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.
344 =item L<http://github.com/jpa/Moose-Doc-JA>
348 =head1 BUILDING CLASSES WITH MOOSE
350 Moose makes every attempt to provide as much convenience as possible during
351 class construction/definition, but still stay out of your way if you want it
352 to. Here are a few items to note when building classes with Moose.
354 Unless specified with C<extends>, any class which uses Moose will
355 inherit from L<Moose::Object>.
357 Moose will also manage all attributes (including inherited ones) that are
358 defined with C<has>. And (assuming you call C<new>, which is inherited from
359 L<Moose::Object>) this includes properly initializing all instance slots,
360 setting defaults where appropriate, and performing any type constraint checking
363 =head1 PROVIDED METHODS
365 Moose provides a number of methods to all your classes, mostly through the
366 inheritance of L<Moose::Object>. There is however, one exception.
372 This is a method which provides access to the current class's metaclass.
376 =head1 EXPORTED FUNCTIONS
378 Moose will export a number of functions into the class's namespace which
379 may then be used to set up the class. These functions all work directly
380 on the current class.
384 =item B<extends (@superclasses)>
386 This function will set the superclass(es) for the current class.
388 This approach is recommended instead of C<use base>, because C<use base>
389 actually C<push>es onto the class's C<@ISA>, whereas C<extends> will
390 replace it. This is important to ensure that classes which do not have
391 superclasses still properly inherit from L<Moose::Object>.
393 =item B<with (@roles)>
395 This will apply a given set of C<@roles> to the local class.
397 =item B<has $name|@$names =E<gt> %options>
399 This will install an attribute of a given C<$name> into the current class. If
400 the first parameter is an array reference, it will create an attribute for
401 every C<$name> in the list. The C<%options> are the same as those provided by
402 L<Class::MOP::Attribute>, in addition to the list below which are provided by
403 Moose (L<Moose::Meta::Attribute> to be more specific):
407 =item I<is =E<gt> 'rw'|'ro'>
409 The I<is> option accepts either I<rw> (for read/write) or I<ro> (for read
410 only). These will create either a read/write accessor or a read-only
411 accessor respectively, using the same name as the C<$name> of the attribute.
413 If you need more control over how your accessors are named, you can
414 use the L<reader|Class::MOP::Attribute/reader>,
415 L<writer|Class::MOP::Attribute/writer> and
416 L<accessor|Class::MOP::Attribute/accessor> options inherited from
417 L<Class::MOP::Attribute>, however if you use those, you won't need the
420 =item I<isa =E<gt> $type_name>
422 The I<isa> option uses Moose's type constraint facilities to set up runtime
423 type checking for this attribute. Moose will perform the checks during class
424 construction, and within any accessors. The C<$type_name> argument must be a
425 string. The string may be either a class name or a type defined using
426 Moose's type definition features. (Refer to L<Moose::Util::TypeConstraints>
427 for information on how to define a new type, and how to retrieve type meta-data).
429 =item I<coerce =E<gt> (1|0)>
431 This will attempt to use coercion with the supplied type constraint to change
432 the value passed into any accessors or constructors. You B<must> have supplied
433 a type constraint in order for this to work. See L<Moose::Cookbook::Basics::Recipe5>
436 =item I<does =E<gt> $role_name>
438 This will accept the name of a role which the value stored in this attribute
439 is expected to have consumed.
441 =item I<required =E<gt> (1|0)>
443 This marks the attribute as being required. This means a value must be
444 supplied during class construction, I<or> the attribute must be lazy
445 and have either a default or a builder. Note that c<required> does not
446 say anything about the attribute's value, which can be C<undef>.
448 =item I<weak_ref =E<gt> (1|0)>
450 This will tell the class to store the value of this attribute as a weakened
451 reference. If an attribute is a weakened reference, it B<cannot> also be
454 =item I<lazy =E<gt> (1|0)>
456 This will tell the class to not create this slot until absolutely necessary.
457 If an attribute is marked as lazy it B<must> have a default supplied.
459 =item I<auto_deref =E<gt> (1|0)>
461 This tells the accessor whether to automatically dereference the value returned.
462 This is only legal if your C<isa> option is either C<ArrayRef> or C<HashRef>.
464 =item I<trigger =E<gt> $code>
466 The I<trigger> option is a CODE reference which will be called after
467 the value of the attribute is set. The CODE ref will be passed the
468 instance itself and the updated value. If the attribute already had a
469 value, this will be passed as the third value to the trigger.
