typo fix
[gitmo/Moo.git] / lib / Moo.pm
CommitLineData
b1eebd55 1package Moo;
6c74d087 2
3use strictures 1;
b1eebd55 4use Moo::_Utils;
e0e12d16 5use B 'perlstring';
a41e15c3 6use Sub::Defer ();
6c74d087 7
b35f7bd5 8our $VERSION = '1.001000'; # 1.1.0
6d71fae7 9$VERSION = eval $VERSION;
10
c2cb1fed 11require Moo::sification;
8c46a8f6 12
14f32032 13our %MAKERS;
14
108f8ddc 15sub _install_tracked {
16 my ($target, $name, $code) = @_;
17 $MAKERS{$target}{exports}{$name} = $code;
18 _install_coderef "${target}::${name}" => "Moo::${name}" => $code;
19}
20
6c74d087 21sub import {
22 my $target = caller;
a16d301e 23 my $class = shift;
de3d4906 24 strictures->import;
1791ba32 25 if ($Moo::Role::INFO{$target} and $Moo::Role::INFO{$target}{is_role}) {
26 die "Cannot import Moo into a role";
27 }
fa93bfb2 28 $MAKERS{$target} ||= {};
108f8ddc 29 _install_tracked $target => extends => sub {
48a51428 30 $class->_set_superclasses($target, @_);
6c49212f 31 $class->_maybe_reset_handlemoose($target);
3d49ee27 32 return;
6c74d087 33 };
108f8ddc 34 _install_tracked $target => with => sub {
faa9ce11 35 require Moo::Role;
6067158c 36 Moo::Role->apply_roles_to_package($target, @_);
6c49212f 37 $class->_maybe_reset_handlemoose($target);
6c74d087 38 };
108f8ddc 39 _install_tracked $target => has => sub {
1d17c7c1 40 my ($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);
51 }
3d49ee27 52 return;
14f32032 53 };
6c74d087 54 foreach my $type (qw(before after around)) {
108f8ddc 55 _install_tracked $target => $type => sub {
faa9ce11 56 require Class::Method::Modifiers;
6c74d087 57 _install_modifier($target, $type, @_);
3d49ee27 58 return;
6c74d087 59 };
60 }
fa93bfb2 61 return if $MAKERS{$target}{is_class}; # already exported into this package
62 $MAKERS{$target}{is_class} = 1;
6c74d087 63 {
64 no strict 'refs';
65 @{"${target}::ISA"} = do {
faa9ce11 66 require Moo::Object; ('Moo::Object');
6c74d087 67 } unless @{"${target}::ISA"};
68 }
3362e41c 69 if ($INC{'Moo/HandleMoose.pm'}) {
70 Moo::HandleMoose::inject_fake_metaclass_for($target);
71 }
6c74d087 72}
73
108f8ddc 74sub unimport {
75 my $target = caller;
76 _unimport_coderefs($target, $MAKERS{$target});
77}
78
48a51428 79sub _set_superclasses {
88aaa04a 80 my $class = shift;
81 my $target = shift;
141b507a 82 foreach my $superclass (@_) {
83 _load_module($superclass);
84 if ($INC{"Role/Tiny.pm"} && $Role::Tiny::INFO{$superclass}) {
88aaa04a 85 require Carp;
141b507a 86 Carp::croak("Can't extend role '$superclass'");
48a51428 87 }
88aaa04a 88 }
89 # Can't do *{...} = \@_ or 5.10.0's mro.pm stops seeing @ISA
90 @{*{_getglob("${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});
95 }
96 no warnings 'once'; # piss off. -- mst
97 $Moo::HandleMoose::MOUSE{$target} = [
98 grep defined, map Mouse::Util::find_meta($_), @_
96b09f21 99 ] if Mouse::Util->can('find_meta');
48a51428 100}
101
6c49212f 102sub _maybe_reset_handlemoose {
103 my ($class, $target) = @_;
104 if ($INC{"Moo/HandleMoose.pm"}) {
105 Moo::HandleMoose::maybe_reinject_fake_metaclass_for($target);
106 }
107}
108
02e9ef74 109sub _accessor_maker_for {
110 my ($class, $target) = @_;
111 return unless $MAKERS{$target};
112 $MAKERS{$target}{accessor} ||= do {
113 my $maker_class = do {
114 if (my $m = do {
115 if (my $defer_target =
