8 $VERSION = eval $VERSION;
9 our $AUTHORITY = 'cpan:STEVAN';
11 use Scalar::Util 'blessed';
18 use Moose::Meta::Class;
19 use Moose::Meta::TypeConstraint;
20 use Moose::Meta::TypeCoercion;
21 use Moose::Meta::Attribute;
22 use Moose::Meta::Instance;
26 use Moose::Meta::Role;
27 use Moose::Meta::Role::Composite;
28 use Moose::Meta::Role::Application;
29 use Moose::Meta::Role::Application::RoleSummation;
30 use Moose::Meta::Role::Application::ToClass;
31 use Moose::Meta::Role::Application::ToRole;
32 use Moose::Meta::Role::Application::ToInstance;
34 use Moose::Util::TypeConstraints;
46 Moose->throw_error("Must derive at least one class") unless @_;
48 # this checks the metaclass to make sure
49 # it is correct, sometimes it can get out
50 # of sync when the classes are being built
51 Moose::Meta::Class->initialize($class)->superclasses(@_);
56 Moose::Util::apply_all_roles(Class::MOP::Class->initialize($class), @_);
63 Moose->throw_error('Usage: has \'name\' => ( key => value, ... )')
66 my %options = ( definition_context => Moose::Util::_caller_info(), @_ );
67 my $attrs = ( ref($name) eq 'ARRAY' ) ? $name : [ ($name) ];
68 Class::MOP::Class->initialize($class)->add_attribute( $_, %options ) for @$attrs;
73 Moose::Util::add_method_modifier($class, 'before', \@_);
78 Moose::Util::add_method_modifier($class, 'after', \@_);
83 Moose::Util::add_method_modifier($class, 'around', \@_);
91 # This check avoids a recursion loop - see
92 # t/100_bugs/020_super_recursion.t
93 return if defined $SUPER_PACKAGE && $SUPER_PACKAGE ne caller();
94 return unless $SUPER_BODY; $SUPER_BODY->(@SUPER_ARGS);
99 my ( $name, $method ) = @_;
100 Class::MOP::Class->initialize($class)->add_override_method_modifier( $name => $method );
105 our ( %INNER_BODY, %INNER_ARGS );
107 if ( my $body = $INNER_BODY{$pkg} ) {
108 my @args = @{ $INNER_ARGS{$pkg} };
109 local $INNER_ARGS{$pkg};
110 local $INNER_BODY{$pkg};
111 return $body->(@args);
119 my ( $name, $method ) = @_;
120 Class::MOP::Class->initialize($class)->add_augment_method_modifier( $name => $method );
123 Moose::Exporter->setup_import_methods(
125 qw( extends with has before after around override augment)
130 \&Scalar::Util::blessed,
135 # This used to be called as a function. This hack preserves
136 # backwards compatibility.
137 if ( $_[0] ne __PACKAGE__ ) {
138 return __PACKAGE__->init_meta(
148 my $class = $args{for_class}
149 or Moose->throw_error("Cannot call init_meta without specifying a for_class");
150 my $base_class = $args{base_class} || 'Moose::Object';
151 my $metaclass = $args{metaclass} || 'Moose::Meta::Class';
153 Moose->throw_error("The Metaclass $metaclass must be a subclass of Moose::Meta::Class.")
154 unless $metaclass->isa('Moose::Meta::Class');
156 # make a subtype for each Moose class
158 unless find_type_constraint($class);
162 if ( $meta = Class::MOP::get_metaclass_by_name($class) ) {
163 unless ( $meta->isa("Moose::Meta::Class") ) {
164 Moose->throw_error("$class already has a metaclass, but it does not inherit $metaclass ($meta)");
167 # no metaclass, no 'meta' method
169 # now we check whether our ancestors have metaclass, and if so borrow that
170 my ( undef, @isa ) = @{ $class->mro::get_linear_isa };
172 foreach my $ancestor ( @isa ) {
173 my $ancestor_meta = Class::MOP::get_metaclass_by_name($ancestor) || next;
175 my $ancestor_meta_class = ($ancestor_meta->is_immutable
176 ? $ancestor_meta->get_mutable_metaclass_name
177 : ref($ancestor_meta));
179 # if we have an ancestor metaclass that inherits $metaclass, we use
180 # that. This is like _fix_metaclass_incompatibility, but we can do it now.
