7 use Scalar::Util 'blessed';
10 use Moose::Deprecated;
15 use Moose::Meta::Class;
16 use Moose::Meta::TypeConstraint;
17 use Moose::Meta::TypeCoercion;
18 use Moose::Meta::Attribute;
19 use Moose::Meta::Instance;
23 use Moose::Meta::Role;
24 use Moose::Meta::Role::Composite;
25 use Moose::Meta::Role::Application;
26 use Moose::Meta::Role::Application::RoleSummation;
27 use Moose::Meta::Role::Application::ToClass;
28 use Moose::Meta::Role::Application::ToRole;
29 use Moose::Meta::Role::Application::ToInstance;
31 use Moose::Util::TypeConstraints;
34 use Moose::Meta::Attribute::Native;
45 Moose->throw_error("Must derive at least one class") unless @_;
47 # this checks the metaclass to make sure
48 # it is correct, sometimes it can get out
49 # of sync when the classes are being built
50 $meta->superclasses(@_);
54 Moose::Util::apply_all_roles(shift, @_);
61 Moose->throw_error('Usage: has \'name\' => ( key => value, ... )')
64 my %options = ( definition_context => Moose::Util::_caller_info(), @_ );
65 my $attrs = ( ref($name) eq 'ARRAY' ) ? $name : [ ($name) ];
66 $meta->add_attribute( $_, %options ) for @$attrs;
70 Moose::Util::add_method_modifier(shift, 'before', \@_);
74 Moose::Util::add_method_modifier(shift, 'after', \@_);
78 Moose::Util::add_method_modifier(shift, 'around', \@_);
86 # This check avoids a recursion loop - see
87 # t/100_bugs/020_super_recursion.t
88 return if defined $SUPER_PACKAGE && $SUPER_PACKAGE ne caller();
89 return unless $SUPER_BODY; $SUPER_BODY->(@SUPER_ARGS);
94 my ( $name, $method ) = @_;
95 $meta->add_override_method_modifier( $name => $method );
100 our ( %INNER_BODY, %INNER_ARGS );
102 if ( my $body = $INNER_BODY{$pkg} ) {
103 my @args = @{ $INNER_ARGS{$pkg} };
104 local $INNER_ARGS{$pkg};
105 local $INNER_BODY{$pkg};
106 return $body->(@args);
114 my ( $name, $method ) = @_;
115 $meta->add_augment_method_modifier( $name => $method );
118 Moose::Exporter->setup_import_methods(
120 qw( extends with has before after around override augment )
125 \&Scalar::Util::blessed,
130 # This used to be called as a function. This hack preserves
131 # backwards compatibility.
132 if ( $_[0] ne __PACKAGE__ ) {
133 Moose::Deprecated::deprecated(
134 feature => 'Moose::init_meta',
135 message => 'Calling Moose::init_meta as a function is deprecated',
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';
152 my $meta_name = exists $args{meta_name} ? $args{meta_name} : 'meta';
154 Moose->throw_error("The Metaclass $metaclass must be a subclass of Moose::Meta::Class.")
155 unless $metaclass->isa('Moose::Meta::Class');
157 # make a subtype for each Moose class
159 unless find_type_constraint($class);
163 if ( $meta = Class::MOP::get_metaclass_by_name($class) ) {
164 unless ( $meta->isa("Moose::Meta::Class") ) {
165 my $error_message = "$class already has a metaclass, but it does not inherit $metaclass ($meta).";
166 if ( $meta->isa('Moose::Meta::Role') ) {
167 Moose->throw_error($error_message . ' You cannot make the same thing a role and a class. Remove either Moose or Moose::Role.');
169 Moose->throw_error($error_message);
175 # now we check whether our ancestors have metaclass, and if so borrow that
176 my ( undef, @isa ) = @{ mro::get_linear_isa($class) };
178 foreach my $ancestor ( @isa ) {
179 my $ancestor_meta = Class::MOP::get_metaclass_by_name($ancestor) || next;
181 my $ancestor_meta_class = $ancestor_meta->_real_ref_name;
183 # if we have an ancestor metaclass that inherits $metaclass, we use
184 # that. This is like _fix_metaclass_incompatibility, but we can do it now.
186 # the case of having an ancestry is not very common, but arises in
188 unless ( $metaclass->isa( $ancestor_meta_class ) ) {
189 if ( $ancestor_meta_class->isa($metaclass) ) {
190 $metaclass = $ancestor_meta_class;
195 $meta = $metaclass->initialize($class);
198 if (defined $meta_name) {
199 # also check for inherited non moose 'meta' method?
