10 $VERSION = eval $VERSION;
11 our $AUTHORITY = 'cpan:STEVAN';
13 use Scalar::Util 'blessed';
14 use Carp 'confess', 'croak', 'cluck';
20 use Moose::Meta::Class;
21 use Moose::Meta::TypeConstraint;
22 use Moose::Meta::TypeCoercion;
23 use Moose::Meta::Attribute;
24 use Moose::Meta::Instance;
28 use Moose::Meta::Role;
29 use Moose::Meta::Role::Composite;
30 use Moose::Meta::Role::Application;
31 use Moose::Meta::Role::Application::RoleSummation;
32 use Moose::Meta::Role::Application::ToClass;
33 use Moose::Meta::Role::Application::ToRole;
34 use Moose::Meta::Role::Application::ToInstance;
36 use Moose::Util::TypeConstraints;
48 croak "Must derive at least one class" unless @_;
51 foreach my $super (@supers) {
52 Class::MOP::load_class($super);
53 croak "You cannot inherit from a Moose Role ($super)"
54 if $super->can('meta') &&
55 blessed $super->meta &&
56 $super->meta->isa('Moose::Meta::Role')
61 # this checks the metaclass to make sure
62 # it is correct, sometimes it can get out
63 # of sync when the classes are being built
64 my $meta = Moose::Meta::Class->initialize($class);
65 $meta->superclasses(@supers);
70 Moose::Util::apply_all_roles(Class::MOP::Class->initialize($class), @_);
76 croak 'Usage: has \'name\' => ( key => value, ... )' if @_ == 1;
78 my $attrs = ( ref($name) eq 'ARRAY' ) ? $name : [ ($name) ];
79 Class::MOP::Class->initialize($class)->add_attribute( $_, %options ) for @$attrs;
84 Moose::Util::add_method_modifier($class, 'before', \@_);
89 Moose::Util::add_method_modifier($class, 'after', \@_);
94 Moose::Util::add_method_modifier($class, 'around', \@_);
98 return unless our $SUPER_BODY; $SUPER_BODY->(our @SUPER_ARGS);
103 my ( $name, $method ) = @_;
104 Class::MOP::Class->initialize($class)->add_override_method_modifier( $name => $method );
109 our ( %INNER_BODY, %INNER_ARGS );
111 if ( my $body = $INNER_BODY{$pkg} ) {
112 my @args = @{ $INNER_ARGS{$pkg} };
113 local $INNER_ARGS{$pkg};
114 local $INNER_BODY{$pkg};
115 return $body->(@args);
123 my ( $name, $method ) = @_;
124 Class::MOP::Class->initialize($class)->add_augment_method_modifier( $name => $method );
129 cluck "The make_immutable keyword has been deprecated, " .
130 "please go back to __PACKAGE__->meta->make_immutable\n";
131 Class::MOP::Class->initialize($class)->make_immutable(@_);
134 Moose::Exporter->setup_import_methods(
136 qw( extends with has before after around override augment make_immutable )
141 \&Scalar::Util::blessed,
146 # This used to be called as a function. This hack preserves
147 # backwards compatibility.
148 if ( $_[0] ne __PACKAGE__ ) {
149 return __PACKAGE__->init_meta(
159 my $class = $args{for_class}
160 or Moose->throw_error("Cannot call init_meta without specifying a for_class");
161 my $base_class = $args{base_class} || 'Moose::Object';
162 my $metaclass = $args{metaclass} || 'Moose::Meta::Class';
164 Moose->throw_error("The Metaclass $metaclass must be a subclass of Moose::Meta::Class.")
165 unless $metaclass->isa('Moose::Meta::Class');
167 # make a subtype for each Moose class
169 unless find_type_constraint($class);
173 if ( $meta = Class::MOP::get_metaclass_by_name($class) ) {
174 unless ( $meta->isa("Moose::Meta::Class") ) {
175 Moose->throw_error("$class already has a metaclass, but it does not inherit $metaclass ($meta)");
178 # no metaclass, no 'meta' method
180 # now we check whether our ancestors have metaclass, and if so borrow that
181 my ( undef, @isa ) = @{ $class->mro::get_linear_isa };
183 foreach my $ancestor ( @isa ) {
184 my $ancestor_meta = Class::MOP::get_metaclass_by_name($ancestor) || next;
186 my $ancestor_meta_class = ($ancestor_meta->is_immutable
187 ? $ancestor_meta->get_mutable_metaclass_name
188 : ref($ancestor_meta));
190 # if we have an ancestor metaclass that inherits $metaclass, we use
191 # that. This is like _fix_metaclass_incompatibility, but we can do it now.
