {
173 my $ancestor_meta = Class::MOP::get_metaclass_by_name($ancestor) || next;
175 my $ancestor_meta_class = ($ancestor_meta->is_immutable
176 ? $ancestor_meta->get_mutable_metaclass_name
177 : ref($ancestor_meta));
179 # if we have an ancestor metaclass that inherits $metaclass, we use
180 # that. This is like _fix_metaclass_incompatibility, but we can do it now.
182 # the case of having an ancestry is not very common, but arises in
184 unless ( $metaclass->isa( $ancestor_meta_class ) ) {
185 if ( $ancestor_meta_class->isa($metaclass) ) {
186 $metaclass = $ancestor_meta_class;
191 $meta = $metaclass->initialize($class);
194 if ( $class->can('meta') ) {
195 # check 'meta' method
197 # it may be inherited
200 # this is the case where the metaclass pragma
201 # was used before the 'use Moose' statement to
202 # override a specific class
203 my $method_meta = $class->meta;
205 ( blessed($method_meta) && $method_meta->isa('Moose::Meta::Class') )
206 || Moose->throw_error("$class already has a &meta function, but it does not return a Moose::Meta::Class ($method_meta)");
208 $meta = $method_meta;
211 unless ( $meta->has_method("meta") ) { # don't overwrite
212 # also check for inherited non moose 'meta' method?
213 # FIXME also skip this if the user requested by passing an option
216 # re-initialize so it inherits properly
217 $metaclass->initialize( ref($_[0]) || $_[0] );
222 # make sure they inherit from Moose::Object
223 $meta->superclasses($base_class)
224 unless $meta->superclasses();
229 # This may be used in some older MooseX extensions.
231 goto &Moose::Exporter::_get_caller;
234 ## make 'em all immutable
237 inline_constructor => 1,
238 constructor_name => "_new",
239 # these are Class::MOP accessors, so they need inlining
240 inline_accessors => 1
241 ) for grep { $_->is_mutable }
244 Moose::Meta::Attribute
246 Moose::Meta::Instance
248 Moose::Meta::TypeCoercion
249 Moose::Meta::TypeCoercion::Union
252 Moose::Meta::Method::Accessor
253 Moose::Meta::Method::Constructor
254 Moose::Meta::Method::Destructor
255 Moose::Meta::Method::Overridden
256 Moose::Meta::Method::Augmented
259 Moose::Meta::Role::Method
260 Moose::Meta::Role::Method::Required
261 Moose::Meta::Role::Method::Conflicting
263 Moose::Meta::Role::Composite
265 Moose::Meta::Role::Application
266 Moose::Meta::Role::Application::RoleSummation
267 Moose::Meta::Role::Application::ToClass
268 Moose::Meta::Role::Application::ToRole
269 Moose::Meta::Role::Application::ToInstance
280 Moose - A postmodern object system for Perl 5
285 use Moose; # automatically turns on strict and warnings
287 has 'x' => (is => 'rw', isa => 'Int');
288 has 'y' => (is => 'rw', isa => 'Int');
301 has 'z' => (is => 'rw', isa => 'Int');
303 after 'clear' => sub {
310 Moose is an extension of the Perl 5 object system.
312 The main goal of Moose is to make Perl 5 Object Oriented programming
313 easier, more consistent and less tedious. With Moose you can to think
314 more about what you want to do and less about the mechanics of OOP.
316 Additionally, Moose is built on top of L<Class::MOP>, which is a
317 metaclass system for Perl 5. This means that Moose not only makes
318 building normal Perl 5 objects better, but it provides the power of
319 metaclass programming as well.
323 If you're new to Moose, the best place to start is the
324 L<Moose::Manual> docs, followed by the L<Moose::Cookbook>. The intro
325 will show you what Moose is, and how it makes Perl 5 OO better.
327 The cookbook recipes on Moose basics will get you up to speed with
328 many of Moose's features quickly. Once you have an idea of what Moose
329 can do, you can use the API documentation to get more detail on
330 features which interest you.
332 =head2 Moose Extensions
334 The C<MooseX::> namespace is the official place to find Moose extensions.
335 These extensions can be found on the CPAN. The easiest way to find them
336 is to search for them (L<http://search.cpan.org/search?query=MooseX::>),
337 or to examine L<Task::Moose> which aims to keep an up-to-date, easily
338 installable list of Moose extensions.
