7 $VERSION = eval $VERSION;
8 our $AUTHORITY = 'cpan:STEVAN';
10 use Scalar::Util 'blessed';
15 use Class::MOP 0.82_01;
17 use Moose::Meta::Class;
18 use Moose::Meta::TypeConstraint;
19 use Moose::Meta::TypeCoercion;
20 use Moose::Meta::Attribute;
21 use Moose::Meta::Instance;
25 use Moose::Meta::Role;
26 use Moose::Meta::Role::Composite;
27 use Moose::Meta::Role::Application;
28 use Moose::Meta::Role::Application::RoleSummation;
29 use Moose::Meta::Role::Application::ToClass;
30 use Moose::Meta::Role::Application::ToRole;
31 use Moose::Meta::Role::Application::ToInstance;
33 use Moose::Util::TypeConstraints;
37 my $level = @_ ? ($_[0] + 1) : 2;
39 @info{qw(package file line)} = caller($level);
52 Moose->throw_error("Must derive at least one class") unless @_;
54 # this checks the metaclass to make sure
55 # it is correct, sometimes it can get out
56 # of sync when the classes are being built
57 Moose::Meta::Class->initialize($class)->superclasses(@_);
62 Moose::Util::apply_all_roles(Class::MOP::Class->initialize($class), @_);
69 Moose->throw_error('Usage: has \'name\' => ( key => value, ... )')
72 my %options = ( definition_context => _caller_info(), @_ );
73 my $attrs = ( ref($name) eq 'ARRAY' ) ? $name : [ ($name) ];
74 Class::MOP::Class->initialize($class)->add_attribute( $_, %options ) for @$attrs;
79 Moose::Util::add_method_modifier($class, 'before', \@_);
84 Moose::Util::add_method_modifier($class, 'after', \@_);
89 Moose::Util::add_method_modifier($class, 'around', \@_);
97 # This check avoids a recursion loop - see
98 # t/100_bugs/020_super_recursion.t
99 return if defined $SUPER_PACKAGE && $SUPER_PACKAGE ne caller();
100 return unless $SUPER_BODY; $SUPER_BODY->(@SUPER_ARGS);
105 my ( $name, $method ) = @_;
106 Class::MOP::Class->initialize($class)->add_override_method_modifier( $name => $method );
111 our ( %INNER_BODY, %INNER_ARGS );
113 if ( my $body = $INNER_BODY{$pkg} ) {
114 my @args = @{ $INNER_ARGS{$pkg} };
115 local $INNER_ARGS{$pkg};
116 local $INNER_BODY{$pkg};
117 return $body->(@args);
125 my ( $name, $method ) = @_;
126 Class::MOP::Class->initialize($class)->add_augment_method_modifier( $name => $method );
129 Moose::Exporter->setup_import_methods(
131 qw( extends with has before after around override augment)
136 \&Scalar::Util::blessed,
141 # This used to be called as a function. This hack preserves
142 # backwards compatibility.
143 if ( $_[0] ne __PACKAGE__ ) {
144 return __PACKAGE__->init_meta(
154 my $class = $args{for_class}
155 or Moose->throw_error("Cannot call init_meta without specifying a for_class");
156 my $base_class = $args{base_class} || 'Moose::Object';
157 my $metaclass = $args{metaclass} || 'Moose::Meta::Class';
159 Moose->throw_error("The Metaclass $metaclass must be a subclass of Moose::Meta::Class.")
160 unless $metaclass->isa('Moose::Meta::Class');
162 # make a subtype for each Moose class
164 unless find_type_constraint($class);
168 if ( $meta = Class::MOP::get_metaclass_by_name($class) ) {
169 unless ( $meta->isa("Moose::Meta::Class") ) {
170 Moose->throw_error("$class already has a metaclass, but it does not inherit $metaclass ($meta)");
173 # no metaclass, no 'meta' method
175 # now we check whether our ancestors have metaclass, and if so borrow that
176 my ( undef, @isa ) = @{ $class->mro::get_linear_isa };
178 foreach my $ancestor ( @isa ) {
179 my $ancestor_meta = Class::MOP::get_metaclass_by_name($ancestor) || next;
181 my $ancestor_meta_class = ($ancestor_meta->is_immutable
182 ? $ancestor_meta->get_mutable_metaclass_name
183 : ref($ancestor_meta));
185 # if we have an ancestor metaclass that inherits $metaclass, we use
186 # that. This is like _fix_metaclass_incompatibility, but we can do it now.