193 # the case of having an ancestry is not very common, but arises in
195 unless ( $metaclass->isa( $ancestor_meta_class ) ) {
196 if ( $ancestor_meta_class->isa($metaclass) ) {
197 $metaclass = $ancestor_meta_class;
202 $meta = $metaclass->initialize($class);
205 if ( $class->can('meta') ) {
206 # check 'meta' method
208 # it may be inherited
211 # this is the case where the metaclass pragma
212 # was used before the 'use Moose' statement to
213 # override a specific class
214 my $method_meta = $class->meta;
216 ( blessed($method_meta) && $method_meta->isa('Moose::Meta::Class') )
217 || Moose->throw_error("$class already has a &meta function, but it does not return a Moose::Meta::Class ($meta)");
219 $meta = $method_meta;
222 unless ( $meta->has_method("meta") ) { # don't overwrite
223 # also check for inherited non moose 'meta' method?
224 # FIXME also skip this if the user requested by passing an option
227 # re-initialize so it inherits properly
228 $metaclass->initialize( ref($_[0]) || $_[0] );
233 # make sure they inherit from Moose::Object
234 $meta->superclasses($base_class)
235 unless $meta->superclasses();
240 # This may be used in some older MooseX extensions.
242 goto &Moose::Exporter::_get_caller;
245 ## make 'em all immutable
247 $_->meta->make_immutable(
248 inline_constructor => 1,
249 constructor_name => "_new",
250 inline_accessors => 1, # these are Class::MOP accessors, so they need inlining
253 Moose::Meta::Attribute
255 Moose::Meta::Instance
257 Moose::Meta::TypeConstraint
258 Moose::Meta::TypeConstraint::Union
259 Moose::Meta::TypeConstraint::Parameterized
260 Moose::Meta::TypeConstraint::Parameterizable
261 Moose::Meta::TypeConstraint::Enum
262 Moose::Meta::TypeConstraint::Class
263 Moose::Meta::TypeConstraint::Role
264 Moose::Meta::TypeConstraint::Registry
265 Moose::Meta::TypeCoercion
266 Moose::Meta::TypeCoercion::Union
269 Moose::Meta::Method::Accessor
270 Moose::Meta::Method::Constructor
271 Moose::Meta::Method::Destructor
272 Moose::Meta::Method::Overriden
273 Moose::Meta::Method::Augmented
276 Moose::Meta::Role::Method
277 Moose::Meta::Role::Method::Required
279 Moose::Meta::Role::Composite
281 Moose::Meta::Role::Application
282 Moose::Meta::Role::Application::RoleSummation
283 Moose::Meta::Role::Application::ToClass
284 Moose::Meta::Role::Application::ToRole
285 Moose::Meta::Role::Application::ToInstance
296 Moose - A postmodern object system for Perl 5
301 use Moose; # automatically turns on strict and warnings
303 has 'x' => (is => 'rw', isa => 'Int');
304 has 'y' => (is => 'rw', isa => 'Int');
317 has 'z' => (is => 'rw', isa => 'Int');
319 after 'clear' => sub {
326 Moose is an extension of the Perl 5 object system.
328 The main goal of Moose is to make Perl 5 Object Oriented programming
329 easier, more consistent and less tedious. With Moose you can to think
330 more about what you want to do and less about the mechanics of OOP.
332 Additionally, Moose is built on top of L<Class::MOP>, which is a
333 metaclass system for Perl 5. This means that Moose not only makes
334 building normal Perl 5 objects better, but it provides the power of
335 metaclass programming as well.
