8 our $VERSION = '1.001000'; # 1.1.0
9 $VERSION = eval $VERSION;
11 require Moo::sification;
15 sub _install_tracked {
16 my ($target, $name, $code) = @_;
17 $MAKERS{$target}{exports}{$name} = $code;
18 _install_coderef "${target}::${name}" => "Moo::${name}" => $code;
25 if ($Moo::Role::INFO{$target} and $Moo::Role::INFO{$target}{is_role}) {
26 die "Cannot import Moo into a role";
28 $MAKERS{$target} ||= {};
29 _install_tracked $target => extends => sub {
30 $class->_set_superclasses($target, @_);
31 $class->_maybe_reset_handlemoose($target);
34 _install_tracked $target => with => sub {
36 Moo::Role->apply_roles_to_package($target, @_);
37 $class->_maybe_reset_handlemoose($target);
39 _install_tracked $target => has => sub {
40 my ($name_proto, %spec) = @_;
41 my $name_isref = ref $name_proto eq 'ARRAY';
42 foreach my $name ($name_isref ? @$name_proto : $name_proto) {
43 # Note that when $name_proto is an arrayref, each attribute
44 # needs a separate \%specs hashref
45 my $spec_ref = $name_isref ? +{%spec} : \%spec;
46 $class->_constructor_maker_for($target)
47 ->register_attribute_specs($name, $spec_ref);
48 $class->_accessor_maker_for($target)
49 ->generate_method($target, $name, $spec_ref);
50 $class->_maybe_reset_handlemoose($target);
54 foreach my $type (qw(before after around)) {
55 _install_tracked $target => $type => sub {
56 require Class::Method::Modifiers;
57 _install_modifier($target, $type, @_);
61 return if $MAKERS{$target}{is_class}; # already exported into this package
62 $MAKERS{$target}{is_class} = 1;
65 @{"${target}::ISA"} = do {
66 require Moo::Object; ('Moo::Object');
67 } unless @{"${target}::ISA"};
69 if ($INC{'Moo/HandleMoose.pm'}) {
70 Moo::HandleMoose::inject_fake_metaclass_for($target);
76 _unimport_coderefs($target, $MAKERS{$target});
79 sub _set_superclasses {
82 foreach my $superclass (@_) {
83 _load_module($superclass);
84 if ($INC{"Role/Tiny.pm"} && $Role::Tiny::INFO{$superclass}) {
86 Carp::croak("Can't extend role '$superclass'");
89 # Can't do *{...} = \@_ or 5.10.0's mro.pm stops seeing @ISA
90 @{*{_getglob("${target}::ISA")}{ARRAY}} = @_;
91 if (my $old = delete $Moo::MAKERS{$target}{constructor}) {
92 delete _getstash($target)->{new};
93 Moo->_constructor_maker_for($target)
94 ->register_attribute_specs(%{$old->all_attribute_specs});
96 no warnings 'once'; # piss off. -- mst
97 $Moo::HandleMoose::MOUSE{$target} = [
98 grep defined, map Mouse::Util::find_meta($_), @_
99 ] if Mouse::Util->can('find_meta');
102 sub _maybe_reset_handlemoose {
103 my ($class, $target) = @_;
104 if ($INC{"Moo/HandleMoose.pm"}) {
105 Moo::HandleMoose::maybe_reinject_fake_metaclass_for($target);
109 sub _accessor_maker_for {
110 my ($class, $target) = @_;
111 return unless $MAKERS{$target};
112 $MAKERS{$target}{accessor} ||= do {
113 my $maker_class = do {
115 if (my $defer_target =
116 (Sub::Defer::defer_info($target->can('new'))||[])->[0]
118 my ($pkg) = ($defer_target =~ /^(.*)::[^:]+$/);
119 $MAKERS{$pkg} && $MAKERS{$pkg}{accessor};
126 require Method::Generate::Accessor;
127 'Method::Generate::Accessor'
134 sub _constructor_maker_for {
135 my ($class, $target, $select_super) = @_;
136 return unless $MAKERS{$target};
137 $MAKERS{$target}{constructor} ||= do {
138 require Method::Generate::Constructor;
140 my ($moo_constructor, $con);
142 if ($select_super && $MAKERS{$select_super}) {
143 $moo_constructor = 1;
144 $con = $MAKERS{$select_super}{constructor};
146 my $t_new = $target->can('new');
148 if ($t_new == Moo::Object->can('new')) {
149 $moo_constructor = 1;
150 } elsif (my $defer_target = (Sub::Defer::defer_info($t_new)||[])->[0]) {
151 my ($pkg) = ($defer_target =~ /^(.*)::[^:]+$/);
153 $moo_constructor = 1;
154 $con = $MAKERS{$pkg}{constructor};
158 $moo_constructor = 1; # no other constructor, make a Moo one
