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 L<Moo> will also create L<Moose type constraints|Moose::Manual::Types> for
285 classes and roles, so that C<< isa => 'MyClass' >> and C<< isa => 'MyRole' >>
286 work the same as for L<Moose> classes and roles.
288 Extending a L<Moose> class or consuming a L<Moose::Role> will also work.
290 So will extending a L<Mouse> class or consuming a L<Mouse::Role> - but note
291 that we don't provide L<Mouse> metaclasses or metaroles so the other way
292 around doesn't work. This feature exists for L<Any::Moose> users porting to
293 L<Moo>; enabling L<Mouse> users to use L<Moo> classes is not a priority for us.
295 This means that there is no need for anything like L<Any::Moose> for Moo
296 code - Moo and Moose code should simply interoperate without problem. To
297 handle L<Mouse> code, you'll likely need an empty Moo role or class consuming
298 or extending the L<Mouse> stuff since it doesn't register true L<Moose>
299 metaclasses like L<Moo> does.
301 If you want types to be upgraded to the L<Moose> types, use
302 L<MooX::Types::MooseLike> and install the L<MooseX::Types> library to
303 match the L<MooX::Types::MooseLike> library you're using - L<Moo> will
304 load the L<MooseX::Types> library and use that type for the newly created
307 If you need to disable the metaclass creation, add:
311 to your code before Moose is loaded, but bear in mind that this switch is
312 currently global and turns the mechanism off entirely so don't put this
315 =head1 MOO VERSUS ANY::MOOSE
317 L<Any::Moose> will load L<Mouse> normally, and L<Moose> in a program using
318 L<Moose> - which theoretically allows you to get the startup time of L<Mouse>
319 without disadvantaging L<Moose> users.
321 Sadly, this doesn't entirely work, since the selection is load order dependent
322 - L<Moo>'s metaclass inflation system explained above in L</MOO AND MOOSE> is
323 significantly more reliable.
325 So if you want to write a CPAN module that loads fast or has only pure perl
326 dependencies but is also fully usable by L<Moose> users, you should be using
329 For a full explanation, see the article
330 L<http://shadow.cat/blog/matt-s-trout/moo-versus-any-moose> which explains
331 the differing strategies in more detail and provides a direct example of
332 where L<Moo> succeeds and L<Any::Moose> fails.
334 =head1 IMPORTED METHODS
338 Foo::Bar->new( attr1 => 3 );
342 Foo::Bar->new({ attr1 => 3 });
347 my ( $class, @args ) = @_;
349 unshift @args, "attr1" if @args % 2 == 1;
356 The default implementation of this method accepts a hash or hash reference of
357 named parameters. If it receives a single argument that isn't a hash reference
360 You can override this method in your class to handle other types of options
361 passed to the constructor.
363 This method should always return a hash reference of named options.
367 Define a C<BUILD> method on your class and the constructor will automatically
368 call the C<BUILD> method from parent down to child after the object has
369 been instantiated. Typically this is used for object validation or possibly
374 If you have a C<DEMOLISH> method anywhere in your inheritance hierarchy,
375 a C<DESTROY> method is created on first object construction which will call
376 C<< $instance->DEMOLISH($in_global_destruction) >> for each C<DEMOLISH>
377 method from child upwards to parents.
379 Note that the C<DESTROY> method is created on first construction of an object
380 of your class in order to not add overhead to classes without C<DEMOLISH>
381 methods; this may prove slightly surprising if you try and define your own.
385 if ($foo->does('Some::Role1')) {
389 Returns true if the object composes in the passed role.
391 =head1 IMPORTED SUBROUTINES
395 extends 'Parent::Class';
397 Declares base class. Multiple superclasses can be passed for multiple
398 inheritance (but please use roles instead).
400 Calling extends more than once will REPLACE your superclasses, not add to
401 them like 'use base' would.
409 with 'Some::Role1', 'Some::Role2';
411 Composes one or more L<Moo::Role> (or L<Role::Tiny>) roles into the current
412 class. An error will be raised if these roles have conflicting methods.
420 Declares an attribute for the class.
432 default => sub { "blah" },
435 Using the C<+> notation, it's possible to override an attribute.
437 The options for C<has> are as follows:
443 B<required>, may be C<ro>, C<lazy>, C<rwp> or C<rw>.
445 C<ro> generates an accessor that dies if you attempt to write to it - i.e.
446 a getter only - by defaulting C<reader> to the name of the attribute.