182 # the case of having an ancestry is not very common, but arises in
184 unless ( $metaclass->isa( $ancestor_meta_class ) ) {
185 if ( $ancestor_meta_class->isa($metaclass) ) {
186 $metaclass = $ancestor_meta_class;
191 $meta = $metaclass->initialize($class);
194 if ( $class->can('meta') ) {
195 # check 'meta' method
197 # it may be inherited
200 # this is the case where the metaclass pragma
201 # was used before the 'use Moose' statement to
202 # override a specific class
203 my $method_meta = $class->meta;
205 ( blessed($method_meta) && $method_meta->isa('Moose::Meta::Class') )
206 || Moose->throw_error("$class already has a &meta function, but it does not return a Moose::Meta::Class ($method_meta)");
208 $meta = $method_meta;
211 unless ( $meta->has_method("meta") ) { # don't overwrite
212 # also check for inherited non moose 'meta' method?
213 # FIXME also skip this if the user requested by passing an option
216 # re-initialize so it inherits properly
217 $metaclass->initialize( ref($_[0]) || $_[0] );
222 # make sure they inherit from Moose::Object
223 $meta->superclasses($base_class)
224 unless $meta->superclasses();
229 # This may be used in some older MooseX extensions.
231 goto &Moose::Exporter::_get_caller;
234 ## make 'em all immutable
237 inline_constructor => 1,
238 constructor_name => "_new",
239 # these are Class::MOP accessors, so they need inlining
240 inline_accessors => 1
241 ) for grep { $_->is_mutable }
244 Moose::Meta::Attribute
246 Moose::Meta::Instance
248 Moose::Meta::TypeCoercion
249 Moose::Meta::TypeCoercion::Union
252 Moose::Meta::Method::Accessor
253 Moose::Meta::Method::Constructor
254 Moose::Meta::Method::Destructor
255 Moose::Meta::Method::Overridden
256 Moose::Meta::Method::Augmented
259 Moose::Meta::Role::Method
260 Moose::Meta::Role::Method::Required
261 Moose::Meta::Role::Method::Conflicting
263 Moose::Meta::Role::Composite
265 Moose::Meta::Role::Application
266 Moose::Meta::Role::Application::RoleSummation
267 Moose::Meta::Role::Application::ToClass
268 Moose::Meta::Role::Application::ToRole
269 Moose::Meta::Role::Application::ToInstance
280 Moose - A postmodern object system for Perl 5
285 use Moose; # automatically turns on strict and warnings
287 has 'x' => (is => 'rw', isa => 'Int');
288 has 'y' => (is => 'rw', isa => 'Int');
301 has 'z' => (is => 'rw', isa => 'Int');
303 after 'clear' => sub {
310 Moose is an extension of the Perl 5 object system.
312 The main goal of Moose is to make Perl 5 Object Oriented programming
313 easier, more consistent and less tedious. With Moose you can to think
314 more about what you want to do and less about the mechanics of OOP.
316 Additionally, Moose is built on top of L<Class::MOP>, which is a
317 metaclass system for Perl 5. This means that Moose not only makes
318 building normal Perl 5 objects better, but it provides the power of
319 metaclass programming as well.
323 If you're new to Moose, the best place to start is the
324 L<Moose::Manual> docs, followed by the L<Moose::Cookbook>. The intro
325 will show you what Moose is, and how it makes Perl 5 OO better.
327 The cookbook recipes on Moose basics will get you up to speed with
328 many of Moose's features quickly. Once you have an idea of what Moose
329 can do, you can use the API documentation to get more detail on
330 features which interest you.
332 =head2 Moose Extensions
334 The C<MooseX::> namespace is the official place to find Moose extensions.
335 These extensions can be found on the CPAN. The easiest way to find them
336 is to search for them (L<http://search.cpan.org/search?query=MooseX::>),
337 or to examine L<Task::Moose> which aims to keep an up-to-date, easily
338 installable list of Moose extensions.
340 =head1 BUILDING CLASSES WITH MOOSE
342 Moose makes every attempt to provide as much convenience as possible during
343 class construction/definition, but still stay out of your way if you want it
344 to. Here are a few items to note when building classes with Moose.
346 Unless specified with C<extends>, any class which uses Moose will
347 inherit from L<Moose::Object>.
