10 $VERSION = eval $VERSION;
11 our $AUTHORITY = 'cpan:STEVAN';
13 use Scalar::Util 'blessed';
14 use Carp 'confess', 'croak', 'cluck';
20 use Moose::Meta::Class;
21 use Moose::Meta::TypeConstraint;
22 use Moose::Meta::TypeCoercion;
23 use Moose::Meta::Attribute;
24 use Moose::Meta::Instance;
28 use Moose::Meta::Role;
29 use Moose::Meta::Role::Composite;
30 use Moose::Meta::Role::Application;
31 use Moose::Meta::Role::Application::RoleSummation;
32 use Moose::Meta::Role::Application::ToClass;
33 use Moose::Meta::Role::Application::ToRole;
34 use Moose::Meta::Role::Application::ToInstance;
36 use Moose::Util::TypeConstraints;
40 my $level = @_ ? ($_[0] + 1) : 2;
42 @info{qw(package file line)} = caller($level);
55 croak "Must derive at least one class" unless @_;
58 foreach my $super (@supers) {
59 Class::MOP::load_class($super);
60 croak "You cannot inherit from a Moose Role ($super)"
61 if $super->can('meta') &&
62 blessed $super->meta &&
63 $super->meta->isa('Moose::Meta::Role')
68 # this checks the metaclass to make sure
69 # it is correct, sometimes it can get out
70 # of sync when the classes are being built
71 my $meta = Moose::Meta::Class->initialize($class);
72 $meta->superclasses(@supers);
77 Moose::Util::apply_all_roles(Class::MOP::Class->initialize($class), @_);
83 croak 'Usage: has \'name\' => ( key => value, ... )' if @_ == 1;
84 my %options = ( definition_context => _caller_info(), @_ );
85 my $attrs = ( ref($name) eq 'ARRAY' ) ? $name : [ ($name) ];
86 Class::MOP::Class->initialize($class)->add_attribute( $_, %options ) for @$attrs;
91 Moose::Util::add_method_modifier($class, 'before', \@_);
96 Moose::Util::add_method_modifier($class, 'after', \@_);
101 Moose::Util::add_method_modifier($class, 'around', \@_);
109 # This check avoids a recursion loop - see
110 # t/100_bugs/020_super_recursion.t
111 return if defined $SUPER_PACKAGE && $SUPER_PACKAGE ne caller();
112 return unless $SUPER_BODY; $SUPER_BODY->(@SUPER_ARGS);
117 my ( $name, $method ) = @_;
118 Class::MOP::Class->initialize($class)->add_override_method_modifier( $name => $method );
123 our ( %INNER_BODY, %INNER_ARGS );
125 if ( my $body = $INNER_BODY{$pkg} ) {
126 my @args = @{ $INNER_ARGS{$pkg} };
127 local $INNER_ARGS{$pkg};
128 local $INNER_BODY{$pkg};
129 return $body->(@args);
137 my ( $name, $method ) = @_;
138 Class::MOP::Class->initialize($class)->add_augment_method_modifier( $name => $method );
141 Moose::Exporter->setup_import_methods(
143 qw( extends with has before after around override augment)
148 \&Scalar::Util::blessed,
153 # This used to be called as a function. This hack preserves
154 # backwards compatibility.
155 if ( $_[0] ne __PACKAGE__ ) {
156 return __PACKAGE__->init_meta(
166 my $class = $args{for_class}
167 or Moose->throw_error("Cannot call init_meta without specifying a for_class");
168 my $base_class = $args{base_class} || 'Moose::Object';
169 my $metaclass = $args{metaclass} || 'Moose::Meta::Class';
171 Moose->throw_error("The Metaclass $metaclass must be a subclass of Moose::Meta::Class.")
172 unless $metaclass->isa('Moose::Meta::Class');
174 # make a subtype for each Moose class
176 unless find_type_constraint($class);
180 if ( $meta = Class::MOP::get_metaclass_by_name($class) ) {
181 unless ( $meta->isa("Moose::Meta::Class") ) {
182 Moose->throw_error("$class already has a metaclass, but it does not inherit $metaclass ($meta)");
185 # no metaclass, no 'meta' method
187 # now we check whether our ancestors have metaclass, and if so borrow that
188 my ( undef, @isa ) = @{ $class->mro::get_linear_isa };
190 foreach my $ancestor ( @isa ) {
191 my $ancestor_meta = Class::MOP::get_metaclass_by_name($ancestor) || next;
193 my $ancestor_meta_class = ($ancestor_meta->is_immutable
194 ? $ancestor_meta->get_mutable_metaclass_name
195 : ref($ancestor_meta));
197 # if we have an ancestor metaclass that inherits $metaclass, we use
198 # that. This is like _fix_metaclass_incompatibility, but we can do it now.