339 If you're new to Moose, the best place to start is the L<Moose::Intro>
340 docs, followed by the L<Moose::Cookbook>. The intro will show you what
341 Moose is, and how it makes Perl 5 OO better.
343 The cookbook recipes on Moose basics will get you up to speed with
344 many of Moose's features quickly. Once you have an idea of what Moose
345 can do, you can use the API documentation to get more detail on
346 features which interest you.
348 =head2 Moose Extensions
350 The C<MooseX::> namespace is the official place to find Moose extensions.
351 These extensions can be found on the CPAN. The easiest way to find them
352 is to search for them (L<http://search.cpan.org/search?query=MooseX::>),
353 or to examine L<Task::Moose> which aims to keep an up-to-date, easily
354 installable list of Moose extensions.
356 =head1 BUILDING CLASSES WITH MOOSE
358 Moose makes every attempt to provide as much convenience as possible during
359 class construction/definition, but still stay out of your way if you want it
360 to. Here are a few items to note when building classes with Moose.
362 Unless specified with C<extends>, any class which uses Moose will
363 inherit from L<Moose::Object>.
365 Moose will also manage all attributes (including inherited ones) that are
366 defined with C<has>. And (assuming you call C<new>, which is inherited from
367 L<Moose::Object>) this includes properly initializing all instance slots,
368 setting defaults where appropriate, and performing any type constraint checking
371 =head1 PROVIDED METHODS
373 Moose provides a number of methods to all your classes, mostly through the
374 inheritance of L<Moose::Object>. There is however, one exception.
380 This is a method which provides access to the current class's metaclass.
384 =head1 EXPORTED FUNCTIONS
386 Moose will export a number of functions into the class's namespace which
387 may then be used to set up the class. These functions all work directly
388 on the current class.
392 =item B<extends (@superclasses)>
394 This function will set the superclass(es) for the current class.
396 This approach is recommended instead of C<use base>, because C<use base>
397 actually C<push>es onto the class's C<@ISA>, whereas C<extends> will
398 replace it. This is important to ensure that classes which do not have
399 superclasses still properly inherit from L<Moose::Object>.
401 =item B<with (@roles)>
403 This will apply a given set of C<@roles> to the local class.
405 =item B<has $name|@$names =E<gt> %options>
407 This will install an attribute of a given C<$name> into the current class. If
408 the first parameter is an array reference, it will create an attribute for
409 every C<$name> in the list. The C<%options> are the same as those provided by
410 L<Class::MOP::Attribute>, in addition to the list below which are provided by
411 Moose (L<Moose::Meta::Attribute> to be more specific):
415 =item I<is =E<gt> 'rw'|'ro'>
417 The I<is> option accepts either I<rw> (for read/write) or I<ro> (for read
418 only). These will create either a read/write accessor or a read-only
419 accessor respectively, using the same name as the C<$name> of the attribute.
421 If you need more control over how your accessors are named, you can
422 use the L<reader|Class::MOP::Attribute/reader>,
423 L<writer|Class::MOP::Attribute/writer> and
424 L<accessor|Class::MOP::Attribute/accessor> options inherited from
425 L<Class::MOP::Attribute>, however if you use those, you won't need the
428 =item I<isa =E<gt> $type_name>
430 The I<isa> option uses Moose's type constraint facilities to set up runtime
431 type checking for this attribute. Moose will perform the checks during class
432 construction, and within any accessors. The C<$type_name> argument must be a
433 string. The string may be either a class name or a type defined using
434 Moose's type definition features. (Refer to L<Moose::Util::TypeConstraints>
435 for information on how to define a new type, and how to retrieve type meta-data).
437 =item I<coerce =E<gt> (1|0)>
439 This will attempt to use coercion with the supplied type constraint to change
440 the value passed into any accessors or constructors. You B<must> have supplied
441 a type constraint in order for this to work. See L<Moose::Cookbook::Basics::Recipe5>
444 =item I<does =E<gt> $role_name>
446 This will accept the name of a role which the value stored in this attribute
447 is expected to have consumed.
