8 $VERSION = eval $VERSION;
9 our $AUTHORITY = 'cpan:STEVAN';
11 use Scalar::Util 'blessed';
18 use Moose::Meta::Class;
19 use Moose::Meta::TypeConstraint;
20 use Moose::Meta::TypeCoercion;
21 use Moose::Meta::Attribute;
22 use Moose::Meta::Instance;
26 use Moose::Meta::Role;
27 use Moose::Meta::Role::Composite;
28 use Moose::Meta::Role::Application;
29 use Moose::Meta::Role::Application::RoleSummation;
30 use Moose::Meta::Role::Application::ToClass;
31 use Moose::Meta::Role::Application::ToRole;
32 use Moose::Meta::Role::Application::ToInstance;
34 use Moose::Util::TypeConstraints;
37 use Moose::Meta::Attribute::Native;
48 Moose->throw_error("Must derive at least one class") unless @_;
50 # this checks the metaclass to make sure
51 # it is correct, sometimes it can get out
52 # of sync when the classes are being built
53 $meta->superclasses(@_);
57 Moose::Util::apply_all_roles(shift, @_);
64 Moose->throw_error('Usage: has \'name\' => ( key => value, ... )')
67 my %options = ( definition_context => Moose::Util::_caller_info(), @_ );
68 my $attrs = ( ref($name) eq 'ARRAY' ) ? $name : [ ($name) ];
69 $meta->add_attribute( $_, %options ) for @$attrs;
73 Moose::Util::add_method_modifier(shift, 'before', \@_);
77 Moose::Util::add_method_modifier(shift, 'after', \@_);
81 Moose::Util::add_method_modifier(shift, 'around', \@_);
89 # This check avoids a recursion loop - see
90 # t/100_bugs/020_super_recursion.t
91 return if defined $SUPER_PACKAGE && $SUPER_PACKAGE ne caller();
92 return unless $SUPER_BODY; $SUPER_BODY->(@SUPER_ARGS);
97 my ( $name, $method ) = @_;
98 $meta->add_override_method_modifier( $name => $method );
103 our ( %INNER_BODY, %INNER_ARGS );
105 if ( my $body = $INNER_BODY{$pkg} ) {
106 my @args = @{ $INNER_ARGS{$pkg} };
107 local $INNER_ARGS{$pkg};
108 local $INNER_BODY{$pkg};
109 return $body->(@args);
117 my ( $name, $method ) = @_;
118 $meta->add_augment_method_modifier( $name => $method );
121 Moose::Exporter->setup_import_methods(
123 qw( extends with has before after around override augment )
128 \&Scalar::Util::blessed,
133 # This used to be called as a function. This hack preserves
134 # backwards compatibility.
135 if ( $_[0] ne __PACKAGE__ ) {
136 return __PACKAGE__->init_meta(
146 my $class = $args{for_class}
147 or Moose->throw_error("Cannot call init_meta without specifying a for_class");
148 my $base_class = $args{base_class} || 'Moose::Object';
149 my $metaclass = $args{metaclass} || 'Moose::Meta::Class';
151 Moose->throw_error("The Metaclass $metaclass must be a subclass of Moose::Meta::Class.")
152 unless $metaclass->isa('Moose::Meta::Class');
154 # make a subtype for each Moose class
156 unless find_type_constraint($class);
160 if ( $meta = Class::MOP::get_metaclass_by_name($class) ) {
161 unless ( $meta->isa("Moose::Meta::Class") ) {
162 Moose->throw_error("$class already has a metaclass, but it does not inherit $metaclass ($meta)");
165 # no metaclass, no 'meta' method
167 # now we check whether our ancestors have metaclass, and if so borrow that
168 my ( undef, @isa ) = @{ $class->mro::get_linear_isa };
170 foreach my $ancestor ( @isa ) {
171 my $ancestor_meta = Class::MOP::get_metaclass_by_name($ancestor) || next;
173 my $ancestor_meta_class = ($ancestor_meta->is_immutable
174 ? $ancestor_meta->_get_mutable_metaclass_name
175 : ref($ancestor_meta));
177 # if we have an ancestor metaclass that inherits $metaclass, we use
178 # that. This is like _fix_metaclass_incompatibility, but we can do it now.