188 # the case of having an ancestry is not very common, but arises in
190 unless ( $metaclass->isa( $ancestor_meta_class ) ) {
191 if ( $ancestor_meta_class->isa($metaclass) ) {
192 $metaclass = $ancestor_meta_class;
197 $meta = $metaclass->initialize($class);
200 if ( $class->can('meta') ) {
201 # check 'meta' method
203 # it may be inherited
206 # this is the case where the metaclass pragma
207 # was used before the 'use Moose' statement to
208 # override a specific class
209 my $method_meta = $class->meta;
211 ( blessed($method_meta) && $method_meta->isa('Moose::Meta::Class') )
212 || Moose->throw_error("$class already has a &meta function, but it does not return a Moose::Meta::Class ($meta)");
214 $meta = $method_meta;
217 unless ( $meta->has_method("meta") ) { # don't overwrite
218 # also check for inherited non moose 'meta' method?
219 # FIXME also skip this if the user requested by passing an option
222 # re-initialize so it inherits properly
223 $metaclass->initialize( ref($_[0]) || $_[0] );
228 # make sure they inherit from Moose::Object
229 $meta->superclasses($base_class)
230 unless $meta->superclasses();
235 # This may be used in some older MooseX extensions.
237 goto &Moose::Exporter::_get_caller;
240 ## make 'em all immutable
243 inline_constructor => 1,
244 constructor_name => "_new",
245 # these are Class::MOP accessors, so they need inlining
246 inline_accessors => 1
247 ) for grep { $_->is_mutable }
250 Moose::Meta::Attribute
252 Moose::Meta::Instance
254 Moose::Meta::TypeCoercion
255 Moose::Meta::TypeCoercion::Union
258 Moose::Meta::Method::Accessor
259 Moose::Meta::Method::Constructor
260 Moose::Meta::Method::Destructor
261 Moose::Meta::Method::Overridden
262 Moose::Meta::Method::Augmented
265 Moose::Meta::Role::Method
266 Moose::Meta::Role::Method::Required
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 I<defined> value must be
441 supplied during class construction, and the attribute may never be set to
442 C<undef> with an accessor.
444 =item I<weak_ref =E<gt> (1|0)>
446 This will tell the class to store the value of this attribute as a weakened
447 reference. If an attribute is a weakened reference, it B<cannot> also be
450 =item I<lazy =E<gt> (1|0)>
452 This will tell the class to not create this slot until absolutely necessary.
453 If an attribute is marked as lazy it B<must> have a default supplied.
455 =item I<auto_deref =E<gt> (1|0)>
457 This tells the accessor whether to automatically dereference the value returned.
458 This is only legal if your C<isa> option is either C<ArrayRef> or C<HashRef>.
460 =item I<trigger =E<gt> $code>
462 The I<trigger> option is a CODE reference which will be called after
463 the value of the attribute is set. The CODE ref will be passed the
464 instance itself and the updated value. You B<cannot> have a trigger on
465 a read-only attribute.
467 B<NOTE:> Triggers will only fire when you B<assign> to the attribute,
468 either in the constructor, or using the writer. Default and built values will
469 B<not> cause the trigger to be fired.
471 =item I<handles =E<gt> ARRAY | HASH | REGEXP | ROLE | CODE>
473 The I<handles> option provides Moose classes with automated delegation features.
474 This is a pretty complex and powerful option. It accepts many different option
475 formats, each with its own benefits and drawbacks.
477 B<NOTE:> The class being delegated to does not need to be a Moose based class,
478 which is why this feature is especially useful when wrapping non-Moose classes.
