8 our $VERSION = '1.000008'; # 1.0.8
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 ($foo->does('Some::Role1')) {
385 Returns true if the object composes in the passed role.
387 =head1 IMPORTED SUBROUTINES
391 extends 'Parent::Class';
393 Declares base class. Multiple superclasses can be passed for multiple
394 inheritance (but please use roles instead).
396 Calling extends more than once will REPLACE your superclasses, not add to
397 them like 'use base' would.
405 with 'Some::Role1', 'Some::Role2';
407 Composes one or more L<Moo::Role> (or L<Role::Tiny>) roles into the current
408 class. An error will be raised if these roles have conflicting methods.
416 Declares an attribute for the class.
418 The options for C<has> are as follows:
424 B<required>, may be C<ro>, C<lazy>, C<rwp> or C<rw>.
426 C<ro> generates an accessor that dies if you attempt to write to it - i.e.
427 a getter only - by defaulting C<reader> to the name of the attribute.
429 C<lazy> generates a reader like C<ro>, but also sets C<lazy> to 1 and
430 C<builder> to C<_build_${attribute_name}> to allow on-demand generated
431 attributes. This feature was my attempt to fix my incompetence when
432 originally designing C<lazy_build>, and is also implemented by
433 L<MooseX::AttributeShortcuts>. There is, however, nothing to stop you
434 using C<lazy> and C<builder> yourself with C<rwp> or C<rw> - it's just that
435 this isn't generally a good idea so we don't provide a shortcut for it.
437 C<rwp> generates a reader like C<ro>, but also sets C<writer> to
438 C<_set_${attribute_name}> for attributes that are designed to be written
439 from inside of the class, but read-only from outside.
440 This feature comes from L<MooseX::AttributeShortcuts>.
442 C<rw> generates a normal getter/setter by defaulting C<accessor> to the
443 name of the attribute.
447 Takes a coderef which is meant to validate the attribute. Unlike L<Moose>, Moo
448 does not include a basic type system, so instead of doing C<< isa => 'Num' >>,
452 die "$_[0] is not a number!" unless looks_like_number $_[0]
455 L<Sub::Quote aware|/SUB QUOTE AWARE>
457 Since L<Moo> does B<not> run the C<isa> check before C<coerce> if a coercion
458 subroutine has been supplied, C<isa> checks are not structural to your code
459 and can, if desired, be omitted on non-debug builds (although if this results
460 in an uncaught bug causing your program to break, the L<Moo> authors guarantee
461 nothing except that you get to keep both halves).
463 If you want L<MooseX::Types> style named types, look at
464 L<MooX::Types::MooseLike>.
466 To cause your C<isa> entries to be automatically mapped to named
467 L<Moose::Meta::TypeConstraint> objects (rather than the default behaviour
468 of creating an anonymous type), set:
470 $Moo::HandleMoose::TYPE_MAP{$isa_coderef} = sub {
471 require MooseX::Types::Something;
472 return MooseX::Types::Something::TypeName();
475 Note that this example is purely illustrative; anything that returns a
476 L<Moose::Meta::TypeConstraint> object or something similar enough to it to
477 make L<Moose> happy is fine.
481 Takes a coderef which is meant to coerce the attribute. The basic idea is to
482 do something like the following:
485 $_[0] + 1 unless $_[0] % 2
488 Note that L<Moo> will always fire your coercion: this is to permit
489 C<isa> entries to be used purely for bug trapping, whereas coercions are
490 always structural to your code. We do, however, apply any supplied C<isa>
491 check after the coercion has run to ensure that it returned a valid value.
493 L<Sub::Quote aware|/SUB QUOTE AWARE>
499 handles => 'RobotRole'
501 Where C<RobotRole> is a role (L<Moo::Role>) that defines an interface which
502 becomes the list of methods to handle.
504 Takes a list of methods
506 handles => [ qw( one two ) ]
516 Takes a coderef which will get called any time the attribute is set. This
517 includes the constructor, but not default or built values. Coderef will be
518 invoked against the object with the new value as an argument.
520 If you set this to just C<1>, it generates a trigger which calls the
521 C<_trigger_${attr_name}> method on C<$self>. This feature comes from
522 L<MooseX::AttributeShortcuts>.
524 Note that Moose also passes the old value, if any; this feature is not yet
527 L<Sub::Quote aware|/SUB QUOTE AWARE>
531 Takes a coderef which will get called with $self as its only argument
532 to populate an attribute if no value is supplied to the constructor - or
533 if the attribute is lazy, when the attribute is first retrieved if no
534 value has yet been provided.
