6 $VERSION = eval $VERSION;
7 our $AUTHORITY = 'cpan:STEVAN';
9 use Scalar::Util 'blessed';
16 use Moose::Meta::Class;
17 use Moose::Meta::TypeConstraint;
18 use Moose::Meta::TypeCoercion;
19 use Moose::Meta::Attribute;
20 use Moose::Meta::Instance;
24 use Moose::Meta::Role;
25 use Moose::Meta::Role::Composite;
26 use Moose::Meta::Role::Application;
27 use Moose::Meta::Role::Application::RoleSummation;
28 use Moose::Meta::Role::Application::ToClass;
29 use Moose::Meta::Role::Application::ToRole;
30 use Moose::Meta::Role::Application::ToInstance;
32 use Moose::Util::TypeConstraints;
36 my $level = @_ ? ($_[0] + 1) : 2;
38 @info{qw(package file line)} = caller($level);
51 Moose->throw_error("Must derive at least one class") unless @_;
53 # this checks the metaclass to make sure
54 # it is correct, sometimes it can get out
55 # of sync when the classes are being built
56 Moose::Meta::Class->initialize($class)->superclasses(@_);
61 Moose::Util::apply_all_roles(Class::MOP::Class->initialize($class), @_);
68 Moose->throw_error('Usage: has \'name\' => ( key => value, ... )')
71 my %options = ( definition_context => _caller_info(), @_ );
72 my $attrs = ( ref($name) eq 'ARRAY' ) ? $name : [ ($name) ];
73 Class::MOP::Class->initialize($class)->add_attribute( $_, %options ) for @$attrs;
78 Moose::Util::add_method_modifier($class, 'before', \@_);
83 Moose::Util::add_method_modifier($class, 'after', \@_);
88 Moose::Util::add_method_modifier($class, 'around', \@_);
96 # This check avoids a recursion loop - see
97 # t/100_bugs/020_super_recursion.t
98 return if defined $SUPER_PACKAGE && $SUPER_PACKAGE ne caller();
99 return unless $SUPER_BODY; $SUPER_BODY->(@SUPER_ARGS);
104 my ( $name, $method ) = @_;
105 Class::MOP::Class->initialize($class)->add_override_method_modifier( $name => $method );
110 our ( %INNER_BODY, %INNER_ARGS );
112 if ( my $body = $INNER_BODY{$pkg} ) {
113 my @args = @{ $INNER_ARGS{$pkg} };
114 local $INNER_ARGS{$pkg};
115 local $INNER_BODY{$pkg};
116 return $body->(@args);
124 my ( $name, $method ) = @_;
125 Class::MOP::Class->initialize($class)->add_augment_method_modifier( $name => $method );
128 Moose::Exporter->setup_import_methods(
130 qw( extends with has before after around override augment)
135 \&Scalar::Util::blessed,
140 # This used to be called as a function. This hack preserves
141 # backwards compatibility.
142 if ( $_[0] ne __PACKAGE__ ) {
143 return __PACKAGE__->init_meta(
153 my $class = $args{for_class}
154 or Moose->throw_error("Cannot call init_meta without specifying a for_class");
155 my $base_class = $args{base_class} || 'Moose::Object';
156 my $metaclass = $args{metaclass} || 'Moose::Meta::Class';
158 Moose->throw_error("The Metaclass $metaclass must be a subclass of Moose::Meta::Class.")
159 unless $metaclass->isa('Moose::Meta::Class');
161 # make a subtype for each Moose class
163 unless find_type_constraint($class);
167 if ( $meta = Class::MOP::get_metaclass_by_name($class) ) {
168 unless ( $meta->isa("Moose::Meta::Class") ) {
169 Moose->throw_error("$class already has a metaclass, but it does not inherit $metaclass ($meta)");
172 # no metaclass, no 'meta' method
174 # now we check whether our ancestors have metaclass, and if so borrow that
175 my ( undef, @isa ) = @{ $class->mro::get_linear_isa };
177 foreach my $ancestor ( @isa ) {
178 my $ancestor_meta = Class::MOP::get_metaclass_by_name($ancestor) || next;
180 my $ancestor_meta_class = ($ancestor_meta->is_immutable
181 ? $ancestor_meta->get_mutable_metaclass_name
182 : ref($ancestor_meta));
184 # if we have an ancestor metaclass that inherits $metaclass, we use
185 # that. This is like _fix_metaclass_incompatibility, but we can do it now.