480 All I<handles> option formats share the following traits:
482 You cannot override a locally defined method with a delegated method; an
483 exception will be thrown if you try. That is to say, if you define C<foo> in
484 your class, you cannot override it with a delegated C<foo>. This is almost never
485 something you would want to do, and if it is, you should do it by hand and not
488 You cannot override any of the methods found in Moose::Object, or the C<BUILD>
489 and C<DEMOLISH> methods. These will not throw an exception, but will silently
490 move on to the next method in the list. My reasoning for this is that you would
491 almost never want to do this, since it usually breaks your class. As with
492 overriding locally defined methods, if you do want to do this, you should do it
493 manually, not with Moose.
495 You do not I<need> to have a reader (or accessor) for the attribute in order
496 to delegate to it. Moose will create a means of accessing the value for you,
497 however this will be several times B<less> efficient then if you had given
498 the attribute a reader (or accessor) to use.
500 Below is the documentation for each option format:
506 This is the most common usage for I<handles>. You basically pass a list of
507 method names to be delegated, and Moose will install a delegation method
512 This is the second most common usage for I<handles>. Instead of a list of
513 method names, you pass a HASH ref where each key is the method name you
514 want installed locally, and its value is the name of the original method
515 in the class being delegated to.
517 This can be very useful for recursive classes like trees. Here is a
518 quick example (soon to be expanded into a Moose::Cookbook recipe):
523 has 'node' => (is => 'rw', isa => 'Any');
528 default => sub { [] }
536 parent_node => 'node',
537 siblings => 'children',
541 In this example, the Tree package gets C<parent_node> and C<siblings> methods,
542 which delegate to the C<node> and C<children> methods (respectively) of the Tree
543 instance stored in the C<parent> slot.
547 The regexp option works very similar to the ARRAY option, except that it builds
548 the list of methods for you. It starts by collecting all possible methods of the
549 class being delegated to, then filters that list using the regexp supplied here.
551 B<NOTE:> An I<isa> option is required when using the regexp option format. This
552 is so that we can determine (at compile time) the method list from the class.
553 Without an I<isa> this is just not possible.
557 With the role option, you specify the name of a role whose "interface" then
558 becomes the list of methods to handle. The "interface" can be defined as; the
559 methods of the role and any required methods of the role. It should be noted
560 that this does B<not> include any method modifiers or generated attribute
561 methods (which is consistent with role composition).
565 This is the option to use when you really want to do something funky. You should
566 only use it if you really know what you are doing, as it involves manual
569 This takes a code reference, which should expect two arguments. The first is the
570 attribute meta-object this I<handles> is attached to. The second is the
571 metaclass of the class being delegated to. It expects you to return a hash (not
572 a HASH ref) of the methods you want mapped.
576 =item I<metaclass =E<gt> $metaclass_name>
578 This tells the class to use a custom attribute metaclass for this particular
579 attribute. Custom attribute metaclasses are useful for extending the
580 capabilities of the I<has> keyword: they are the simplest way to extend the MOP,
581 but they are still a fairly advanced topic and too much to cover here, see
582 L<Moose::Cookbook::Meta::Recipe1> for more information.
584 The default behavior here is to just load C<$metaclass_name>; however, we also
585 have a way to alias to a shorter name. This will first look to see if
586 B<Moose::Meta::Attribute::Custom::$metaclass_name> exists. If it does, Moose
587 will then check to see if that has the method C<register_implementation>, which
588 should return the actual name of the custom attribute metaclass. If there is no
589 C<register_implementation> method, it will fall back to using
590 B<Moose::Meta::Attribute::Custom::$metaclass_name> as the metaclass name.
592 =item I<traits =E<gt> [ @role_names ]>
594 This tells Moose to take the list of C<@role_names> and apply them to the
595 attribute meta-object. This is very similar to the I<metaclass> option, but
596 allows you to use more than one extension at a time.
598 See L<TRAIT NAME RESOLUTION> for details on how a trait name is
599 resolved to a class name.