180 # the case of having an ancestry is not very common, but arises in
182 unless ( $metaclass->isa( $ancestor_meta_class ) ) {
183 if ( $ancestor_meta_class->isa($metaclass) ) {
184 $metaclass = $ancestor_meta_class;
189 $meta = $metaclass->initialize($class);
192 if ( $class->can('meta') ) {
193 # check 'meta' method
195 # it may be inherited
198 # this is the case where the metaclass pragma
199 # was used before the 'use Moose' statement to
200 # override a specific class
201 my $method_meta = $class->meta;
203 ( blessed($method_meta) && $method_meta->isa('Moose::Meta::Class') )
204 || Moose->throw_error("$class already has a &meta function, but it does not return a Moose::Meta::Class ($method_meta)");
206 $meta = $method_meta;
209 unless ( $meta->has_method("meta") ) { # don't overwrite
210 # also check for inherited non moose 'meta' method?
211 # FIXME also skip this if the user requested by passing an option
214 # re-initialize so it inherits properly
215 $metaclass->initialize( ref($_[0]) || $_[0] );
220 # make sure they inherit from Moose::Object
221 $meta->superclasses($base_class)
222 unless $meta->superclasses();
227 # This may be used in some older MooseX extensions.
229 goto &Moose::Exporter::_get_caller;
232 ## make 'em all immutable
235 inline_constructor => 1,
236 constructor_name => "_new",
237 # these are Class::MOP accessors, so they need inlining
238 inline_accessors => 1
239 ) for grep { $_->is_mutable }
242 Moose::Meta::Attribute
244 Moose::Meta::Instance
246 Moose::Meta::TypeCoercion
247 Moose::Meta::TypeCoercion::Union
250 Moose::Meta::Method::Accessor
251 Moose::Meta::Method::Constructor
252 Moose::Meta::Method::Destructor
253 Moose::Meta::Method::Overridden
254 Moose::Meta::Method::Augmented
257 Moose::Meta::Role::Method
258 Moose::Meta::Role::Method::Required
259 Moose::Meta::Role::Method::Conflicting
261 Moose::Meta::Role::Composite
263 Moose::Meta::Role::Application
264 Moose::Meta::Role::Application::RoleSummation
265 Moose::Meta::Role::Application::ToClass
266 Moose::Meta::Role::Application::ToRole
267 Moose::Meta::Role::Application::ToInstance
278 Moose - A postmodern object system for Perl 5
283 use Moose; # automatically turns on strict and warnings
285 has 'x' => (is => 'rw', isa => 'Int');
286 has 'y' => (is => 'rw', isa => 'Int');
299 has 'z' => (is => 'rw', isa => 'Int');
301 after 'clear' => sub {
308 Moose is an extension of the Perl 5 object system.
310 The main goal of Moose is to make Perl 5 Object Oriented programming
311 easier, more consistent and less tedious. With Moose you can to think
312 more about what you want to do and less about the mechanics of OOP.
314 Additionally, Moose is built on top of L<Class::MOP>, which is a
315 metaclass system for Perl 5. This means that Moose not only makes
316 building normal Perl 5 objects better, but it provides the power of
317 metaclass programming as well.
321 If you're new to Moose, the best place to start is the
322 L<Moose::Manual> docs, followed by the L<Moose::Cookbook>. The intro
323 will show you what Moose is, and how it makes Perl 5 OO better.
325 The cookbook recipes on Moose basics will get you up to speed with
326 many of Moose's features quickly. Once you have an idea of what Moose
327 can do, you can use the API documentation to get more detail on
328 features which interest you.
330 =head2 Moose Extensions
332 The C<MooseX::> namespace is the official place to find Moose extensions.
333 These extensions can be found on the CPAN. The easiest way to find them
334 is to search for them (L<http://search.cpan.org/search?query=MooseX::>),
335 or to examine L<Task::Moose> which aims to keep an up-to-date, easily
336 installable list of Moose extensions.
340 Much of the Moose documentation has been translated into other languages.
346 Japanese docs can be found at L<http://perldoc.perlassociation.org/pod/Moose-Doc-JA/index.html>. The source POD files can be found in GitHub: L<http://github.com/jpa/Moose-Doc-JA>
350 =head1 BUILDING CLASSES WITH MOOSE
352 Moose makes every attempt to provide as much convenience as possible during
353 class construction/definition, but still stay out of your way if you want it
354 to. Here are a few items to note when building classes with Moose.
356 Unless specified with C<extends>, any class which uses Moose will
357 inherit from L<Moose::Object>.