349 Moose will also manage all attributes (including inherited ones) that are
350 defined with C<has>. And (assuming you call C<new>, which is inherited from
351 L<Moose::Object>) this includes properly initializing all instance slots,
352 setting defaults where appropriate, and performing any type constraint checking
355 =head1 PROVIDED METHODS
357 Moose provides a number of methods to all your classes, mostly through the
358 inheritance of L<Moose::Object>. There is however, one exception.
364 This is a method which provides access to the current class's metaclass.
368 =head1 EXPORTED FUNCTIONS
370 Moose will export a number of functions into the class's namespace which
371 may then be used to set up the class. These functions all work directly
372 on the current class.
376 =item B<extends (@superclasses)>
378 This function will set the superclass(es) for the current class.
380 This approach is recommended instead of C<use base>, because C<use base>
381 actually C<push>es onto the class's C<@ISA>, whereas C<extends> will
382 replace it. This is important to ensure that classes which do not have
383 superclasses still properly inherit from L<Moose::Object>.
385 =item B<with (@roles)>
387 This will apply a given set of C<@roles> to the local class.
389 =item B<has $name|@$names =E<gt> %options>
391 This will install an attribute of a given C<$name> into the current class. If
392 the first parameter is an array reference, it will create an attribute for
393 every C<$name> in the list. The C<%options> are the same as those provided by
394 L<Class::MOP::Attribute>, in addition to the list below which are provided by
395 Moose (L<Moose::Meta::Attribute> to be more specific):
399 =item I<is =E<gt> 'rw'|'ro'>
401 The I<is> option accepts either I<rw> (for read/write) or I<ro> (for read
402 only). These will create either a read/write accessor or a read-only
403 accessor respectively, using the same name as the C<$name> of the attribute.
405 If you need more control over how your accessors are named, you can
406 use the L<reader|Class::MOP::Attribute/reader>,
407 L<writer|Class::MOP::Attribute/writer> and
408 L<accessor|Class::MOP::Attribute/accessor> options inherited from
409 L<Class::MOP::Attribute>, however if you use those, you won't need the
412 =item I<isa =E<gt> $type_name>
414 The I<isa> option uses Moose's type constraint facilities to set up runtime
415 type checking for this attribute. Moose will perform the checks during class
416 construction, and within any accessors. The C<$type_name> argument must be a
417 string. The string may be either a class name or a type defined using
418 Moose's type definition features. (Refer to L<Moose::Util::TypeConstraints>
419 for information on how to define a new type, and how to retrieve type meta-data).
421 =item I<coerce =E<gt> (1|0)>
423 This will attempt to use coercion with the supplied type constraint to change
424 the value passed into any accessors or constructors. You B<must> have supplied
425 a type constraint in order for this to work. See L<Moose::Cookbook::Basics::Recipe5>
428 =item I<does =E<gt> $role_name>
430 This will accept the name of a role which the value stored in this attribute
431 is expected to have consumed.
433 =item I<required =E<gt> (1|0)>
435 This marks the attribute as being required. This means a value must be
436 supplied during class construction, I<or> the attribute must be lazy
437 and have either a default or a builder. Note that c<required> does not
438 say anything about the attribute's value, which can be C<undef>.
440 =item I<weak_ref =E<gt> (1|0)>
442 This will tell the class to store the value of this attribute as a weakened
443 reference. If an attribute is a weakened reference, it B<cannot> also be
446 =item I<lazy =E<gt> (1|0)>
448 This will tell the class to not create this slot until absolutely necessary.
449 If an attribute is marked as lazy it B<must> have a default supplied.
451 =item I<auto_deref =E<gt> (1|0)>
453 This tells the accessor whether to automatically dereference the value returned.
454 This is only legal if your C<isa> option is either C<ArrayRef> or C<HashRef>.
456 =item I<trigger =E<gt> $code>
458 The I<trigger> option is a CODE reference which will be called after
459 the value of the attribute is set. The CODE ref will be passed the
460 instance itself and the updated value. You B<can> have a trigger on
461 a read-only attribute.
463 B<NOTE:> Triggers will only fire when you B<assign> to the attribute,
464 either in the constructor, or using the writer. Default and built values will
465 B<not> cause the trigger to be fired.
467 =item I<handles =E<gt> ARRAY | HASH | REGEXP | ROLE | DUCKTYPE | CODE>
469 The I<handles> option provides Moose classes with automated delegation features.
470 This is a pretty complex and powerful option. It accepts many different option
471 formats, each with its own benefits and drawbacks.