187 # the case of having an ancestry is not very common, but arises in
189 unless ( $metaclass->isa( $ancestor_meta_class ) ) {
190 if ( $ancestor_meta_class->isa($metaclass) ) {
191 $metaclass = $ancestor_meta_class;
196 $meta = $metaclass->initialize($class);
199 if ( $class->can('meta') ) {
200 # check 'meta' method
202 # it may be inherited
205 # this is the case where the metaclass pragma
206 # was used before the 'use Moose' statement to
207 # override a specific class
208 my $method_meta = $class->meta;
210 ( blessed($method_meta) && $method_meta->isa('Moose::Meta::Class') )
211 || Moose->throw_error("$class already has a &meta function, but it does not return a Moose::Meta::Class ($method_meta)");
213 $meta = $method_meta;
216 unless ( $meta->has_method("meta") ) { # don't overwrite
217 # also check for inherited non moose 'meta' method?
218 # FIXME also skip this if the user requested by passing an option
221 # re-initialize so it inherits properly
222 $metaclass->initialize( ref($_[0]) || $_[0] );
227 # make sure they inherit from Moose::Object
228 $meta->superclasses($base_class)
229 unless $meta->superclasses();
234 # This may be used in some older MooseX extensions.
236 goto &Moose::Exporter::_get_caller;
239 ## make 'em all immutable
242 inline_constructor => 1,
243 constructor_name => "_new",
244 # these are Class::MOP accessors, so they need inlining
245 inline_accessors => 1
246 ) for grep { $_->is_mutable }
249 Moose::Meta::Attribute
251 Moose::Meta::Instance
253 Moose::Meta::TypeCoercion
254 Moose::Meta::TypeCoercion::Union
257 Moose::Meta::Method::Accessor
258 Moose::Meta::Method::Constructor
259 Moose::Meta::Method::Destructor
260 Moose::Meta::Method::Overridden
261 Moose::Meta::Method::Augmented
264 Moose::Meta::Role::Method
265 Moose::Meta::Role::Method::Required
266 Moose::Meta::Role::Method::Conflicting
268 Moose::Meta::Role::Composite
270 Moose::Meta::Role::Application
271 Moose::Meta::Role::Application::RoleSummation
272 Moose::Meta::Role::Application::ToClass
273 Moose::Meta::Role::Application::ToRole
274 Moose::Meta::Role::Application::ToInstance
285 Moose - A postmodern object system for Perl 5
290 use Moose; # automatically turns on strict and warnings
292 has 'x' => (is => 'rw', isa => 'Int');
293 has 'y' => (is => 'rw', isa => 'Int');
306 has 'z' => (is => 'rw', isa => 'Int');
308 after 'clear' => sub {
315 Moose is an extension of the Perl 5 object system.
317 The main goal of Moose is to make Perl 5 Object Oriented programming
318 easier, more consistent and less tedious. With Moose you can to think
319 more about what you want to do and less about the mechanics of OOP.
321 Additionally, Moose is built on top of L<Class::MOP>, which is a
322 metaclass system for Perl 5. This means that Moose not only makes
323 building normal Perl 5 objects better, but it provides the power of
324 metaclass programming as well.
328 If you're new to Moose, the best place to start is the
329 L<Moose::Manual> docs, followed by the L<Moose::Cookbook>. The intro
330 will show you what Moose is, and how it makes Perl 5 OO better.
332 The cookbook recipes on Moose basics will get you up to speed with
333 many of Moose's features quickly. Once you have an idea of what Moose
334 can do, you can use the API documentation to get more detail on
335 features which interest you.
337 =head2 Moose Extensions
339 The C<MooseX::> namespace is the official place to find Moose extensions.
340 These extensions can be found on the CPAN. The easiest way to find them
341 is to search for them (L<http://search.cpan.org/search?query=MooseX::>),
342 or to examine L<Task::Moose> which aims to keep an up-to-date, easily
343 installable list of Moose extensions.
345 =head1 BUILDING CLASSES WITH MOOSE
347 Moose makes every attempt to provide as much convenience as possible during
348 class construction/definition, but still stay out of your way if you want it
349 to. Here are a few items to note when building classes with Moose.