449 =item I<required =E<gt> (1|0)>
451 This marks the attribute as being required. This means a I<defined> value must be
452 supplied during class construction, and the attribute may never be set to
453 C<undef> with an accessor.
455 =item I<weak_ref =E<gt> (1|0)>
457 This will tell the class to store the value of this attribute as a weakened
458 reference. If an attribute is a weakened reference, it B<cannot> also be
461 =item I<lazy =E<gt> (1|0)>
463 This will tell the class to not create this slot until absolutely necessary.
464 If an attribute is marked as lazy it B<must> have a default supplied.
466 =item I<auto_deref =E<gt> (1|0)>
468 This tells the accessor whether to automatically dereference the value returned.
469 This is only legal if your C<isa> option is either C<ArrayRef> or C<HashRef>.
471 =item I<trigger =E<gt> $code>
473 The I<trigger> option is a CODE reference which will be called after the value of
474 the attribute is set. The CODE ref will be passed the instance itself, the
475 updated value and the attribute meta-object (this is for more advanced fiddling
476 and can typically be ignored). You B<cannot> have a trigger on a read-only
479 B<NOTE:> Triggers will only fire when you B<assign> to the attribute,
480 either in the constructor, or using the writer. Default and built values will
481 B<not> cause the trigger to be fired.
483 =item I<handles =E<gt> ARRAY | HASH | REGEXP | ROLE | CODE>
485 The I<handles> option provides Moose classes with automated delegation features.
486 This is a pretty complex and powerful option. It accepts many different option
487 formats, each with its own benefits and drawbacks.
489 B<NOTE:> The class being delegated to does not need to be a Moose based class,
490 which is why this feature is especially useful when wrapping non-Moose classes.
492 All I<handles> option formats share the following traits:
494 You cannot override a locally defined method with a delegated method; an
495 exception will be thrown if you try. That is to say, if you define C<foo> in
496 your class, you cannot override it with a delegated C<foo>. This is almost never
497 something you would want to do, and if it is, you should do it by hand and not
500 You cannot override any of the methods found in Moose::Object, or the C<BUILD>
501 and C<DEMOLISH> methods. These will not throw an exception, but will silently
502 move on to the next method in the list. My reasoning for this is that you would
503 almost never want to do this, since it usually breaks your class. As with
504 overriding locally defined methods, if you do want to do this, you should do it
505 manually, not with Moose.
507 You do not I<need> to have a reader (or accessor) for the attribute in order
508 to delegate to it. Moose will create a means of accessing the value for you,
509 however this will be several times B<less> efficient then if you had given
510 the attribute a reader (or accessor) to use.
512 Below is the documentation for each option format:
518 This is the most common usage for I<handles>. You basically pass a list of
519 method names to be delegated, and Moose will install a delegation method
524 This is the second most common usage for I<handles>. Instead of a list of
525 method names, you pass a HASH ref where each key is the method name you
526 want installed locally, and its value is the name of the original method
527 in the class being delegated to.
529 This can be very useful for recursive classes like trees. Here is a
530 quick example (soon to be expanded into a Moose::Cookbook recipe):
535 has 'node' => (is => 'rw', isa => 'Any');
540 default => sub { [] }
548 parent_node => 'node',
549 siblings => 'children',
553 In this example, the Tree package gets C<parent_node> and C<siblings> methods,
554 which delegate to the C<node> and C<children> methods (respectively) of the Tree
555 instance stored in the C<parent> slot.
559 The regexp option works very similar to the ARRAY option, except that it builds
560 the list of methods for you. It starts by collecting all possible methods of the
561 class being delegated to, then filters that list using the regexp supplied here.
563 B<NOTE:> An I<isa> option is required when using the regexp option format. This
564 is so that we can determine (at compile time) the method list from the class.
565 Without an I<isa> this is just not possible.
569 With the role option, you specify the name of a role whose "interface" then
570 becomes the list of methods to handle. The "interface" can be defined as; the
571 methods of the role and any required methods of the role. It should be noted
572 that this does B<not> include any method modifiers or generated attribute
573 methods (which is consistent with role composition).
577 This is the option to use when you really want to do something funky. You should
578 only use it if you really know what you are doing, as it involves manual
581 This takes a code reference, which should expect two arguments. The first is the
582 attribute meta-object this I<handles> is attached to. The second is the
583 metaclass of the class being delegated to. It expects you to return a hash (not
584 a HASH ref) of the methods you want mapped.