200 # the case of having an ancestry is not very common, but arises in
202 unless ( $metaclass->isa( $ancestor_meta_class ) ) {
203 if ( $ancestor_meta_class->isa($metaclass) ) {
204 $metaclass = $ancestor_meta_class;
209 $meta = $metaclass->initialize($class);
212 if ( $class->can('meta') ) {
213 # check 'meta' method
215 # it may be inherited
218 # this is the case where the metaclass pragma
219 # was used before the 'use Moose' statement to
220 # override a specific class
221 my $method_meta = $class->meta;
223 ( blessed($method_meta) && $method_meta->isa('Moose::Meta::Class') )
224 || Moose->throw_error("$class already has a &meta function, but it does not return a Moose::Meta::Class ($meta)");
226 $meta = $method_meta;
229 unless ( $meta->has_method("meta") ) { # don't overwrite
230 # also check for inherited non moose 'meta' method?
231 # FIXME also skip this if the user requested by passing an option
234 # re-initialize so it inherits properly
235 $metaclass->initialize( ref($_[0]) || $_[0] );
240 # make sure they inherit from Moose::Object
241 $meta->superclasses($base_class)
242 unless $meta->superclasses();
247 # This may be used in some older MooseX extensions.
249 goto &Moose::Exporter::_get_caller;
252 ## make 'em all immutable
255 inline_constructor => 1,
256 constructor_name => "_new",
257 # these are Class::MOP accessors, so they need inlining
258 inline_accessors => 1
259 ) for grep { $_->is_mutable }
262 Moose::Meta::Attribute
264 Moose::Meta::Instance
266 Moose::Meta::TypeCoercion
267 Moose::Meta::TypeCoercion::Union
270 Moose::Meta::Method::Accessor
271 Moose::Meta::Method::Constructor
272 Moose::Meta::Method::Destructor
273 Moose::Meta::Method::Overriden
274 Moose::Meta::Method::Augmented
277 Moose::Meta::Role::Method
278 Moose::Meta::Role::Method::Required
280 Moose::Meta::Role::Composite
282 Moose::Meta::Role::Application
283 Moose::Meta::Role::Application::RoleSummation
284 Moose::Meta::Role::Application::ToClass
285 Moose::Meta::Role::Application::ToRole
286 Moose::Meta::Role::Application::ToInstance
297 Moose - A postmodern object system for Perl 5
302 use Moose; # automatically turns on strict and warnings
304 has 'x' => (is => 'rw', isa => 'Int');
305 has 'y' => (is => 'rw', isa => 'Int');
318 has 'z' => (is => 'rw', isa => 'Int');
320 after 'clear' => sub {
327 Moose is an extension of the Perl 5 object system.
329 The main goal of Moose is to make Perl 5 Object Oriented programming
330 easier, more consistent and less tedious. With Moose you can to think
331 more about what you want to do and less about the mechanics of OOP.
333 Additionally, Moose is built on top of L<Class::MOP>, which is a
334 metaclass system for Perl 5. This means that Moose not only makes
335 building normal Perl 5 objects better, but it provides the power of
336 metaclass programming as well.
340 If you're new to Moose, the best place to start is the L<Moose::Intro>
341 docs, followed by the L<Moose::Cookbook>. The intro will show you what
342 Moose is, and how it makes Perl 5 OO better.
344 The cookbook recipes on Moose basics will get you up to speed with
345 many of Moose's features quickly. Once you have an idea of what Moose
346 can do, you can use the API documentation to get more detail on
347 features which interest you.