473 B<NOTE:> The class being delegated to does not need to be a Moose based class,
474 which is why this feature is especially useful when wrapping non-Moose classes.
476 All I<handles> option formats share the following traits:
478 You cannot override a locally defined method with a delegated method; an
479 exception will be thrown if you try. That is to say, if you define C<foo> in
480 your class, you cannot override it with a delegated C<foo>. This is almost never
481 something you would want to do, and if it is, you should do it by hand and not
484 You cannot override any of the methods found in Moose::Object, or the C<BUILD>
485 and C<DEMOLISH> methods. These will not throw an exception, but will silently
486 move on to the next method in the list. My reasoning for this is that you would
487 almost never want to do this, since it usually breaks your class. As with
488 overriding locally defined methods, if you do want to do this, you should do it
489 manually, not with Moose.
491 You do not I<need> to have a reader (or accessor) for the attribute in order
492 to delegate to it. Moose will create a means of accessing the value for you,
493 however this will be several times B<less> efficient then if you had given
494 the attribute a reader (or accessor) to use.
496 Below is the documentation for each option format:
502 This is the most common usage for I<handles>. You basically pass a list of
503 method names to be delegated, and Moose will install a delegation method
508 This is the second most common usage for I<handles>. Instead of a list of
509 method names, you pass a HASH ref where each key is the method name you
510 want installed locally, and its value is the name of the original method
511 in the class being delegated to.
513 This can be very useful for recursive classes like trees. Here is a
514 quick example (soon to be expanded into a Moose::Cookbook recipe):
519 has 'node' => (is => 'rw', isa => 'Any');
524 default => sub { [] }
532 parent_node => 'node',
533 siblings => 'children',
537 In this example, the Tree package gets C<parent_node> and C<siblings> methods,
538 which delegate to the C<node> and C<children> methods (respectively) of the Tree
539 instance stored in the C<parent> slot.
541 You may also use an array reference to curry arguments to the original method.
545 handles => { set_foo => [ set => [ 'foo' ] ] },
548 # $self->set_foo(...) calls $self->thing->set('foo', ...)
550 The first element of the array reference is the original method name, and the
551 second is an array reference of curried arguments.
555 The regexp option works very similar to the ARRAY option, except that it builds
556 the list of methods for you. It starts by collecting all possible methods of the
557 class being delegated to, then filters that list using the regexp supplied here.
559 B<NOTE:> An I<isa> option is required when using the regexp option format. This
560 is so that we can determine (at compile time) the method list from the class.
561 Without an I<isa> this is just not possible.
565 With the role option, you specify the name of a role whose "interface" then
566 becomes the list of methods to handle. The "interface" can be defined as; the
567 methods of the role and any required methods of the role. It should be noted
568 that this does B<not> include any method modifiers or generated attribute
569 methods (which is consistent with role composition).
573 With the duck type option, you pass a duck type object whose "interface" then
574 becomes the list of methods to handle. The "interface" can be defined as; the
575 list of methods passed to C<duck_type> to create a duck type object. For more
576 information on C<duck_type> please check
577 L<Moose::Util::TypeConstraint|Moose::Util::TypeConstraint>.
581 This is the option to use when you really want to do something funky. You should
582 only use it if you really know what you are doing, as it involves manual
585 This takes a code reference, which should expect two arguments. The first is the
586 attribute meta-object this I<handles> is attached to. The second is the
587 metaclass of the class being delegated to. It expects you to return a hash (not
588 a HASH ref) of the methods you want mapped.
592 =item I<metaclass =E<gt> $metaclass_name>
594 This tells the class to use a custom attribute metaclass for this particular
595 attribute. Custom attribute metaclasses are useful for extending the
596 capabilities of the I<has> keyword: they are the simplest way to extend the MOP,
597 but they are still a fairly advanced topic and too much to cover here, see
598 L<Moose::Cookbook::Meta::Recipe1> for more information.
600 The default behavior here is to just load C<$metaclass_name>; however, we also
601 have a way to alias to a shorter name. This will first look to see if
602 B<Moose::Meta::Attribute::Custom::$metaclass_name> exists. If it does, Moose
603 will then check to see if that has the method C<register_implementation>, which
604 should return the actual name of the custom attribute metaclass. If there is no
605 C<register_implementation> method, it will fall back to using
606 B<Moose::Meta::Attribute::Custom::$metaclass_name> as the metaclass name.
608 =item I<traits =E<gt> [ @role_names ]>
610 This tells Moose to take the list of C<@role_names> and apply them to the
611 attribute meta-object. This is very similar to the I<metaclass> option, but
612 allows you to use more than one extension at a time.