340 =head1 BUILDING CLASSES WITH MOOSE
342 Moose makes every attempt to provide as much convenience as possible during
343 class construction/definition, but still stay out of your way if you want it
344 to. Here are a few items to note when building classes with Moose.
346 Unless specified with C<extends>, any class which uses Moose will
347 inherit from L<Moose::Object>.
349 Moose will also manage all attributes (including inherited ones) that are
350 defined with C<has>. And (assuming you call C<new>, which is inherited from
351 L<Moose::Object>) this includes properly initializing all instance slots,
352 setting defaults where appropriate, and performing any type constraint checking
355 =head1 PROVIDED METHODS
357 Moose provides a number of methods to all your classes, mostly through the
358 inheritance of L<Moose::Object>. There is however, one exception.
364 This is a method which provides access to the current class's metaclass.
368 =head1 EXPORTED FUNCTIONS
370 Moose will export a number of functions into the class's namespace which
371 may then be used to set up the class. These functions all work directly
372 on the current class.
376 =item B<extends (@superclasses)>
378 This function will set the superclass(es) for the current class.
380 This approach is recommended instead of C<use base>, because C<use base>
381 actually C<push>es onto the class's C<@ISA>, whereas C<extends> will
382 replace it. This is important to ensure that classes which do not have
383 superclasses still properly inherit from L<Moose::Object>.
385 =item B<with (@roles)>
387 This will apply a given set of C<@roles> to the local class.
389 =item B<has $name|@$names =E<gt> %options>
391 This will install an attribute of a given C<$name> into the current class. If
392 the first parameter is an array reference, it will create an attribute for
393 every C<$name> in the list. The C<%options> are the same as those provided by
394 L<Class::MOP::Attribute>, in addition to the list below which are provided by
395 Moose (L<Moose::Meta::Attribute> to be more specific):
399 =item I<is =E<gt> 'rw'|'ro'>
401 The I<is> option accepts either I<rw> (for read/write) or I<ro> (for read
402 only). These will create either a read/write accessor or a read-only
403 accessor respectively, using the same name as the C<$name> of the attribute.
405 If you need more control over how your accessors are named, you can
406 use the L<reader|Class::MOP::Attribute/reader>,
407 L<writer|Class::MOP::Attribute/writer> and
408 L<accessor|Class::MOP::Attribute/accessor> options inherited from
409 L<Class::MOP::Attribute>, however if you use those, you won't need the
412 =item I<isa =E<gt> $type_name>
414 The I<isa> option uses Moose's type constraint facilities to set up runtime
415 type checking for this attribute. Moose will perform the checks during class
416 construction, and within any accessors. The C<$type_name> argument must be a
417 string. The string may be either a class name or a type defined using
418 Moose's type definition features. (Refer to L<Moose::Util::TypeConstraints>
419 for information on how to define a new type, and how to retrieve type meta-data).
421 =item I<coerce =E<gt> (1|0)>
423 This will attempt to use coercion with the supplied type constraint to change
424 the value passed into any accessors or constructors. You B<must> have supplied
425 a type constraint in order for this to work. See L<Moose::Cookbook::Basics::Recipe5>
428 =item I<does =E<gt> $role_name>
430 This will accept the name of a role which the value stored in this attribute
431 is expected to have consumed.
433 =item I<required =E<gt> (1|0)>
435 This marks the attribute as being required. This means a value must be
436 supplied during class construction, I<or> the attribute must be lazy
437 and have either a default or a builder. Note that c<required> does not
438 say anything about the attribute's value, which can be C<undef>.
440 =item I<weak_ref =E<gt> (1|0)>
442 This will tell the class to store the value of this attribute as a weakened
443 reference. If an attribute is a weakened reference, it B<cannot> also be
446 =item I<lazy =E<gt> (1|0)>
448 This will tell the class to not create this slot until absolutely necessary.
449 If an attribute is marked as lazy it B<must> have a default supplied.
451 =item I<auto_deref =E<gt> (1|0)>
453 This tells the accessor whether to automatically dereference the value returned.
454 This is only legal if your C<isa> option is either C<ArrayRef> or C<HashRef>.
456 =item I<trigger =E<gt> $code>
458 The I<trigger> option is a CODE reference which will be called after
459 the value of the attribute is set. The CODE ref will be passed the
460 instance itself and the updated value. You B<can> have a trigger on
461 a read-only attribute.