349 =head2 Moose Extensions
351 The C<MooseX::> namespace is the official place to find Moose extensions.
352 These extensions can be found on the CPAN. The easiest way to find them
353 is to search for them (L<http://search.cpan.org/search?query=MooseX::>),
354 or to examine L<Task::Moose> which aims to keep an up-to-date, easily
355 installable list of Moose extensions.
357 =head1 BUILDING CLASSES WITH MOOSE
359 Moose makes every attempt to provide as much convenience as possible during
360 class construction/definition, but still stay out of your way if you want it
361 to. Here are a few items to note when building classes with Moose.
363 Unless specified with C<extends>, any class which uses Moose will
364 inherit from L<Moose::Object>.
366 Moose will also manage all attributes (including inherited ones) that are
367 defined with C<has>. And (assuming you call C<new>, which is inherited from
368 L<Moose::Object>) this includes properly initializing all instance slots,
369 setting defaults where appropriate, and performing any type constraint checking
372 =head1 PROVIDED METHODS
374 Moose provides a number of methods to all your classes, mostly through the
375 inheritance of L<Moose::Object>. There is however, one exception.
381 This is a method which provides access to the current class's metaclass.
385 =head1 EXPORTED FUNCTIONS
387 Moose will export a number of functions into the class's namespace which
388 may then be used to set up the class. These functions all work directly
389 on the current class.
393 =item B<extends (@superclasses)>
395 This function will set the superclass(es) for the current class.
397 This approach is recommended instead of C<use base>, because C<use base>
398 actually C<push>es onto the class's C<@ISA>, whereas C<extends> will
399 replace it. This is important to ensure that classes which do not have
400 superclasses still properly inherit from L<Moose::Object>.
402 =item B<with (@roles)>
404 This will apply a given set of C<@roles> to the local class.
406 =item B<has $name|@$names =E<gt> %options>
408 This will install an attribute of a given C<$name> into the current class. If
409 the first parameter is an array reference, it will create an attribute for
410 every C<$name> in the list. The C<%options> are the same as those provided by
411 L<Class::MOP::Attribute>, in addition to the list below which are provided by
412 Moose (L<Moose::Meta::Attribute> to be more specific):
416 =item I<is =E<gt> 'rw'|'ro'>
418 The I<is> option accepts either I<rw> (for read/write) or I<ro> (for read
419 only). These will create either a read/write accessor or a read-only
420 accessor respectively, using the same name as the C<$name> of the attribute.
422 If you need more control over how your accessors are named, you can
423 use the L<reader|Class::MOP::Attribute/reader>,
424 L<writer|Class::MOP::Attribute/writer> and
425 L<accessor|Class::MOP::Attribute/accessor> options inherited from
426 L<Class::MOP::Attribute>, however if you use those, you won't need the
429 =item I<isa =E<gt> $type_name>
431 The I<isa> option uses Moose's type constraint facilities to set up runtime
432 type checking for this attribute. Moose will perform the checks during class
433 construction, and within any accessors. The C<$type_name> argument must be a
434 string. The string may be either a class name or a type defined using
435 Moose's type definition features. (Refer to L<Moose::Util::TypeConstraints>
436 for information on how to define a new type, and how to retrieve type meta-data).
438 =item I<coerce =E<gt> (1|0)>
440 This will attempt to use coercion with the supplied type constraint to change
441 the value passed into any accessors or constructors. You B<must> have supplied
442 a type constraint in order for this to work. See L<Moose::Cookbook::Basics::Recipe5>
445 =item I<does =E<gt> $role_name>
447 This will accept the name of a role which the value stored in this attribute
448 is expected to have consumed.