614 See L<TRAIT NAME RESOLUTION> for details on how a trait name is
615 resolved to a class name.
617 Also see L<Moose::Cookbook::Meta::Recipe3> for a metaclass trait
620 =item I<builder> => Str
622 The value of this key is the name of the method that will be called to
623 obtain the value used to initialize the attribute. See the L<builder
624 option docs in Class::MOP::Attribute|Class::MOP::Attribute/builder>
625 and/or L<Moose::Cookbook::Basics::Recipe9> for more information.
627 =item I<default> => SCALAR | CODE
629 The value of this key is the default value which will initialize the attribute.
631 NOTE: If the value is a simple scalar (string or number), then it can
632 be just passed as is. However, if you wish to initialize it with a
633 HASH or ARRAY ref, then you need to wrap that inside a CODE reference.
634 See the L<default option docs in
635 Class::MOP::Attribute|Class::MOP::Attribute/default> for more
638 =item I<clearer> => Str
640 Creates a method allowing you to clear the value, see the L<clearer option
641 docs in Class::MOP::Attribute|Class::MOP::Attribute/clearer> for more
644 =item I<predicate> => Str
646 Creates a method to perform a basic test to see if a value has been set in the
647 attribute, see the L<predicate option docs in
648 Class::MOP::Attribute|Class::MOP::Attribute/predicate> for more information.
650 =item I<lazy_build> => (0|1)
652 Automatically define lazy => 1 as well as builder => "_build_$attr", clearer =>
653 "clear_$attr', predicate => 'has_$attr' unless they are already defined.
655 =item I<initializer> => Str
657 This may be a method name (referring to a method on the class with
658 this attribute) or a CODE ref. The initializer is used to set the
659 attribute value on an instance when the attribute is set during
660 instance initialization (but not when the value is being assigned
661 to). See the L<initializer option docs in
662 Class::MOP::Attribute|Class::MOP::Attribute/initializer> for more
665 =item I<documentation> => $string
667 An arbitrary string that can be retrieved later by calling C<<
668 $attr->documentation >>.
674 =item B<has +$name =E<gt> %options>
676 This is variation on the normal attribute creator C<has> which allows you to
677 clone and extend an attribute from a superclass or from a role. Here is an
678 example of the superclass usage:
686 default => 'Hello, I am a Foo'
694 has '+message' => (default => 'Hello I am My::Foo');
696 What is happening here is that B<My::Foo> is cloning the C<message> attribute
697 from its parent class B<Foo>, retaining the C<is =E<gt> 'rw'> and C<isa =E<gt>
698 'Str'> characteristics, but changing the value in C<default>.
700 Here is another example, but within the context of a role:
708 default => 'Hello, I am a Foo'
716 has '+message' => (default => 'Hello I am My::Foo');
718 In this case, we are basically taking the attribute which the role supplied
719 and altering it within the bounds of this feature.
721 Note that you can only extend an attribute from either a superclass or a role,
722 you cannot extend an attribute in a role that composes over an attribute from
725 Aside from where the attributes come from (one from superclass, the other
726 from a role), this feature works exactly the same. This feature is restricted
727 somewhat, so as to try and force at least I<some> sanity into it. You are only
728 allowed to change the following attributes:
734 Change the default value of an attribute.
738 Change whether the attribute attempts to coerce a value passed to it.
742 Change if the attribute is required to have a value.
744 =item I<documentation>
746 Change the documentation string associated with the attribute.
750 Change if the attribute lazily initializes the slot.
754 You I<are> allowed to change the type without restriction.
756 It is recommended that you use this freedom with caution. We used to
757 only allow for extension only if the type was a subtype of the parent's
758 type, but we felt that was too restrictive and is better left as a
763 You are allowed to B<add> a new C<handles> definition, but you are B<not>
764 allowed to I<change> one.