359 Moose will also manage all attributes (including inherited ones) that are
360 defined with C<has>. And (assuming you call C<new>, which is inherited from
361 L<Moose::Object>) this includes properly initializing all instance slots,
362 setting defaults where appropriate, and performing any type constraint checking
365 =head1 PROVIDED METHODS
367 Moose provides a number of methods to all your classes, mostly through the
368 inheritance of L<Moose::Object>. There is however, one exception.
374 This is a method which provides access to the current class's metaclass.
378 =head1 EXPORTED FUNCTIONS
380 Moose will export a number of functions into the class's namespace which
381 may then be used to set up the class. These functions all work directly
382 on the current class.
386 =item B<extends (@superclasses)>
388 This function will set the superclass(es) for the current class.
390 This approach is recommended instead of C<use base>, because C<use base>
391 actually C<push>es onto the class's C<@ISA>, whereas C<extends> will
392 replace it. This is important to ensure that classes which do not have
393 superclasses still properly inherit from L<Moose::Object>.
395 =item B<with (@roles)>
397 This will apply a given set of C<@roles> to the local class.
399 =item B<has $name|@$names =E<gt> %options>
401 This will install an attribute of a given C<$name> into the current class. If
402 the first parameter is an array reference, it will create an attribute for
403 every C<$name> in the list. The C<%options> are the same as those provided by
404 L<Class::MOP::Attribute>, in addition to the list below which are provided by
405 Moose (L<Moose::Meta::Attribute> to be more specific):
409 =item I<is =E<gt> 'rw'|'ro'>
411 The I<is> option accepts either I<rw> (for read/write) or I<ro> (for read
412 only). These will create either a read/write accessor or a read-only
413 accessor respectively, using the same name as the C<$name> of the attribute.
415 If you need more control over how your accessors are named, you can
416 use the L<reader|Class::MOP::Attribute/reader>,
417 L<writer|Class::MOP::Attribute/writer> and
418 L<accessor|Class::MOP::Attribute/accessor> options inherited from
419 L<Class::MOP::Attribute>, however if you use those, you won't need the
422 =item I<isa =E<gt> $type_name>
424 The I<isa> option uses Moose's type constraint facilities to set up runtime
425 type checking for this attribute. Moose will perform the checks during class
426 construction, and within any accessors. The C<$type_name> argument must be a
427 string. The string may be either a class name or a type defined using
428 Moose's type definition features. (Refer to L<Moose::Util::TypeConstraints>
429 for information on how to define a new type, and how to retrieve type meta-data).
431 =item I<coerce =E<gt> (1|0)>
433 This will attempt to use coercion with the supplied type constraint to change
434 the value passed into any accessors or constructors. You B<must> have supplied
435 a type constraint in order for this to work. See L<Moose::Cookbook::Basics::Recipe5>
438 =item I<does =E<gt> $role_name>
440 This will accept the name of a role which the value stored in this attribute
441 is expected to have consumed.
443 =item I<required =E<gt> (1|0)>
445 This marks the attribute as being required. This means a value must be
446 supplied during class construction, I<or> the attribute must be lazy
447 and have either a default or a builder. Note that c<required> does not
448 say anything about the attribute's value, which can be C<undef>.
450 =item I<weak_ref =E<gt> (1|0)>
452 This will tell the class to store the value of this attribute as a weakened
453 reference. If an attribute is a weakened reference, it B<cannot> also be
456 =item I<lazy =E<gt> (1|0)>
458 This will tell the class to not create this slot until absolutely necessary.
459 If an attribute is marked as lazy it B<must> have a default supplied.
461 =item I<auto_deref =E<gt> (1|0)>
463 This tells the accessor whether to automatically dereference the value returned.
464 This is only legal if your C<isa> option is either C<ArrayRef> or C<HashRef>.
466 =item I<trigger =E<gt> $code>
468 The I<trigger> option is a CODE reference which will be called after
469 the value of the attribute is set. The CODE ref will be passed the
470 instance itself and the updated value. If the attribute already had a
471 value, this will be passed as the third value to the trigger.