448 C<lazy> generates a reader like C<ro>, but also sets C<lazy> to 1 and
449 C<builder> to C<_build_${attribute_name}> to allow on-demand generated
450 attributes. This feature was my attempt to fix my incompetence when
451 originally designing C<lazy_build>, and is also implemented by
452 L<MooseX::AttributeShortcuts>. There is, however, nothing to stop you
453 using C<lazy> and C<builder> yourself with C<rwp> or C<rw> - it's just that
454 this isn't generally a good idea so we don't provide a shortcut for it.
456 C<rwp> generates a reader like C<ro>, but also sets C<writer> to
457 C<_set_${attribute_name}> for attributes that are designed to be written
458 from inside of the class, but read-only from outside.
459 This feature comes from L<MooseX::AttributeShortcuts>.
461 C<rw> generates a normal getter/setter by defaulting C<accessor> to the
462 name of the attribute.
466 Takes a coderef which is meant to validate the attribute. Unlike L<Moose>, Moo
467 does not include a basic type system, so instead of doing C<< isa => 'Num' >>,
471 die "$_[0] is not a number!" unless looks_like_number $_[0]
474 Note that the return value is ignored, only whether the sub lives or
477 L<Sub::Quote aware|/SUB QUOTE AWARE>
479 Since L<Moo> does B<not> run the C<isa> check before C<coerce> if a coercion
480 subroutine has been supplied, C<isa> checks are not structural to your code
481 and can, if desired, be omitted on non-debug builds (although if this results
482 in an uncaught bug causing your program to break, the L<Moo> authors guarantee
483 nothing except that you get to keep both halves).
485 If you want L<MooseX::Types> style named types, look at
486 L<MooX::Types::MooseLike>.
488 To cause your C<isa> entries to be automatically mapped to named
489 L<Moose::Meta::TypeConstraint> objects (rather than the default behaviour
490 of creating an anonymous type), set:
492 $Moo::HandleMoose::TYPE_MAP{$isa_coderef} = sub {
493 require MooseX::Types::Something;
494 return MooseX::Types::Something::TypeName();
497 Note that this example is purely illustrative; anything that returns a
498 L<Moose::Meta::TypeConstraint> object or something similar enough to it to
499 make L<Moose> happy is fine.
503 Takes a coderef which is meant to coerce the attribute. The basic idea is to
504 do something like the following:
507 $_[0] + 1 unless $_[0] % 2
510 Note that L<Moo> will always fire your coercion: this is to permit
511 C<isa> entries to be used purely for bug trapping, whereas coercions are
512 always structural to your code. We do, however, apply any supplied C<isa>
513 check after the coercion has run to ensure that it returned a valid value.
515 L<Sub::Quote aware|/SUB QUOTE AWARE>
521 handles => 'RobotRole'
523 Where C<RobotRole> is a role (L<Moo::Role>) that defines an interface which
524 becomes the list of methods to handle.
526 Takes a list of methods
528 handles => [ qw( one two ) ]
538 Takes a coderef which will get called any time the attribute is set. This
539 includes the constructor, but not default or built values. Coderef will be
540 invoked against the object with the new value as an argument.
542 If you set this to just C<1>, it generates a trigger which calls the
543 C<_trigger_${attr_name}> method on C<$self>. This feature comes from
544 L<MooseX::AttributeShortcuts>.
546 Note that Moose also passes the old value, if any; this feature is not yet
549 L<Sub::Quote aware|/SUB QUOTE AWARE>
553 Takes a coderef which will get called with $self as its only argument
554 to populate an attribute if no value is supplied to the constructor - or
555 if the attribute is lazy, when the attribute is first retrieved if no
556 value has yet been provided.
558 If a simple scalar is provided, it will be inlined as a string. Any non-code
559 reference (hash, array) will result in an error - for that case instead use
560 a code reference that returns the desired value.
562 Note that if your default is fired during new() there is no guarantee that
563 other attributes have been populated yet so you should not rely on their
566 L<Sub::Quote aware|/SUB QUOTE AWARE>
570 Takes a method name which will return true if an attribute has a value.
572 If you set this to just C<1>, the predicate is automatically named
573 C<has_${attr_name}> if your attribute's name does not start with an
574 underscore, or C<_has_${attr_name_without_the_underscore}> if it does.