161 ($con ? ref($con) : 'Method::Generate::Constructor')
164 accessor_generator => $class->_accessor_maker_for($target),
165 construction_string => (
167 ? ($con ? $con->construction_string : undef)
168 : ('$class->'.$target.'::SUPER::new($class->can(q[FOREIGNBUILDARGS]) ? $class->FOREIGNBUILDARGS(@_) : @_)')
170 subconstructor_handler => (
171 ' if ($Moo::MAKERS{$class}) {'."\n"
172 .' '.$class.'->_constructor_maker_for($class,'.perlstring($target).');'."\n"
173 .' return $class->new(@_)'.";\n"
174 .' } elsif ($INC{"Moose.pm"} and my $meta = Class::MOP::get_metaclass_by_name($class)) {'."\n"
175 .' return $meta->new_object($class->BUILDARGS(@_));'."\n"
180 ->register_attribute_specs(%{$con?$con->all_attribute_specs:{}})
191 Moo - Minimalist Object Orientation (with Moose compatiblity)
201 my $amount = shift || 1;
203 $self->pounds( $self->pounds - $amount );
213 die "Only SWEET-TREATZ supported!" unless $_[0] eq 'SWEET-TREATZ'
219 isa => sub { die "$_[0] is too much cat food!" unless $_[0] < 15 },
226 my $full = Cat::Food->new(
227 taste => 'DELICIOUS.',
228 brand => 'SWEET-TREATZ',
238 This module is an extremely light-weight subset of L<Moose> optimised for
239 rapid startup and "pay only for what you use".
241 It also avoids depending on any XS modules to allow simple deployments. The
242 name C<Moo> is based on the idea that it provides almost -- but not quite -- two
245 Unlike L<Mouse> this module does not aim at full compatibility with
246 L<Moose>'s surface syntax, preferring instead of provide full interoperability
247 via the metaclass inflation capabilities described in L</MOO AND MOOSE>.
249 For a full list of the minor differences between L<Moose> and L<Moo>'s surface
250 syntax, see L</INCOMPATIBILITIES WITH MOOSE>.
252 =head1 WHY MOO EXISTS
254 If you want a full object system with a rich Metaprotocol, L<Moose> is
257 However, sometimes you're writing a command line script or a CGI script
258 where fast startup is essential, or code designed to be deployed as a single
259 file via L<App::FatPacker>, or you're writing a CPAN module and you want it
260 to be usable by people with those constraints.
262 I've tried several times to use L<Mouse> but it's 3x the size of Moo and
263 takes longer to load than most of my Moo based CGI scripts take to run.
265 If you don't want L<Moose>, you don't want "less metaprotocol" like L<Mouse>,
266 you want "as little as possible" -- which means "no metaprotocol", which is
269 Better still, if you install and load L<Moose>, we set up metaclasses for your
270 L<Moo> classes and L<Moo::Role> roles, so you can use them in L<Moose> code
271 without ever noticing that some of your codebase is using L<Moo>.
273 Hence, Moo exists as its name -- Minimal Object Orientation -- with a pledge
274 to make it smooth to upgrade to L<Moose> when you need more than minimal
279 If L<Moo> detects L<Moose> being loaded, it will automatically register
280 metaclasses for your L<Moo> and L<Moo::Role> packages, so you should be able
281 to use them in L<Moose> code without anybody ever noticing you aren't using
284 Extending a L<Moose> class or consuming a L<Moose::Role> will also work.
286 So will extending a L<Mouse> class or consuming a L<Mouse::Role> - but note
287 that we don't provide L<Mouse> metaclasses or metaroles so the other way
288 around doesn't work. This feature exists for L<Any::Moose> users porting to
289 L<Moo>; enabling L<Mouse> users to use L<Moo> classes is not a priority for us.
291 This means that there is no need for anything like L<Any::Moose> for Moo
292 code - Moo and Moose code should simply interoperate without problem. To
293 handle L<Mouse> code, you'll likely need an empty Moo role or class consuming
294 or extending the L<Mouse> stuff since it doesn't register true L<Moose>
295 metaclasses like L<Moo> does.