351 Unless specified with C<extends>, any class which uses Moose will
352 inherit from L<Moose::Object>.
354 Moose will also manage all attributes (including inherited ones) that are
355 defined with C<has>. And (assuming you call C<new>, which is inherited from
356 L<Moose::Object>) this includes properly initializing all instance slots,
357 setting defaults where appropriate, and performing any type constraint checking
360 =head1 PROVIDED METHODS
362 Moose provides a number of methods to all your classes, mostly through the
363 inheritance of L<Moose::Object>. There is however, one exception.
369 This is a method which provides access to the current class's metaclass.
373 =head1 EXPORTED FUNCTIONS
375 Moose will export a number of functions into the class's namespace which
376 may then be used to set up the class. These functions all work directly
377 on the current class.
381 =item B<extends (@superclasses)>
383 This function will set the superclass(es) for the current class.
385 This approach is recommended instead of C<use base>, because C<use base>
386 actually C<push>es onto the class's C<@ISA>, whereas C<extends> will
387 replace it. This is important to ensure that classes which do not have
388 superclasses still properly inherit from L<Moose::Object>.
390 =item B<with (@roles)>
392 This will apply a given set of C<@roles> to the local class.
394 =item B<has $name|@$names =E<gt> %options>
396 This will install an attribute of a given C<$name> into the current class. If
397 the first parameter is an array reference, it will create an attribute for
398 every C<$name> in the list. The C<%options> are the same as those provided by
399 L<Class::MOP::Attribute>, in addition to the list below which are provided by
400 Moose (L<Moose::Meta::Attribute> to be more specific):
404 =item I<is =E<gt> 'rw'|'ro'>
406 The I<is> option accepts either I<rw> (for read/write) or I<ro> (for read
407 only). These will create either a read/write accessor or a read-only
408 accessor respectively, using the same name as the C<$name> of the attribute.
410 If you need more control over how your accessors are named, you can
411 use the L<reader|Class::MOP::Attribute/reader>,
412 L<writer|Class::MOP::Attribute/writer> and
413 L<accessor|Class::MOP::Attribute/accessor> options inherited from
414 L<Class::MOP::Attribute>, however if you use those, you won't need the
417 =item I<isa =E<gt> $type_name>
419 The I<isa> option uses Moose's type constraint facilities to set up runtime
420 type checking for this attribute. Moose will perform the checks during class
421 construction, and within any accessors. The C<$type_name> argument must be a
422 string. The string may be either a class name or a type defined using
423 Moose's type definition features. (Refer to L<Moose::Util::TypeConstraints>
424 for information on how to define a new type, and how to retrieve type meta-data).
426 =item I<coerce =E<gt> (1|0)>
428 This will attempt to use coercion with the supplied type constraint to change
429 the value passed into any accessors or constructors. You B<must> have supplied
430 a type constraint in order for this to work. See L<Moose::Cookbook::Basics::Recipe5>
433 =item I<does =E<gt> $role_name>
435 This will accept the name of a role which the value stored in this attribute
436 is expected to have consumed.
438 =item I<required =E<gt> (1|0)>
440 This marks the attribute as being required. This means a value must be
441 supplied during class construction, I<or> the attribute must be lazy
442 and have either a default or a builder. Note that c<required> does not
443 say anything about the attribute's value, which can be C<undef>.
445 =item I<weak_ref =E<gt> (1|0)>
447 This will tell the class to store the value of this attribute as a weakened
448 reference. If an attribute is a weakened reference, it B<cannot> also be
451 =item I<lazy =E<gt> (1|0)>
453 This will tell the class to not create this slot until absolutely necessary.
454 If an attribute is marked as lazy it B<must> have a default supplied.
456 =item I<auto_deref =E<gt> (1|0)>
458 This tells the accessor whether to automatically dereference the value returned.
459 This is only legal if your C<isa> option is either C<ArrayRef> or C<HashRef>.
461 =item I<trigger =E<gt> $code>
463 The I<trigger> option is a CODE reference which will be called after
464 the value of the attribute is set. The CODE ref will be passed the
465 instance itself and the updated value. You B<can> have a trigger on
466 a read-only attribute.