588 =item I<metaclass =E<gt> $metaclass_name>
590 This tells the class to use a custom attribute metaclass for this particular
591 attribute. Custom attribute metaclasses are useful for extending the
592 capabilities of the I<has> keyword: they are the simplest way to extend the MOP,
593 but they are still a fairly advanced topic and too much to cover here, see
594 L<Moose::Cookbook::Meta::Recipe1> for more information.
596 The default behavior here is to just load C<$metaclass_name>; however, we also
597 have a way to alias to a shorter name. This will first look to see if
598 B<Moose::Meta::Attribute::Custom::$metaclass_name> exists. If it does, Moose
599 will then check to see if that has the method C<register_implementation>, which
600 should return the actual name of the custom attribute metaclass. If there is no
601 C<register_implementation> method, it will fall back to using
602 B<Moose::Meta::Attribute::Custom::$metaclass_name> as the metaclass name.
604 =item I<traits =E<gt> [ @role_names ]>
606 This tells Moose to take the list of C<@role_names> and apply them to the
607 attribute meta-object. This is very similar to the I<metaclass> option, but
608 allows you to use more than one extension at a time.
610 See L<TRAIT NAME RESOLUTION> for details on how a trait name is
611 resolved to a class name.
613 Also see L<Moose::Cookbook::Meta::Recipe3> for a metaclass trait
618 The value of this key is the name of the method that will be called to
619 obtain the value used to initialize the attribute. See the L<builder
620 option docs in Class::MOP::Attribute|Class::MOP::Attribute/builder>
621 for more information.
625 The value of this key is the default value which will initialize the attribute.
627 NOTE: If the value is a simple scalar (string or number), then it can
628 be just passed as is. However, if you wish to initialize it with a
629 HASH or ARRAY ref, then you need to wrap that inside a CODE reference.
630 See the L<default option docs in
631 Class::MOP::Attribute|Class::MOP::Attribute/default> for more
636 This may be a method name (referring to a method on the class with
637 this attribute) or a CODE ref. The initializer is used to set the
638 attribute value on an instance when the attribute is set during
639 instance initialization (but not when the value is being assigned
640 to). See the L<initializer option docs in
641 Class::MOP::Attribute|Class::MOP::Attribute/initializer> for more
646 Allows you to clear the value, see the L<clearer option docs in
647 Class::MOP::Attribute|Class::MOP::Attribute/clearer> for more
652 Basic test to see if a value has been set in the attribute, see the
653 L<predicate option docs in
654 Class::MOP::Attribute|Class::MOP::Attribute/predicate> for more
659 =item B<has +$name =E<gt> %options>
661 This is variation on the normal attibute creator C<has> which allows you to
662 clone and extend an attribute from a superclass or from a role. Here is an
663 example of the superclass usage:
671 default => 'Hello, I am a Foo'
679 has '+message' => (default => 'Hello I am My::Foo');
681 What is happening here is that B<My::Foo> is cloning the C<message> attribute
682 from its parent class B<Foo>, retaining the C<is =E<gt> 'rw'> and C<isa =E<gt>
683 'Str'> characteristics, but changing the value in C<default>.
685 Here is another example, but within the context of a role:
693 default => 'Hello, I am a Foo'
701 has '+message' => (default => 'Hello I am My::Foo');
703 In this case, we are basically taking the attribute which the role supplied
704 and altering it within the bounds of this feature.
706 Aside from where the attributes come from (one from superclass, the other
707 from a role), this feature works exactly the same. This feature is restricted
708 somewhat, so as to try and force at least I<some> sanity into it. You are only
709 allowed to change the following attributes:
715 Change the default value of an attribute.
719 Change whether the attribute attempts to coerce a value passed to it.
723 Change if the attribute is required to have a value.
725 =item I<documentation>
727 Change the documentation string associated with the attribute.
731 Change if the attribute lazily initializes the slot.
735 You I<are> allowed to change the type without restriction.
737 It is recommended that you use this freedom with caution. We used to
738 only allow for extension only if the type was a subtype of the parent's
739 type, but we felt that was too restrictive and is better left as a
744 You are allowed to B<add> a new C<handles> definition, but you are B<not>
745 allowed to I<change> one.