297 If you want types to be upgraded to the L<Moose> types, use
298 L<MooX::Types::MooseLike> and install the L<MooseX::Types> library to
299 match the L<MooX::Types::MooseLike> library you're using - L<Moo> will
300 load the L<MooseX::Types> library and use that type for the newly created
303 If you need to disable the metaclass creation, add:
307 to your code before Moose is loaded, but bear in mind that this switch is
308 currently global and turns the mechanism off entirely so don't put this
311 =head1 MOO VERSUS ANY::MOOSE
313 L<Any::Moose> will load L<Mouse> normally, and L<Moose> in a program using
314 L<Moose> - which theoretically allows you to get the startup time of L<Mouse>
315 without disadvantaging L<Moose> users.
317 Sadly, this doesn't entirely work, since the selection is load order dependent
318 - L<Moo>'s metaclass inflation system explained above in L</MOO AND MOOSE> is
319 significantly more reliable.
321 So if you want to write a CPAN module that loads fast or has only pure perl
322 dependencies but is also fully usable by L<Moose> users, you should be using
325 For a full explanation, see the article
326 L<http://shadow.cat/blog/matt-s-trout/moo-versus-any-moose> which explains
327 the differing strategies in more detail and provides a direct example of
328 where L<Moo> succeeds and L<Any::Moose> fails.
330 =head1 IMPORTED METHODS
334 Foo::Bar->new( attr1 => 3 );
338 Foo::Bar->new({ attr1 => 3 });
343 my ( $class, @args ) = @_;
345 unshift @args, "attr1" if @args % 2 == 1;
352 The default implementation of this method accepts a hash or hash reference of
353 named parameters. If it receives a single argument that isn't a hash reference
356 You can override this method in your class to handle other types of options
357 passed to the constructor.
359 This method should always return a hash reference of named options.
363 Define a C<BUILD> method on your class and the constructor will automatically
364 call the C<BUILD> method from parent down to child after the object has
365 been instantiated. Typically this is used for object validation or possibly
370 If you have a C<DEMOLISH> method anywhere in your inheritance hierarchy,
371 a C<DESTROY> method is created on first object construction which will call
372 C<< $instance->DEMOLISH($in_global_destruction) >> for each C<DEMOLISH>
373 method from child upwards to parents.
375 Note that the C<DESTROY> method is created on first construction of an object
376 of your class in order to not add overhead to classes without C<DEMOLISH>
377 methods; this may prove slightly surprising if you try and define your own.
381 if ($foo->does('Some::Role1')) {
385 Returns true if the object composes in the passed role.
387 =head1 IMPORTED SUBROUTINES
391 extends 'Parent::Class';
393 Declares base class. Multiple superclasses can be passed for multiple
394 inheritance (but please use roles instead).
396 Calling extends more than once will REPLACE your superclasses, not add to
397 them like 'use base' would.
405 with 'Some::Role1', 'Some::Role2';
407 Composes one or more L<Moo::Role> (or L<Role::Tiny>) roles into the current
408 class. An error will be raised if these roles have conflicting methods.
416 Declares an attribute for the class.
428 default => sub { "blah" },
431 Using the C<+> notation, it's possible to override an attribute.
433 The options for C<has> are as follows:
439 B<required>, may be C<ro>, C<lazy>, C<rwp> or C<rw>.
441 C<ro> generates an accessor that dies if you attempt to write to it - i.e.
442 a getter only - by defaulting C<reader> to the name of the attribute.
444 C<lazy> generates a reader like C<ro>, but also sets C<lazy> to 1 and
445 C<builder> to C<_build_${attribute_name}> to allow on-demand generated
446 attributes. This feature was my attempt to fix my incompetence when
447 originally designing C<lazy_build>, and is also implemented by
448 L<MooseX::AttributeShortcuts>. There is, however, nothing to stop you
449 using C<lazy> and C<builder> yourself with C<rwp> or C<rw> - it's just that
450 this isn't generally a good idea so we don't provide a shortcut for it.