200 my $existing = $meta->get_method($meta_name);
201 if ($existing && !$existing->isa('Class::MOP::Method::Meta')) {
202 Carp::cluck "Moose is overwriting an existing method named "
203 . "$meta_name in class $class with a method "
204 . "which returns the class's metaclass. If this is "
205 . "actually what you want, you should remove the "
206 . "existing method, otherwise, you should rename or "
207 . "disable this generated method using the "
208 . "'-meta_name' option to 'use Moose'.";
210 $meta->_add_meta_method($meta_name);
213 # make sure they inherit from Moose::Object
214 $meta->superclasses($base_class)
215 unless $meta->superclasses();
220 # This may be used in some older MooseX extensions.
222 goto &Moose::Exporter::_get_caller;
225 ## make 'em all immutable
228 inline_constructor => 1,
229 constructor_name => "_new",
230 # these are Class::MOP accessors, so they need inlining
231 inline_accessors => 1
232 ) for grep { $_->is_mutable }
235 Moose::Meta::Attribute
237 Moose::Meta::Instance
239 Moose::Meta::TypeCoercion
240 Moose::Meta::TypeCoercion::Union
243 Moose::Meta::Method::Accessor
244 Moose::Meta::Method::Constructor
245 Moose::Meta::Method::Destructor
246 Moose::Meta::Method::Overridden
247 Moose::Meta::Method::Augmented
250 Moose::Meta::Role::Attribute
251 Moose::Meta::Role::Method
252 Moose::Meta::Role::Method::Required
253 Moose::Meta::Role::Method::Conflicting
255 Moose::Meta::Role::Composite
257 Moose::Meta::Role::Application
258 Moose::Meta::Role::Application::RoleSummation
259 Moose::Meta::Role::Application::ToClass
260 Moose::Meta::Role::Application::ToRole
261 Moose::Meta::Role::Application::ToInstance
264 Moose::Meta::Mixin::AttributeCore->meta->make_immutable(
265 inline_constructor => 0,
266 constructor_name => undef,
271 # ABSTRACT: A postmodern object system for Perl 5
280 use Moose; # automatically turns on strict and warnings
282 has 'x' => (is => 'rw', isa => 'Int');
283 has 'y' => (is => 'rw', isa => 'Int');
296 has 'z' => (is => 'rw', isa => 'Int');
298 after 'clear' => sub {
305 Moose is an extension of the Perl 5 object system.
307 The main goal of Moose is to make Perl 5 Object Oriented programming
308 easier, more consistent, and less tedious. With Moose you can think
309 more about what you want to do and less about the mechanics of OOP.
311 Additionally, Moose is built on top of L<Class::MOP>, which is a
312 metaclass system for Perl 5. This means that Moose not only makes
313 building normal Perl 5 objects better, but it provides the power of
314 metaclass programming as well.
318 If you're new to Moose, the best place to start is the
319 L<Moose::Manual> docs, followed by the L<Moose::Cookbook>. The intro
320 will show you what Moose is, and how it makes Perl 5 OO better.
322 The cookbook recipes on Moose basics will get you up to speed with
323 many of Moose's features quickly. Once you have an idea of what Moose
324 can do, you can use the API documentation to get more detail on
325 features which interest you.
327 =head2 Moose Extensions
329 The C<MooseX::> namespace is the official place to find Moose extensions.
330 These extensions can be found on the CPAN. The easiest way to find them
331 is to search for them (L<http://search.cpan.org/search?query=MooseX::>),
332 or to examine L<Task::Moose> which aims to keep an up-to-date, easily
333 installable list of Moose extensions.
337 Much of the Moose documentation has been translated into other languages.
343 Japanese docs can be found at
344 L<http://perldoc.perlassociation.org/pod/Moose-Doc-JA/index.html>. The
345 source POD files can be found in GitHub:
346 L<http://github.com/jpa/Moose-Doc-JA>
350 =head1 BUILDING CLASSES WITH MOOSE
352 Moose makes every attempt to provide as much convenience as possible during
353 class construction/definition, but still stay out of your way if you want it
354 to. Here are a few items to note when building classes with Moose.