116 (Sub::Defer::defer_info($target->can('new'))||[])->[0]
117 ) {
118 my ($pkg) = ($defer_target =~ /^(.*)::[^:]+$/);
119 $MAKERS{$pkg} && $MAKERS{$pkg}{accessor};
120 } else {
121 undef;
122 }
123 }) {
124 ref($m);
125 } else {
126 require Method::Generate::Accessor;
127 'Method::Generate::Accessor'
128 }
129 };
130 $maker_class->new;
131 }
132}
133
a16d301e 134sub _constructor_maker_for {
c4570291 135 my ($class, $target, $select_super) = @_;
a16d301e 136 return unless $MAKERS{$target};
137 $MAKERS{$target}{constructor} ||= do {
faa9ce11 138 require Method::Generate::Constructor;
139 require Sub::Defer;
c4570291 140 my ($moo_constructor, $con);
de5c0e53 141
c4570291 142 if ($select_super && $MAKERS{$select_super}) {
143 $moo_constructor = 1;
144 $con = $MAKERS{$select_super}{constructor};
145 } else {
de5c0e53 146 my $t_new = $target->can('new');
c4570291 147 if ($t_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 =~ /^(.*)::[^:]+$/);
152 if ($MAKERS{$pkg}) {
153 $moo_constructor = 1;
154 $con = $MAKERS{$pkg}{constructor};
155 }
156 }
157 } else {
158 $moo_constructor = 1; # no other constructor, make a Moo one
159 }
de5c0e53 160 };
02e9ef74 161 ($con ? ref($con) : 'Method::Generate::Constructor')
a16d301e 162 ->new(
163 package => $target,
02e9ef74 164 accessor_generator => $class->_accessor_maker_for($target),
53875e2c 165 construction_string => (
166 $moo_constructor
167 ? ($con ? $con->construction_string : undef)
e963cc96 168 : ('$class->'.$target.'::SUPER::new($class->can(q[FOREIGNBUILDARGS]) ? $class->FOREIGNBUILDARGS(@_) : @_)')
e0e12d16 169 ),
76ab3977 170 subconstructor_handler => (
171 ' if ($Moo::MAKERS{$class}) {'."\n"
172 .' '.$class.'->_constructor_maker_for($class,'.perlstring($target).');'."\n"
173 .' return $class->new(@_)'.";\n"
346177ba 174 .' } elsif ($INC{"Moose.pm"} and my $meta = Class::MOP::get_metaclass_by_name($class)) {'."\n"
eea41fb2 175 .' return $meta->new_object($class->BUILDARGS(@_));'."\n"
76ab3977 176 .' }'."\n"
e0e12d16 177 ),
a16d301e 178 )
179 ->install_delayed
de5c0e53 180 ->register_attribute_specs(%{$con?$con->all_attribute_specs:{}})
a16d301e 181 }
182}
183
6c74d087 1841;
a17be455 185=pod
186
187=encoding utf-8
8146585e 188
505f8b7a 189=head1 NAME
190
c1c6bd6d 191Moo - Minimalist Object Orientation (with Moose compatibility)
505f8b7a 192
8146585e 193=head1 SYNOPSIS
194
195 package Cat::Food;
196
197 use Moo;
8146585e 198
199 sub feed_lion {
200 my $self = shift;
201 my $amount = shift || 1;
202
203 $self->pounds( $self->pounds - $amount );
204 }
205
206 has taste => (
207 is => 'ro',
208 );
209
210 has brand => (
211 is => 'ro',
212 isa => sub {
213 die "Only SWEET-TREATZ supported!" unless $_[0] eq 'SWEET-TREATZ'
214 },
16382e05 215 );
8146585e 216
217 has pounds => (
218 is => 'rw',
c9f73a63 219 isa => sub { die "$_[0] is too much cat food!" unless $_[0] < 15 },
8146585e 220 );
221
222 1;
223
52e8f144 224And elsewhere:
8146585e 225
226 my $full = Cat::Food->new(
227 taste => 'DELICIOUS.',
228 brand => 'SWEET-TREATZ',
229 pounds => 10,
230 );
231
232 $full->feed_lion;
233
234 say $full->pounds;
235
236=head1 DESCRIPTION
237
71bd6a81 238This module is an extremely light-weight subset of L<Moose> optimised for
52e8f144 239rapid startup and "pay only for what you use".