471 You B<can> have a trigger on a read-only attribute.
473 B<NOTE:> Triggers will only fire when you B<assign> to the attribute,
474 either in the constructor, or using the writer. Default and built values will
475 B<not> cause the trigger to be fired.
477 =item I<handles =E<gt> ARRAY | HASH | REGEXP | ROLE | DUCKTYPE | CODE>
479 The I<handles> option provides Moose classes with automated delegation features.
480 This is a pretty complex and powerful option. It accepts many different option
481 formats, each with its own benefits and drawbacks.
483 B<NOTE:> The class being delegated to does not need to be a Moose based class,
484 which is why this feature is especially useful when wrapping non-Moose classes.
486 All I<handles> option formats share the following traits:
488 You cannot override a locally defined method with a delegated method; an
489 exception will be thrown if you try. That is to say, if you define C<foo> in
490 your class, you cannot override it with a delegated C<foo>. This is almost never
491 something you would want to do, and if it is, you should do it by hand and not
494 You cannot override any of the methods found in Moose::Object, or the C<BUILD>
495 and C<DEMOLISH> methods. These will not throw an exception, but will silently
496 move on to the next method in the list. My reasoning for this is that you would
497 almost never want to do this, since it usually breaks your class. As with
498 overriding locally defined methods, if you do want to do this, you should do it
499 manually, not with Moose.
501 You do not I<need> to have a reader (or accessor) for the attribute in order
502 to delegate to it. Moose will create a means of accessing the value for you,
503 however this will be several times B<less> efficient then if you had given
504 the attribute a reader (or accessor) to use.
506 Below is the documentation for each option format:
512 This is the most common usage for I<handles>. You basically pass a list of
513 method names to be delegated, and Moose will install a delegation method
518 This is the second most common usage for I<handles>. Instead of a list of
519 method names, you pass a HASH ref where each key is the method name you
520 want installed locally, and its value is the name of the original method
521 in the class being delegated to.
523 This can be very useful for recursive classes like trees. Here is a
524 quick example (soon to be expanded into a Moose::Cookbook recipe):
529 has 'node' => (is => 'rw', isa => 'Any');
534 default => sub { [] }
542 parent_node => 'node',
543 siblings => 'children',
547 In this example, the Tree package gets C<parent_node> and C<siblings> methods,
548 which delegate to the C<node> and C<children> methods (respectively) of the Tree
549 instance stored in the C<parent> slot.
551 You may also use an array reference to curry arguments to the original method.
555 handles => { set_foo => [ set => 'foo' ] },
558 # $self->set_foo(...) calls $self->thing->set('foo', ...)
560 The first element of the array reference is the original method name, and the
561 rest is a list of curried arguments.
565 The regexp option works very similar to the ARRAY option, except that it builds
566 the list of methods for you. It starts by collecting all possible methods of the
567 class being delegated to, then filters that list using the regexp supplied here.
569 B<NOTE:> An I<isa> option is required when using the regexp option format. This
570 is so that we can determine (at compile time) the method list from the class.
571 Without an I<isa> this is just not possible.
575 With the role option, you specify the name of a role whose "interface" then
576 becomes the list of methods to handle. The "interface" can be defined as; the
577 methods of the role and any required methods of the role. It should be noted
578 that this does B<not> include any method modifiers or generated attribute
579 methods (which is consistent with role composition).
583 With the duck type option, you pass a duck type object whose "interface" then
584 becomes the list of methods to handle. The "interface" can be defined as; the
585 list of methods passed to C<duck_type> to create a duck type object. For more
586 information on C<duck_type> please check
587 L<Moose::Util::TypeConstraints>.
591 This is the option to use when you really want to do something funky. You should
592 only use it if you really know what you are doing, as it involves manual
595 This takes a code reference, which should expect two arguments. The first is the
596 attribute meta-object this I<handles> is attached to. The second is the
597 metaclass of the class being delegated to. It expects you to return a hash (not
598 a HASH ref) of the methods you want mapped.
602 =item I<metaclass =E<gt> $metaclass_name>
604 This tells the class to use a custom attribute metaclass for this particular
605 attribute. Custom attribute metaclasses are useful for extending the
606 capabilities of the I<has> keyword: they are the simplest way to extend the MOP,
607 but they are still a fairly advanced topic and too much to cover here, see
608 L<Moose::Cookbook::Meta::Recipe1> for more information.
610 See L<Metaclass and Trait Name Resolution> for details on how a metaclass name
611 is resolved to a class name.