463 B<NOTE:> Triggers will only fire when you B<assign> to the attribute,
464 either in the constructor, or using the writer. Default and built values will
465 B<not> cause the trigger to be fired.
467 =item I<handles =E<gt> ARRAY | HASH | REGEXP | ROLE | DUCKTYPE | CODE>
469 The I<handles> option provides Moose classes with automated delegation features.
470 This is a pretty complex and powerful option. It accepts many different option
471 formats, each with its own benefits and drawbacks.
473 B<NOTE:> The class being delegated to does not need to be a Moose based class,
474 which is why this feature is especially useful when wrapping non-Moose classes.
476 All I<handles> option formats share the following traits:
478 You cannot override a locally defined method with a delegated method; an
479 exception will be thrown if you try. That is to say, if you define C<foo> in
480 your class, you cannot override it with a delegated C<foo>. This is almost never
481 something you would want to do, and if it is, you should do it by hand and not
484 You cannot override any of the methods found in Moose::Object, or the C<BUILD>
485 and C<DEMOLISH> methods. These will not throw an exception, but will silently
486 move on to the next method in the list. My reasoning for this is that you would
487 almost never want to do this, since it usually breaks your class. As with
488 overriding locally defined methods, if you do want to do this, you should do it
489 manually, not with Moose.
491 You do not I<need> to have a reader (or accessor) for the attribute in order
492 to delegate to it. Moose will create a means of accessing the value for you,
493 however this will be several times B<less> efficient then if you had given
494 the attribute a reader (or accessor) to use.
496 Below is the documentation for each option format:
502 This is the most common usage for I<handles>. You basically pass a list of
503 method names to be delegated, and Moose will install a delegation method
508 This is the second most common usage for I<handles>. Instead of a list of
509 method names, you pass a HASH ref where each key is the method name you
510 want installed locally, and its value is the name of the original method
511 in the class being delegated to.
513 This can be very useful for recursive classes like trees. Here is a
514 quick example (soon to be expanded into a Moose::Cookbook recipe):
519 has 'node' => (is => 'rw', isa => 'Any');
524 default => sub { [] }
532 parent_node => 'node',
533 siblings => 'children',
537 In this example, the Tree package gets C<parent_node> and C<siblings> methods,
538 which delegate to the C<node> and C<children> methods (respectively) of the Tree
539 instance stored in the C<parent> slot.
543 The regexp option works very similar to the ARRAY option, except that it builds
544 the list of methods for you. It starts by collecting all possible methods of the
545 class being delegated to, then filters that list using the regexp supplied here.
547 B<NOTE:> An I<isa> option is required when using the regexp option format. This
548 is so that we can determine (at compile time) the method list from the class.
549 Without an I<isa> this is just not possible.
553 With the role option, you specify the name of a role whose "interface" then
554 becomes the list of methods to handle. The "interface" can be defined as; the
555 methods of the role and any required methods of the role. It should be noted
556 that this does B<not> include any method modifiers or generated attribute
557 methods (which is consistent with role composition).
561 With the duck type option, you pass a duck type object whose "interface" then
562 becomes the list of methods to handle. The "interface" can be defined as; the
563 list of methods passed to C<duck_type> to create a duck type object. For more
564 information on C<duck_type> please check
565 L<Moose::Util::TypeConstraints>.
569 This is the option to use when you really want to do something funky. You should
570 only use it if you really know what you are doing, as it involves manual
573 This takes a code reference, which should expect two arguments. The first is the
574 attribute meta-object this I<handles> is attached to. The second is the
575 metaclass of the class being delegated to. It expects you to return a hash (not
576 a HASH ref) of the methods you want mapped.
580 =item I<metaclass =E<gt> $metaclass_name>
582 This tells the class to use a custom attribute metaclass for this particular
583 attribute. Custom attribute metaclasses are useful for extending the
584 capabilities of the I<has> keyword: they are the simplest way to extend the MOP,
585 but they are still a fairly advanced topic and too much to cover here, see
586 L<Moose::Cookbook::Meta::Recipe1> for more information.
588 The default behavior here is to just load C<$metaclass_name>; however, we also
589 have a way to alias to a shorter name. This will first look to see if
590 B<Moose::Meta::Attribute::Custom::$metaclass_name> exists. If it does, Moose
591 will then check to see if that has the method C<register_implementation>, which
592 should return the actual name of the custom attribute metaclass. If there is no
593 C<register_implementation> method, it will fall back to using
594 B<Moose::Meta::Attribute::Custom::$metaclass_name> as the metaclass name.
596 =item I<traits =E<gt> [ @role_names ]>
598 This tells Moose to take the list of C<@role_names> and apply them to the
599 attribute meta-object. This is very similar to the I<metaclass> option, but
600 allows you to use more than one extension at a time.