71bd6a81 240
8146585e 241It also avoids depending on any XS modules to allow simple deployments. The
52e8f144 242name C<Moo> is based on the idea that it provides almost -- but not quite -- two
8146585e 243thirds of L<Moose>.
244
52e8f144 245Unlike L<Mouse> this module does not aim at full compatibility with
71bd6a81 246L<Moose>'s surface syntax, preferring instead of provide full interoperability
5f0ba39b 247via the metaclass inflation capabilities described in L</MOO AND MOOSE>.
71bd6a81 248
249For a full list of the minor differences between L<Moose> and L<Moo>'s surface
21717718 250syntax, see L</INCOMPATIBILITIES WITH MOOSE>.
8146585e 251
5d5bb71d 252=head1 WHY MOO EXISTS
253
254If you want a full object system with a rich Metaprotocol, L<Moose> is
255already wonderful.
256
71bd6a81 257However, sometimes you're writing a command line script or a CGI script
258where fast startup is essential, or code designed to be deployed as a single
259file via L<App::FatPacker>, or you're writing a CPAN module and you want it
260to be usable by people with those constraints.
261
5d5bb71d 262I've tried several times to use L<Mouse> but it's 3x the size of Moo and
263takes longer to load than most of my Moo based CGI scripts take to run.
264
265If you don't want L<Moose>, you don't want "less metaprotocol" like L<Mouse>,
52e8f144 266you want "as little as possible" -- which means "no metaprotocol", which is
5d5bb71d 267what Moo provides.
268
71bd6a81 269Better still, if you install and load L<Moose>, we set up metaclasses for your
270L<Moo> classes and L<Moo::Role> roles, so you can use them in L<Moose> code
271without ever noticing that some of your codebase is using L<Moo>.
5d5bb71d 272
52e8f144 273Hence, Moo exists as its name -- Minimal Object Orientation -- with a pledge
5d5bb71d 274to make it smooth to upgrade to L<Moose> when you need more than minimal
275features.
276
71bd6a81 277=head1 MOO AND MOOSE
1fce5bc9 278
279If L<Moo> detects L<Moose> being loaded, it will automatically register
280metaclasses for your L<Moo> and L<Moo::Role> packages, so you should be able
a297a9ab 281to use them in L<Moose> code without anybody ever noticing you aren't using
1fce5bc9 282L<Moose> everywhere.
283
9a3fc505 284L<Moo> will also create L<Moose type constraints|Moose::Manual::Types> for
285classes and roles, so that C<< isa => 'MyClass' >> and C<< isa => 'MyRole' >>
286work the same as for L<Moose> classes and roles.
287
a297a9ab 288Extending a L<Moose> class or consuming a L<Moose::Role> will also work.
1fce5bc9 289
a297a9ab 290So will extending a L<Mouse> class or consuming a L<Mouse::Role> - but note
291that we don't provide L<Mouse> metaclasses or metaroles so the other way
292around doesn't work. This feature exists for L<Any::Moose> users porting to
52e8f144 293L<Moo>; enabling L<Mouse> users to use L<Moo> classes is not a priority for us.
c100c04c 294
660f3db2 295This means that there is no need for anything like L<Any::Moose> for Moo
c100c04c 296code - Moo and Moose code should simply interoperate without problem. To
297handle L<Mouse> code, you'll likely need an empty Moo role or class consuming
298or extending the L<Mouse> stuff since it doesn't register true L<Moose>
71bd6a81 299metaclasses like L<Moo> does.
300
301If you want types to be upgraded to the L<Moose> types, use
302L<MooX::Types::MooseLike> and install the L<MooseX::Types> library to
303match the L<MooX::Types::MooseLike> library you're using - L<Moo> will
304load the L<MooseX::Types> library and use that type for the newly created
305metaclass.