468 B<NOTE:> Triggers will only fire when you B<assign> to the attribute,
469 either in the constructor, or using the writer. Default and built values will
470 B<not> cause the trigger to be fired.
472 =item I<handles =E<gt> ARRAY | HASH | REGEXP | ROLE | DUCKTYPE | CODE>
474 The I<handles> option provides Moose classes with automated delegation features.
475 This is a pretty complex and powerful option. It accepts many different option
476 formats, each with its own benefits and drawbacks.
478 B<NOTE:> The class being delegated to does not need to be a Moose based class,
479 which is why this feature is especially useful when wrapping non-Moose classes.
481 All I<handles> option formats share the following traits:
483 You cannot override a locally defined method with a delegated method; an
484 exception will be thrown if you try. That is to say, if you define C<foo> in
485 your class, you cannot override it with a delegated C<foo>. This is almost never
486 something you would want to do, and if it is, you should do it by hand and not
489 You cannot override any of the methods found in Moose::Object, or the C<BUILD>
490 and C<DEMOLISH> methods. These will not throw an exception, but will silently
491 move on to the next method in the list. My reasoning for this is that you would
492 almost never want to do this, since it usually breaks your class. As with
493 overriding locally defined methods, if you do want to do this, you should do it
494 manually, not with Moose.
496 You do not I<need> to have a reader (or accessor) for the attribute in order
497 to delegate to it. Moose will create a means of accessing the value for you,
498 however this will be several times B<less> efficient then if you had given
499 the attribute a reader (or accessor) to use.
501 Below is the documentation for each option format:
507 This is the most common usage for I<handles>. You basically pass a list of
508 method names to be delegated, and Moose will install a delegation method
513 This is the second most common usage for I<handles>. Instead of a list of
514 method names, you pass a HASH ref where each key is the method name you
515 want installed locally, and its value is the name of the original method
516 in the class being delegated to.
518 This can be very useful for recursive classes like trees. Here is a
519 quick example (soon to be expanded into a Moose::Cookbook recipe):
524 has 'node' => (is => 'rw', isa => 'Any');
529 default => sub { [] }
537 parent_node => 'node',
538 siblings => 'children',
542 In this example, the Tree package gets C<parent_node> and C<siblings> methods,
543 which delegate to the C<node> and C<children> methods (respectively) of the Tree
544 instance stored in the C<parent> slot.
548 The regexp option works very similar to the ARRAY option, except that it builds
549 the list of methods for you. It starts by collecting all possible methods of the
550 class being delegated to, then filters that list using the regexp supplied here.
552 B<NOTE:> An I<isa> option is required when using the regexp option format. This
553 is so that we can determine (at compile time) the method list from the class.
554 Without an I<isa> this is just not possible.
558 With the role option, you specify the name of a role whose "interface" then
559 becomes the list of methods to handle. The "interface" can be defined as; the
560 methods of the role and any required methods of the role. It should be noted
561 that this does B<not> include any method modifiers or generated attribute
562 methods (which is consistent with role composition).
566 With the duck type option, you pass a duck type object whose "interface" then
567 becomes the list of methods to handle. The "interface" can be defined as; the
568 list of methods passed to C<duck_type> to create a duck type object. For more
569 information on C<duck_type> please check
570 L<Moose::Util::TypeConstraint|Moose::Util::TypeConstraint>.
574 This is the option to use when you really want to do something funky. You should
575 only use it if you really know what you are doing, as it involves manual
578 This takes a code reference, which should expect two arguments. The first is the
579 attribute meta-object this I<handles> is attached to. The second is the
580 metaclass of the class being delegated to. It expects you to return a hash (not
581 a HASH ref) of the methods you want mapped.
585 =item I<metaclass =E<gt> $metaclass_name>
587 This tells the class to use a custom attribute metaclass for this particular
588 attribute. Custom attribute metaclasses are useful for extending the
589 capabilities of the I<has> keyword: they are the simplest way to extend the MOP,
590 but they are still a fairly advanced topic and too much to cover here, see
591 L<Moose::Cookbook::Meta::Recipe1> for more information.
593 The default behavior here is to just load C<$metaclass_name>; however, we also
594 have a way to alias to a shorter name. This will first look to see if
595 B<Moose::Meta::Attribute::Custom::$metaclass_name> exists. If it does, Moose
596 will then check to see if that has the method C<register_implementation>, which
597 should return the actual name of the custom attribute metaclass. If there is no
598 C<register_implementation> method, it will fall back to using
599 B<Moose::Meta::Attribute::Custom::$metaclass_name> as the metaclass name.
601 =item I<traits =E<gt> [ @role_names ]>
603 This tells Moose to take the list of C<@role_names> and apply them to the
604 attribute meta-object. This is very similar to the I<metaclass> option, but
605 allows you to use more than one extension at a time.