613 =item I<traits =E<gt> [ @role_names ]>
615 This tells Moose to take the list of C<@role_names> and apply them to the
616 attribute meta-object. This is very similar to the I<metaclass> option, but
617 allows you to use more than one extension at a time.
619 See L<Metaclass and Trait Name Resolution> for details on how a trait name is
620 resolved to a role name.
622 Also see L<Moose::Cookbook::Meta::Recipe3> for a metaclass trait
625 =item I<builder> => Str
627 The value of this key is the name of the method that will be called to
628 obtain the value used to initialize the attribute. See the L<builder
629 option docs in Class::MOP::Attribute|Class::MOP::Attribute/builder>
630 and/or L<Moose::Cookbook::Basics::Recipe8> for more information.
632 =item I<default> => SCALAR | CODE
634 The value of this key is the default value which will initialize the attribute.
636 NOTE: If the value is a simple scalar (string or number), then it can
637 be just passed as is. However, if you wish to initialize it with a
638 HASH or ARRAY ref, then you need to wrap that inside a CODE reference.
639 See the L<default option docs in
640 Class::MOP::Attribute|Class::MOP::Attribute/default> for more
643 =item I<clearer> => Str
645 Creates a method allowing you to clear the value, see the L<clearer option
646 docs in Class::MOP::Attribute|Class::MOP::Attribute/clearer> for more
649 =item I<predicate> => Str
651 Creates a method to perform a basic test to see if a value has been set in the
652 attribute, see the L<predicate option docs in
653 Class::MOP::Attribute|Class::MOP::Attribute/predicate> for more information.
655 =item I<lazy_build> => (0|1)
657 Automatically define lazy => 1 as well as builder => "_build_$attr", clearer =>
658 "clear_$attr', predicate => 'has_$attr' unless they are already defined.
660 =item I<initializer> => Str
662 This may be a method name (referring to a method on the class with
663 this attribute) or a CODE ref. The initializer is used to set the
664 attribute value on an instance when the attribute is set during
665 instance initialization (but not when the value is being assigned
666 to). See the L<initializer option docs in
667 Class::MOP::Attribute|Class::MOP::Attribute/initializer> for more
670 =item I<documentation> => $string
672 An arbitrary string that can be retrieved later by calling C<<
673 $attr->documentation >>.
679 =item B<has +$name =E<gt> %options>
681 This is variation on the normal attribute creator C<has> which allows you to
682 clone and extend an attribute from a superclass or from a role. Here is an
683 example of the superclass usage:
691 default => 'Hello, I am a Foo'
699 has '+message' => (default => 'Hello I am My::Foo');
701 What is happening here is that B<My::Foo> is cloning the C<message> attribute
702 from its parent class B<Foo>, retaining the C<is =E<gt> 'rw'> and C<isa =E<gt>
703 'Str'> characteristics, but changing the value in C<default>.
705 Here is another example, but within the context of a role:
713 default => 'Hello, I am a Foo'
721 has '+message' => (default => 'Hello I am My::Foo');
723 In this case, we are basically taking the attribute which the role supplied
724 and altering it within the bounds of this feature.
726 Note that you can only extend an attribute from either a superclass or a role,
727 you cannot extend an attribute in a role that composes over an attribute from
730 Aside from where the attributes come from (one from superclass, the other
731 from a role), this feature works exactly the same. This feature is restricted
732 somewhat, so as to try and force at least I<some> sanity into it. You are only
733 allowed to change the following attributes:
739 Change the default value of an attribute.
743 Change whether the attribute attempts to coerce a value passed to it.
747 Change if the attribute is required to have a value.
749 =item I<documentation>
751 Change the documentation string associated with the attribute.
755 Change if the attribute lazily initializes the slot.
759 You I<are> allowed to change the type without restriction.
761 It is recommended that you use this freedom with caution. We used to
762 only allow for extension only if the type was a subtype of the parent's
763 type, but we felt that was too restrictive and is better left as a
768 You are allowed to B<add> a new C<handles> definition, but you are B<not>
769 allowed to I<change> one.
773 You are allowed to B<add> a new C<builder> definition, but you are B<not>
774 allowed to I<change> one.