575 This feature comes from L<MooseX::AttributeShortcuts>.
579 Takes a method name which will be called to create the attribute - functions
580 exactly like default except that instead of calling
588 The following features come from L<MooseX::AttributeShortcuts>:
590 If you set this to just C<1>, the builder is automatically named
591 C<_build_${attr_name}>.
593 If you set this to a coderef or code-convertible object, that variable will be
594 installed under C<$class::_build_${attr_name}> and the builder set to the same
599 Takes a method name which will clear the attribute.
601 If you set this to just C<1>, the clearer is automatically named
602 C<clear_${attr_name}> if your attribute's name does not start with an
603 underscore, or <_clear_${attr_name_without_the_underscore}> if it does.
604 This feature comes from L<MooseX::AttributeShortcuts>.
608 B<Boolean>. Set this if you want values for the attribute to be grabbed
609 lazily. This is usually a good idea if you have a L</builder> which requires
610 another attribute to be set.
614 B<Boolean>. Set this if the attribute must be passed on instantiation.
618 The value of this attribute will be the name of the method to get the value of
619 the attribute. If you like Java style methods, you might set this to
624 The value of this attribute will be the name of the method to set the value of
625 the attribute. If you like Java style methods, you might set this to
630 B<Boolean>. Set this if you want the reference that the attribute contains to
631 be weakened; use this when circular references are possible, which will cause
636 Takes the name of the key to look for at instantiation time of the object. A
637 common use of this is to make an underscored attribute have a non-underscored
638 initialization name. C<undef> means that passing the value in on instantiation
645 before foo => sub { ... };
647 See L<< Class::Method::Modifiers/before method(s) => sub { ... } >> for full
652 around foo => sub { ... };
654 See L<< Class::Method::Modifiers/around method(s) => sub { ... } >> for full
659 after foo => sub { ... };
661 See L<< Class::Method::Modifiers/after method(s) => sub { ... } >> for full
664 =head1 SUB QUOTE AWARE
666 L<Sub::Quote/quote_sub> allows us to create coderefs that are "inlineable,"
667 giving us a handy, XS-free speed boost. Any option that is L<Sub::Quote>
668 aware can take advantage of this.
670 To do this, you can write
677 isa => quote_sub(q{ die "Not <3" unless $_[0] < 3 })
680 which will be inlined as
683 local @_ = ($_[0]->{foo});
684 die "Not <3" unless $_[0] < 3;
687 or to avoid localizing @_,
691 isa => quote_sub(q{ my ($val) = @_; die "Not <3" unless $val < 3 })
694 which will be inlined as
697 my ($val) = ($_[0]->{foo});
698 die "Not <3" unless $val < 3;
701 See L<Sub::Quote> for more information, including how to pass lexical
702 captures that will also be compiled into the subroutine.
704 =head1 INCOMPATIBILITIES WITH MOOSE
706 There is no built-in type system. C<isa> is verified with a coderef; if you
707 need complex types, just make a library of coderefs, or better yet, functions
708 that return quoted subs. L<MooX::Types::MooseLike> provides a similar API
709 to L<MooseX::Types::Moose> so that you can write
711 has days_to_live => (is => 'ro', isa => Int);
713 and have it work with both; it is hoped that providing only subrefs as an
714 API will encourage the use of other type systems as well, since it's
715 probably the weakest part of Moose design-wise.
717 C<initializer> is not supported in core since the author considers it to be a
718 bad idea and Moose best practices recommend avoiding it. Meanwhile C<trigger> or
719 C<coerce> are more likely to be able to fulfill your needs.
721 There is no meta object. If you need this level of complexity you wanted
722 L<Moose> - Moo succeeds at being small because it explicitly does not
723 provide a metaprotocol. However, if you load L<Moose>, then
725 Class::MOP::class_of($moo_class_or_role)
727 will return an appropriate metaclass pre-populated by L<Moo>.
729 No support for C<super>, C<override>, C<inner>, or C<augment> - the author
730 considers augment to be a bad idea, and override can be translated:
732 override foo => sub {
739 my ($orig, $self) = (shift, shift);
745 The C<dump> method is not provided by default. The author suggests loading
746 L<Devel::Dwarn> into C<main::> (via C<perl -MDevel::Dwarn ...> for example) and
747 using C<$obj-E<gt>$::Dwarn()> instead.