607 See L<TRAIT NAME RESOLUTION> for details on how a trait name is
608 resolved to a class name.
610 Also see L<Moose::Cookbook::Meta::Recipe3> for a metaclass trait
613 =item I<builder> => Str
615 The value of this key is the name of the method that will be called to
616 obtain the value used to initialize the attribute. See the L<builder
617 option docs in Class::MOP::Attribute|Class::MOP::Attribute/builder>
618 and/or L<Moose::Cookbook::Basics::Recipe9> for more information.
620 =item I<default> => SCALAR | CODE
622 The value of this key is the default value which will initialize the attribute.
624 NOTE: If the value is a simple scalar (string or number), then it can
625 be just passed as is. However, if you wish to initialize it with a
626 HASH or ARRAY ref, then you need to wrap that inside a CODE reference.
627 See the L<default option docs in
628 Class::MOP::Attribute|Class::MOP::Attribute/default> for more
631 =item I<clearer> => Str
633 Creates a method allowing you to clear the value, see the L<clearer option
634 docs in Class::MOP::Attribute|Class::MOP::Attribute/clearer> for more
637 =item I<predicate> => Str
639 Creates a method to perform a basic test to see if a value has been set in the
640 attribute, see the L<predicate option docs in
641 Class::MOP::Attribute|Class::MOP::Attribute/predicate> for more information.
643 =item I<lazy_build> => (0|1)
645 Automatically define lazy => 1 as well as builder => "_build_$attr", clearer =>
646 "clear_$attr', predicate => 'has_$attr' unless they are already defined.
648 =item I<initializer> => Str
650 This may be a method name (referring to a method on the class with
651 this attribute) or a CODE ref. The initializer is used to set the
652 attribute value on an instance when the attribute is set during
653 instance initialization (but not when the value is being assigned
654 to). See the L<initializer option docs in
655 Class::MOP::Attribute|Class::MOP::Attribute/initializer> for more
658 =item I<documentation> => $string
660 An arbitrary string that can be retrieved later by calling C<<
661 $attr->documentation >>.
667 =item B<has +$name =E<gt> %options>
669 This is variation on the normal attribute creator C<has> which allows you to
670 clone and extend an attribute from a superclass or from a role. Here is an
671 example of the superclass usage:
679 default => 'Hello, I am a Foo'
687 has '+message' => (default => 'Hello I am My::Foo');
689 What is happening here is that B<My::Foo> is cloning the C<message> attribute
690 from its parent class B<Foo>, retaining the C<is =E<gt> 'rw'> and C<isa =E<gt>
691 'Str'> characteristics, but changing the value in C<default>.
693 Here is another example, but within the context of a role:
701 default => 'Hello, I am a Foo'
709 has '+message' => (default => 'Hello I am My::Foo');
711 In this case, we are basically taking the attribute which the role supplied
712 and altering it within the bounds of this feature.
714 Note that you can only extend an attribute from either a superclass or a role,
715 you cannot extend an attribute in a role that composes over an attribute from
718 Aside from where the attributes come from (one from superclass, the other
719 from a role), this feature works exactly the same. This feature is restricted
720 somewhat, so as to try and force at least I<some> sanity into it. You are only
721 allowed to change the following attributes:
727 Change the default value of an attribute.
731 Change whether the attribute attempts to coerce a value passed to it.
735 Change if the attribute is required to have a value.
737 =item I<documentation>
739 Change the documentation string associated with the attribute.
743 Change if the attribute lazily initializes the slot.
747 You I<are> allowed to change the type without restriction.
749 It is recommended that you use this freedom with caution. We used to
750 only allow for extension only if the type was a subtype of the parent's
751 type, but we felt that was too restrictive and is better left as a
756 You are allowed to B<add> a new C<handles> definition, but you are B<not>
757 allowed to I<change> one.
761 You are allowed to B<add> a new C<builder> definition, but you are B<not>
762 allowed to I<change> one.