601 Also see L<Moose::Cookbook::Meta::Recipe3> for a metaclass trait
604 =item I<builder> => Str
606 The value of this key is the name of the method that will be called to
607 obtain the value used to initialize the attribute. See the L<builder
608 option docs in Class::MOP::Attribute|Class::MOP::Attribute/builder>
609 and/or L<Moose::Cookbook::Basics::Recipe9> for more information.
611 =item I<default> => SCALAR | CODE
613 The value of this key is the default value which will initialize the attribute.
615 NOTE: If the value is a simple scalar (string or number), then it can
616 be just passed as is. However, if you wish to initialize it with a
617 HASH or ARRAY ref, then you need to wrap that inside a CODE reference.
618 See the L<default option docs in
619 Class::MOP::Attribute|Class::MOP::Attribute/default> for more
622 =item I<clearer> => Str
624 Creates a method allowing you to clear the value, see the L<clearer option
625 docs in Class::MOP::Attribute|Class::MOP::Attribute/clearer> for more
628 =item I<predicate> => Str
630 Creates a method to perform a basic test to see if a value has been set in the
631 attribute, see the L<predicate option docs in
632 Class::MOP::Attribute|Class::MOP::Attribute/predicate> for more information.
634 =item I<lazy_build> => (0|1)
636 Automatically define lazy => 1 as well as builder => "_build_$attr", clearer =>
637 "clear_$attr', predicate => 'has_$attr' unless they are already defined.
639 =item I<initializer> => Str
641 This may be a method name (referring to a method on the class with
642 this attribute) or a CODE ref. The initializer is used to set the
643 attribute value on an instance when the attribute is set during
644 instance initialization (but not when the value is being assigned
645 to). See the L<initializer option docs in
646 Class::MOP::Attribute|Class::MOP::Attribute/initializer> for more
651 =item B<has +$name =E<gt> %options>
653 This is variation on the normal attribute creator C<has> which allows you to
654 clone and extend an attribute from a superclass or from a role. Here is an
655 example of the superclass usage:
663 default => 'Hello, I am a Foo'
671 has '+message' => (default => 'Hello I am My::Foo');
673 What is happening here is that B<My::Foo> is cloning the C<message> attribute
674 from its parent class B<Foo>, retaining the C<is =E<gt> 'rw'> and C<isa =E<gt>
675 'Str'> characteristics, but changing the value in C<default>.
677 Here is another example, but within the context of a role:
685 default => 'Hello, I am a Foo'
693 has '+message' => (default => 'Hello I am My::Foo');
695 In this case, we are basically taking the attribute which the role supplied
696 and altering it within the bounds of this feature.
698 Aside from where the attributes come from (one from superclass, the other
699 from a role), this feature works exactly the same. This feature is restricted
700 somewhat, so as to try and force at least I<some> sanity into it. You are only
701 allowed to change the following attributes:
707 Change the default value of an attribute.
711 Change whether the attribute attempts to coerce a value passed to it.
715 Change if the attribute is required to have a value.
717 =item I<documentation>
719 Change the documentation string associated with the attribute.
723 Change if the attribute lazily initializes the slot.
727 You I<are> allowed to change the type without restriction.
729 It is recommended that you use this freedom with caution. We used to
730 only allow for extension only if the type was a subtype of the parent's
731 type, but we felt that was too restrictive and is better left as a
736 You are allowed to B<add> a new C<handles> definition, but you are B<not>
737 allowed to I<change> one.
741 You are allowed to B<add> a new C<builder> definition, but you are B<not>
742 allowed to I<change> one.
746 You are allowed to B<add> a new C<metaclass> definition, but you are
747 B<not> allowed to I<change> one.
751 You are allowed to B<add> additional traits to the C<traits> definition.
752 These traits will be composed into the attribute, but preexisting traits
753 B<are not> overridden, or removed.
757 =item B<before $name|@names =E<gt> sub { ... }>
759 =item B<after $name|@names =E<gt> sub { ... }>
761 =item B<around $name|@names =E<gt> sub { ... }>
763 This three items are syntactic sugar for the before, after, and around method
764 modifier features that L<Class::MOP> provides. More information on these may be
765 found in the L<Class::MOP::Class documentation|Class::MOP::Class/"Method
770 The keyword C<super> is a no-op when called outside of an C<override> method. In
771 the context of an C<override> method, it will call the next most appropriate
772 superclass method with the same arguments as the original method.