536 Note that if your default is fired during new() there is no guarantee that
537 other attributes have been populated yet so you should not rely on their
540 L<Sub::Quote aware|/SUB QUOTE AWARE>
544 Takes a method name which will return true if an attribute has a value.
546 If you set this to just C<1>, the predicate is automatically named
547 C<has_${attr_name}> if your attribute's name does not start with an
548 underscore, or <_has_${attr_name_without_the_underscore}> if it does.
549 This feature comes from L<MooseX::AttributeShortcuts>.
553 Takes a method name which will be called to create the attribute - functions
554 exactly like default except that instead of calling
562 The following features come from L<MooseX::AttributeShortcuts>:
564 If you set this to just C<1>, the builder is automatically named
565 C<_build_${attr_name}>.
567 If you set this to a coderef or code-convertible object, that variable will be
568 installed under C<$class::_build_${attr_name}> and the builder set to the same
573 Takes a method name which will clear the attribute.
575 If you set this to just C<1>, the clearer is automatically named
576 C<clear_${attr_name}> if your attribute's name does not start with an
577 underscore, or <_clear_${attr_name_without_the_underscore}> if it does.
578 This feature comes from L<MooseX::AttributeShortcuts>.
582 B<Boolean>. Set this if you want values for the attribute to be grabbed
583 lazily. This is usually a good idea if you have a L</builder> which requires
584 another attribute to be set.
588 B<Boolean>. Set this if the attribute must be passed on instantiation.
592 The value of this attribute will be the name of the method to get the value of
593 the attribute. If you like Java style methods, you might set this to
598 The value of this attribute will be the name of the method to set the value of
599 the attribute. If you like Java style methods, you might set this to
604 B<Boolean>. Set this if you want the reference that the attribute contains to
605 be weakened; use this when circular references are possible, which will cause
610 Takes the name of the key to look for at instantiation time of the object. A
611 common use of this is to make an underscored attribute have a non-underscored
612 initialization name. C<undef> means that passing the value in on instantiation
619 before foo => sub { ... };
621 See L<< Class::Method::Modifiers/before method(s) => sub { ... } >> for full
626 around foo => sub { ... };
628 See L<< Class::Method::Modifiers/around method(s) => sub { ... } >> for full
633 after foo => sub { ... };
635 See L<< Class::Method::Modifiers/after method(s) => sub { ... } >> for full
638 =head1 SUB QUOTE AWARE
640 L<Sub::Quote/quote_sub> allows us to create coderefs that are "inlineable,"
641 giving us a handy, XS-free speed boost. Any option that is L<Sub::Quote>
642 aware can take advantage of this.
644 To do this, you can write
651 isa => quote_sub(q{ die "Not <3" unless $_[0] < 3 })
654 which will be inlined as
657 local @_ = ($_[0]->{foo});
658 die "Not <3" unless $_[0] < 3;
661 or to avoid localizing @_,
665 isa => quote_sub(q{ my ($val) = @_; die "Not <3" unless $val < 3 })
668 which will be inlined as
671 my ($val) = ($_[0]->{foo});
672 die "Not <3" unless $val < 3;
675 See L<Sub::Quote> for more information, including how to pass lexical
676 captures that will also be compiled into the subroutine.
678 =head1 INCOMPATIBILITIES WITH MOOSE
680 There is no built-in type system. C<isa> is verified with a coderef; if you
681 need complex types, just make a library of coderefs, or better yet, functions
682 that return quoted subs. L<MooX::Types::MooseLike> provides a similar API
683 to L<MooseX::Types::Moose> so that you can write
685 has days_to_live => (is => 'ro', isa => Int);
687 and have it work with both; it is hoped that providing only subrefs as an
688 API will encourage the use of other type systems as well, since it's
689 probably the weakest part of Moose design-wise.
691 C<initializer> is not supported in core since the author considers it to be a
692 bad idea but may be supported by an extension in future. Meanwhile C<trigger> or
693 C<coerce> are more likely to be able to fulfill your needs.
695 There is no meta object. If you need this level of complexity you wanted
696 L<Moose> - Moo succeeds at being small because it explicitly does not
697 provide a metaprotocol. However, if you load L<Moose>, then
699 Class::MOP::class_of($moo_class_or_role)
701 will return an appropriate metaclass pre-populated by L<Moo>.