450 =item I<required =E<gt> (1|0)>
452 This marks the attribute as being required. This means a I<defined> value must be
453 supplied during class construction, and the attribute may never be set to
454 C<undef> with an accessor.
456 =item I<weak_ref =E<gt> (1|0)>
458 This will tell the class to store the value of this attribute as a weakened
459 reference. If an attribute is a weakened reference, it B<cannot> also be
462 =item I<lazy =E<gt> (1|0)>
464 This will tell the class to not create this slot until absolutely necessary.
465 If an attribute is marked as lazy it B<must> have a default supplied.
467 =item I<auto_deref =E<gt> (1|0)>
469 This tells the accessor whether to automatically dereference the value returned.
470 This is only legal if your C<isa> option is either C<ArrayRef> or C<HashRef>.
472 =item I<trigger =E<gt> $code>
474 The I<trigger> option is a CODE reference which will be called after the value of
475 the attribute is set. The CODE ref will be passed the instance itself, the
476 updated value and the attribute meta-object (this is for more advanced fiddling
477 and can typically be ignored). You B<cannot> have a trigger on a read-only
480 B<NOTE:> Triggers will only fire when you B<assign> to the attribute,
481 either in the constructor, or using the writer. Default and built values will
482 B<not> cause the trigger to be fired.
484 =item I<handles =E<gt> ARRAY | HASH | REGEXP | ROLE | CODE>
486 The I<handles> option provides Moose classes with automated delegation features.
487 This is a pretty complex and powerful option. It accepts many different option
488 formats, each with its own benefits and drawbacks.
490 B<NOTE:> The class being delegated to does not need to be a Moose based class,
491 which is why this feature is especially useful when wrapping non-Moose classes.
493 All I<handles> option formats share the following traits:
495 You cannot override a locally defined method with a delegated method; an
496 exception will be thrown if you try. That is to say, if you define C<foo> in
497 your class, you cannot override it with a delegated C<foo>. This is almost never
498 something you would want to do, and if it is, you should do it by hand and not
501 You cannot override any of the methods found in Moose::Object, or the C<BUILD>
502 and C<DEMOLISH> methods. These will not throw an exception, but will silently
503 move on to the next method in the list. My reasoning for this is that you would
504 almost never want to do this, since it usually breaks your class. As with
505 overriding locally defined methods, if you do want to do this, you should do it
506 manually, not with Moose.
508 You do not I<need> to have a reader (or accessor) for the attribute in order
509 to delegate to it. Moose will create a means of accessing the value for you,
510 however this will be several times B<less> efficient then if you had given
511 the attribute a reader (or accessor) to use.
513 Below is the documentation for each option format:
519 This is the most common usage for I<handles>. You basically pass a list of
520 method names to be delegated, and Moose will install a delegation method
525 This is the second most common usage for I<handles>. Instead of a list of
526 method names, you pass a HASH ref where each key is the method name you
527 want installed locally, and its value is the name of the original method
528 in the class being delegated to.
530 This can be very useful for recursive classes like trees. Here is a
531 quick example (soon to be expanded into a Moose::Cookbook recipe):
536 has 'node' => (is => 'rw', isa => 'Any');
541 default => sub { [] }
549 parent_node => 'node',
550 siblings => 'children',
554 In this example, the Tree package gets C<parent_node> and C<siblings> methods,
555 which delegate to the C<node> and C<children> methods (respectively) of the Tree
556 instance stored in the C<parent> slot.
560 The regexp option works very similar to the ARRAY option, except that it builds
561 the list of methods for you. It starts by collecting all possible methods of the
562 class being delegated to, then filters that list using the regexp supplied here.
564 B<NOTE:> An I<isa> option is required when using the regexp option format. This
565 is so that we can determine (at compile time) the method list from the class.
566 Without an I<isa> this is just not possible.
570 With the role option, you specify the name of a role whose "interface" then
571 becomes the list of methods to handle. The "interface" can be defined as; the
572 methods of the role and any required methods of the role. It should be noted
573 that this does B<not> include any method modifiers or generated attribute
574 methods (which is consistent with role composition).
578 This is the option to use when you really want to do something funky. You should
579 only use it if you really know what you are doing, as it involves manual
582 This takes a code reference, which should expect two arguments. The first is the
583 attribute meta-object this I<handles> is attached to. The second is the
584 metaclass of the class being delegated to. It expects you to return a hash (not
585 a HASH ref) of the methods you want mapped.