660f3db2 306
1fce5bc9 307If you need to disable the metaclass creation, add:
308
309 no Moo::sification;
310
311to your code before Moose is loaded, but bear in mind that this switch is
a297a9ab 312currently global and turns the mechanism off entirely so don't put this
313in library code.
1fce5bc9 314
c687d016 315=head1 MOO VERSUS ANY::MOOSE
316
317L<Any::Moose> will load L<Mouse> normally, and L<Moose> in a program using
318L<Moose> - which theoretically allows you to get the startup time of L<Mouse>
319without disadvantaging L<Moose> users.
320
321Sadly, 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
323significantly more reliable.
324
325So if you want to write a CPAN module that loads fast or has only pure perl
326dependencies but is also fully usable by L<Moose> users, you should be using
327L<Moo>.
328
329For a full explanation, see the article
330L<http://shadow.cat/blog/matt-s-trout/moo-versus-any-moose> which explains
331the differing strategies in more detail and provides a direct example of
332where L<Moo> succeeds and L<Any::Moose> fails.
333
8146585e 334=head1 IMPORTED METHODS
335
336=head2 new
337
338 Foo::Bar->new( attr1 => 3 );
339
340or
341
342 Foo::Bar->new({ attr1 => 3 });
343
2e575bcd 344=head2 BUILDARGS
345
f2eac33e 346 sub BUILDARGS {
a17be455 347 my ( $class, @args ) = @_;
348
349 unshift @args, "attr1" if @args % 2 == 1;
350
f2eac33e 351 return { @args };
a17be455 352 };
353
354 Foo::Bar->new( 3 );
355
356The default implementation of this method accepts a hash or hash reference of
357named parameters. If it receives a single argument that isn't a hash reference
358it throws an error.
359
360You can override this method in your class to handle other types of options
361passed to the constructor.
362
363This method should always return a hash reference of named options.
2e575bcd 364
2d00f3d6 365=head2 BUILD
8146585e 366
2d00f3d6 367Define a C<BUILD> method on your class and the constructor will automatically
368call the C<BUILD> method from parent down to child after the object has
369been instantiated. Typically this is used for object validation or possibly
370logging.
8146585e 371
2d00f3d6 372=head2 DEMOLISH
c2cc003f 373
debb3fcd 374If you have a C<DEMOLISH> method anywhere in your inheritance hierarchy,
375a C<DESTROY> method is created on first object construction which will call
c2cc003f 376C<< $instance->DEMOLISH($in_global_destruction) >> for each C<DEMOLISH>
debb3fcd 377method from child upwards to parents.
378
379Note that the C<DESTROY> method is created on first construction of an object
380of your class in order to not add overhead to classes without C<DEMOLISH>
381methods; this may prove slightly surprising if you try and define your own.
c2cc003f 382
8146585e 383=head2 does
384
385 if ($foo->does('Some::Role1')) {
386 ...
387 }
388
389Returns true if the object composes in the passed role.
390
391=head1 IMPORTED SUBROUTINES
392
393=head2 extends
394
395 extends 'Parent::Class';
396
2e575bcd 397Declares base class. Multiple superclasses can be passed for multiple
398inheritance (but please use roles instead).
399
400Calling extends more than once will REPLACE your superclasses, not add to
401them like 'use base' would.
8146585e 402
403=head2 with
404
405 with 'Some::Role1';
8146585e 406
f9755246 407or
408
409 with 'Some::Role1', 'Some::Role2';
410
411Composes one or more L<Moo::Role> (or L<Role::Tiny>) roles into the current
412class. An error will be raised if these roles have conflicting methods.
8146585e 413
414=head2 has
415
416 has attr => (
417 is => 'ro',
418 );
419
420Declares an attribute for the class.
421
1c9916fa 422 package Foo;
423 use Moo;
424 has 'attr' => (
425 is => 'ro'
426 );
d56136b9 427
1c9916fa 428 package Bar;
429 use Moo;
430 extends 'Foo';
d56136b9 431 has '+attr' => (
432 default => sub { "blah" },
433 );
434
435Using the C<+> notation, it's possible to override an attribute.
436
8146585e 437The options for C<has> are as follows:
438
439=over 2
440
441=item * is
442
6577509a 443B<required>, may be C<ro>, C<lazy>, C<rwp> or C<rw>.