749 You are allowed to B<add> a new C<builder> definition, but you are B<not>
750 allowed to I<change> one.
754 You are allowed to B<add> a new C<metaclass> definition, but you are
755 B<not> allowed to I<change> one.
759 You are allowed to B<add> additional traits to the C<traits> definition.
760 These traits will be composed into the attribute, but pre-existing traits
761 B<are not> overridden, or removed.
765 =item B<before $name|@names =E<gt> sub { ... }>
767 =item B<after $name|@names =E<gt> sub { ... }>
769 =item B<around $name|@names =E<gt> sub { ... }>
771 This three items are syntactic sugar for the before, after, and around method
772 modifier features that L<Class::MOP> provides. More information on these may be
773 found in the L<Class::MOP::Class documentation|Class::MOP::Class/"Method
778 The keyword C<super> is a no-op when called outside of an C<override> method. In
779 the context of an C<override> method, it will call the next most appropriate
780 superclass method with the same arguments as the original method.
782 =item B<override ($name, &sub)>
784 An C<override> method is a way of explicitly saying "I am overriding this
785 method from my superclass". You can call C<super> within this method, and
786 it will work as expected. The same thing I<can> be accomplished with a normal
787 method call and the C<SUPER::> pseudo-package; it is really your choice.
791 The keyword C<inner>, much like C<super>, is a no-op outside of the context of
792 an C<augment> method. You can think of C<inner> as being the inverse of
793 C<super>; the details of how C<inner> and C<augment> work is best described in
794 the L<Moose::Cookbook::Basics::Recipe6>.
796 =item B<augment ($name, &sub)>
798 An C<augment> method, is a way of explicitly saying "I am augmenting this
799 method from my superclass". Once again, the details of how C<inner> and
800 C<augment> work is best described in the L<Moose::Cookbook::Basics::Recipe6>.
804 This is the C<Carp::confess> function, and exported here because I use it
809 This is the C<Scalar::Util::blessed> function, it is exported here because I
810 use it all the time. It is highly recommended that this is used instead of
811 C<ref> anywhere you need to test for an object's class name.
815 =head1 METACLASS TRAITS
817 When you use Moose, you can also specify traits which will be applied
820 use Moose -traits => 'My::Trait';
822 This is very similar to the attribute traits feature. When you do
823 this, your class's C<meta> object will have the specified traits
824 applied to it. See L<TRAIT NAME RESOLUTION> for more details.
826 =head1 TRAIT NAME RESOLUTION
828 By default, when given a trait name, Moose simply tries to load a
829 class of the same name. If such a class does not exist, it then looks
830 for for a class matching
831 B<Moose::Meta::$type::Custom::Trait::$trait_name>. The C<$type>
832 variable here will be one of B<Attribute> or B<Class>, depending on
833 what the trait is being applied to.
835 If a class with this long name exists, Moose checks to see if it has
836 the method C<register_implementation>. This method is expected to
837 return the I<real> class name of the trait. If there is no
838 C<register_implementation> method, it will fall back to using
839 B<Moose::Meta::$type::Custom::Trait::$trait> as the trait name.
841 If all this is confusing, take a look at
842 L<Moose::Cookbook::Meta::Recipe3>, which demonstrates how to create an
845 =head1 UNIMPORTING FUNCTIONS
849 Moose offers a way to remove the keywords it exports, through the C<unimport>
850 method. You simply have to say C<no Moose> at the bottom of your code for this
851 to work. Here is an example:
856 has 'first_name' => (is => 'rw', isa => 'Str');
857 has 'last_name' => (is => 'rw', isa => 'Str');
861 $self->first_name . ' ' . $self->last_name
864 no Moose; # keywords are removed from the Person package
866 =head1 EXTENDING AND EMBEDDING MOOSE
868 To learn more about extending Moose, we recommend checking out the
869 "Extending" recipes in the L<Moose::Cookbook>, starting with
870 L<Moose::Cookbook::Extending::Recipe1>, which provides an overview of
871 all the different ways you might extend Moose.