589 =item I<metaclass =E<gt> $metaclass_name>
591 This tells the class to use a custom attribute metaclass for this particular
592 attribute. Custom attribute metaclasses are useful for extending the
593 capabilities of the I<has> keyword: they are the simplest way to extend the MOP,
594 but they are still a fairly advanced topic and too much to cover here, see
595 L<Moose::Cookbook::Meta::Recipe1> for more information.
597 The default behavior here is to just load C<$metaclass_name>; however, we also
598 have a way to alias to a shorter name. This will first look to see if
599 B<Moose::Meta::Attribute::Custom::$metaclass_name> exists. If it does, Moose
600 will then check to see if that has the method C<register_implementation>, which
601 should return the actual name of the custom attribute metaclass. If there is no
602 C<register_implementation> method, it will fall back to using
603 B<Moose::Meta::Attribute::Custom::$metaclass_name> as the metaclass name.
605 =item I<traits =E<gt> [ @role_names ]>
607 This tells Moose to take the list of C<@role_names> and apply them to the
608 attribute meta-object. This is very similar to the I<metaclass> option, but
609 allows you to use more than one extension at a time.
611 See L<TRAIT NAME RESOLUTION> for details on how a trait name is
612 resolved to a class name.
614 Also see L<Moose::Cookbook::Meta::Recipe3> for a metaclass trait
617 =item I<builder> => Str
619 The value of this key is the name of the method that will be called to
620 obtain the value used to initialize the attribute. See the L<builder
621 option docs in Class::MOP::Attribute|Class::MOP::Attribute/builder>
622 for more information.
624 =item I<default> => SCALAR | CODE
626 The value of this key is the default value which will initialize the attribute.
628 NOTE: If the value is a simple scalar (string or number), then it can
629 be just passed as is. However, if you wish to initialize it with a
630 HASH or ARRAY ref, then you need to wrap that inside a CODE reference.
631 See the L<default option docs in
632 Class::MOP::Attribute|Class::MOP::Attribute/default> for more
635 =item I<clearer> => Str
637 Creates a method allowing you to clear the value, see the L<clearer option
638 docs in Class::MOP::Attribute|Class::MOP::Attribute/clearer> for more
641 =item I<predicate> => Str
643 Creates a method to perform a basic test to see if a value has been set in the
644 attribute, see the L<predicate option docs in
645 Class::MOP::Attribute|Class::MOP::Attribute/predicate> for more information.
647 =item I<lazy_build> => (0|1)
649 Automatically define lazy => 1 as well as builder => "_build_$attr", clearer =>
650 "clear_$attr', predicate => 'has_$attr' unless they are already defined.
652 =item I<initializer> => Str
654 This may be a method name (referring to a method on the class with
655 this attribute) or a CODE ref. The initializer is used to set the
656 attribute value on an instance when the attribute is set during
657 instance initialization (but not when the value is being assigned
658 to). See the L<initializer option docs in
659 Class::MOP::Attribute|Class::MOP::Attribute/initializer> for more
664 =item B<has +$name =E<gt> %options>
666 This is variation on the normal attribute creator C<has> which allows you to
667 clone and extend an attribute from a superclass or from a role. Here is an
668 example of the superclass usage:
676 default => 'Hello, I am a Foo'
684 has '+message' => (default => 'Hello I am My::Foo');
686 What is happening here is that B<My::Foo> is cloning the C<message> attribute
687 from its parent class B<Foo>, retaining the C<is =E<gt> 'rw'> and C<isa =E<gt>
688 'Str'> characteristics, but changing the value in C<default>.
690 Here is another example, but within the context of a role:
698 default => 'Hello, I am a Foo'
706 has '+message' => (default => 'Hello I am My::Foo');
708 In this case, we are basically taking the attribute which the role supplied
709 and altering it within the bounds of this feature.
711 Aside from where the attributes come from (one from superclass, the other
712 from a role), this feature works exactly the same. This feature is restricted
713 somewhat, so as to try and force at least I<some> sanity into it. You are only
714 allowed to change the following attributes:
720 Change the default value of an attribute.
724 Change whether the attribute attempts to coerce a value passed to it.
728 Change if the attribute is required to have a value.
730 =item I<documentation>
732 Change the documentation string associated with the attribute.
736 Change if the attribute lazily initializes the slot.
740 You I<are> allowed to change the type without restriction.
742 It is recommended that you use this freedom with caution. We used to
743 only allow for extension only if the type was a subtype of the parent's
744 type, but we felt that was too restrictive and is better left as a
749 You are allowed to B<add> a new C<handles> definition, but you are B<not>
750 allowed to I<change> one.