766 You are allowed to B<add> a new C<metaclass> definition, but you are
767 B<not> allowed to I<change> one.
771 You are allowed to B<add> additional traits to the C<traits> definition.
772 These traits will be composed into the attribute, but preexisting traits
773 B<are not> overridden, or removed.
777 =item B<before $name|@names =E<gt> sub { ... }>
779 =item B<after $name|@names =E<gt> sub { ... }>
781 =item B<around $name|@names =E<gt> sub { ... }>
783 This three items are syntactic sugar for the before, after, and around method
784 modifier features that L<Class::MOP> provides. More information on these may be
785 found in the L<Class::MOP::Class documentation|Class::MOP::Class/"Method
790 The keyword C<super> is a no-op when called outside of an C<override> method. In
791 the context of an C<override> method, it will call the next most appropriate
792 superclass method with the same arguments as the original method.
794 =item B<override ($name, &sub)>
796 An C<override> method is a way of explicitly saying "I am overriding this
797 method from my superclass". You can call C<super> within this method, and
798 it will work as expected. The same thing I<can> be accomplished with a normal
799 method call and the C<SUPER::> pseudo-package; it is really your choice.
803 The keyword C<inner>, much like C<super>, is a no-op outside of the context of
804 an C<augment> method. You can think of C<inner> as being the inverse of
805 C<super>; the details of how C<inner> and C<augment> work is best described in
806 the L<Moose::Cookbook::Basics::Recipe6>.
808 =item B<augment ($name, &sub)>
810 An C<augment> method, is a way of explicitly saying "I am augmenting this
811 method from my superclass". Once again, the details of how C<inner> and
812 C<augment> work is best described in the L<Moose::Cookbook::Basics::Recipe6>.
816 This is the C<Carp::confess> function, and exported here because I use it
821 This is the C<Scalar::Util::blessed> function, it is exported here because I
822 use it all the time. It is highly recommended that this is used instead of
823 C<ref> anywhere you need to test for an object's class name.
829 When you use Moose, you can specify which metaclass to use:
831 use Moose -metaclass => 'My::Meta::Class';
833 You can also specify traits which will be applied to your metaclass:
835 use Moose -traits => 'My::Trait';
837 This is very similar to the attribute traits feature. When you do
838 this, your class's C<meta> object will have the specified traits
839 applied to it. See L<TRAIT NAME RESOLUTION> for more details.
841 =head2 Trait Name Resolution
843 By default, when given a trait name, Moose simply tries to load a
844 class of the same name. If such a class does not exist, it then looks
845 for for a class matching
846 B<Moose::Meta::$type::Custom::Trait::$trait_name>. The C<$type>
847 variable here will be one of B<Attribute> or B<Class>, depending on
848 what the trait is being applied to.
850 If a class with this long name exists, Moose checks to see if it has
851 the method C<register_implementation>. This method is expected to
852 return the I<real> class name of the trait. If there is no
853 C<register_implementation> method, it will fall back to using
854 B<Moose::Meta::$type::Custom::Trait::$trait> as the trait name.
856 If all this is confusing, take a look at
857 L<Moose::Cookbook::Meta::Recipe3>, which demonstrates how to create an
860 =head1 UNIMPORTING FUNCTIONS
864 Moose offers a way to remove the keywords it exports, through the C<unimport>
865 method. You simply have to say C<no Moose> at the bottom of your code for this
866 to work. Here is an example:
871 has 'first_name' => (is => 'rw', isa => 'Str');
872 has 'last_name' => (is => 'rw', isa => 'Str');
876 $self->first_name . ' ' . $self->last_name
879 no Moose; # keywords are removed from the Person package
881 =head1 EXTENDING AND EMBEDDING MOOSE
883 To learn more about extending Moose, we recommend checking out the
884 "Extending" recipes in the L<Moose::Cookbook>, starting with
885 L<Moose::Cookbook::Extending::Recipe1>, which provides an overview of
886 all the different ways you might extend Moose.
888 =head2 B<< Moose->init_meta(for_class => $class, base_class => $baseclass, metaclass => $metaclass) >>
890 The C<init_meta> method sets up the metaclass object for the class
891 specified by C<for_class>. This method injects a a C<meta> accessor
892 into the class so you can get at this object. It also sets the class's
893 superclass to C<base_class>, with L<Moose::Object> as the default.