778 You are allowed to B<add> a new C<metaclass> definition, but you are
779 B<not> allowed to I<change> one.
783 You are allowed to B<add> additional traits to the C<traits> definition.
784 These traits will be composed into the attribute, but preexisting traits
785 B<are not> overridden, or removed.
789 =item B<before $name|@names =E<gt> sub { ... }>
791 =item B<after $name|@names =E<gt> sub { ... }>
793 =item B<around $name|@names =E<gt> sub { ... }>
795 These three items are syntactic sugar for the before, after, and around method
796 modifier features that L<Class::MOP> provides. More information on these may be
797 found in L<Moose::Manual::MethodModifiers> and the
798 L<Class::MOP::Class documentation|Class::MOP::Class/"Method Modifiers">.
802 The keyword C<super> is a no-op when called outside of an C<override> method. In
803 the context of an C<override> method, it will call the next most appropriate
804 superclass method with the same arguments as the original method.
806 =item B<override ($name, &sub)>
808 An C<override> method is a way of explicitly saying "I am overriding this
809 method from my superclass". You can call C<super> within this method, and
810 it will work as expected. The same thing I<can> be accomplished with a normal
811 method call and the C<SUPER::> pseudo-package; it is really your choice.
815 The keyword C<inner>, much like C<super>, is a no-op outside of the context of
816 an C<augment> method. You can think of C<inner> as being the inverse of
817 C<super>; the details of how C<inner> and C<augment> work is best described in
818 the L<Moose::Cookbook::Basics::Recipe6>.
820 =item B<augment ($name, &sub)>
822 An C<augment> method, is a way of explicitly saying "I am augmenting this
823 method from my superclass". Once again, the details of how C<inner> and
824 C<augment> work is best described in the L<Moose::Cookbook::Basics::Recipe6>.
828 This is the C<Carp::confess> function, and exported here because I use it
833 This is the C<Scalar::Util::blessed> function, it is exported here because I
834 use it all the time. It is highly recommended that this is used instead of
835 C<ref> anywhere you need to test for an object's class name.
841 When you use Moose, you can specify which metaclass to use:
843 use Moose -metaclass => 'My::Meta::Class';
845 You can also specify traits which will be applied to your metaclass:
847 use Moose -traits => 'My::Trait';
849 This is very similar to the attribute traits feature. When you do
850 this, your class's C<meta> object will have the specified traits
851 applied to it. See L<Metaclass and Trait Name Resolution> for more
854 =head2 Metaclass and Trait Name Resolution
856 By default, when given a trait name, Moose simply tries to load a
857 class of the same name. If such a class does not exist, it then looks
858 for for a class matching
859 B<Moose::Meta::$type::Custom::Trait::$trait_name>. The C<$type>
860 variable here will be one of B<Attribute> or B<Class>, depending on
861 what the trait is being applied to.
863 If a class with this long name exists, Moose checks to see if it has
864 the method C<register_implementation>. This method is expected to
865 return the I<real> class name of the trait. If there is no
866 C<register_implementation> method, it will fall back to using
867 B<Moose::Meta::$type::Custom::Trait::$trait> as the trait name.
869 The lookup method for metaclasses is the same, except that it looks
870 for a class matching B<Moose::Meta::$type::Custom::$metaclass_name>.
872 If all this is confusing, take a look at
873 L<Moose::Cookbook::Meta::Recipe3>, which demonstrates how to create an
876 =head1 UNIMPORTING FUNCTIONS
880 Moose offers a way to remove the keywords it exports, through the C<unimport>
881 method. You simply have to say C<no Moose> at the bottom of your code for this
882 to work. Here is an example:
887 has 'first_name' => (is => 'rw', isa => 'Str');
888 has 'last_name' => (is => 'rw', isa => 'Str');
892 $self->first_name . ' ' . $self->last_name
895 no Moose; # keywords are removed from the Person package
897 =head1 EXTENDING AND EMBEDDING MOOSE
899 To learn more about extending Moose, we recommend checking out the
900 "Extending" recipes in the L<Moose::Cookbook>, starting with
901 L<Moose::Cookbook::Extending::Recipe1>, which provides an overview of
902 all the different ways you might extend Moose.
904 =head2 B<< Moose->init_meta(for_class => $class, base_class => $baseclass, metaclass => $metaclass) >>
906 The C<init_meta> method sets up the metaclass object for the class
907 specified by C<for_class>. This method injects a a C<meta> accessor
908 into the class so you can get at this object. It also sets the class's
909 superclass to C<base_class>, with L<Moose::Object> as the default.