754 You are allowed to B<add> a new C<builder> definition, but you are B<not>
755 allowed to I<change> one.
759 You are allowed to B<add> a new C<metaclass> definition, but you are
760 B<not> allowed to I<change> one.
764 You are allowed to B<add> additional traits to the C<traits> definition.
765 These traits will be composed into the attribute, but pre-existing traits
766 B<are not> overridden, or removed.
770 =item B<before $name|@names =E<gt> sub { ... }>
772 =item B<after $name|@names =E<gt> sub { ... }>
774 =item B<around $name|@names =E<gt> sub { ... }>
776 This three items are syntactic sugar for the before, after, and around method
777 modifier features that L<Class::MOP> provides. More information on these may be
778 found in the L<Class::MOP::Class documentation|Class::MOP::Class/"Method
783 The keyword C<super> is a no-op when called outside of an C<override> method. In
784 the context of an C<override> method, it will call the next most appropriate
785 superclass method with the same arguments as the original method.
787 =item B<override ($name, &sub)>
789 An C<override> method is a way of explicitly saying "I am overriding this
790 method from my superclass". You can call C<super> within this method, and
791 it will work as expected. The same thing I<can> be accomplished with a normal
792 method call and the C<SUPER::> pseudo-package; it is really your choice.
796 The keyword C<inner>, much like C<super>, is a no-op outside of the context of
797 an C<augment> method. You can think of C<inner> as being the inverse of
798 C<super>; the details of how C<inner> and C<augment> work is best described in
799 the L<Moose::Cookbook::Basics::Recipe6>.
801 =item B<augment ($name, &sub)>
803 An C<augment> method, is a way of explicitly saying "I am augmenting this
804 method from my superclass". Once again, the details of how C<inner> and
805 C<augment> work is best described in the L<Moose::Cookbook::Basics::Recipe6>.
809 This is the C<Carp::confess> function, and exported here because I use it
814 This is the C<Scalar::Util::blessed> function, it is exported here because I
815 use it all the time. It is highly recommended that this is used instead of
816 C<ref> anywhere you need to test for an object's class name.
820 =head1 METACLASS TRAITS
822 When you use Moose, you can also specify traits which will be applied
825 use Moose -traits => 'My::Trait';
827 This is very similar to the attribute traits feature. When you do
828 this, your class's C<meta> object will have the specified traits
829 applied to it. See L<TRAIT NAME RESOLUTION> for more details.
831 =head1 TRAIT NAME RESOLUTION
833 By default, when given a trait name, Moose simply tries to load a
834 class of the same name. If such a class does not exist, it then looks
835 for for a class matching
836 B<Moose::Meta::$type::Custom::Trait::$trait_name>. The C<$type>
837 variable here will be one of B<Attribute> or B<Class>, depending on
838 what the trait is being applied to.
840 If a class with this long name exists, Moose checks to see if it has
841 the method C<register_implementation>. This method is expected to
842 return the I<real> class name of the trait. If there is no
843 C<register_implementation> method, it will fall back to using
844 B<Moose::Meta::$type::Custom::Trait::$trait> as the trait name.
846 If all this is confusing, take a look at
847 L<Moose::Cookbook::Meta::Recipe3>, which demonstrates how to create an
850 =head1 UNIMPORTING FUNCTIONS
854 Moose offers a way to remove the keywords it exports, through the C<unimport>
855 method. You simply have to say C<no Moose> at the bottom of your code for this
856 to work. Here is an example:
861 has 'first_name' => (is => 'rw', isa => 'Str');
862 has 'last_name' => (is => 'rw', isa => 'Str');
866 $self->first_name . ' ' . $self->last_name
869 no Moose; # keywords are removed from the Person package
871 =head1 EXTENDING AND EMBEDDING MOOSE
873 To learn more about extending Moose, we recommend checking out the
874 "Extending" recipes in the L<Moose::Cookbook>, starting with
875 L<Moose::Cookbook::Extending::Recipe1>, which provides an overview of
876 all the different ways you might extend Moose.