356 When you C<use Moose>, Moose will set the class's parent class to
357 L<Moose::Object>, I<unless> the class using Moose already has a parent
358 class. In addition, specifying a parent with C<extends> will change the parent
361 Moose will also manage all attributes (including inherited ones) that are
362 defined with C<has>. And (assuming you call C<new>, which is inherited from
363 L<Moose::Object>) this includes properly initializing all instance slots,
364 setting defaults where appropriate, and performing any type constraint checking
367 =head1 PROVIDED METHODS
369 Moose provides a number of methods to all your classes, mostly through the
370 inheritance of L<Moose::Object>. There is however, one exception.
376 This is a method which provides access to the current class's metaclass.
380 =head1 EXPORTED FUNCTIONS
382 Moose will export a number of functions into the class's namespace which
383 may then be used to set up the class. These functions all work directly
384 on the current class.
388 =item B<extends (@superclasses)>
390 This function will set the superclass(es) for the current class.
392 This approach is recommended instead of C<use base>, because C<use base>
393 actually C<push>es onto the class's C<@ISA>, whereas C<extends> will
394 replace it. This is important to ensure that classes which do not have
395 superclasses still properly inherit from L<Moose::Object>.
397 Each superclass can be followed by a hash reference with options. Currently,
398 only L<-version|Class::MOP/Class Loading Options> is recognized:
400 extends 'My::Parent' => { -version => 0.01 },
401 'My::OtherParent' => { -version => 0.03 };
403 An exception will be thrown if the version requirements are not
406 =item B<with (@roles)>
408 This will apply a given set of C<@roles> to the local class.
410 Like with C<extends>, each specified role can be followed by a hash
411 reference with a L<-version|Class::MOP/Class Loading Options> option:
413 with 'My::Role' => { -version => 0.32 },
414 'My::Otherrole' => { -version => 0.23 };
416 The specified version requirements must be satisfied, otherwise an
417 exception will be thrown.
419 If your role takes options or arguments, they can be passed along in the
420 hash reference as well.
422 =item B<has $name|@$names =E<gt> %options>
424 This will install an attribute of a given C<$name> into the current class. If
425 the first parameter is an array reference, it will create an attribute for
426 every C<$name> in the list. The C<%options> are the same as those provided by
427 L<Class::MOP::Attribute>, in addition to the list below which are provided by
428 Moose (L<Moose::Meta::Attribute> to be more specific):
432 =item I<is =E<gt> 'rw'|'ro'>
434 The I<is> option accepts either I<rw> (for read/write) or I<ro> (for read
435 only). These will create either a read/write accessor or a read-only
436 accessor respectively, using the same name as the C<$name> of the attribute.
438 If you need more control over how your accessors are named, you can
439 use the L<reader|Class::MOP::Attribute/reader>,
440 L<writer|Class::MOP::Attribute/writer> and
441 L<accessor|Class::MOP::Attribute/accessor> options inherited from
442 L<Class::MOP::Attribute>, however if you use those, you won't need the
445 =item I<isa =E<gt> $type_name>
447 The I<isa> option uses Moose's type constraint facilities to set up runtime
448 type checking for this attribute. Moose will perform the checks during class
449 construction, and within any accessors. The C<$type_name> argument must be a
450 string. The string may be either a class name or a type defined using
451 Moose's type definition features. (Refer to L<Moose::Util::TypeConstraints>
452 for information on how to define a new type, and how to retrieve type meta-data).
454 =item I<coerce =E<gt> (1|0)>
456 This will attempt to use coercion with the supplied type constraint to change
457 the value passed into any accessors or constructors. You B<must> supply a type
458 constraint, and that type constraint B<must> define a coercion. See
459 L<Moose::Cookbook::Basics::Recipe5> for an example.
461 =item I<does =E<gt> $role_name>
463 This will accept the name of a role which the value stored in this attribute
464 is expected to have consumed.
466 =item I<required =E<gt> (1|0)>
468 This marks the attribute as being required. This means a value must be
469 supplied during class construction, I<or> the attribute must be lazy
470 and have either a default or a builder. Note that c<required> does not
471 say anything about the attribute's value, which can be C<undef>.
473 =item I<weak_ref =E<gt> (1|0)>
475 This will tell the class to store the value of this attribute as a weakened
476 reference. If an attribute is a weakened reference, it B<cannot> also be
477 coerced. Note that when a weak ref expires, the attribute's value becomes
478 undefined, and is still considered to be set for purposes of predicate,
481 =item I<lazy =E<gt> (1|0)>
483 This will tell the class to not create this slot until absolutely necessary.
484 If an attribute is marked as lazy it B<must> have a default supplied.
486 =item I<auto_deref =E<gt> (1|0)>
488 This tells the accessor to automatically dereference the value of this
489 attribute when called in list context. The accessor will still return a
490 reference when called in scalar context. If this behavior isn't desirable,
491 L<Moose::Meta::Attribute::Native::Trait::Array/elements> or
492 L<Moose::Meta::Attribute::Native::Trait::Hash/elements> may be a better
493 choice. The I<auto_deref> option is only legal if your I<isa> option is
494 either C<ArrayRef> or C<HashRef>.