911 C<init_meta> returns the metaclass object for C<$class>.
913 You can specify an alternate metaclass with the C<metaclass> option.
915 For more detail on this topic, see L<Moose::Cookbook::Extending::Recipe2>.
917 This method used to be documented as a function which accepted
918 positional parameters. This calling style will still work for
919 backwards compatibility, but is deprecated.
923 Moose's C<import> method supports the L<Sub::Exporter> form of C<{into =E<gt> $pkg}>
924 and C<{into_level =E<gt> 1}>.
926 B<NOTE>: Doing this is more or less deprecated. Use L<Moose::Exporter>
927 instead, which lets you stack multiple C<Moose.pm>-alike modules
928 sanely. It handles getting the exported functions into the right place
931 =head2 B<throw_error>
933 An alias for C<confess>, used by internally by Moose.
935 =head1 METACLASS COMPATIBILITY AND MOOSE
937 Metaclass compatibility is a thorny subject. You should start by
938 reading the "About Metaclass compatibility" section in the
941 Moose will attempt to resolve a few cases of metaclass incompatibility
942 when you set the superclasses for a class, unlike C<Class::MOP>, which
943 simply dies if the metaclasses are incompatible.
945 In actuality, Moose fixes incompatibility for I<all> of a class's
946 metaclasses, not just the class metaclass. That includes the instance
947 metaclass, attribute metaclass, as well as its constructor class and
948 destructor class. However, for simplicity this discussion will just
949 refer to "metaclass", meaning the class metaclass, most of the time.
951 Moose has two algorithms for fixing metaclass incompatibility.
953 The first algorithm is very simple. If all the metaclass for the
954 parent is a I<subclass> of the child's metaclass, then we simply
955 replace the child's metaclass with the parent's.
957 The second algorithm is more complicated. It tries to determine if the
958 metaclasses only "differ by roles". This means that the parent and
959 child's metaclass share a common ancestor in their respective
960 hierarchies, and that the subclasses under the common ancestor are
961 only different because of role applications. This case is actually
962 fairly common when you mix and match various C<MooseX::*> modules,
963 many of which apply roles to the metaclass.
965 If the parent and child do differ by roles, Moose replaces the
966 metaclass in the child with a newly created metaclass. This metaclass
967 is a subclass of the parent's metaclass, does all of the roles that
968 the child's metaclass did before being replaced. Effectively, this
969 means the new metaclass does all of the roles done by both the
970 parent's and child's original metaclasses.
972 Ultimately, this is all transparent to you except in the case of an
973 unresolvable conflict.
975 =head2 The MooseX:: namespace
977 Generally if you're writing an extension I<for> Moose itself you'll want
978 to put your extension in the C<MooseX::> namespace. This namespace is
979 specifically for extensions that make Moose better or different in some
980 fundamental way. It is traditionally B<not> for a package that just happens
981 to use Moose. This namespace follows from the examples of the C<LWPx::>
982 and C<DBIx::> namespaces that perform the same function for C<LWP> and C<DBI>
991 It should be noted that C<super> and C<inner> B<cannot> be used in the same
992 method. However, they may be combined within the same class hierarchy; see
993 F<t/014_override_augment_inner_super.t> for an example.
995 The reason for this is that C<super> is only valid within a method
996 with the C<override> modifier, and C<inner> will never be valid within an
997 C<override> method. In fact, C<augment> will skip over any C<override> methods
998 when searching for its appropriate C<inner>.
1000 This might seem like a restriction, but I am of the opinion that keeping these
1001 two features separate (yet interoperable) actually makes them easy to use, since
1002 their behavior is then easier to predict. Time will tell whether I am right or
1003 not (UPDATE: so far so good).
1009 We offer both a mailing list and a very active IRC channel.
1011 The mailing list is L<moose@perl.org>. You must be subscribed to send
1012 a message. To subscribe, send an empty message to
1013 L<moose-subscribe@perl.org>
1015 You can also visit us at L<#moose on
1016 irc.perl.org|irc://irc.perl.org/#moose>. This channel is quite active,
1017 and questions at all levels (on Moose-related topics ;) are welcome.
1019 =head1 ACKNOWLEDGEMENTS
1023 =item I blame Sam Vilain for introducing me to the insanity that is meta-models.
1025 =item I blame Audrey Tang for then encouraging my meta-model habit in #perl6.