873 =head2 B<< Moose->init_meta(for_class => $class, base_class => $baseclass, metaclass => $metaclass) >>
875 The C<init_meta> method sets up the metaclass object for the class
876 specified by C<for_class>. This method injects a a C<meta> accessor
877 into the class so you can get at this object. It also sets the class's
878 superclass to C<base_class>, with L<Moose::Object> as the default.
880 You can specify an alternate metaclass with the C<metaclass> parameter.
882 For more detail on this topic, see L<Moose::Cookbook::Extending::Recipe2>.
884 This method used to be documented as a function which accepted
885 positional parameters. This calling style will still work for
886 backwards compatibility, but is deprecated.
890 Moose's C<import> method supports the L<Sub::Exporter> form of C<{into =E<gt> $pkg}>
891 and C<{into_level =E<gt> 1}>.
893 B<NOTE>: Doing this is more or less deprecated. Use L<Moose::Exporter>
894 instead, which lets you stack multiple C<Moose.pm>-alike modules
895 sanely. It handles getting the exported functions into the right place
898 =head2 B<throw_error>
900 An alias for C<confess>, used by internally by Moose.
902 =head1 METACLASS COMPATIBILITY AND MOOSE
904 Metaclass compatibility is a thorny subject. You should start by
905 reading the "About Metaclass compatibility" section in the
908 Moose will attempt to resolve a few cases of metaclass incompatibility
909 when you set the superclasses for a class, unlike C<Class::MOP>, which
910 simply dies if the metaclasses are incompatible.
912 In actuality, Moose fixes incompatibility for I<all> of a class's
913 metaclasses, not just the class metaclass. That includes the instance
914 metaclass, attribute metaclass, as well as its constructor class and
915 destructor class. However, for simplicity this discussion will just
916 refer to "metaclass", meaning the class metaclass, most of the time.
918 Moose has two algorithms for fixing metaclass incompatibility.
920 The first algorithm is very simple. If all the metaclass for the
921 parent is a I<subclass> of the child's metaclass, then we simply
922 replace the child's metaclass with the parent's.
924 The second algorithm is more complicated. It tries to determine if the
925 metaclasses only "differ by roles". This means that the parent and
926 child's metaclass share a common ancestor in their respective
927 hierarchies, and that the subclasses under the common ancestor are
928 only different because of role applications. This case is actually
929 fairly common when you mix and match various C<MooseX::*> modules,
930 many of which apply roles to the metaclass.
932 If the parent and child do differ by roles, Moose replaces the
933 metaclass in the child with a newly created metaclass. This metaclass
934 is a subclass of the parent's metaclass, does all of the roles that
935 the child's metaclass did before being replaced. Effectively, this
936 means the new metaclass does all of the roles done by both the
937 parent's and child's original metaclasses.
939 Ultimately, this is all transparent to you except in the case of an
940 unresolvable conflict.
942 =head2 The MooseX:: namespace
944 Generally if you're writing an extension I<for> Moose itself you'll want
945 to put your extension in the C<MooseX::> namespace. This namespace is
946 specifically for extensions that make Moose better or different in some
947 fundamental way. It is traditionally B<not> for a package that just happens
948 to use Moose. This namespace follows from the examples of the C<LWPx::>
949 and C<DBIx::> namespaces that perform the same function for C<LWP> and C<DBI>
958 It should be noted that C<super> and C<inner> B<cannot> be used in the same
959 method. However, they may be combined within the same class hierarchy; see
960 F<t/014_override_augment_inner_super.t> for an example.
962 The reason for this is that C<super> is only valid within a method
963 with the C<override> modifier, and C<inner> will never be valid within an
964 C<override> method. In fact, C<augment> will skip over any C<override> methods
965 when searching for its appropriate C<inner>.
967 This might seem like a restriction, but I am of the opinion that keeping these
968 two features separate (yet interoperable) actually makes them easy to use, since
969 their behavior is then easier to predict. Time will tell whether I am right or
970 not (UPDATE: so far so good).
974 =head1 ACKNOWLEDGEMENTS
978 =item I blame Sam Vilain for introducing me to the insanity that is meta-models.
980 =item I blame Audrey Tang for then encouraging my meta-model habit in #perl6.