878 =head2 B<< Moose->init_meta(for_class => $class, base_class => $baseclass, metaclass => $metaclass) >>
880 The C<init_meta> method sets up the metaclass object for the class
881 specified by C<for_class>. This method injects a a C<meta> accessor
882 into the class so you can get at this object. It also sets the class's
883 superclass to C<base_class>, with L<Moose::Object> as the default.
885 You can specify an alternate metaclass with the C<metaclass> parameter.
887 For more detail on this topic, see L<Moose::Cookbook::Extending::Recipe2>.
889 This method used to be documented as a function which accepted
890 positional parameters. This calling style will still work for
891 backwards compatibility, but is deprecated.
895 Moose's C<import> method supports the L<Sub::Exporter> form of C<{into =E<gt> $pkg}>
896 and C<{into_level =E<gt> 1}>.
898 B<NOTE>: Doing this is more or less deprecated. Use L<Moose::Exporter>
899 instead, which lets you stack multiple C<Moose.pm>-alike modules
900 sanely. It handles getting the exported functions into the right place
903 =head2 B<throw_error>
905 An alias for C<confess>, used by internally by Moose.
907 =head1 METACLASS COMPATIBILITY AND MOOSE
909 Metaclass compatibility is a thorny subject. You should start by
910 reading the "About Metaclass compatibility" section in the
913 Moose will attempt to resolve a few cases of metaclass incompatibility
914 when you set the superclasses for a class, unlike C<Class::MOP>, which
915 simply dies if the metaclasses are incompatible.
917 In actuality, Moose fixes incompatibility for I<all> of a class's
918 metaclasses, not just the class metaclass. That includes the instance
919 metaclass, attribute metaclass, as well as its constructor class and
920 destructor class. However, for simplicity this discussion will just
921 refer to "metaclass", meaning the class metaclass, most of the time.
923 Moose has two algorithms for fixing metaclass incompatibility.
925 The first algorithm is very simple. If all the metaclass for the
926 parent is a I<subclass> of the child's metaclass, then we simply
927 replace the child's metaclass with the parent's.
929 The second algorithm is more complicated. It tries to determine if the
930 metaclasses only "differ by roles". This means that the parent and
931 child's metaclass share a common ancestor in their respective
932 hierarchies, and that the subclasses under the common ancestor are
933 only different because of role applications. This case is actually
934 fairly common when you mix and match various C<MooseX::*> modules,
935 many of which apply roles to the metaclass.
937 If the parent and child do differ by roles, Moose replaces the
938 metaclass in the child with a newly created metaclass. This metaclass
939 is a subclass of the parent's metaclass, does all of the roles that
940 the child's metaclass did before being replaced. Effectively, this
941 means the new metaclass does all of the roles done by both the
942 parent's and child's original metaclasses.
944 Ultimately, this is all transparent to you except in the case of an
945 unresolvable conflict.
947 =head2 The MooseX:: namespace
949 Generally if you're writing an extension I<for> Moose itself you'll want
950 to put your extension in the C<MooseX::> namespace. This namespace is
951 specifically for extensions that make Moose better or different in some
952 fundamental way. It is traditionally B<not> for a package that just happens
953 to use Moose. This namespace follows from the examples of the C<LWPx::>
954 and C<DBIx::> namespaces that perform the same function for C<LWP> and C<DBI>
963 It should be noted that C<super> and C<inner> B<cannot> be used in the same
964 method. However, they may be combined within the same class hierarchy; see
965 F<t/014_override_augment_inner_super.t> for an example.
967 The reason for this is that C<super> is only valid within a method
968 with the C<override> modifier, and C<inner> will never be valid within an
969 C<override> method. In fact, C<augment> will skip over any C<override> methods
970 when searching for its appropriate C<inner>.
972 This might seem like a restriction, but I am of the opinion that keeping these
973 two features separate (yet interoperable) actually makes them easy to use, since
974 their behavior is then easier to predict. Time will tell whether I am right or
975 not (UPDATE: so far so good).
981 We offer both a mailing list and a very active IRC channel.
983 The mailing list is L<moose@perl.org>. You must be subscribed to send
984 a message. To subscribe, send an empty message to
985 L<moose-subscribe@perl.org>
987 You can also visit us at L<#moose on
988 irc.perl.org|irc://irc.perl.org/#moose>. This channel is quite active,
989 and questions at all levels (on Moose-related topics ;) are welcome.