1027 =item Without Yuval "nothingmuch" Kogman this module would not be possible,
1028 and it certainly wouldn't have this name ;P
1030 =item The basis of the TypeContraints module was Rob Kinyon's idea
1031 originally, I just ran with it.
1033 =item Thanks to mst & chansen and the whole #moose posse for all the
1034 early ideas/feature-requests/encouragement/bug-finding.
1036 =item Thanks to David "Theory" Wheeler for meta-discussions and spelling fixes.
1044 =item L<http://www.iinteractive.com/moose>
1046 This is the official web home of Moose, it contains links to our public SVN repository
1047 as well as links to a number of talks and articles on Moose and Moose related
1050 =item The Moose is flying, a tutorial by Randal Schwartz
1052 Part 1 - L<http://www.stonehenge.com/merlyn/LinuxMag/col94.html>
1054 Part 2 - L<http://www.stonehenge.com/merlyn/LinuxMag/col95.html>
1056 =item Several Moose extension modules in the C<MooseX::> namespace.
1058 See L<http://search.cpan.org/search?query=MooseX::> for extensions.
1060 =item Moose stats on ohloh.net - L<http://www.ohloh.net/projects/moose>
1068 =item The Art of the MetaObject Protocol
1070 I mention this in the L<Class::MOP> docs too, this book was critical in
1071 the development of both modules and is highly recommended.
1079 =item L<http://www.cs.utah.edu/plt/publications/oopsla04-gff.pdf>
1081 This paper (suggested by lbr on #moose) was what lead to the implementation
1082 of the C<super>/C<override> and C<inner>/C<augment> features. If you really
1083 want to understand them, I suggest you read this.
1089 All complex software has bugs lurking in it, and this module is no
1092 Please report any bugs to C<bug-moose@rt.cpan.org>, or through the web
1093 interface at L<http://rt.cpan.org>.
1095 =head1 FEATURE REQUESTS
1097 We are very strict about what features we add to the Moose core, especially
1098 the user-visible features. Instead we have made sure that the underlying
1099 meta-system of Moose is as extensible as possible so that you can add your
1100 own features easily.
1102 That said, occasionally there is a feature needed in the meta-system
1103 to support your planned extension, in which case you should either
1104 email the mailing list (moose@perl.org) or join us on IRC at
1105 L<irc://irc.perl.org/#moose> to discuss. The
1106 L<Moose::Manual::Contributing> has more detail about how and when you
1111 Moose is an open project, there are at this point dozens of people who have
1112 contributed, and can contribute. If you have added anything to the Moose
1113 project you have a commit bit on this file and can add your name to the list.
1117 However there are only a few people with the rights to release a new version
1118 of Moose. The Moose Cabal are the people to go to with questions regarding
1119 the wider purview of Moose, and help out maintaining not just the code
1120 but the community as well.
1122 Stevan (stevan) Little E<lt>stevan@iinteractive.comE<gt>
1124 Yuval (nothingmuch) Kogman
1126 Shawn (sartak) Moore E<lt>sartak@bestpractical.comE<gt>
1128 Dave (autarch) Rolsky E<lt>autarch@urth.orgE<gt>
1130 Jesse (doy) Luehrs E<lt>doy at tozt dot netE<gt>
1132 Hans Dieter (confound) Pearcey E<lt>hdp@pobox.comE<gt>
1134 =head2 OTHER CONTRIBUTORS
1138 Adam (Alias) Kennedy
1140 Anders (Debolaz) Nor Berle
1142 Nathan (kolibrie) Gray
1144 Christian (chansen) Hansen
1146 Eric (ewilhelm) Wilhelm
1148 Guillermo (groditi) Roditi
1150 Jess (castaway) Robinson
1154 Robert (phaylon) Sedlacek
1158 Scott (konobi) McWhirter
1160 Shlomi (rindolf) Fish
1162 Chris (perigrin) Prather
1164 Wallace (wreis) Reis
1166 Jonathan (jrockway) Rockway
1168 Piotr (dexter) Roszatycki
1170 Sam (mugwump) Vilain
1174 Dylan Hardison (doc fixes)
1176 ... and many other #moose folks
1178 =head1 COPYRIGHT AND LICENSE
1180 Copyright 2006-2009 by Infinity Interactive, Inc.
1182 L<http://www.iinteractive.com>
1184 This library is free software; you can redistribute it and/or modify
1185 it under the same terms as Perl itself.