496 =item I<trigger =E<gt> $code>
498 The I<trigger> option is a CODE reference which will be called after
499 the value of the attribute is set. The CODE ref is passed the
500 instance itself, the updated value, and the original value if the
501 attribute was already set.
503 You B<can> have a trigger on a read-only attribute.
505 B<NOTE:> Triggers will only fire when you B<assign> to the attribute,
506 either in the constructor, or using the writer. Default and built values will
507 B<not> cause the trigger to be fired.
509 =item I<handles =E<gt> ARRAY | HASH | REGEXP | ROLE | ROLETYPE | DUCKTYPE | CODE>
511 The I<handles> option provides Moose classes with automated delegation features.
512 This is a pretty complex and powerful option. It accepts many different option
513 formats, each with its own benefits and drawbacks.
515 B<NOTE:> The class being delegated to does not need to be a Moose based class,
516 which is why this feature is especially useful when wrapping non-Moose classes.
518 All I<handles> option formats share the following traits:
520 You cannot override a locally defined method with a delegated method; an
521 exception will be thrown if you try. That is to say, if you define C<foo> in
522 your class, you cannot override it with a delegated C<foo>. This is almost never
523 something you would want to do, and if it is, you should do it by hand and not
526 You cannot override any of the methods found in Moose::Object, or the C<BUILD>
527 and C<DEMOLISH> methods. These will not throw an exception, but will silently
528 move on to the next method in the list. My reasoning for this is that you would
529 almost never want to do this, since it usually breaks your class. As with
530 overriding locally defined methods, if you do want to do this, you should do it
531 manually, not with Moose.
533 You do not I<need> to have a reader (or accessor) for the attribute in order
534 to delegate to it. Moose will create a means of accessing the value for you,
535 however this will be several times B<less> efficient then if you had given
536 the attribute a reader (or accessor) to use.
538 Below is the documentation for each option format:
544 This is the most common usage for I<handles>. You basically pass a list of
545 method names to be delegated, and Moose will install a delegation method
550 This is the second most common usage for I<handles>. Instead of a list of
551 method names, you pass a HASH ref where each key is the method name you
552 want installed locally, and its value is the name of the original method
553 in the class being delegated to.
555 This can be very useful for recursive classes like trees. Here is a
556 quick example (soon to be expanded into a Moose::Cookbook recipe):
561 has 'node' => (is => 'rw', isa => 'Any');
566 default => sub { [] }
574 parent_node => 'node',
575 siblings => 'children',
579 In this example, the Tree package gets C<parent_node> and C<siblings> methods,
580 which delegate to the C<node> and C<children> methods (respectively) of the Tree
581 instance stored in the C<parent> slot.
583 You may also use an array reference to curry arguments to the original method.
587 handles => { set_foo => [ set => 'foo' ] },
590 # $self->set_foo(...) calls $self->thing->set('foo', ...)
592 The first element of the array reference is the original method name, and the
593 rest is a list of curried arguments.
597 The regexp option works very similar to the ARRAY option, except that it builds
598 the list of methods for you. It starts by collecting all possible methods of the
599 class being delegated to, then filters that list using the regexp supplied here.
601 B<NOTE:> An I<isa> option is required when using the regexp option format. This
602 is so that we can determine (at compile time) the method list from the class.
603 Without an I<isa> this is just not possible.
605 =item C<ROLE> or C<ROLETYPE>
607 With the role option, you specify the name of a role or a
608 L<role type|Moose::Meta::TypeConstraint::Role> whose "interface" then becomes
609 the list of methods to handle. The "interface" can be defined as; the methods
610 of the role and any required methods of the role. It should be noted that this
611 does B<not> include any method modifiers or generated attribute methods (which
612 is consistent with role composition).