602 See L<TRAIT NAME RESOLUTION> for details on how a trait name is
603 resolved to a class name.
605 Also see L<Moose::Cookbook::Meta::Recipe3> for a metaclass trait
608 =item I<builder> => Str
610 The value of this key is the name of the method that will be called to
611 obtain the value used to initialize the attribute. See the L<builder
612 option docs in Class::MOP::Attribute|Class::MOP::Attribute/builder>
613 and/or L<Moose::Cookbook::Basics::Recipe9> for more information.
615 =item I<default> => SCALAR | CODE
617 The value of this key is the default value which will initialize the attribute.
619 NOTE: If the value is a simple scalar (string or number), then it can
620 be just passed as is. However, if you wish to initialize it with a
621 HASH or ARRAY ref, then you need to wrap that inside a CODE reference.
622 See the L<default option docs in
623 Class::MOP::Attribute|Class::MOP::Attribute/default> for more
626 =item I<clearer> => Str
628 Creates a method allowing you to clear the value, see the L<clearer option
629 docs in Class::MOP::Attribute|Class::MOP::Attribute/clearer> for more
632 =item I<predicate> => Str
634 Creates a method to perform a basic test to see if a value has been set in the
635 attribute, see the L<predicate option docs in
636 Class::MOP::Attribute|Class::MOP::Attribute/predicate> for more information.
638 =item I<lazy_build> => (0|1)
640 Automatically define lazy => 1 as well as builder => "_build_$attr", clearer =>
641 "clear_$attr', predicate => 'has_$attr' unless they are already defined.
643 =item I<initializer> => Str
645 This may be a method name (referring to a method on the class with
646 this attribute) or a CODE ref. The initializer is used to set the
647 attribute value on an instance when the attribute is set during
648 instance initialization (but not when the value is being assigned
649 to). See the L<initializer option docs in
650 Class::MOP::Attribute|Class::MOP::Attribute/initializer> for more
653 =item I<documentation> => $string
655 An arbitrary string that can be retrieved later by calling C<<
656 $attr->documentation >>.
662 =item B<has +$name =E<gt> %options>
664 This is variation on the normal attribute creator C<has> which allows you to
665 clone and extend an attribute from a superclass or from a role. Here is an
666 example of the superclass usage:
674 default => 'Hello, I am a Foo'
682 has '+message' => (default => 'Hello I am My::Foo');
684 What is happening here is that B<My::Foo> is cloning the C<message> attribute
685 from its parent class B<Foo>, retaining the C<is =E<gt> 'rw'> and C<isa =E<gt>
686 'Str'> characteristics, but changing the value in C<default>.
688 Here is another example, but within the context of a role:
696 default => 'Hello, I am a Foo'
704 has '+message' => (default => 'Hello I am My::Foo');
706 In this case, we are basically taking the attribute which the role supplied
707 and altering it within the bounds of this feature.
709 Note that you can only extend an attribute from either a superclass or a role,
710 you cannot extend an attribute in a role that composes over an attribute from
713 Aside from where the attributes come from (one from superclass, the other
714 from a role), this feature works exactly the same. This feature is restricted
715 somewhat, so as to try and force at least I<some> sanity into it. You are only
716 allowed to change the following attributes:
722 Change the default value of an attribute.
726 Change whether the attribute attempts to coerce a value passed to it.
730 Change if the attribute is required to have a value.
732 =item I<documentation>
734 Change the documentation string associated with the attribute.
738 Change if the attribute lazily initializes the slot.
742 You I<are> allowed to change the type without restriction.
744 It is recommended that you use this freedom with caution. We used to
745 only allow for extension only if the type was a subtype of the parent's
746 type, but we felt that was too restrictive and is better left as a
751 You are allowed to B<add> a new C<handles> definition, but you are B<not>
752 allowed to I<change> one.