71db76ce 444
445C<ro> generates an accessor that dies if you attempt to write to it - i.e.
446a getter only - by defaulting C<reader> to the name of the attribute.
447
71db76ce 448C<lazy> generates a reader like C<ro>, but also sets C<lazy> to 1 and
449C<builder> to C<_build_${attribute_name}> to allow on-demand generated
450attributes. This feature was my attempt to fix my incompetence when
451originally designing C<lazy_build>, and is also implemented by
876b1e94 452L<MooseX::AttributeShortcuts>. There is, however, nothing to stop you
453using C<lazy> and C<builder> yourself with C<rwp> or C<rw> - it's just that
454this isn't generally a good idea so we don't provide a shortcut for it.
71db76ce 455
456C<rwp> generates a reader like C<ro>, but also sets C<writer> to
457C<_set_${attribute_name}> for attributes that are designed to be written
458from inside of the class, but read-only from outside.
459This feature comes from L<MooseX::AttributeShortcuts>.
8146585e 460
6577509a 461C<rw> generates a normal getter/setter by defaulting C<accessor> to the
462name of the attribute.
463
8146585e 464=item * isa
465
52e8f144 466Takes a coderef which is meant to validate the attribute. Unlike L<Moose>, Moo
8146585e 467does not include a basic type system, so instead of doing C<< isa => 'Num' >>,
468one should do
469
c9f73a63 470 isa => sub {
8146585e 471 die "$_[0] is not a number!" unless looks_like_number $_[0]
472 },
473
9a3fc505 474Note that the return value is ignored, only whether the sub lives or
475dies matters.
476
8146585e 477L<Sub::Quote aware|/SUB QUOTE AWARE>
478
c4074652 479Since L<Moo> does B<not> run the C<isa> check before C<coerce> if a coercion
480subroutine has been supplied, C<isa> checks are not structural to your code
481and can, if desired, be omitted on non-debug builds (although if this results
482in an uncaught bug causing your program to break, the L<Moo> authors guarantee
483nothing except that you get to keep both halves).
484
71db76ce 485If you want L<MooseX::Types> style named types, look at
486L<MooX::Types::MooseLike>.
487
488To cause your C<isa> entries to be automatically mapped to named
489L<Moose::Meta::TypeConstraint> objects (rather than the default behaviour
490of creating an anonymous type), set:
491
492 $Moo::HandleMoose::TYPE_MAP{$isa_coderef} = sub {
493 require MooseX::Types::Something;
494 return MooseX::Types::Something::TypeName();
495 };
496
497Note that this example is purely illustrative; anything that returns a
498L<Moose::Meta::TypeConstraint> object or something similar enough to it to
499make L<Moose> happy is fine.
500
8146585e 501=item * coerce
502
503Takes a coderef which is meant to coerce the attribute. The basic idea is to
504do something like the following:
505
c9f73a63 506 coerce => sub {
8146585e 507 $_[0] + 1 unless $_[0] % 2
508 },
509
52e8f144 510Note that L<Moo> will always fire your coercion: this is to permit
511C<isa> entries to be used purely for bug trapping, whereas coercions are
c4074652 512always structural to your code. We do, however, apply any supplied C<isa>
513check after the coercion has run to ensure that it returned a valid value.
8146585e 514
23a3e34e 515L<Sub::Quote aware|/SUB QUOTE AWARE>
2e575bcd 516
e1efec09 517=item * handles
518
519Takes a string
520
69673ca7 521 handles => 'RobotRole'
522
523Where C<RobotRole> is a role (L<Moo::Role>) that defines an interface which
524becomes the list of methods to handle.
e1efec09 525
526Takes a list of methods
527
528 handles => [ qw( one two ) ]
529
530Takes a hashref
531
532 handles => {
533 un => 'one',
534 }
535
cc7ad717 536=item * C<trigger>
8146585e 537
6fe5100d 538Takes a coderef which will get called any time the attribute is set. This
cc7ad717 539includes the constructor, but not default or built values. Coderef will be
540invoked against the object with the new value as an argument.