616 With the duck type option, you pass a duck type object whose "interface" then
617 becomes the list of methods to handle. The "interface" can be defined as the
618 list of methods passed to C<duck_type> to create a duck type object. For more
619 information on C<duck_type> please check
620 L<Moose::Util::TypeConstraints>.
624 This is the option to use when you really want to do something funky. You should
625 only use it if you really know what you are doing, as it involves manual
628 This takes a code reference, which should expect two arguments. The first is the
629 attribute meta-object this I<handles> is attached to. The second is the
630 metaclass of the class being delegated to. It expects you to return a hash (not
631 a HASH ref) of the methods you want mapped.
635 =item I<metaclass =E<gt> $metaclass_name>
637 This tells the class to use a custom attribute metaclass for this particular
638 attribute. Custom attribute metaclasses are useful for extending the
639 capabilities of the I<has> keyword: they are the simplest way to extend the MOP,
640 but they are still a fairly advanced topic and too much to cover here. See
641 L<Moose::Cookbook::Meta::Recipe1> for more information.
643 See L<Metaclass and Trait Name Resolution> for details on how a metaclass name
644 is resolved to a class name.
646 =item I<traits =E<gt> [ @role_names ]>
648 This tells Moose to take the list of C<@role_names> and apply them to the
649 attribute meta-object. This is very similar to the I<metaclass> option, but
650 allows you to use more than one extension at a time.
652 See L<Metaclass and Trait Name Resolution> for details on how a trait name is
653 resolved to a role name.
655 Also see L<Moose::Cookbook::Meta::Recipe3> for a metaclass trait
658 =item I<builder> => Str
660 The value of this key is the name of the method that will be called to
661 obtain the value used to initialize the attribute. See the L<builder
662 option docs in Class::MOP::Attribute|Class::MOP::Attribute/builder>
663 and/or L<Moose::Cookbook::Basics::Recipe8> for more information.
665 =item I<default> => SCALAR | CODE
667 The value of this key is the default value which will initialize the attribute.
669 NOTE: If the value is a simple scalar (string or number), then it can
670 be just passed as is. However, if you wish to initialize it with a
671 HASH or ARRAY ref, then you need to wrap that inside a CODE reference.
672 See the L<default option docs in
673 Class::MOP::Attribute|Class::MOP::Attribute/default> for more
676 =item I<clearer> => Str
678 Creates a method allowing you to clear the value. See the L<clearer option
679 docs in Class::MOP::Attribute|Class::MOP::Attribute/clearer> for more
682 =item I<predicate> => Str
684 Creates a method to perform a basic test to see if a value has been set in the
685 attribute. See the L<predicate option docs in
686 Class::MOP::Attribute|Class::MOP::Attribute/predicate> for more information.
688 Note that the predicate will return true even for a C<weak_ref> attribute
689 whose value has expired.
691 =item I<lazy_build> => (0|1)
693 Automatically define lazy => 1 as well as builder => "_build_$attr", clearer =>
694 "clear_$attr', predicate => 'has_$attr' unless they are already defined.
696 =item I<initializer> => Str
698 This may be a method name (referring to a method on the class with
699 this attribute) or a CODE ref. The initializer is used to set the
700 attribute value on an instance when the attribute is set during
701 instance initialization (but not when the value is being assigned
702 to). See the L<initializer option docs in
703 Class::MOP::Attribute|Class::MOP::Attribute/initializer> for more
706 =item I<documentation> => $string
708 An arbitrary string that can be retrieved later by calling C<<
709 $attr->documentation >>.
715 =item B<has +$name =E<gt> %options>
717 This is variation on the normal attribute creator C<has> which allows you to
718 clone and extend an attribute from a superclass or from a role. Here is an
719 example of the superclass usage:
727 default => 'Hello, I am a Foo'
735 has '+message' => (default => 'Hello I am My::Foo');
737 What is happening here is that B<My::Foo> is cloning the C<message> attribute
738 from its parent class B<Foo>, retaining the C<is =E<gt> 'rw'> and C<isa =E<gt>
739 'Str'> characteristics, but changing the value in C<default>.
741 Here is another example, but within the context of a role:
749 default => 'Hello, I am a Foo'
757 has '+message' => (default => 'Hello I am My::Foo');
759 In this case, we are basically taking the attribute which the role supplied
760 and altering it within the bounds of this feature.