756 You are allowed to B<add> a new C<builder> definition, but you are B<not>
757 allowed to I<change> one.
761 You are allowed to B<add> a new C<metaclass> definition, but you are
762 B<not> allowed to I<change> one.
766 You are allowed to B<add> additional traits to the C<traits> definition.
767 These traits will be composed into the attribute, but preexisting traits
768 B<are not> overridden, or removed.
772 =item B<before $name|@names =E<gt> sub { ... }>
774 =item B<after $name|@names =E<gt> sub { ... }>
776 =item B<around $name|@names =E<gt> sub { ... }>
778 This three items are syntactic sugar for the before, after, and around method
779 modifier features that L<Class::MOP> provides. More information on these may be
780 found in the L<Class::MOP::Class documentation|Class::MOP::Class/"Method
785 The keyword C<super> is a no-op when called outside of an C<override> method. In
786 the context of an C<override> method, it will call the next most appropriate
787 superclass method with the same arguments as the original method.
789 =item B<override ($name, &sub)>
791 An C<override> method is a way of explicitly saying "I am overriding this
792 method from my superclass". You can call C<super> within this method, and
793 it will work as expected. The same thing I<can> be accomplished with a normal
794 method call and the C<SUPER::> pseudo-package; it is really your choice.
798 The keyword C<inner>, much like C<super>, is a no-op outside of the context of
799 an C<augment> method. You can think of C<inner> as being the inverse of
800 C<super>; the details of how C<inner> and C<augment> work is best described in
801 the L<Moose::Cookbook::Basics::Recipe6>.
803 =item B<augment ($name, &sub)>
805 An C<augment> method, is a way of explicitly saying "I am augmenting this
806 method from my superclass". Once again, the details of how C<inner> and
807 C<augment> work is best described in the L<Moose::Cookbook::Basics::Recipe6>.
811 This is the C<Carp::confess> function, and exported here because I use it
816 This is the C<Scalar::Util::blessed> function, it is exported here because I
817 use it all the time. It is highly recommended that this is used instead of
818 C<ref> anywhere you need to test for an object's class name.
824 When you use Moose, you can specify which metaclass to use:
826 use Moose -metaclass => 'My::Meta::Class';
828 You can also specify traits which will be applied to your metaclass:
830 use Moose -traits => 'My::Trait';
832 This is very similar to the attribute traits feature. When you do
833 this, your class's C<meta> object will have the specified traits
834 applied to it. See L<TRAIT NAME RESOLUTION> for more details.
836 =head2 Trait Name Resolution
838 By default, when given a trait name, Moose simply tries to load a
839 class of the same name. If such a class does not exist, it then looks
840 for for a class matching
841 B<Moose::Meta::$type::Custom::Trait::$trait_name>. The C<$type>
842 variable here will be one of B<Attribute> or B<Class>, depending on
843 what the trait is being applied to.
845 If a class with this long name exists, Moose checks to see if it has
846 the method C<register_implementation>. This method is expected to
847 return the I<real> class name of the trait. If there is no
848 C<register_implementation> method, it will fall back to using
849 B<Moose::Meta::$type::Custom::Trait::$trait> as the trait name.
851 If all this is confusing, take a look at
852 L<Moose::Cookbook::Meta::Recipe3>, which demonstrates how to create an
855 =head1 UNIMPORTING FUNCTIONS
859 Moose offers a way to remove the keywords it exports, through the C<unimport>
860 method. You simply have to say C<no Moose> at the bottom of your code for this
861 to work. Here is an example:
866 has 'first_name' => (is => 'rw', isa => 'Str');
867 has 'last_name' => (is => 'rw', isa => 'Str');
871 $self->first_name . ' ' . $self->last_name
874 no Moose; # keywords are removed from the Person package
876 =head1 EXTENDING AND EMBEDDING MOOSE
878 To learn more about extending Moose, we recommend checking out the
879 "Extending" recipes in the L<Moose::Cookbook>, starting with
880 L<Moose::Cookbook::Extending::Recipe1>, which provides an overview of
881 all the different ways you might extend Moose.
883 =head2 B<< Moose->init_meta(for_class => $class, base_class => $baseclass, metaclass => $metaclass) >>
885 The C<init_meta> method sets up the metaclass object for the class
886 specified by C<for_class>. This method injects a a C<meta> accessor
887 into the class so you can get at this object. It also sets the class's
888 superclass to C<base_class>, with L<Moose::Object> as the default.