8146585e 541
71db76ce 542If you set this to just C<1>, it generates a trigger which calls the
543C<_trigger_${attr_name}> method on C<$self>. This feature comes from
544L<MooseX::AttributeShortcuts>.
545
2e575bcd 546Note that Moose also passes the old value, if any; this feature is not yet
547supported.
548
8146585e 549L<Sub::Quote aware|/SUB QUOTE AWARE>
550
52e8f144 551=item * C<default>
8146585e 552
2e575bcd 553Takes a coderef which will get called with $self as its only argument
554to populate an attribute if no value is supplied to the constructor - or
555if the attribute is lazy, when the attribute is first retrieved if no
556value has yet been provided.
557
0e43f98f 558If a simple scalar is provided, it will be inlined as a string. Any non-code
559reference (hash, array) will result in an error - for that case instead use
560a code reference that returns the desired value.
561
2e575bcd 562Note that if your default is fired during new() there is no guarantee that
563other attributes have been populated yet so you should not rely on their
564existence.
8146585e 565
566L<Sub::Quote aware|/SUB QUOTE AWARE>
567
52e8f144 568=item * C<predicate>
8146585e 569
2e575bcd 570Takes a method name which will return true if an attribute has a value.
8146585e 571
71db76ce 572If you set this to just C<1>, the predicate is automatically named
573C<has_${attr_name}> if your attribute's name does not start with an
157aa466 574underscore, or C<_has_${attr_name_without_the_underscore}> if it does.
71db76ce 575This feature comes from L<MooseX::AttributeShortcuts>.
8146585e 576
52e8f144 577=item * C<builder>
8146585e 578
2e575bcd 579Takes a method name which will be called to create the attribute - functions
580exactly like default except that instead of calling
581
582 $default->($self);
583
584Moo will call
585
586 $self->$builder;
8146585e 587
4752c97b 588The following features come from L<MooseX::AttributeShortcuts>:
589
ba19b6a9 590If you set this to just C<1>, the builder is automatically named
4752c97b 591C<_build_${attr_name}>.
592
593If you set this to a coderef or code-convertible object, that variable will be
594installed under C<$class::_build_${attr_name}> and the builder set to the same
595name.
71db76ce 596
52e8f144 597=item * C<clearer>
8146585e 598
599Takes a method name which will clear the attribute.
600
71db76ce 601If you set this to just C<1>, the clearer is automatically named
602C<clear_${attr_name}> if your attribute's name does not start with an
603underscore, or <_clear_${attr_name_without_the_underscore}> if it does.
604This feature comes from L<MooseX::AttributeShortcuts>.
605
52e8f144 606=item * C<lazy>
8146585e 607
608B<Boolean>. Set this if you want values for the attribute to be grabbed
609lazily. This is usually a good idea if you have a L</builder> which requires
610another attribute to be set.
611
52e8f144 612=item * C<required>
8146585e 613
614B<Boolean>. Set this if the attribute must be passed on instantiation.
615
52e8f144 616=item * C<reader>
1eba910c 617
618The value of this attribute will be the name of the method to get the value of
619the attribute. If you like Java style methods, you might set this to
620C<get_foo>
621
52e8f144 622=item * C<writer>
1eba910c 623
624The value of this attribute will be the name of the method to set the value of
625the attribute. If you like Java style methods, you might set this to
52e8f144 626C<set_foo>.
1eba910c 627
52e8f144 628=item * C<weak_ref>
8146585e 629
630B<Boolean>. Set this if you want the reference that the attribute contains to
631be weakened; use this when circular references are possible, which will cause
632leaks.
633
52e8f144 634=item * C<init_arg>
8146585e 635
636Takes the name of the key to look for at instantiation time of the object. A
637common use of this is to make an underscored attribute have a non-underscored
638initialization name. C<undef> means that passing the value in on instantiation
71db76ce 639is ignored.
8146585e 640
641=back
642
643=head2 before
644
645 before foo => sub { ... };
646
647See L<< Class::Method::Modifiers/before method(s) => sub { ... } >> for full
648documentation.
649
650=head2 around
651
652 around foo => sub { ... };
653
654See L<< Class::Method::Modifiers/around method(s) => sub { ... } >> for full
655documentation.