473 You B<can> have a trigger on a read-only attribute.
475 B<NOTE:> Triggers will only fire when you B<assign> to the attribute,
476 either in the constructor, or using the writer. Default and built values will
477 B<not> cause the trigger to be fired.
479 =item I<handles =E<gt> ARRAY | HASH | REGEXP | ROLE | DUCKTYPE | CODE>
481 The I<handles> option provides Moose classes with automated delegation features.
482 This is a pretty complex and powerful option. It accepts many different option
483 formats, each with its own benefits and drawbacks.
485 B<NOTE:> The class being delegated to does not need to be a Moose based class,
486 which is why this feature is especially useful when wrapping non-Moose classes.
488 All I<handles> option formats share the following traits:
490 You cannot override a locally defined method with a delegated method; an
491 exception will be thrown if you try. That is to say, if you define C<foo> in
492 your class, you cannot override it with a delegated C<foo>. This is almost never
493 something you would want to do, and if it is, you should do it by hand and not
496 You cannot override any of the methods found in Moose::Object, or the C<BUILD>
497 and C<DEMOLISH> methods. These will not throw an exception, but will silently
498 move on to the next method in the list. My reasoning for this is that you would
499 almost never want to do this, since it usually breaks your class. As with
500 overriding locally defined methods, if you do want to do this, you should do it
501 manually, not with Moose.
503 You do not I<need> to have a reader (or accessor) for the attribute in order
504 to delegate to it. Moose will create a means of accessing the value for you,
505 however this will be several times B<less> efficient then if you had given
506 the attribute a reader (or accessor) to use.
508 Below is the documentation for each option format:
514 This is the most common usage for I<handles>. You basically pass a list of
515 method names to be delegated, and Moose will install a delegation method
520 This is the second most common usage for I<handles>. Instead of a list of
521 method names, you pass a HASH ref where each key is the method name you
522 want installed locally, and its value is the name of the original method
523 in the class being delegated to.
525 This can be very useful for recursive classes like trees. Here is a
526 quick example (soon to be expanded into a Moose::Cookbook recipe):
531 has 'node' => (is => 'rw', isa => 'Any');
536 default => sub { [] }
544 parent_node => 'node',
545 siblings => 'children',
549 In this example, the Tree package gets C<parent_node> and C<siblings> methods,
550 which delegate to the C<node> and C<children> methods (respectively) of the Tree
551 instance stored in the C<parent> slot.
553 You may also use an array reference to curry arguments to the original method.
557 handles => { set_foo => [ set => 'foo' ] },
560 # $self->set_foo(...) calls $self->thing->set('foo', ...)
562 The first element of the array reference is the original method name, and the
563 rest is a list of curried arguments.
567 The regexp option works very similar to the ARRAY option, except that it builds
568 the list of methods for you. It starts by collecting all possible methods of the
569 class being delegated to, then filters that list using the regexp supplied here.
571 B<NOTE:> An I<isa> option is required when using the regexp option format. This
572 is so that we can determine (at compile time) the method list from the class.
573 Without an I<isa> this is just not possible.
577 With the role option, you specify the name of a role whose "interface" then
578 becomes the list of methods to handle. The "interface" can be defined as; the
579 methods of the role and any required methods of the role. It should be noted
580 that this does B<not> include any method modifiers or generated attribute
581 methods (which is consistent with role composition).
585 With the duck type option, you pass a duck type object whose "interface" then
586 becomes the list of methods to handle. The "interface" can be defined as; the
587 list of methods passed to C<duck_type> to create a duck type object. For more
588 information on C<duck_type> please check
589 L<Moose::Util::TypeConstraints>.
593 This is the option to use when you really want to do something funky. You should
594 only use it if you really know what you are doing, as it involves manual
597 This takes a code reference, which should expect two arguments. The first is the
598 attribute meta-object this I<handles> is attached to. The second is the
599 metaclass of the class being delegated to. It expects you to return a hash (not
600 a HASH ref) of the methods you want mapped.
604 =item I<metaclass =E<gt> $metaclass_name>
606 This tells the class to use a custom attribute metaclass for this particular
607 attribute. Custom attribute metaclasses are useful for extending the
608 capabilities of the I<has> keyword: they are the simplest way to extend the MOP,
609 but they are still a fairly advanced topic and too much to cover here, see
610 L<Moose::Cookbook::Meta::Recipe1> for more information.
612 See L<Metaclass and Trait Name Resolution> for details on how a metaclass name
613 is resolved to a class name.
615 =item I<traits =E<gt> [ @role_names ]>
617 This tells Moose to take the list of C<@role_names> and apply them to the
618 attribute meta-object. This is very similar to the I<metaclass> option, but
619 allows you to use more than one extension at a time.