895 C<init_meta> returns the metaclass object for C<$class>.
897 You can specify an alternate metaclass with the C<metaclass> option.
899 For more detail on this topic, see L<Moose::Cookbook::Extending::Recipe2>.
901 This method used to be documented as a function which accepted
902 positional parameters. This calling style will still work for
903 backwards compatibility, but is deprecated.
907 Moose's C<import> method supports the L<Sub::Exporter> form of C<{into =E<gt> $pkg}>
908 and C<{into_level =E<gt> 1}>.
910 B<NOTE>: Doing this is more or less deprecated. Use L<Moose::Exporter>
911 instead, which lets you stack multiple C<Moose.pm>-alike modules
912 sanely. It handles getting the exported functions into the right place
915 =head2 B<throw_error>
917 An alias for C<confess>, used by internally by Moose.
919 =head1 METACLASS COMPATIBILITY AND MOOSE
921 Metaclass compatibility is a thorny subject. You should start by
922 reading the "About Metaclass compatibility" section in the
925 Moose will attempt to resolve a few cases of metaclass incompatibility
926 when you set the superclasses for a class, unlike C<Class::MOP>, which
927 simply dies if the metaclasses are incompatible.
929 In actuality, Moose fixes incompatibility for I<all> of a class's
930 metaclasses, not just the class metaclass. That includes the instance
931 metaclass, attribute metaclass, as well as its constructor class and
932 destructor class. However, for simplicity this discussion will just
933 refer to "metaclass", meaning the class metaclass, most of the time.
935 Moose has two algorithms for fixing metaclass incompatibility.
937 The first algorithm is very simple. If all the metaclass for the
938 parent is a I<subclass> of the child's metaclass, then we simply
939 replace the child's metaclass with the parent's.
941 The second algorithm is more complicated. It tries to determine if the
942 metaclasses only "differ by roles". This means that the parent and
943 child's metaclass share a common ancestor in their respective
944 hierarchies, and that the subclasses under the common ancestor are
945 only different because of role applications. This case is actually
946 fairly common when you mix and match various C<MooseX::*> modules,
947 many of which apply roles to the metaclass.
949 If the parent and child do differ by roles, Moose replaces the
950 metaclass in the child with a newly created metaclass. This metaclass
951 is a subclass of the parent's metaclass, does all of the roles that
952 the child's metaclass did before being replaced. Effectively, this
953 means the new metaclass does all of the roles done by both the
954 parent's and child's original metaclasses.
956 Ultimately, this is all transparent to you except in the case of an
957 unresolvable conflict.
959 =head2 The MooseX:: namespace
961 Generally if you're writing an extension I<for> Moose itself you'll want
962 to put your extension in the C<MooseX::> namespace. This namespace is
963 specifically for extensions that make Moose better or different in some
964 fundamental way. It is traditionally B<not> for a package that just happens
965 to use Moose. This namespace follows from the examples of the C<LWPx::>
966 and C<DBIx::> namespaces that perform the same function for C<LWP> and C<DBI>
975 It should be noted that C<super> and C<inner> B<cannot> be used in the same
976 method. However, they may be combined within the same class hierarchy; see
977 F<t/014_override_augment_inner_super.t> for an example.
979 The reason for this is that C<super> is only valid within a method
980 with the C<override> modifier, and C<inner> will never be valid within an
981 C<override> method. In fact, C<augment> will skip over any C<override> methods
982 when searching for its appropriate C<inner>.
984 This might seem like a restriction, but I am of the opinion that keeping these
985 two features separate (yet interoperable) actually makes them easy to use, since
986 their behavior is then easier to predict. Time will tell whether I am right or
987 not (UPDATE: so far so good).
993 We offer both a mailing list and a very active IRC channel.
995 The mailing list is L<moose@perl.org>. You must be subscribed to send
996 a message. To subscribe, send an empty message to
997 L<moose-subscribe@perl.org>
999 You can also visit us at L<#moose on
1000 irc.perl.org|irc://irc.perl.org/#moose>. This channel is quite active,
1001 and questions at all levels (on Moose-related topics ;) are welcome.
1003 =head1 ACKNOWLEDGEMENTS
1007 =item I blame Sam Vilain for introducing me to the insanity that is meta-models.