762 Note that you can only extend an attribute from either a superclass or a role,
763 you cannot extend an attribute in a role that composes over an attribute from
766 Aside from where the attributes come from (one from superclass, the other
767 from a role), this feature works exactly the same. This feature is restricted
768 somewhat, so as to try and force at least I<some> sanity into it. You are only
769 allowed to change the following attributes:
775 Change the default value of an attribute.
779 Change whether the attribute attempts to coerce a value passed to it.
783 Change if the attribute is required to have a value.
785 =item I<documentation>
787 Change the documentation string associated with the attribute.
791 Change if the attribute lazily initializes the slot.
795 You I<are> allowed to change the type without restriction.
797 It is recommended that you use this freedom with caution. We used to
798 only allow for extension only if the type was a subtype of the parent's
799 type, but we felt that was too restrictive and is better left as a
804 You are allowed to B<add> a new C<handles> definition, but you are B<not>
805 allowed to I<change> one.
809 You are allowed to B<add> a new C<builder> definition, but you are B<not>
810 allowed to I<change> one.
814 You are allowed to B<add> a new C<metaclass> definition, but you are
815 B<not> allowed to I<change> one.
819 You are allowed to B<add> additional traits to the C<traits> definition.
820 These traits will be composed into the attribute, but preexisting traits
821 B<are not> overridden, or removed.
825 =item B<before $name|@names|\@names|qr/.../ =E<gt> sub { ... }>
827 =item B<after $name|@names|\@names|qr/.../ =E<gt> sub { ... }>
829 =item B<around $name|@names|\@names|qr/.../ =E<gt> sub { ... }>
831 These three items are syntactic sugar for the before, after, and around method
832 modifier features that L<Class::MOP> provides. More information on these may be
833 found in L<Moose::Manual::MethodModifiers> and the
834 L<Class::MOP::Class documentation|Class::MOP::Class/"Method Modifiers">.
838 The keyword C<super> is a no-op when called outside of an C<override> method. In
839 the context of an C<override> method, it will call the next most appropriate
840 superclass method with the same arguments as the original method.
842 =item B<override ($name, &sub)>
844 An C<override> method is a way of explicitly saying "I am overriding this
845 method from my superclass". You can call C<super> within this method, and
846 it will work as expected. The same thing I<can> be accomplished with a normal
847 method call and the C<SUPER::> pseudo-package; it is really your choice.
851 The keyword C<inner>, much like C<super>, is a no-op outside of the context of
852 an C<augment> method. You can think of C<inner> as being the inverse of
853 C<super>; the details of how C<inner> and C<augment> work is best described in
854 the L<Moose::Cookbook::Basics::Recipe6>.
856 =item B<augment ($name, &sub)>
858 An C<augment> method, is a way of explicitly saying "I am augmenting this
859 method from my superclass". Once again, the details of how C<inner> and
860 C<augment> work is best described in the L<Moose::Cookbook::Basics::Recipe6>.
864 This is the C<Carp::confess> function, and exported here because I use it
869 This is the C<Scalar::Util::blessed> function. It is exported here because I
870 use it all the time. It is highly recommended that this is used instead of
871 C<ref> anywhere you need to test for an object's class name.
877 When you use Moose, you can specify which metaclass to use:
879 use Moose -metaclass => 'My::Meta::Class';
881 You can also specify traits which will be applied to your metaclass:
883 use Moose -traits => 'My::Trait';
885 This is very similar to the attribute traits feature. When you do
886 this, your class's C<meta> object will have the specified traits
887 applied to it. See L<Metaclass and Trait Name Resolution> for more
890 =head2 Metaclass and Trait Name Resolution
892 By default, when given a trait name, Moose simply tries to load a
893 class of the same name. If such a class does not exist, it then looks
894 for for a class matching
895 B<Moose::Meta::$type::Custom::Trait::$trait_name>. The C<$type>
896 variable here will be one of B<Attribute> or B<Class>, depending on
897 what the trait is being applied to.
899 If a class with this long name exists, Moose checks to see if it has
900 the method C<register_implementation>. This method is expected to
901 return the I<real> class name of the trait. If there is no
902 C<register_implementation> method, it will fall back to using
903 B<Moose::Meta::$type::Custom::Trait::$trait> as the trait name.
905 The lookup method for metaclasses is the same, except that it looks
906 for a class matching B<Moose::Meta::$type::Custom::$metaclass_name>.