621 See L<Metaclass and Trait Name Resolution> for details on how a trait name is
622 resolved to a role name.
624 Also see L<Moose::Cookbook::Meta::Recipe3> for a metaclass trait
627 =item I<builder> => Str
629 The value of this key is the name of the method that will be called to
630 obtain the value used to initialize the attribute. See the L<builder
631 option docs in Class::MOP::Attribute|Class::MOP::Attribute/builder>
632 and/or L<Moose::Cookbook::Basics::Recipe8> for more information.
634 =item I<default> => SCALAR | CODE
636 The value of this key is the default value which will initialize the attribute.
638 NOTE: If the value is a simple scalar (string or number), then it can
639 be just passed as is. However, if you wish to initialize it with a
640 HASH or ARRAY ref, then you need to wrap that inside a CODE reference.
641 See the L<default option docs in
642 Class::MOP::Attribute|Class::MOP::Attribute/default> for more
645 =item I<clearer> => Str
647 Creates a method allowing you to clear the value, see the L<clearer option
648 docs in Class::MOP::Attribute|Class::MOP::Attribute/clearer> for more
651 =item I<predicate> => Str
653 Creates a method to perform a basic test to see if a value has been set in the
654 attribute, see the L<predicate option docs in
655 Class::MOP::Attribute|Class::MOP::Attribute/predicate> for more information.
657 =item I<lazy_build> => (0|1)
659 Automatically define lazy => 1 as well as builder => "_build_$attr", clearer =>
660 "clear_$attr', predicate => 'has_$attr' unless they are already defined.
662 =item I<initializer> => Str
664 This may be a method name (referring to a method on the class with
665 this attribute) or a CODE ref. The initializer is used to set the
666 attribute value on an instance when the attribute is set during
667 instance initialization (but not when the value is being assigned
668 to). See the L<initializer option docs in
669 Class::MOP::Attribute|Class::MOP::Attribute/initializer> for more
672 =item I<documentation> => $string
674 An arbitrary string that can be retrieved later by calling C<<
675 $attr->documentation >>.
681 =item B<has +$name =E<gt> %options>
683 This is variation on the normal attribute creator C<has> which allows you to
684 clone and extend an attribute from a superclass or from a role. Here is an
685 example of the superclass usage:
693 default => 'Hello, I am a Foo'
701 has '+message' => (default => 'Hello I am My::Foo');
703 What is happening here is that B<My::Foo> is cloning the C<message> attribute
704 from its parent class B<Foo>, retaining the C<is =E<gt> 'rw'> and C<isa =E<gt>
705 'Str'> characteristics, but changing the value in C<default>.
707 Here is another example, but within the context of a role:
715 default => 'Hello, I am a Foo'
723 has '+message' => (default => 'Hello I am My::Foo');
725 In this case, we are basically taking the attribute which the role supplied
726 and altering it within the bounds of this feature.
728 Note that you can only extend an attribute from either a superclass or a role,
729 you cannot extend an attribute in a role that composes over an attribute from
732 Aside from where the attributes come from (one from superclass, the other
733 from a role), this feature works exactly the same. This feature is restricted
734 somewhat, so as to try and force at least I<some> sanity into it. You are only
735 allowed to change the following attributes:
741 Change the default value of an attribute.
745 Change whether the attribute attempts to coerce a value passed to it.
749 Change if the attribute is required to have a value.
751 =item I<documentation>
753 Change the documentation string associated with the attribute.
757 Change if the attribute lazily initializes the slot.
761 You I<are> allowed to change the type without restriction.
763 It is recommended that you use this freedom with caution. We used to
764 only allow for extension only if the type was a subtype of the parent's
765 type, but we felt that was too restrictive and is better left as a
770 You are allowed to B<add> a new C<handles> definition, but you are B<not>
771 allowed to I<change> one.
775 You are allowed to B<add> a new C<builder> definition, but you are B<not>
776 allowed to I<change> one.