656
657=head2 after
658
659 after foo => sub { ... };
660
661See L<< Class::Method::Modifiers/after method(s) => sub { ... } >> for full
662documentation.
663
8146585e 664=head1 SUB QUOTE AWARE
665
666L<Sub::Quote/quote_sub> allows us to create coderefs that are "inlineable,"
667giving us a handy, XS-free speed boost. Any option that is L<Sub::Quote>
668aware can take advantage of this.
669
c9f73a63 670To do this, you can write
671
672 use Moo;
673 use Sub::Quote;
674
675 has foo => (
3b4a915a 676 is => 'ro',
677 isa => quote_sub(q{ die "Not <3" unless $_[0] < 3 })
c9f73a63 678 );
679
680which will be inlined as
681
682 do {
683 local @_ = ($_[0]->{foo});
684 die "Not <3" unless $_[0] < 3;
685 }
686
687or to avoid localizing @_,
688
689 has foo => (
3b4a915a 690 is => 'ro',
691 isa => quote_sub(q{ my ($val) = @_; die "Not <3" unless $val < 3 })
c9f73a63 692 );
693
694which will be inlined as
695
696 do {
697 my ($val) = ($_[0]->{foo});
698 die "Not <3" unless $val < 3;
699 }
700
701See L<Sub::Quote> for more information, including how to pass lexical
52e8f144 702captures that will also be compiled into the subroutine.
c9f73a63 703
2e575bcd 704=head1 INCOMPATIBILITIES WITH MOOSE
8146585e 705
52e8f144 706There is no built-in type system. C<isa> is verified with a coderef; if you
8146585e 707need complex types, just make a library of coderefs, or better yet, functions
5902c1fc 708that return quoted subs. L<MooX::Types::MooseLike> provides a similar API
709to L<MooseX::Types::Moose> so that you can write
710
711 has days_to_live => (is => 'ro', isa => Int);
712
713and have it work with both; it is hoped that providing only subrefs as an
714API will encourage the use of other type systems as well, since it's
715probably the weakest part of Moose design-wise.
8146585e 716
2e575bcd 717C<initializer> is not supported in core since the author considers it to be a
0e43f98f 718bad idea and Moose best practices recommend avoiding it. Meanwhile C<trigger> or
f88623a1 719C<coerce> are more likely to be able to fulfill your needs.
8146585e 720
721There is no meta object. If you need this level of complexity you wanted
2e575bcd 722L<Moose> - Moo succeeds at being small because it explicitly does not
f9755246 723provide a metaprotocol. However, if you load L<Moose>, then
724
725 Class::MOP::class_of($moo_class_or_role)
726
727will return an appropriate metaclass pre-populated by L<Moo>.
8146585e 728
13e41b70 729No support for C<super>, C<override>, C<inner>, or C<augment> - the author
730considers augment to be a bad idea, and override can be translated:
731
732 override foo => sub {
733 ...
734 super();
735 ...
736 };
737
738 around foo => sub {
739 my ($orig, $self) = (shift, shift);
740 ...
741 $self->$orig(@_);
742 ...
743 };
8146585e 744
f2eac33e 745The C<dump> method is not provided by default. The author suggests loading
c96a6326 746L<Devel::Dwarn> into C<main::> (via C<perl -MDevel::Dwarn ...> for example) and
747using C<$obj-E<gt>$::Dwarn()> instead.
748
0e43f98f 749L</default> only supports coderefs and plain scalars, because passing a hash
750or array reference as a default is almost always incorrect since the value is
751then shared between all objects using that default.
8146585e 752
f9755246 753C<lazy_build> is not supported; you are instead encouraged to use the
52e8f144 754C<< is => 'lazy' >> option supported by L<Moo> and L<MooseX::AttributeShortcuts>.
8146585e 755
0e43f98f 756C<auto_deref> is not supported since the author considers it a bad idea and
757it has been considered best practice to avoid it for some time.
8146585e 758
f9755246 759C<documentation> will show up in a L<Moose> metaclass created from your class
c4074652 760but is otherwise ignored. Then again, L<Moose> ignores it as well, so this
f9755246 761is arguably not an incompatibility.