908 If all this is confusing, take a look at
909 L<Moose::Cookbook::Meta::Recipe3>, which demonstrates how to create an
912 =head1 UNIMPORTING FUNCTIONS
916 Moose offers a way to remove the keywords it exports, through the C<unimport>
917 method. You simply have to say C<no Moose> at the bottom of your code for this
918 to work. Here is an example:
923 has 'first_name' => (is => 'rw', isa => 'Str');
924 has 'last_name' => (is => 'rw', isa => 'Str');
928 $self->first_name . ' ' . $self->last_name
931 no Moose; # keywords are removed from the Person package
933 =head1 EXTENDING AND EMBEDDING MOOSE
935 To learn more about extending Moose, we recommend checking out the
936 "Extending" recipes in the L<Moose::Cookbook>, starting with
937 L<Moose::Cookbook::Extending::Recipe1>, which provides an overview of
938 all the different ways you might extend Moose.
940 =head2 B<< Moose->init_meta(for_class => $class, base_class => $baseclass, metaclass => $metaclass) >>
942 The C<init_meta> method sets up the metaclass object for the class
943 specified by C<for_class>. This method injects a a C<meta> accessor
944 into the class so you can get at this object. It also sets the class's
945 superclass to C<base_class>, with L<Moose::Object> as the default.
947 C<init_meta> returns the metaclass object for C<$class>.
949 You can specify an alternate metaclass with the C<metaclass> option.
951 For more detail on this topic, see L<Moose::Cookbook::Extending::Recipe2>.
953 This method used to be documented as a function which accepted
954 positional parameters. This calling style will still work for
955 backwards compatibility, but is deprecated.
959 Moose's C<import> method supports the L<Sub::Exporter> form of C<{into =E<gt> $pkg}>
960 and C<{into_level =E<gt> 1}>.
962 B<NOTE>: Doing this is more or less deprecated. Use L<Moose::Exporter>
963 instead, which lets you stack multiple C<Moose.pm>-alike modules
964 sanely. It handles getting the exported functions into the right place
967 =head2 B<throw_error>
969 An alias for C<confess>, used internally by Moose.
971 =head2 The MooseX:: namespace
973 Generally if you're writing an extension I<for> Moose itself you'll want
974 to put your extension in the C<MooseX::> namespace. This namespace is
975 specifically for extensions that make Moose better or different in some
976 fundamental way. It is traditionally B<not> for a package that just happens
977 to use Moose. This namespace follows from the examples of the C<LWPx::>
978 and C<DBIx::> namespaces that perform the same function for C<LWP> and C<DBI>
981 =head1 METACLASS COMPATIBILITY AND MOOSE
983 Metaclass compatibility is a thorny subject. You should start by
984 reading the "About Metaclass compatibility" section in the
987 Moose will attempt to resolve a few cases of metaclass incompatibility
988 when you set the superclasses for a class, in addition to the cases that
989 C<Class::MOP> handles.
991 Moose tries to determine if the metaclasses only "differ by roles". This
992 means that the parent and child's metaclass share a common ancestor in
993 their respective hierarchies, and that the subclasses under the common
994 ancestor are only different because of role applications. This case is
995 actually fairly common when you mix and match various C<MooseX::*>
996 modules, many of which apply roles to the metaclass.
998 If the parent and child do differ by roles, Moose replaces the
999 metaclass in the child with a newly created metaclass. This metaclass
1000 is a subclass of the parent's metaclass which does all of the roles that
1001 the child's metaclass did before being replaced. Effectively, this
1002 means the new metaclass does all of the roles done by both the
1003 parent's and child's original metaclasses.
1005 Ultimately, this is all transparent to you except in the case of an
1006 unresolvable conflict.
1014 It should be noted that C<super> and C<inner> B<cannot> be used in the same
1015 method. However, they may be combined within the same class hierarchy; see
1016 F<t/014_override_augment_inner_super.t> for an example.
1018 The reason for this is that C<super> is only valid within a method
1019 with the C<override> modifier, and C<inner> will never be valid within an
1020 C<override> method. In fact, C<augment> will skip over any C<override> methods
1021 when searching for its appropriate C<inner>.
1023 This might seem like a restriction, but I am of the opinion that keeping these
1024 two features separate (yet interoperable) actually makes them easy to use, since
1025 their behavior is then easier to predict. Time will tell whether I am right or
1026 not (UPDATE: so far so good).
1032 We offer both a mailing list and a very active IRC channel.
1034 The mailing list is L<moose@perl.org>. You must be subscribed to send
1035 a message. To subscribe, send an empty message to
1036 L<moose-subscribe@perl.org>
1038 You can also visit us at C<#moose> on L<irc://irc.perl.org/#moose>
1039 This channel is quite active, and questions at all levels (on Moose-related
1040 topics ;) are welcome.