452 C<rwp> generates a reader like C<ro>, but also sets C<writer> to
453 C<_set_${attribute_name}> for attributes that are designed to be written
454 from inside of the class, but read-only from outside.
455 This feature comes from L<MooseX::AttributeShortcuts>.
457 C<rw> generates a normal getter/setter by defaulting C<accessor> to the
458 name of the attribute.
462 Takes a coderef which is meant to validate the attribute. Unlike L<Moose>, Moo
463 does not include a basic type system, so instead of doing C<< isa => 'Num' >>,
467 die "$_[0] is not a number!" unless looks_like_number $_[0]
470 L<Sub::Quote aware|/SUB QUOTE AWARE>
472 Since L<Moo> does B<not> run the C<isa> check before C<coerce> if a coercion
473 subroutine has been supplied, C<isa> checks are not structural to your code
474 and can, if desired, be omitted on non-debug builds (although if this results
475 in an uncaught bug causing your program to break, the L<Moo> authors guarantee
476 nothing except that you get to keep both halves).
478 If you want L<MooseX::Types> style named types, look at
479 L<MooX::Types::MooseLike>.
481 To cause your C<isa> entries to be automatically mapped to named
482 L<Moose::Meta::TypeConstraint> objects (rather than the default behaviour
483 of creating an anonymous type), set:
485 $Moo::HandleMoose::TYPE_MAP{$isa_coderef} = sub {
486 require MooseX::Types::Something;
487 return MooseX::Types::Something::TypeName();
490 Note that this example is purely illustrative; anything that returns a
491 L<Moose::Meta::TypeConstraint> object or something similar enough to it to
492 make L<Moose> happy is fine.
496 Takes a coderef which is meant to coerce the attribute. The basic idea is to
497 do something like the following:
500 $_[0] + 1 unless $_[0] % 2
503 Note that L<Moo> will always fire your coercion: this is to permit
504 C<isa> entries to be used purely for bug trapping, whereas coercions are
505 always structural to your code. We do, however, apply any supplied C<isa>
506 check after the coercion has run to ensure that it returned a valid value.
508 L<Sub::Quote aware|/SUB QUOTE AWARE>
514 handles => 'RobotRole'
516 Where C<RobotRole> is a role (L<Moo::Role>) that defines an interface which
517 becomes the list of methods to handle.
519 Takes a list of methods
521 handles => [ qw( one two ) ]
531 Takes a coderef which will get called any time the attribute is set. This
532 includes the constructor, but not default or built values. Coderef will be
533 invoked against the object with the new value as an argument.
535 If you set this to just C<1>, it generates a trigger which calls the
536 C<_trigger_${attr_name}> method on C<$self>. This feature comes from
537 L<MooseX::AttributeShortcuts>.
539 Note that Moose also passes the old value, if any; this feature is not yet
542 L<Sub::Quote aware|/SUB QUOTE AWARE>
546 Takes a coderef which will get called with $self as its only argument
547 to populate an attribute if no value is supplied to the constructor - or
548 if the attribute is lazy, when the attribute is first retrieved if no
549 value has yet been provided.
551 If a simple scalar is provided, it will be inlined as a string. Any non-code
552 reference (hash, array) will result in an error - for that case instead use
553 a code reference that returns the desired value.
555 Note that if your default is fired during new() there is no guarantee that
556 other attributes have been populated yet so you should not rely on their
559 L<Sub::Quote aware|/SUB QUOTE AWARE>
563 Takes a method name which will return true if an attribute has a value.
565 If you set this to just C<1>, the predicate is automatically named
566 C<has_${attr_name}> if your attribute's name does not start with an
567 underscore, or C<_has_${attr_name_without_the_underscore}> if it does.