749 L</default> only supports coderefs and plain scalars, because passing a hash
750 or array reference as a default is almost always incorrect since the value is
751 then shared between all objects using that default.
753 C<lazy_build> is not supported; you are instead encouraged to use the
754 C<< is => 'lazy' >> option supported by L<Moo> and L<MooseX::AttributeShortcuts>.
756 C<auto_deref> is not supported since the author considers it a bad idea and
757 it has been considered best practice to avoid it for some time.
759 C<documentation> will show up in a L<Moose> metaclass created from your class
760 but is otherwise ignored. Then again, L<Moose> ignores it as well, so this
761 is arguably not an incompatibility.
763 Since C<coerce> does not require C<isa> to be defined but L<Moose> does
764 require it, the metaclass inflation for coerce alone is a trifle insane
765 and if you attempt to subtype the result will almost certainly break.
767 Handling of warnings: when you C<use Moo> we enable FATAL warnings. The nearest
768 similar invocation for L<Moose> would be:
771 use warnings FATAL => "all";
773 Additionally, L<Moo> supports a set of attribute option shortcuts intended to
774 reduce common boilerplate. The set of shortcuts is the same as in the L<Moose>
775 module L<MooseX::AttributeShortcuts> as of its version 0.009+. So if you:
780 The nearest L<Moose> invocation would be:
785 use warnings FATAL => "all";
786 use MooseX::AttributeShortcuts;
788 or, if you're inheriting from a non-Moose class,
793 use MooseX::NonMoose;
794 use warnings FATAL => "all";
795 use MooseX::AttributeShortcuts;
797 Finally, Moose requires you to call
799 __PACKAGE__->meta->make_immutable;
801 at the end of your class to get an inlined (i.e. not horribly slow)
802 constructor. Moo does it automatically the first time ->new is called
803 on your class. (C<make_immutable> is a no-op in Moo to ease migration.)
805 An extension L<MooX::late> exists to ease translating Moose packages
806 to Moo by providing a more Moose-like interface.
810 Users' IRC: #moose on irc.perl.org
812 =for html <a href="http://chat.mibbit.com/#moose@irc.perl.org">(click for instant chatroom login)</a>
814 Development and contribution IRC: #web-simple on irc.perl.org
816 =for html <a href="http://chat.mibbit.com/#web-simple@irc.perl.org">(click for instant chatroom login)</a>
818 Bugtracker: L<http://rt.cpan.org/NoAuth/Bugs.html?Dist=Moo>
820 Git repository: L<git://git.shadowcat.co.uk/gitmo/Moo.git>
822 Git web access: L<http://git.shadowcat.co.uk/gitweb/gitweb.cgi?p=gitmo/Moo.git>
826 mst - Matt S. Trout (cpan:MSTROUT) <mst@shadowcat.co.uk>
830 dg - David Leadbeater (cpan:DGL) <dgl@dgl.cx>
832 frew - Arthur Axel "fREW" Schmidt (cpan:FREW) <frioux@gmail.com>
834 hobbs - Andrew Rodland (cpan:ARODLAND) <arodland@cpan.org>
836 jnap - John Napiorkowski (cpan:JJNAPIORK) <jjn1056@yahoo.com>
838 ribasushi - Peter Rabbitson (cpan:RIBASUSHI) <ribasushi@cpan.org>
840 chip - Chip Salzenberg (cpan:CHIPS) <chip@pobox.com>
842 ajgb - Alex J. G. Burzyński (cpan:AJGB) <ajgb@cpan.org>
844 doy - Jesse Luehrs (cpan:DOY) <doy at tozt dot net>
846 perigrin - Chris Prather (cpan:PERIGRIN) <chris@prather.org>
848 Mithaldu - Christian Walde (cpan:MITHALDU) <walde.christian@googlemail.com>
850 ilmari - Dagfinn Ilmari Mannsåker (cpan:ILMARI) <ilmari@ilmari.org>
852 tobyink - Toby Inkster (cpan:TOBYINK) <tobyink@cpan.org>
854 haarg - Graham Knop (cpan:HAARG) <haarg@cpan.org>
856 mattp - Matt Phillips (cpan:MATTP) <mattp@cpan.org>
860 Copyright (c) 2010-2011 the Moo L</AUTHOR> and L</CONTRIBUTORS>
865 This library is free software and may be distributed under the same terms
866 as perl itself. See L<http://dev.perl.org/licenses/>.