768 You are allowed to B<add> a new C<builder> definition, but you are B<not>
769 allowed to I<change> one.
773 You are allowed to B<add> a new C<metaclass> definition, but you are
774 B<not> allowed to I<change> one.
778 You are allowed to B<add> additional traits to the C<traits> definition.
779 These traits will be composed into the attribute, but preexisting traits
780 B<are not> overridden, or removed.
784 =item B<before $name|@names =E<gt> sub { ... }>
786 =item B<after $name|@names =E<gt> sub { ... }>
788 =item B<around $name|@names =E<gt> sub { ... }>
790 This three items are syntactic sugar for the before, after, and around method
791 modifier features that L<Class::MOP> provides. More information on these may be
792 found in the L<Class::MOP::Class documentation|Class::MOP::Class/"Method
797 The keyword C<super> is a no-op when called outside of an C<override> method. In
798 the context of an C<override> method, it will call the next most appropriate
799 superclass method with the same arguments as the original method.
801 =item B<override ($name, &sub)>
803 An C<override> method is a way of explicitly saying "I am overriding this
804 method from my superclass". You can call C<super> within this method, and
805 it will work as expected. The same thing I<can> be accomplished with a normal
806 method call and the C<SUPER::> pseudo-package; it is really your choice.
810 The keyword C<inner>, much like C<super>, is a no-op outside of the context of
811 an C<augment> method. You can think of C<inner> as being the inverse of
812 C<super>; the details of how C<inner> and C<augment> work is best described in
813 the L<Moose::Cookbook::Basics::Recipe6>.
815 =item B<augment ($name, &sub)>
817 An C<augment> method, is a way of explicitly saying "I am augmenting this
818 method from my superclass". Once again, the details of how C<inner> and
819 C<augment> work is best described in the L<Moose::Cookbook::Basics::Recipe6>.
823 This is the C<Carp::confess> function, and exported here because I use it
828 This is the C<Scalar::Util::blessed> function, it is exported here because I
829 use it all the time. It is highly recommended that this is used instead of
830 C<ref> anywhere you need to test for an object's class name.
836 When you use Moose, you can specify which metaclass to use:
838 use Moose -metaclass => 'My::Meta::Class';
840 You can also specify traits which will be applied to your metaclass:
842 use Moose -traits => 'My::Trait';
844 This is very similar to the attribute traits feature. When you do
845 this, your class's C<meta> object will have the specified traits
846 applied to it. See L<TRAIT NAME RESOLUTION> for more details.
848 =head2 Trait Name Resolution
850 By default, when given a trait name, Moose simply tries to load a
851 class of the same name. If such a class does not exist, it then looks
852 for for a class matching
853 B<Moose::Meta::$type::Custom::Trait::$trait_name>. The C<$type>
854 variable here will be one of B<Attribute> or B<Class>, depending on
855 what the trait is being applied to.
857 If a class with this long name exists, Moose checks to see if it has
858 the method C<register_implementation>. This method is expected to
859 return the I<real> class name of the trait. If there is no
860 C<register_implementation> method, it will fall back to using
861 B<Moose::Meta::$type::Custom::Trait::$trait> as the trait name.
863 If all this is confusing, take a look at
864 L<Moose::Cookbook::Meta::Recipe3>, which demonstrates how to create an
867 =head1 UNIMPORTING FUNCTIONS
871 Moose offers a way to remove the keywords it exports, through the C<unimport>
872 method. You simply have to say C<no Moose> at the bottom of your code for this
873 to work. Here is an example:
878 has 'first_name' => (is => 'rw', isa => 'Str');
879 has 'last_name' => (is => 'rw', isa => 'Str');
883 $self->first_name . ' ' . $self->last_name
886 no Moose; # keywords are removed from the Person package
888 =head1 EXTENDING AND EMBEDDING MOOSE
890 To learn more about extending Moose, we recommend checking out the
891 "Extending" recipes in the L<Moose::Cookbook>, starting with
892 L<Moose::Cookbook::Extending::Recipe1>, which provides an overview of
893 all the different ways you might extend Moose.
895 =head2 B<< Moose->init_meta(for_class => $class, base_class => $baseclass, metaclass => $metaclass) >>
897 The C<init_meta> method sets up the metaclass object for the class
898 specified by C<for_class>. This method injects a a C<meta> accessor
899 into the class so you can get at this object. It also sets the class's
900 superclass to C<base_class>, with L<Moose::Object> as the default.