568 This feature comes from L<MooseX::AttributeShortcuts>.
572 Takes a method name which will be called to create the attribute - functions
573 exactly like default except that instead of calling
581 The following features come from L<MooseX::AttributeShortcuts>:
583 If you set this to just C<1>, the builder is automatically named
584 C<_build_${attr_name}>.
586 If you set this to a coderef or code-convertible object, that variable will be
587 installed under C<$class::_build_${attr_name}> and the builder set to the same
592 Takes a method name which will clear the attribute.
594 If you set this to just C<1>, the clearer is automatically named
595 C<clear_${attr_name}> if your attribute's name does not start with an
596 underscore, or <_clear_${attr_name_without_the_underscore}> if it does.
597 This feature comes from L<MooseX::AttributeShortcuts>.
601 B<Boolean>. Set this if you want values for the attribute to be grabbed
602 lazily. This is usually a good idea if you have a L</builder> which requires
603 another attribute to be set.
607 B<Boolean>. Set this if the attribute must be passed on instantiation.
611 The value of this attribute will be the name of the method to get the value of
612 the attribute. If you like Java style methods, you might set this to
617 The value of this attribute will be the name of the method to set the value of
618 the attribute. If you like Java style methods, you might set this to
623 B<Boolean>. Set this if you want the reference that the attribute contains to
624 be weakened; use this when circular references are possible, which will cause
629 Takes the name of the key to look for at instantiation time of the object. A
630 common use of this is to make an underscored attribute have a non-underscored
631 initialization name. C<undef> means that passing the value in on instantiation
638 before foo => sub { ... };
640 See L<< Class::Method::Modifiers/before method(s) => sub { ... } >> for full
645 around foo => sub { ... };
647 See L<< Class::Method::Modifiers/around method(s) => sub { ... } >> for full
652 after foo => sub { ... };
654 See L<< Class::Method::Modifiers/after method(s) => sub { ... } >> for full
657 =head1 SUB QUOTE AWARE
659 L<Sub::Quote/quote_sub> allows us to create coderefs that are "inlineable,"
660 giving us a handy, XS-free speed boost. Any option that is L<Sub::Quote>
661 aware can take advantage of this.
663 To do this, you can write
670 isa => quote_sub(q{ die "Not <3" unless $_[0] < 3 })
673 which will be inlined as
676 local @_ = ($_[0]->{foo});
677 die "Not <3" unless $_[0] < 3;
680 or to avoid localizing @_,
684 isa => quote_sub(q{ my ($val) = @_; die "Not <3" unless $val < 3 })
687 which will be inlined as
690 my ($val) = ($_[0]->{foo});
691 die "Not <3" unless $val < 3;
694 See L<Sub::Quote> for more information, including how to pass lexical
695 captures that will also be compiled into the subroutine.
697 =head1 INCOMPATIBILITIES WITH MOOSE
699 There is no built-in type system. C<isa> is verified with a coderef; if you
700 need complex types, just make a library of coderefs, or better yet, functions
701 that return quoted subs. L<MooX::Types::MooseLike> provides a similar API
702 to L<MooseX::Types::Moose> so that you can write
704 has days_to_live => (is => 'ro', isa => Int);
706 and have it work with both; it is hoped that providing only subrefs as an
707 API will encourage the use of other type systems as well, since it's
708 probably the weakest part of Moose design-wise.
710 C<initializer> is not supported in core since the author considers it to be a
711 bad idea and Moose best practices recommend avoiding it. Meanwhile C<trigger> or
712 C<coerce> are more likely to be able to fulfill your needs.
714 There is no meta object. If you need this level of complexity you wanted
715 L<Moose> - Moo succeeds at being small because it explicitly does not
716 provide a metaprotocol. However, if you load L<Moose>, then
718 Class::MOP::class_of($moo_class_or_role)
720 will return an appropriate metaclass pre-populated by L<Moo>.
722 No support for C<super>, C<override>, C<inner>, or C<augment> - the author
723 considers augment to be a bad idea, and override can be translated:
725 override foo => sub {
732 my ($orig, $self) = (shift, shift);
738 The C<dump> method is not provided by default. The author suggests loading
739 L<Devel::Dwarn> into C<main::> (via C<perl -MDevel::Dwarn ...> for example) and
740 using C<$obj-E<gt>$::Dwarn()> instead.
742 L</default> only supports coderefs and plain scalars, because passing a hash
743 or array reference as a default is almost always incorrect since the value is
744 then shared between all objects using that default.