780 You are allowed to B<add> a new C<metaclass> definition, but you are
781 B<not> allowed to I<change> one.
785 You are allowed to B<add> additional traits to the C<traits> definition.
786 These traits will be composed into the attribute, but preexisting traits
787 B<are not> overridden, or removed.
791 =item B<before $name|@names =E<gt> sub { ... }>
793 =item B<after $name|@names =E<gt> sub { ... }>
795 =item B<around $name|@names =E<gt> sub { ... }>
797 These three items are syntactic sugar for the before, after, and around method
798 modifier features that L<Class::MOP> provides. More information on these may be
799 found in L<Moose::Manual::MethodModifiers> and the
800 L<Class::MOP::Class documentation|Class::MOP::Class/"Method Modifiers">.
804 The keyword C<super> is a no-op when called outside of an C<override> method. In
805 the context of an C<override> method, it will call the next most appropriate
806 superclass method with the same arguments as the original method.
808 =item B<override ($name, &sub)>
810 An C<override> method is a way of explicitly saying "I am overriding this
811 method from my superclass". You can call C<super> within this method, and
812 it will work as expected. The same thing I<can> be accomplished with a normal
813 method call and the C<SUPER::> pseudo-package; it is really your choice.
817 The keyword C<inner>, much like C<super>, is a no-op outside of the context of
818 an C<augment> method. You can think of C<inner> as being the inverse of
819 C<super>; the details of how C<inner> and C<augment> work is best described in
820 the L<Moose::Cookbook::Basics::Recipe6>.
822 =item B<augment ($name, &sub)>
824 An C<augment> method, is a way of explicitly saying "I am augmenting this
825 method from my superclass". Once again, the details of how C<inner> and
826 C<augment> work is best described in the L<Moose::Cookbook::Basics::Recipe6>.
830 This is the C<Carp::confess> function, and exported here because I use it
835 This is the C<Scalar::Util::blessed> function, it is exported here because I
836 use it all the time. It is highly recommended that this is used instead of
837 C<ref> anywhere you need to test for an object's class name.
843 When you use Moose, you can specify which metaclass to use:
845 use Moose -metaclass => 'My::Meta::Class';
847 You can also specify traits which will be applied to your metaclass:
849 use Moose -traits => 'My::Trait';
851 This is very similar to the attribute traits feature. When you do
852 this, your class's C<meta> object will have the specified traits
853 applied to it. See L<Metaclass and Trait Name Resolution> for more
856 =head2 Metaclass and Trait Name Resolution
858 By default, when given a trait name, Moose simply tries to load a
859 class of the same name. If such a class does not exist, it then looks
860 for for a class matching
861 B<Moose::Meta::$type::Custom::Trait::$trait_name>. The C<$type>
862 variable here will be one of B<Attribute> or B<Class>, depending on
863 what the trait is being applied to.
865 If a class with this long name exists, Moose checks to see if it has
866 the method C<register_implementation>. This method is expected to
867 return the I<real> class name of the trait. If there is no
868 C<register_implementation> method, it will fall back to using
869 B<Moose::Meta::$type::Custom::Trait::$trait> as the trait name.
871 The lookup method for metaclasses is the same, except that it looks
872 for a class matching B<Moose::Meta::$type::Custom::$metaclass_name>.
874 If all this is confusing, take a look at
875 L<Moose::Cookbook::Meta::Recipe3>, which demonstrates how to create an
878 =head1 UNIMPORTING FUNCTIONS
882 Moose offers a way to remove the keywords it exports, through the C<unimport>
883 method. You simply have to say C<no Moose> at the bottom of your code for this
884 to work. Here is an example:
889 has 'first_name' => (is => 'rw', isa => 'Str');
890 has 'last_name' => (is => 'rw', isa => 'Str');
894 $self->first_name . ' ' . $self->last_name
897 no Moose; # keywords are removed from the Person package
899 =head1 EXTENDING AND EMBEDDING MOOSE
901 To learn more about extending Moose, we recommend checking out the
902 "Extending" recipes in the L<Moose::Cookbook>, starting with
903 L<Moose::Cookbook::Extending::Recipe1>, which provides an overview of
904 all the different ways you might extend Moose.
906 =head2 B<< Moose->init_meta(for_class => $class, base_class => $baseclass, metaclass => $metaclass) >>
908 The C<init_meta> method sets up the metaclass object for the class
909 specified by C<for_class>. This method injects a a C<meta> accessor
910 into the class so you can get at this object. It also sets the class's
911 superclass to C<base_class>, with L<Moose::Object> as the default.