774 =item B<override ($name, &sub)>
776 An C<override> method is a way of explicitly saying "I am overriding this
777 method from my superclass". You can call C<super> within this method, and
778 it will work as expected. The same thing I<can> be accomplished with a normal
779 method call and the C<SUPER::> pseudo-package; it is really your choice.
783 The keyword C<inner>, much like C<super>, is a no-op outside of the context of
784 an C<augment> method. You can think of C<inner> as being the inverse of
785 C<super>; the details of how C<inner> and C<augment> work is best described in
786 the L<Moose::Cookbook::Basics::Recipe6>.
788 =item B<augment ($name, &sub)>
790 An C<augment> method, is a way of explicitly saying "I am augmenting this
791 method from my superclass". Once again, the details of how C<inner> and
792 C<augment> work is best described in the L<Moose::Cookbook::Basics::Recipe6>.
796 This is the C<Carp::confess> function, and exported here because I use it
801 This is the C<Scalar::Util::blessed> function, it is exported here because I
802 use it all the time. It is highly recommended that this is used instead of
803 C<ref> anywhere you need to test for an object's class name.
809 When you use Moose, you can specify which metaclass to use:
811 use Moose -metaclass => 'My::Meta::Class';
813 You can also specify traits which will be applied to your metaclass:
815 use Moose -traits => 'My::Trait';
817 This is very similar to the attribute traits feature. When you do
818 this, your class's C<meta> object will have the specified traits
819 applied to it. See L<TRAIT NAME RESOLUTION> for more details.
821 =head2 Trait Name Resolution
823 By default, when given a trait name, Moose simply tries to load a
824 class of the same name. If such a class does not exist, it then looks
825 for for a class matching
826 B<Moose::Meta::$type::Custom::Trait::$trait_name>. The C<$type>
827 variable here will be one of B<Attribute> or B<Class>, depending on
828 what the trait is being applied to.
830 If a class with this long name exists, Moose checks to see if it has
831 the method C<register_implementation>. This method is expected to
832 return the I<real> class name of the trait. If there is no
833 C<register_implementation> method, it will fall back to using
834 B<Moose::Meta::$type::Custom::Trait::$trait> as the trait name.
836 If all this is confusing, take a look at
837 L<Moose::Cookbook::Meta::Recipe3>, which demonstrates how to create an
840 =head1 UNIMPORTING FUNCTIONS
844 Moose offers a way to remove the keywords it exports, through the C<unimport>
845 method. You simply have to say C<no Moose> at the bottom of your code for this
846 to work. Here is an example:
851 has 'first_name' => (is => 'rw', isa => 'Str');
852 has 'last_name' => (is => 'rw', isa => 'Str');
856 $self->first_name . ' ' . $self->last_name
859 no Moose; # keywords are removed from the Person package
861 =head1 EXTENDING AND EMBEDDING MOOSE
863 To learn more about extending Moose, we recommend checking out the
864 "Extending" recipes in the L<Moose::Cookbook>, starting with
865 L<Moose::Cookbook::Extending::Recipe1>, which provides an overview of
866 all the different ways you might extend Moose.
868 =head2 B<< Moose->init_meta(for_class => $class, base_class => $baseclass, metaclass => $metaclass) >>
870 The C<init_meta> method sets up the metaclass object for the class
871 specified by C<for_class>. This method injects a a C<meta> accessor
872 into the class so you can get at this object. It also sets the class's
873 superclass to C<base_class>, with L<Moose::Object> as the default.
875 C<init_meta> returns the metaclass object for C<$class>.
877 You can specify an alternate metaclass with the C<metaclass> option.
879 For more detail on this topic, see L<Moose::Cookbook::Extending::Recipe2>.
881 This method used to be documented as a function which accepted
882 positional parameters. This calling style will still work for
883 backwards compatibility, but is deprecated.