746 C<lazy_build> is not supported; you are instead encouraged to use the
747 C<< is => 'lazy' >> option supported by L<Moo> and L<MooseX::AttributeShortcuts>.
749 C<auto_deref> is not supported since the author considers it a bad idea and
750 it has been considered best practice to avoid it for some time.
752 C<documentation> will show up in a L<Moose> metaclass created from your class
753 but is otherwise ignored. Then again, L<Moose> ignores it as well, so this
754 is arguably not an incompatibility.
756 Since C<coerce> does not require C<isa> to be defined but L<Moose> does
757 require it, the metaclass inflation for coerce alone is a trifle insane
758 and if you attempt to subtype the result will almost certainly break.
760 Handling of warnings: when you C<use Moo> we enable FATAL warnings. The nearest
761 similar invocation for L<Moose> would be:
764 use warnings FATAL => "all";
766 Additionally, L<Moo> supports a set of attribute option shortcuts intended to
767 reduce common boilerplate. The set of shortcuts is the same as in the L<Moose>
768 module L<MooseX::AttributeShortcuts> as of its version 0.009+. So if you:
773 The nearest L<Moose> invocation would be:
778 use warnings FATAL => "all";
779 use MooseX::AttributeShortcuts;
781 or, if you're inheriting from a non-Moose class,
786 use MooseX::NonMoose;
787 use warnings FATAL => "all";
788 use MooseX::AttributeShortcuts;
790 Finally, Moose requires you to call
792 __PACKAGE__->meta->make_immutable;
794 at the end of your class to get an inlined (i.e. not horribly slow)
795 constructor. Moo does it automatically the first time ->new is called
796 on your class. (C<make_immutable> is a no-op in Moo to ease migration.)
798 An extension L<MooX::late> exists to ease translating Moose packages
799 to Moo by providing a more Moose-like interface.
803 Users' IRC: #moose on irc.perl.org
805 =for html <a href="http://chat.mibbit.com/#moose@irc.perl.org">(click for instant chatroom login)</a>
807 Development and contribution IRC: #web-simple on irc.perl.org
809 =for html <a href="http://chat.mibbit.com/#web-simple@irc.perl.org">(click for instant chatroom login)</a>
811 Bugtracker: L<http://rt.cpan.org/NoAuth/Bugs.html?Dist=Moo>
813 Git repository: L<git://git.shadowcat.co.uk/gitmo/Moo.git>
815 Git web access: L<http://git.shadowcat.co.uk/gitweb/gitweb.cgi?p=gitmo/Moo.git>
819 mst - Matt S. Trout (cpan:MSTROUT) <mst@shadowcat.co.uk>
823 dg - David Leadbeater (cpan:DGL) <dgl@dgl.cx>
825 frew - Arthur Axel "fREW" Schmidt (cpan:FREW) <frioux@gmail.com>
827 hobbs - Andrew Rodland (cpan:ARODLAND) <arodland@cpan.org>
829 jnap - John Napiorkowski (cpan:JJNAPIORK) <jjn1056@yahoo.com>
831 ribasushi - Peter Rabbitson (cpan:RIBASUSHI) <ribasushi@cpan.org>
833 chip - Chip Salzenberg (cpan:CHIPS) <chip@pobox.com>
835 ajgb - Alex J. G. Burzyński (cpan:AJGB) <ajgb@cpan.org>
837 doy - Jesse Luehrs (cpan:DOY) <doy at tozt dot net>
839 perigrin - Chris Prather (cpan:PERIGRIN) <chris@prather.org>
841 Mithaldu - Christian Walde (cpan:MITHALDU) <walde.christian@googlemail.com>
843 ilmari - Dagfinn Ilmari Mannsåker (cpan:ILMARI) <ilmari@ilmari.org>
845 tobyink - Toby Inkster (cpan:TOBYINK) <tobyink@cpan.org>
847 haarg - Graham Knop (cpan:HAARG) <haarg@cpan.org>
849 mattp - Matt Phillips (cpan:MATTP) <mattp@cpan.org>
853 Copyright (c) 2010-2011 the Moo L</AUTHOR> and L</CONTRIBUTORS>
858 This library is free software and may be distributed under the same terms
859 as perl itself. See L<http://dev.perl.org/licenses/>.