902 C<init_meta> returns the metaclass object for C<$class>.
904 You can specify an alternate metaclass with the C<metaclass> option.
906 For more detail on this topic, see L<Moose::Cookbook::Extending::Recipe2>.
908 This method used to be documented as a function which accepted
909 positional parameters. This calling style will still work for
910 backwards compatibility, but is deprecated.
914 Moose's C<import> method supports the L<Sub::Exporter> form of C<{into =E<gt> $pkg}>
915 and C<{into_level =E<gt> 1}>.
917 B<NOTE>: Doing this is more or less deprecated. Use L<Moose::Exporter>
918 instead, which lets you stack multiple C<Moose.pm>-alike modules
919 sanely. It handles getting the exported functions into the right place
922 =head2 B<throw_error>
924 An alias for C<confess>, used by internally by Moose.
926 =head1 METACLASS COMPATIBILITY AND MOOSE
928 Metaclass compatibility is a thorny subject. You should start by
929 reading the "About Metaclass compatibility" section in the
932 Moose will attempt to resolve a few cases of metaclass incompatibility
933 when you set the superclasses for a class, unlike C<Class::MOP>, which
934 simply dies if the metaclasses are incompatible.
936 In actuality, Moose fixes incompatibility for I<all> of a class's
937 metaclasses, not just the class metaclass. That includes the instance
938 metaclass, attribute metaclass, as well as its constructor class and
939 destructor class. However, for simplicity this discussion will just
940 refer to "metaclass", meaning the class metaclass, most of the time.
942 Moose has two algorithms for fixing metaclass incompatibility.
944 The first algorithm is very simple. If all the metaclass for the
945 parent is a I<subclass> of the child's metaclass, then we simply
946 replace the child's metaclass with the parent's.
948 The second algorithm is more complicated. It tries to determine if the
949 metaclasses only "differ by roles". This means that the parent and
950 child's metaclass share a common ancestor in their respective
951 hierarchies, and that the subclasses under the common ancestor are
952 only different because of role applications. This case is actually
953 fairly common when you mix and match various C<MooseX::*> modules,
954 many of which apply roles to the metaclass.
956 If the parent and child do differ by roles, Moose replaces the
957 metaclass in the child with a newly created metaclass. This metaclass
958 is a subclass of the parent's metaclass, does all of the roles that
959 the child's metaclass did before being replaced. Effectively, this
960 means the new metaclass does all of the roles done by both the
961 parent's and child's original metaclasses.
963 Ultimately, this is all transparent to you except in the case of an
964 unresolvable conflict.
966 =head2 The MooseX:: namespace
968 Generally if you're writing an extension I<for> Moose itself you'll want
969 to put your extension in the C<MooseX::> namespace. This namespace is
970 specifically for extensions that make Moose better or different in some
971 fundamental way. It is traditionally B<not> for a package that just happens
972 to use Moose. This namespace follows from the examples of the C<LWPx::>
973 and C<DBIx::> namespaces that perform the same function for C<LWP> and C<DBI>
982 It should be noted that C<super> and C<inner> B<cannot> be used in the same
983 method. However, they may be combined within the same class hierarchy; see
984 F<t/014_override_augment_inner_super.t> for an example.
986 The reason for this is that C<super> is only valid within a method
987 with the C<override> modifier, and C<inner> will never be valid within an
988 C<override> method. In fact, C<augment> will skip over any C<override> methods
989 when searching for its appropriate C<inner>.
991 This might seem like a restriction, but I am of the opinion that keeping these
992 two features separate (yet interoperable) actually makes them easy to use, since
993 their behavior is then easier to predict. Time will tell whether I am right or
994 not (UPDATE: so far so good).
1000 We offer both a mailing list and a very active IRC channel.
1002 The mailing list is L<moose@perl.org>. You must be subscribed to send
1003 a message. To subscribe, send an empty message to
1004 L<moose-subscribe@perl.org>
1006 You can also visit us at L<#moose on
1007 irc.perl.org|irc://irc.perl.org/#moose>. This channel is quite active,
1008 and questions at all levels (on Moose-related topics ;) are welcome.
1010 =head1 ACKNOWLEDGEMENTS
1014 =item I blame Sam Vilain for introducing me to the insanity that is meta-models.