1042 =head1 ACKNOWLEDGEMENTS
1046 =item I blame Sam Vilain for introducing me to the insanity that is meta-models.
1048 =item I blame Audrey Tang for then encouraging my meta-model habit in #perl6.
1050 =item Without Yuval "nothingmuch" Kogman this module would not be possible,
1051 and it certainly wouldn't have this name ;P
1053 =item The basis of the TypeContraints module was Rob Kinyon's idea
1054 originally, I just ran with it.
1056 =item Thanks to mst & chansen and the whole #moose posse for all the
1057 early ideas/feature-requests/encouragement/bug-finding.
1059 =item Thanks to David "Theory" Wheeler for meta-discussions and spelling fixes.
1067 =item L<http://www.iinteractive.com/moose>
1069 This is the official web home of Moose, it contains links to our public git repository
1070 as well as links to a number of talks and articles on Moose and Moose related
1073 =item The Moose is flying, a tutorial by Randal Schwartz
1075 Part 1 - L<http://www.stonehenge.com/merlyn/LinuxMag/col94.html>
1077 Part 2 - L<http://www.stonehenge.com/merlyn/LinuxMag/col95.html>
1079 =item Several Moose extension modules in the C<MooseX::> namespace.
1081 See L<http://search.cpan.org/search?query=MooseX::> for extensions.
1083 =item Moose stats on ohloh.net - L<http://www.ohloh.net/projects/moose>
1091 =item The Art of the MetaObject Protocol
1093 I mention this in the L<Class::MOP> docs too, as this book was critical in
1094 the development of both modules and is highly recommended.
1102 =item L<http://www.cs.utah.edu/plt/publications/oopsla04-gff.pdf>
1104 This paper (suggested by lbr on #moose) was what lead to the implementation
1105 of the C<super>/C<override> and C<inner>/C<augment> features. If you really
1106 want to understand them, I suggest you read this.
1112 All complex software has bugs lurking in it, and this module is no
1115 Please report any bugs to C<bug-moose@rt.cpan.org>, or through the web
1116 interface at L<http://rt.cpan.org>.
1118 You can also discuss feature requests or possible bugs on the Moose mailing
1119 list (moose@perl.org) or on IRC at L<irc://irc.perl.org/#moose>.
1121 =head1 FEATURE REQUESTS
1123 We are very strict about what features we add to the Moose core, especially
1124 the user-visible features. Instead we have made sure that the underlying
1125 meta-system of Moose is as extensible as possible so that you can add your
1126 own features easily.
1128 That said, occasionally there is a feature needed in the meta-system
1129 to support your planned extension, in which case you should either
1130 email the mailing list (moose@perl.org) or join us on IRC at
1131 L<irc://irc.perl.org/#moose> to discuss. The
1132 L<Moose::Manual::Contributing> has more detail about how and when you
1137 There are only a few people with the rights to release a new version
1138 of Moose. The Moose Cabal are the people to go to with questions regarding
1139 the wider purview of Moose. They help maintain not just the code
1140 but the community as well.
1142 Stevan (stevan) Little E<lt>stevan@iinteractive.comE<gt>
1144 Jesse (doy) Luehrs E<lt>doy at tozt dot netE<gt>
1146 Yuval (nothingmuch) Kogman
1148 Shawn (sartak) Moore E<lt>sartak@bestpractical.comE<gt>
1150 Hans Dieter (confound) Pearcey E<lt>hdp@pobox.comE<gt>
1152 Chris (perigrin) Prather
1154 Florian Ragwitz E<lt>rafl@debian.orgE<gt>
1156 Dave (autarch) Rolsky E<lt>autarch@urth.orgE<gt>
1162 Adam (Alias) Kennedy
1164 Anders (Debolaz) Nor Berle
1166 Chris (perigrin) Prather
1168 Christian (chansen) Hansen
1172 Dylan Hardison (doc fixes)
1174 Eric (ewilhelm) Wilhelm
1178 Florian (rafl) Ragwitz
1180 Guillermo (groditi) Roditi
1186 Jess (castaway) Robinson
1188 Jonathan (jrockway) Rockway
1192 Nathan (kolibrie) Gray
1194 Paul (frodwith) Driver
1196 Piotr (dexter) Roszatycki
1200 Robert (phaylon) Sedlacek
1204 Sam (mugwump) Vilain
1206 Scott (konobi) McWhirter
1208 Shawn (Sartak) Moore
1210 Shlomi (rindolf) Fish
1214 Wallace (wreis) Reis
1216 ... and many other #moose folks