887 Moose's C<import> method supports the L<Sub::Exporter> form of C<{into =E<gt> $pkg}>
888 and C<{into_level =E<gt> 1}>.
890 B<NOTE>: Doing this is more or less deprecated. Use L<Moose::Exporter>
891 instead, which lets you stack multiple C<Moose.pm>-alike modules
892 sanely. It handles getting the exported functions into the right place
895 =head2 B<throw_error>
897 An alias for C<confess>, used by internally by Moose.
899 =head1 METACLASS COMPATIBILITY AND MOOSE
901 Metaclass compatibility is a thorny subject. You should start by
902 reading the "About Metaclass compatibility" section in the
905 Moose will attempt to resolve a few cases of metaclass incompatibility
906 when you set the superclasses for a class, unlike C<Class::MOP>, which
907 simply dies if the metaclasses are incompatible.
909 In actuality, Moose fixes incompatibility for I<all> of a class's
910 metaclasses, not just the class metaclass. That includes the instance
911 metaclass, attribute metaclass, as well as its constructor class and
912 destructor class. However, for simplicity this discussion will just
913 refer to "metaclass", meaning the class metaclass, most of the time.
915 Moose has two algorithms for fixing metaclass incompatibility.
917 The first algorithm is very simple. If all the metaclass for the
918 parent is a I<subclass> of the child's metaclass, then we simply
919 replace the child's metaclass with the parent's.
921 The second algorithm is more complicated. It tries to determine if the
922 metaclasses only "differ by roles". This means that the parent and
923 child's metaclass share a common ancestor in their respective
924 hierarchies, and that the subclasses under the common ancestor are
925 only different because of role applications. This case is actually
926 fairly common when you mix and match various C<MooseX::*> modules,
927 many of which apply roles to the metaclass.
929 If the parent and child do differ by roles, Moose replaces the
930 metaclass in the child with a newly created metaclass. This metaclass
931 is a subclass of the parent's metaclass, does all of the roles that
932 the child's metaclass did before being replaced. Effectively, this
933 means the new metaclass does all of the roles done by both the
934 parent's and child's original metaclasses.
936 Ultimately, this is all transparent to you except in the case of an
937 unresolvable conflict.
939 =head2 The MooseX:: namespace
941 Generally if you're writing an extension I<for> Moose itself you'll want
942 to put your extension in the C<MooseX::> namespace. This namespace is
943 specifically for extensions that make Moose better or different in some
944 fundamental way. It is traditionally B<not> for a package that just happens
945 to use Moose. This namespace follows from the examples of the C<LWPx::>
946 and C<DBIx::> namespaces that perform the same function for C<LWP> and C<DBI>
955 It should be noted that C<super> and C<inner> B<cannot> be used in the same
956 method. However, they may be combined within the same class hierarchy; see
957 F<t/014_override_augment_inner_super.t> for an example.
959 The reason for this is that C<super> is only valid within a method
960 with the C<override> modifier, and C<inner> will never be valid within an
961 C<override> method. In fact, C<augment> will skip over any C<override> methods
962 when searching for its appropriate C<inner>.
964 This might seem like a restriction, but I am of the opinion that keeping these
965 two features separate (yet interoperable) actually makes them easy to use, since
966 their behavior is then easier to predict. Time will tell whether I am right or
967 not (UPDATE: so far so good).
973 We offer both a mailing list and a very active IRC channel.
975 The mailing list is L<moose@perl.org>. You must be subscribed to send
976 a message. To subscribe, send an empty message to
977 L<moose-subscribe@perl.org>
979 You can also visit us at L<#moose on
980 irc.perl.org|irc://irc.perl.org/#moose>. This channel is quite active,
981 and questions at all levels (on Moose-related topics ;) are welcome.
983 =head1 ACKNOWLEDGEMENTS
987 =item I blame Sam Vilain for introducing me to the insanity that is meta-models.
989 =item I blame Audrey Tang for then encouraging my meta-model habit in #perl6.