703 No support for C<super>, C<override>, C<inner>, or C<augment> - the author
704 considers augment to be a bad idea, and override can be translated:
706 override foo => sub {
713 my ($orig, $self) = (shift, shift);
719 The C<dump> method is not provided by default. The author suggests loading
720 L<Devel::Dwarn> into C<main::> (via C<perl -MDevel::Dwarn ...> for example) and
721 using C<$obj-E<gt>$::Dwarn()> instead.
723 L</default> only supports coderefs, because doing otherwise is usually a
726 C<lazy_build> is not supported; you are instead encouraged to use the
727 C<< is => 'lazy' >> option supported by L<Moo> and L<MooseX::AttributeShortcuts>.
729 C<auto_deref> is not supported since the author considers it a bad idea.
731 C<documentation> will show up in a L<Moose> metaclass created from your class
732 but is otherwise ignored. Then again, L<Moose> ignores it as well, so this
733 is arguably not an incompatibility.
735 Since C<coerce> does not require C<isa> to be defined but L<Moose> does
736 require it, the metaclass inflation for coerce alone is a trifle insane
737 and if you attempt to subtype the result will almost certainly break.
739 Handling of warnings: when you C<use Moo> we enable FATAL warnings. The nearest
740 similar invocation for L<Moose> would be:
743 use warnings FATAL => "all";
745 Additionally, L<Moo> supports a set of attribute option shortcuts intended to
746 reduce common boilerplate. The set of shortcuts is the same as in the L<Moose>
747 module L<MooseX::AttributeShortcuts> as of its version 0.009+. So if you:
752 The nearest L<Moose> invocation would be:
757 use warnings FATAL => "all";
758 use MooseX::AttributeShortcuts;
760 or, if you're inheriting from a non-Moose class,
765 use MooseX::NonMoose;
766 use warnings FATAL => "all";
767 use MooseX::AttributeShortcuts;
769 Finally, Moose requires you to call
771 __PACKAGE__->meta->make_immutable;
773 at the end of your class to get an inlined (i.e. not horribly slow)
774 constructor. Moo does it automatically the first time ->new is called
777 An extension L<MooX::late> exists to ease translating Moose packages
778 to Moo by providing a more Moose-like interface.
782 Users' IRC: #moose on irc.perl.org
784 =for html <a href="http://chat.mibbit.com/#moose@irc.perl.org">(click for instant chatroom login)</a>
786 Development and contribution IRC: #web-simple on irc.perl.org
788 =for html <a href="http://chat.mibbit.com/#web-simple@irc.perl.org">(click for instant chatroom login)</a>
790 Bugtracker: L<http://rt.cpan.org/NoAuth/Bugs.html?Dist=Moo>
792 Git repository: L<git://git.shadowcat.co.uk/gitmo/Moo.git>
794 Git web access: L<http://git.shadowcat.co.uk/gitweb/gitweb.cgi?p=gitmo/Moo.git>
798 mst - Matt S. Trout (cpan:MSTROUT) <mst@shadowcat.co.uk>
802 dg - David Leadbeater (cpan:DGL) <dgl@dgl.cx>
804 frew - Arthur Axel "fREW" Schmidt (cpan:FREW) <frioux@gmail.com>
806 hobbs - Andrew Rodland (cpan:ARODLAND) <arodland@cpan.org>
808 jnap - John Napiorkowski (cpan:JJNAPIORK) <jjn1056@yahoo.com>
810 ribasushi - Peter Rabbitson (cpan:RIBASUSHI) <ribasushi@cpan.org>
812 chip - Chip Salzenberg (cpan:CHIPS) <chip@pobox.com>
814 ajgb - Alex J. G. Burzyński (cpan:AJGB) <ajgb@cpan.org>
816 doy - Jesse Luehrs (cpan:DOY) <doy at tozt dot net>
818 perigrin - Chris Prather (cpan:PERIGRIN) <chris@prather.org>
820 Mithaldu - Christian Walde (cpan:MITHALDU) <walde.christian@googlemail.com>
822 ilmari - Dagfinn Ilmari Mannsåker (cpan:ILMARI) <ilmari@ilmari.org>
824 tobyink - Toby Inkster (cpan:TOBYINK) <tobyink@cpan.org>
826 haarg - Graham Knop (cpan:HAARG) <haarg@cpan.org>
828 mattp - Matt Phillips (cpan:MATTP) <mattp@cpan.org>
832 Copyright (c) 2010-2011 the Moo L</AUTHOR> and L</CONTRIBUTORS>
837 This library is free software and may be distributed under the same terms
838 as perl itself. See L<http://dev.perl.org/licenses/>.