991 =head1 ACKNOWLEDGEMENTS
995 =item I blame Sam Vilain for introducing me to the insanity that is meta-models.
997 =item I blame Audrey Tang for then encouraging my meta-model habit in #perl6.
999 =item Without Yuval "nothingmuch" Kogman this module would not be possible,
1000 and it certainly wouldn't have this name ;P
1002 =item The basis of the TypeContraints module was Rob Kinyon's idea
1003 originally, I just ran with it.
1005 =item Thanks to mst & chansen and the whole #moose posse for all the
1006 early ideas/feature-requests/encouragement/bug-finding.
1008 =item Thanks to David "Theory" Wheeler for meta-discussions and spelling fixes.
1016 =item L<http://www.iinteractive.com/moose>
1018 This is the official web home of Moose, it contains links to our public SVN repo
1019 as well as links to a number of talks and articles on Moose and Moose related
1022 =item The Moose is flying, a tutorial by Randal Schwartz
1024 Part 1 - L<http://www.stonehenge.com/merlyn/LinuxMag/col94.html>
1026 Part 2 - L<http://www.stonehenge.com/merlyn/LinuxMag/col95.html>
1028 =item Several Moose extension modules in the C<MooseX::> namespace.
1030 See L<http://search.cpan.org/search?query=MooseX::> for extensions.
1032 =item Moose stats on ohloh.net - L<http://www.ohloh.net/projects/moose>
1040 =item The Art of the MetaObject Protocol
1042 I mention this in the L<Class::MOP> docs too, this book was critical in
1043 the development of both modules and is highly recommended.
1051 =item L<http://www.cs.utah.edu/plt/publications/oopsla04-gff.pdf>
1053 This paper (suggested by lbr on #moose) was what lead to the implementation
1054 of the C<super>/C<override> and C<inner>/C<augment> features. If you really
1055 want to understand them, I suggest you read this.
1061 All complex software has bugs lurking in it, and this module is no
1062 exception. If you find a bug please either email me, or add the bug
1065 =head1 FEATURE REQUESTS
1067 We are very strict about what features we add to the Moose core, especially
1068 the user-visible features. Instead we have made sure that the underlying
1069 meta-system of Moose is as extensible as possible so that you can add your
1070 own features easily. That said, occasionally there is a feature needed in the
1071 meta-system to support your planned extension, in which case you should
1072 either email the mailing list or join us on irc at #moose to discuss.
1076 Moose is an open project, there are at this point dozens of people who have
1077 contributed, and can contribute. If you have added anything to the Moose
1078 project you have a commit bit on this file and can add your name to the list.
1082 However there are only a few people with the rights to release a new version
1083 of Moose. The Moose Cabal are the people to go to with questions regarding
1084 the wider purview of Moose, and help out maintaining not just the code
1085 but the community as well.
1087 Stevan (stevan) Little E<lt>stevan@iinteractive.comE<gt>
1089 Yuval (nothingmuch) Kogman
1091 Shawn (sartak) Moore
1093 Dave (autarch) Rolsky E<lt>autarch@urth.orgE<gt>
1095 =head2 OTHER CONTRIBUTORS
1099 Adam (Alias) Kennedy
1101 Anders (Debolaz) Nor Berle
1103 Nathan (kolibre) Gray
1105 Christian (chansen) Hansen
1107 Hans Dieter (confound) Pearcey
1109 Eric (ewilhelm) Wilhelm
1111 Guillermo (groditi) Roditi
1113 Jess (castaway) Robinson
1117 Robert (phaylon) Sedlacek
1121 Scott (konobi) McWhirter
1123 Shlomi (rindolf) Fish
1125 Chris (perigrin) Prather
1127 Wallace (wreis) Reis
1129 Jonathan (jrockway) Rockway
1131 Piotr (dexter) Roszatycki
1133 Sam (mugwump) Vilain
1137 ... and many other #moose folks
1139 =head1 COPYRIGHT AND LICENSE
1141 Copyright 2006-2009 by Infinity Interactive, Inc.
1143 L<http://www.iinteractive.com>
1145 This library is free software; you can redistribute it and/or modify
1146 it under the same terms as Perl itself.