1016 =item I blame Audrey Tang for then encouraging my meta-model habit in #perl6.
1018 =item Without Yuval "nothingmuch" Kogman this module would not be possible,
1019 and it certainly wouldn't have this name ;P
1021 =item The basis of the TypeContraints module was Rob Kinyon's idea
1022 originally, I just ran with it.
1024 =item Thanks to mst & chansen and the whole #moose posse for all the
1025 early ideas/feature-requests/encouragement/bug-finding.
1027 =item Thanks to David "Theory" Wheeler for meta-discussions and spelling fixes.
1035 =item L<http://www.iinteractive.com/moose>
1037 This is the official web home of Moose, it contains links to our public SVN repository
1038 as well as links to a number of talks and articles on Moose and Moose related
1041 =item The Moose is flying, a tutorial by Randal Schwartz
1043 Part 1 - L<http://www.stonehenge.com/merlyn/LinuxMag/col94.html>
1045 Part 2 - L<http://www.stonehenge.com/merlyn/LinuxMag/col95.html>
1047 =item Several Moose extension modules in the C<MooseX::> namespace.
1049 See L<http://search.cpan.org/search?query=MooseX::> for extensions.
1051 =item Moose stats on ohloh.net - L<http://www.ohloh.net/projects/moose>
1059 =item The Art of the MetaObject Protocol
1061 I mention this in the L<Class::MOP> docs too, this book was critical in
1062 the development of both modules and is highly recommended.
1070 =item L<http://www.cs.utah.edu/plt/publications/oopsla04-gff.pdf>
1072 This paper (suggested by lbr on #moose) was what lead to the implementation
1073 of the C<super>/C<override> and C<inner>/C<augment> features. If you really
1074 want to understand them, I suggest you read this.
1080 All complex software has bugs lurking in it, and this module is no
1083 Please report any bugs to C<bug-moose@rt.cpan.org>, or through the web
1084 interface at L<http://rt.cpan.org>.
1086 =head1 FEATURE REQUESTS
1088 We are very strict about what features we add to the Moose core, especially
1089 the user-visible features. Instead we have made sure that the underlying
1090 meta-system of Moose is as extensible as possible so that you can add your
1091 own features easily.
1093 That said, occasionally there is a feature needed in the meta-system
1094 to support your planned extension, in which case you should either
1095 email the mailing list (moose@perl.org) or join us on IRC at
1096 L<irc://irc.perl.org/#moose> to discuss. The
1097 L<Moose::Manual::Contributing> has more detail about how and when you
1102 Moose is an open project, there are at this point dozens of people who have
1103 contributed, and can contribute. If you have added anything to the Moose
1104 project you have a commit bit on this file and can add your name to the list.
1108 However there are only a few people with the rights to release a new version
1109 of Moose. The Moose Cabal are the people to go to with questions regarding
1110 the wider purview of Moose, and help out maintaining not just the code
1111 but the community as well.
1113 Stevan (stevan) Little E<lt>stevan@iinteractive.comE<gt>
1115 Yuval (nothingmuch) Kogman
1117 Shawn (sartak) Moore
1119 Dave (autarch) Rolsky E<lt>autarch@urth.orgE<gt>
1121 =head2 OTHER CONTRIBUTORS
1125 Adam (Alias) Kennedy
1127 Anders (Debolaz) Nor Berle
1129 Nathan (kolibrie) Gray
1131 Christian (chansen) Hansen
1133 Hans Dieter (confound) Pearcey
1135 Eric (ewilhelm) Wilhelm
1137 Guillermo (groditi) Roditi
1139 Jess (castaway) Robinson
1143 Robert (phaylon) Sedlacek
1147 Scott (konobi) McWhirter
1149 Shlomi (rindolf) Fish
1151 Chris (perigrin) Prather
1153 Wallace (wreis) Reis
1155 Jonathan (jrockway) Rockway
1157 Piotr (dexter) Roszatycki
1159 Sam (mugwump) Vilain
1163 Dylan Hardison (doc fixes)
1165 ... and many other #moose folks
1167 =head1 COPYRIGHT AND LICENSE
1169 Copyright 2006-2009 by Infinity Interactive, Inc.
1171 L<http://www.iinteractive.com>
1173 This library is free software; you can redistribute it and/or modify
1174 it under the same terms as Perl itself.