982 =item Without Yuval "nothingmuch" Kogman this module would not be possible,
983 and it certainly wouldn't have this name ;P
985 =item The basis of the TypeContraints module was Rob Kinyon's idea
986 originally, I just ran with it.
988 =item Thanks to mst & chansen and the whole #moose posse for all the
989 early ideas/feature-requests/encouragement/bug-finding.
991 =item Thanks to David "Theory" Wheeler for meta-discussions and spelling fixes.
999 =item L<http://www.iinteractive.com/moose>
1001 This is the official web home of Moose, it contains links to our public SVN repo
1002 as well as links to a number of talks and articles on Moose and Moose related
1005 =item L<Moose::Cookbook> - How to cook a Moose
1007 =item The Moose is flying, a tutorial by Randal Schwartz
1009 Part 1 - L<http://www.stonehenge.com/merlyn/LinuxMag/col94.html>
1011 Part 2 - L<http://www.stonehenge.com/merlyn/LinuxMag/col95.html>
1013 =item L<Class::MOP> documentation
1015 =item The #moose channel on irc.perl.org
1017 =item The Moose mailing list - moose@perl.org
1019 =item Moose stats on ohloh.net - L<http://www.ohloh.net/projects/moose>
1021 =item Several Moose extension modules in the C<MooseX::> namespace.
1023 See L<http://search.cpan.org/search?query=MooseX::> for extensions.
1031 =item The Art of the MetaObject Protocol
1033 I mention this in the L<Class::MOP> docs too, this book was critical in
1034 the development of both modules and is highly recommended.
1042 =item L<http://www.cs.utah.edu/plt/publications/oopsla04-gff.pdf>
1044 This paper (suggested by lbr on #moose) was what lead to the implementation
1045 of the C<super>/C<override> and C<inner>/C<augment> features. If you really
1046 want to understand them, I suggest you read this.
1052 All complex software has bugs lurking in it, and this module is no
1053 exception. If you find a bug please either email me, or add the bug
1056 =head1 FEATURE REQUESTS
1058 We are very strict about what features we add to the Moose core, especially
1059 the user-visible features. Instead we have made sure that the underlying
1060 meta-system of Moose is as extensible as possible so that you can add your
1061 own features easily. That said, occasionally there is a feature needed in the
1062 meta-system to support your planned extension, in which case you should
1063 either email the mailing list or join us on irc at #moose to discuss.
1067 Moose is an open project, there are at this point dozens of people who have
1068 contributed, and can contribute. If you have added anything to the Moose
1069 project you have a commit bit on this file and can add your name to the list.
1073 However there are only a few people with the rights to release a new version
1074 of Moose. The Moose Cabal are the people to go to with questions regarding
1075 the wider purview of Moose, and help out maintaining not just the code
1076 but the community as well.
1078 Stevan (stevan) Little E<lt>stevan@iinteractive.comE<gt>
1080 Yuval (nothingmuch) Kogman
1082 Shawn (sartak) Moore
1084 Dave (autarch) Rolsky E<lt>autarch@urth.orgE<gt>
1086 =head2 OTHER CONTRIBUTORS
1090 Adam (Alias) Kennedy
1092 Anders (Debolaz) Nor Berle
1094 Nathan (kolibre) Gray
1096 Christian (chansen) Hansen
1098 Hans Dieter (confound) Pearcey
1100 Eric (ewilhelm) Wilhelm
1102 Guillermo (groditi) Roditi
1104 Jess (castaway) Robinson
1108 Robert (phaylon) Sedlacek
1112 Scott (konobi) McWhirter
1114 Shlomi (rindolf) Fish
1116 Chris (perigrin) Prather
1118 Wallace (wreis) Reis
1120 Jonathan (jrockway) Rockway
1122 Piotr (dexter) Roszatycki
1124 Sam (mugwump) Vilain
1126 ... and many other #moose folks
1128 =head1 COPYRIGHT AND LICENSE
1130 Copyright 2006-2008 by Infinity Interactive, Inc.
1132 L<http://www.iinteractive.com>
1134 This library is free software; you can redistribute it and/or modify
1135 it under the same terms as Perl itself.