890 C<init_meta> returns the metaclass object for C<$class>.
892 You can specify an alternate metaclass with the C<metaclass> option.
894 For more detail on this topic, see L<Moose::Cookbook::Extending::Recipe2>.
896 This method used to be documented as a function which accepted
897 positional parameters. This calling style will still work for
898 backwards compatibility, but is deprecated.
902 Moose's C<import> method supports the L<Sub::Exporter> form of C<{into =E<gt> $pkg}>
903 and C<{into_level =E<gt> 1}>.
905 B<NOTE>: Doing this is more or less deprecated. Use L<Moose::Exporter>
906 instead, which lets you stack multiple C<Moose.pm>-alike modules
907 sanely. It handles getting the exported functions into the right place
910 =head2 B<throw_error>
912 An alias for C<confess>, used by internally by Moose.
914 =head1 METACLASS COMPATIBILITY AND MOOSE
916 Metaclass compatibility is a thorny subject. You should start by
917 reading the "About Metaclass compatibility" section in the
920 Moose will attempt to resolve a few cases of metaclass incompatibility
921 when you set the superclasses for a class, unlike C<Class::MOP>, which
922 simply dies if the metaclasses are incompatible.
924 In actuality, Moose fixes incompatibility for I<all> of a class's
925 metaclasses, not just the class metaclass. That includes the instance
926 metaclass, attribute metaclass, as well as its constructor class and
927 destructor class. However, for simplicity this discussion will just
928 refer to "metaclass", meaning the class metaclass, most of the time.
930 Moose has two algorithms for fixing metaclass incompatibility.
932 The first algorithm is very simple. If all the metaclass for the
933 parent is a I<subclass> of the child's metaclass, then we simply
934 replace the child's metaclass with the parent's.
936 The second algorithm is more complicated. It tries to determine if the
937 metaclasses only "differ by roles". This means that the parent and
938 child's metaclass share a common ancestor in their respective
939 hierarchies, and that the subclasses under the common ancestor are
940 only different because of role applications. This case is actually
941 fairly common when you mix and match various C<MooseX::*> modules,
942 many of which apply roles to the metaclass.
944 If the parent and child do differ by roles, Moose replaces the
945 metaclass in the child with a newly created metaclass. This metaclass
946 is a subclass of the parent's metaclass, does all of the roles that
947 the child's metaclass did before being replaced. Effectively, this
948 means the new metaclass does all of the roles done by both the
949 parent's and child's original metaclasses.
951 Ultimately, this is all transparent to you except in the case of an
952 unresolvable conflict.
954 =head2 The MooseX:: namespace
956 Generally if you're writing an extension I<for> Moose itself you'll want
957 to put your extension in the C<MooseX::> namespace. This namespace is
958 specifically for extensions that make Moose better or different in some
959 fundamental way. It is traditionally B<not> for a package that just happens
960 to use Moose. This namespace follows from the examples of the C<LWPx::>
961 and C<DBIx::> namespaces that perform the same function for C<LWP> and C<DBI>
970 It should be noted that C<super> and C<inner> B<cannot> be used in the same
971 method. However, they may be combined within the same class hierarchy; see
972 F<t/014_override_augment_inner_super.t> for an example.
974 The reason for this is that C<super> is only valid within a method
975 with the C<override> modifier, and C<inner> will never be valid within an
976 C<override> method. In fact, C<augment> will skip over any C<override> methods
977 when searching for its appropriate C<inner>.
979 This might seem like a restriction, but I am of the opinion that keeping these
980 two features separate (yet interoperable) actually makes them easy to use, since
981 their behavior is then easier to predict. Time will tell whether I am right or
982 not (UPDATE: so far so good).
988 We offer both a mailing list and a very active IRC channel.
990 The mailing list is L<moose@perl.org>. You must be subscribed to send
991 a message. To subscribe, send an empty message to
992 L<moose-subscribe@perl.org>
994 You can also visit us at L<#moose on
995 irc.perl.org|irc://irc.perl.org/#moose>. This channel is quite active,
996 and questions at all levels (on Moose-related topics ;) are welcome.
998 =head1 ACKNOWLEDGEMENTS
1002 =item I blame Sam Vilain for introducing me to the insanity that is meta-models.