913 C<init_meta> returns the metaclass object for C<$class>.
915 You can specify an alternate metaclass with the C<metaclass> option.
917 For more detail on this topic, see L<Moose::Cookbook::Extending::Recipe2>.
919 This method used to be documented as a function which accepted
920 positional parameters. This calling style will still work for
921 backwards compatibility, but is deprecated.
925 Moose's C<import> method supports the L<Sub::Exporter> form of C<{into =E<gt> $pkg}>
926 and C<{into_level =E<gt> 1}>.
928 B<NOTE>: Doing this is more or less deprecated. Use L<Moose::Exporter>
929 instead, which lets you stack multiple C<Moose.pm>-alike modules
930 sanely. It handles getting the exported functions into the right place
933 =head2 B<throw_error>
935 An alias for C<confess>, used by internally by Moose.
937 =head1 METACLASS COMPATIBILITY AND MOOSE
939 Metaclass compatibility is a thorny subject. You should start by
940 reading the "About Metaclass compatibility" section in the
943 Moose will attempt to resolve a few cases of metaclass incompatibility
944 when you set the superclasses for a class, unlike C<Class::MOP>, which
945 simply dies if the metaclasses are incompatible.
947 In actuality, Moose fixes incompatibility for I<all> of a class's
948 metaclasses, not just the class metaclass. That includes the instance
949 metaclass, attribute metaclass, as well as its constructor class and
950 destructor class. However, for simplicity this discussion will just
951 refer to "metaclass", meaning the class metaclass, most of the time.
953 Moose has two algorithms for fixing metaclass incompatibility.
955 The first algorithm is very simple. If all the metaclass for the
956 parent is a I<subclass> of the child's metaclass, then we simply
957 replace the child's metaclass with the parent's.
959 The second algorithm is more complicated. It tries to determine if the
960 metaclasses only "differ by roles". This means that the parent and
961 child's metaclass share a common ancestor in their respective
962 hierarchies, and that the subclasses under the common ancestor are
963 only different because of role applications. This case is actually
964 fairly common when you mix and match various C<MooseX::*> modules,
965 many of which apply roles to the metaclass.
967 If the parent and child do differ by roles, Moose replaces the
968 metaclass in the child with a newly created metaclass. This metaclass
969 is a subclass of the parent's metaclass, does all of the roles that
970 the child's metaclass did before being replaced. Effectively, this
971 means the new metaclass does all of the roles done by both the
972 parent's and child's original metaclasses.
974 Ultimately, this is all transparent to you except in the case of an
975 unresolvable conflict.
977 =head2 The MooseX:: namespace
979 Generally if you're writing an extension I<for> Moose itself you'll want
980 to put your extension in the C<MooseX::> namespace. This namespace is
981 specifically for extensions that make Moose better or different in some
982 fundamental way. It is traditionally B<not> for a package that just happens
983 to use Moose. This namespace follows from the examples of the C<LWPx::>
984 and C<DBIx::> namespaces that perform the same function for C<LWP> and C<DBI>
993 It should be noted that C<super> and C<inner> B<cannot> be used in the same
994 method. However, they may be combined within the same class hierarchy; see
995 F<t/014_override_augment_inner_super.t> for an example.
997 The reason for this is that C<super> is only valid within a method
998 with the C<override> modifier, and C<inner> will never be valid within an
999 C<override> method. In fact, C<augment> will skip over any C<override> methods
1000 when searching for its appropriate C<inner>.
1002 This might seem like a restriction, but I am of the opinion that keeping these
1003 two features separate (yet interoperable) actually makes them easy to use, since
1004 their behavior is then easier to predict. Time will tell whether I am right or
1005 not (UPDATE: so far so good).
1011 We offer both a mailing list and a very active IRC channel.
1013 The mailing list is L<moose@perl.org>. You must be subscribed to send
1014 a message. To subscribe, send an empty message to
1015 L<moose-subscribe@perl.org>
1017 You can also visit us at L<#moose on
1018 irc.perl.org|irc://irc.perl.org/#moose>. This channel is quite active,
1019 and questions at all levels (on Moose-related topics ;) are welcome.
1021 =head1 ACKNOWLEDGEMENTS
1025 =item I blame Sam Vilain for introducing me to the insanity that is meta-models.
1027 =item I blame Audrey Tang for then encouraging my meta-model habit in #perl6.
1029 =item Without Yuval "nothingmuch" Kogman this module would not be possible,
1030 and it certainly wouldn't have this name ;P
1032 =item The basis of the TypeContraints module was Rob Kinyon's idea
1033 originally, I just ran with it.