991 =item Without Yuval "nothingmuch" Kogman this module would not be possible,
992 and it certainly wouldn't have this name ;P
994 =item The basis of the TypeContraints module was Rob Kinyon's idea
995 originally, I just ran with it.
997 =item Thanks to mst & chansen and the whole #moose posse for all the
998 early ideas/feature-requests/encouragement/bug-finding.
1000 =item Thanks to David "Theory" Wheeler for meta-discussions and spelling fixes.
1008 =item L<http://www.iinteractive.com/moose>
1010 This is the official web home of Moose, it contains links to our public SVN repository
1011 as well as links to a number of talks and articles on Moose and Moose related
1014 =item The Moose is flying, a tutorial by Randal Schwartz
1016 Part 1 - L<http://www.stonehenge.com/merlyn/LinuxMag/col94.html>
1018 Part 2 - L<http://www.stonehenge.com/merlyn/LinuxMag/col95.html>
1020 =item Several Moose extension modules in the C<MooseX::> namespace.
1022 See L<http://search.cpan.org/search?query=MooseX::> for extensions.
1024 =item Moose stats on ohloh.net - L<http://www.ohloh.net/projects/moose>
1032 =item The Art of the MetaObject Protocol
1034 I mention this in the L<Class::MOP> docs too, this book was critical in
1035 the development of both modules and is highly recommended.
1043 =item L<http://www.cs.utah.edu/plt/publications/oopsla04-gff.pdf>
1045 This paper (suggested by lbr on #moose) was what lead to the implementation
1046 of the C<super>/C<override> and C<inner>/C<augment> features. If you really
1047 want to understand them, I suggest you read this.
1053 All complex software has bugs lurking in it, and this module is no
1056 Please report any bugs to C<bug-moose@rt.cpan.org>, or through the web
1057 interface at L<http://rt.cpan.org>.
1059 =head1 FEATURE REQUESTS
1061 We are very strict about what features we add to the Moose core, especially
1062 the user-visible features. Instead we have made sure that the underlying
1063 meta-system of Moose is as extensible as possible so that you can add your
1064 own features easily.
1066 That said, occasionally there is a feature needed in the meta-system
1067 to support your planned extension, in which case you should either
1068 email the mailing list (moose@perl.org) or join us on IRC at
1069 L<irc://irc.perl.org/#moose> to discuss. The
1070 L<Moose::Manual::Contributing> has more detail about how and when you
1075 Moose is an open project, there are at this point dozens of people who have
1076 contributed, and can contribute. If you have added anything to the Moose
1077 project you have a commit bit on this file and can add your name to the list.
1081 However there are only a few people with the rights to release a new version
1082 of Moose. The Moose Cabal are the people to go to with questions regarding
1083 the wider purview of Moose, and help out maintaining not just the code
1084 but the community as well.
1086 Stevan (stevan) Little E<lt>stevan@iinteractive.comE<gt>
1088 Yuval (nothingmuch) Kogman
1090 Shawn (sartak) Moore
1092 Dave (autarch) Rolsky E<lt>autarch@urth.orgE<gt>
1094 =head2 OTHER CONTRIBUTORS
1098 Adam (Alias) Kennedy
1100 Anders (Debolaz) Nor Berle
1102 Nathan (kolibrie) Gray
1104 Christian (chansen) Hansen
1106 Hans Dieter (confound) Pearcey
1108 Eric (ewilhelm) Wilhelm
1110 Guillermo (groditi) Roditi
1112 Jess (castaway) Robinson
1116 Robert (phaylon) Sedlacek
1120 Scott (konobi) McWhirter
1122 Shlomi (rindolf) Fish
1124 Chris (perigrin) Prather
1126 Wallace (wreis) Reis
1128 Jonathan (jrockway) Rockway
1130 Piotr (dexter) Roszatycki
1132 Sam (mugwump) Vilain
1136 ... and many other #moose folks
1138 =head1 COPYRIGHT AND LICENSE
1140 Copyright 2006-2009 by Infinity Interactive, Inc.
1142 L<http://www.iinteractive.com>
1144 This library is free software; you can redistribute it and/or modify
1145 it under the same terms as Perl itself.