1009 =item I blame Audrey Tang for then encouraging my meta-model habit in #perl6.
1011 =item Without Yuval "nothingmuch" Kogman this module would not be possible,
1012 and it certainly wouldn't have this name ;P
1014 =item The basis of the TypeContraints module was Rob Kinyon's idea
1015 originally, I just ran with it.
1017 =item Thanks to mst & chansen and the whole #moose posse for all the
1018 early ideas/feature-requests/encouragement/bug-finding.
1020 =item Thanks to David "Theory" Wheeler for meta-discussions and spelling fixes.
1028 =item L<http://www.iinteractive.com/moose>
1030 This is the official web home of Moose, it contains links to our public SVN repository
1031 as well as links to a number of talks and articles on Moose and Moose related
1034 =item The Moose is flying, a tutorial by Randal Schwartz
1036 Part 1 - L<http://www.stonehenge.com/merlyn/LinuxMag/col94.html>
1038 Part 2 - L<http://www.stonehenge.com/merlyn/LinuxMag/col95.html>
1040 =item Several Moose extension modules in the C<MooseX::> namespace.
1042 See L<http://search.cpan.org/search?query=MooseX::> for extensions.
1044 =item Moose stats on ohloh.net - L<http://www.ohloh.net/projects/moose>
1052 =item The Art of the MetaObject Protocol
1054 I mention this in the L<Class::MOP> docs too, this book was critical in
1055 the development of both modules and is highly recommended.
1063 =item L<http://www.cs.utah.edu/plt/publications/oopsla04-gff.pdf>
1065 This paper (suggested by lbr on #moose) was what lead to the implementation
1066 of the C<super>/C<override> and C<inner>/C<augment> features. If you really
1067 want to understand them, I suggest you read this.
1073 All complex software has bugs lurking in it, and this module is no
1076 Please report any bugs to C<bug-moose@rt.cpan.org>, or through the web
1077 interface at L<http://rt.cpan.org>.
1079 =head1 FEATURE REQUESTS
1081 We are very strict about what features we add to the Moose core, especially
1082 the user-visible features. Instead we have made sure that the underlying
1083 meta-system of Moose is as extensible as possible so that you can add your
1084 own features easily.
1086 That said, occasionally there is a feature needed in the meta-system
1087 to support your planned extension, in which case you should either
1088 email the mailing list (moose@perl.org) or join us on IRC at
1089 L<irc://irc.perl.org/#moose> to discuss. The
1090 L<Moose::Manual::Contributing> has more detail about how and when you
1095 Moose is an open project, there are at this point dozens of people who have
1096 contributed, and can contribute. If you have added anything to the Moose
1097 project you have a commit bit on this file and can add your name to the list.
1101 However there are only a few people with the rights to release a new version
1102 of Moose. The Moose Cabal are the people to go to with questions regarding
1103 the wider purview of Moose, and help out maintaining not just the code
1104 but the community as well.
1106 Stevan (stevan) Little E<lt>stevan@iinteractive.comE<gt>
1108 Yuval (nothingmuch) Kogman
1110 Shawn (sartak) Moore
1112 Dave (autarch) Rolsky E<lt>autarch@urth.orgE<gt>
1114 =head2 OTHER CONTRIBUTORS
1118 Adam (Alias) Kennedy
1120 Anders (Debolaz) Nor Berle
1122 Nathan (kolibrie) Gray
1124 Christian (chansen) Hansen
1126 Hans Dieter (confound) Pearcey
1128 Eric (ewilhelm) Wilhelm
1130 Guillermo (groditi) Roditi
1132 Jess (castaway) Robinson
1136 Robert (phaylon) Sedlacek
1140 Scott (konobi) McWhirter
1142 Shlomi (rindolf) Fish
1144 Chris (perigrin) Prather
1146 Wallace (wreis) Reis
1148 Jonathan (jrockway) Rockway
1150 Piotr (dexter) Roszatycki
1152 Sam (mugwump) Vilain
1156 Dylan Hardison (doc fixes)
1158 ... and many other #moose folks
1160 =head1 COPYRIGHT AND LICENSE
1162 Copyright 2006-2009 by Infinity Interactive, Inc.
1164 L<http://www.iinteractive.com>
1166 This library is free software; you can redistribute it and/or modify
1167 it under the same terms as Perl itself.