1035 =item Thanks to mst & chansen and the whole #moose posse for all the
1036 early ideas/feature-requests/encouragement/bug-finding.
1038 =item Thanks to David "Theory" Wheeler for meta-discussions and spelling fixes.
1046 =item L<http://www.iinteractive.com/moose>
1048 This is the official web home of Moose, it contains links to our public SVN repository
1049 as well as links to a number of talks and articles on Moose and Moose related
1052 =item The Moose is flying, a tutorial by Randal Schwartz
1054 Part 1 - L<http://www.stonehenge.com/merlyn/LinuxMag/col94.html>
1056 Part 2 - L<http://www.stonehenge.com/merlyn/LinuxMag/col95.html>
1058 =item Several Moose extension modules in the C<MooseX::> namespace.
1060 See L<http://search.cpan.org/search?query=MooseX::> for extensions.
1062 =item Moose stats on ohloh.net - L<http://www.ohloh.net/projects/moose>
1070 =item The Art of the MetaObject Protocol
1072 I mention this in the L<Class::MOP> docs too, this book was critical in
1073 the development of both modules and is highly recommended.
1081 =item L<http://www.cs.utah.edu/plt/publications/oopsla04-gff.pdf>
1083 This paper (suggested by lbr on #moose) was what lead to the implementation
1084 of the C<super>/C<override> and C<inner>/C<augment> features. If you really
1085 want to understand them, I suggest you read this.
1091 All complex software has bugs lurking in it, and this module is no
1094 Please report any bugs to C<bug-moose@rt.cpan.org>, or through the web
1095 interface at L<http://rt.cpan.org>.
1097 =head1 FEATURE REQUESTS
1099 We are very strict about what features we add to the Moose core, especially
1100 the user-visible features. Instead we have made sure that the underlying
1101 meta-system of Moose is as extensible as possible so that you can add your
1102 own features easily.
1104 That said, occasionally there is a feature needed in the meta-system
1105 to support your planned extension, in which case you should either
1106 email the mailing list (moose@perl.org) or join us on IRC at
1107 L<irc://irc.perl.org/#moose> to discuss. The
1108 L<Moose::Manual::Contributing> has more detail about how and when you
1113 Moose is an open project, there are at this point dozens of people who have
1114 contributed, and can contribute. If you have added anything to the Moose
1115 project you have a commit bit on this file and can add your name to the list.
1119 However there are only a few people with the rights to release a new version
1120 of Moose. The Moose Cabal are the people to go to with questions regarding
1121 the wider purview of Moose, and help out maintaining not just the code
1122 but the community as well.
1124 Stevan (stevan) Little E<lt>stevan@iinteractive.comE<gt>
1126 Yuval (nothingmuch) Kogman
1128 Shawn (sartak) Moore E<lt>sartak@bestpractical.comE<gt>
1130 Dave (autarch) Rolsky E<lt>autarch@urth.orgE<gt>
1132 Jesse (doy) Luehrs E<lt>doy at tozt dot netE<gt>
1134 Hans Dieter (confound) Pearcey E<lt>hdp@pobox.comE<gt>
1136 Chris (perigrin) Prather
1138 Florian Ragwitz E<lt>rafl@debian.orgE<gt>
1140 =head2 OTHER CONTRIBUTORS
1144 Adam (Alias) Kennedy
1146 Anders (Debolaz) Nor Berle
1148 Nathan (kolibrie) Gray
1150 Christian (chansen) Hansen
1152 Eric (ewilhelm) Wilhelm
1154 Guillermo (groditi) Roditi
1156 Jess (castaway) Robinson
1160 Robert (phaylon) Sedlacek
1164 Scott (konobi) McWhirter
1166 Shlomi (rindolf) Fish
1168 Wallace (wreis) Reis
1170 Jonathan (jrockway) Rockway
1172 Piotr (dexter) Roszatycki
1174 Sam (mugwump) Vilain
1178 Dylan Hardison (doc fixes)
1180 ... and many other #moose folks
1182 =head1 COPYRIGHT AND LICENSE
1184 Copyright 2006-2009 by Infinity Interactive, Inc.
1186 L<http://www.iinteractive.com>
1188 This library is free software; you can redistribute it and/or modify
1189 it under the same terms as Perl itself.