1004 =item I blame Audrey Tang for then encouraging my meta-model habit in #perl6.
1006 =item Without Yuval "nothingmuch" Kogman this module would not be possible,
1007 and it certainly wouldn't have this name ;P
1009 =item The basis of the TypeContraints module was Rob Kinyon's idea
1010 originally, I just ran with it.
1012 =item Thanks to mst & chansen and the whole #moose posse for all the
1013 early ideas/feature-requests/encouragement/bug-finding.
1015 =item Thanks to David "Theory" Wheeler for meta-discussions and spelling fixes.
1023 =item L<http://www.iinteractive.com/moose>
1025 This is the official web home of Moose, it contains links to our public SVN repository
1026 as well as links to a number of talks and articles on Moose and Moose related
1029 =item The Moose is flying, a tutorial by Randal Schwartz
1031 Part 1 - L<http://www.stonehenge.com/merlyn/LinuxMag/col94.html>
1033 Part 2 - L<http://www.stonehenge.com/merlyn/LinuxMag/col95.html>
1035 =item Several Moose extension modules in the C<MooseX::> namespace.
1037 See L<http://search.cpan.org/search?query=MooseX::> for extensions.
1039 =item Moose stats on ohloh.net - L<http://www.ohloh.net/projects/moose>
1047 =item The Art of the MetaObject Protocol
1049 I mention this in the L<Class::MOP> docs too, this book was critical in
1050 the development of both modules and is highly recommended.
1058 =item L<http://www.cs.utah.edu/plt/publications/oopsla04-gff.pdf>
1060 This paper (suggested by lbr on #moose) was what lead to the implementation
1061 of the C<super>/C<override> and C<inner>/C<augment> features. If you really
1062 want to understand them, I suggest you read this.
1068 All complex software has bugs lurking in it, and this module is no
1071 Please report any bugs to C<bug-moose@rt.cpan.org>, or through the web
1072 interface at L<http://rt.cpan.org>.
1074 =head1 FEATURE REQUESTS
1076 We are very strict about what features we add to the Moose core, especially
1077 the user-visible features. Instead we have made sure that the underlying
1078 meta-system of Moose is as extensible as possible so that you can add your
1079 own features easily.
1081 That said, occasionally there is a feature needed in the meta-system
1082 to support your planned extension, in which case you should either
1083 email the mailing list (moose@perl.org) or join us on IRC at
1084 L<irc://irc.perl.org/#moose> to discuss. The
1085 L<Moose::Manual::Contributing> has more detail about how and when you
1090 Moose is an open project, there are at this point dozens of people who have
1091 contributed, and can contribute. If you have added anything to the Moose
1092 project you have a commit bit on this file and can add your name to the list.
1096 However there are only a few people with the rights to release a new version
1097 of Moose. The Moose Cabal are the people to go to with questions regarding
1098 the wider purview of Moose, and help out maintaining not just the code
1099 but the community as well.
1101 Stevan (stevan) Little E<lt>stevan@iinteractive.comE<gt>
1103 Yuval (nothingmuch) Kogman
1105 Shawn (sartak) Moore
1107 Dave (autarch) Rolsky E<lt>autarch@urth.orgE<gt>
1109 =head2 OTHER CONTRIBUTORS
1113 Adam (Alias) Kennedy
1115 Anders (Debolaz) Nor Berle
1117 Nathan (kolibrie) Gray
1119 Christian (chansen) Hansen
1121 Hans Dieter (confound) Pearcey
1123 Eric (ewilhelm) Wilhelm
1125 Guillermo (groditi) Roditi
1127 Jess (castaway) Robinson
1131 Robert (phaylon) Sedlacek
1135 Scott (konobi) McWhirter
1137 Shlomi (rindolf) Fish
1139 Chris (perigrin) Prather
1141 Wallace (wreis) Reis
1143 Jonathan (jrockway) Rockway
1145 Piotr (dexter) Roszatycki
1147 Sam (mugwump) Vilain
1151 Dylan Hardison (doc fixes)
1153 ... and many other #moose folks
1155 =head1 COPYRIGHT AND LICENSE
1157 Copyright 2006-2009 by Infinity Interactive, Inc.
1159 L<http://www.iinteractive.com>
1161 This library is free software; you can redistribute it and/or modify
1162 it under the same terms as Perl itself.