40f3e3aa 762
c4074652 763Since C<coerce> does not require C<isa> to be defined but L<Moose> does
52e8f144 764require it, the metaclass inflation for coerce alone is a trifle insane
c4074652 765and if you attempt to subtype the result will almost certainly break.
766
69673ca7 767Handling of warnings: when you C<use Moo> we enable FATAL warnings. The nearest
768similar invocation for L<Moose> would be:
769
770 use Moose;
771 use warnings FATAL => "all";
772
773Additionally, L<Moo> supports a set of attribute option shortcuts intended to
774reduce common boilerplate. The set of shortcuts is the same as in the L<Moose>
239d4711 775module L<MooseX::AttributeShortcuts> as of its version 0.009+. So if you:
69673ca7 776
777 package MyClass;
778 use Moo;
779
780The nearest L<Moose> invocation would be:
781
782 package MyClass;
783
784 use Moose;
785 use warnings FATAL => "all";
786 use MooseX::AttributeShortcuts;
787
5902c1fc 788or, if you're inheriting from a non-Moose class,
789
790 package MyClass;
791
792 use Moose;
793 use MooseX::NonMoose;
794 use warnings FATAL => "all";
795 use MooseX::AttributeShortcuts;
796
797Finally, Moose requires you to call
798
799 __PACKAGE__->meta->make_immutable;
800
801at the end of your class to get an inlined (i.e. not horribly slow)
802constructor. Moo does it automatically the first time ->new is called
917f27ca 803on your class. (C<make_immutable> is a no-op in Moo to ease migration.)
5902c1fc 804
6ad9aeab 805An extension L<MooX::late> exists to ease translating Moose packages
806to Moo by providing a more Moose-like interface.
807
660f3db2 808=head1 SUPPORT
809
cb21f16e 810Users' IRC: #moose on irc.perl.org
9836a6ee 811
cb21f16e 812=for html <a href="http://chat.mibbit.com/#moose@irc.perl.org">(click for instant chatroom login)</a>
813
814Development and contribution IRC: #web-simple on irc.perl.org
815
816=for html <a href="http://chat.mibbit.com/#web-simple@irc.perl.org">(click for instant chatroom login)</a>
072d158f 817
818Bugtracker: L<http://rt.cpan.org/NoAuth/Bugs.html?Dist=Moo>
819
820Git repository: L<git://git.shadowcat.co.uk/gitmo/Moo.git>
821
822Git web access: L<http://git.shadowcat.co.uk/gitweb/gitweb.cgi?p=gitmo/Moo.git>
660f3db2 823
40f3e3aa 824=head1 AUTHOR
825
826mst - Matt S. Trout (cpan:MSTROUT) <mst@shadowcat.co.uk>
827
828=head1 CONTRIBUTORS
829
5da684a2 830dg - David Leadbeater (cpan:DGL) <dgl@dgl.cx>
831
832frew - Arthur Axel "fREW" Schmidt (cpan:FREW) <frioux@gmail.com>
833
834hobbs - Andrew Rodland (cpan:ARODLAND) <arodland@cpan.org>
835
836jnap - John Napiorkowski (cpan:JJNAPIORK) <jjn1056@yahoo.com>
837
838ribasushi - Peter Rabbitson (cpan:RIBASUSHI) <ribasushi@cpan.org>
40f3e3aa 839
11f7a042 840chip - Chip Salzenberg (cpan:CHIPS) <chip@pobox.com>
841
a17be455 842ajgb - Alex J. G. Burzyński (cpan:AJGB) <ajgb@cpan.org>
843
7b8177f8 844doy - Jesse Luehrs (cpan:DOY) <doy at tozt dot net>
845
1fb2de92 846perigrin - Chris Prather (cpan:PERIGRIN) <chris@prather.org>
847
3202e039 848Mithaldu - Christian Walde (cpan:MITHALDU) <walde.christian@googlemail.com>
849
e355471c 850ilmari - Dagfinn Ilmari Mannsåker (cpan:ILMARI) <ilmari@ilmari.org>
851
1d17c7c1 852tobyink - Toby Inkster (cpan:TOBYINK) <tobyink@cpan.org>
853
d092b5ff 854haarg - Graham Knop (cpan:HAARG) <haarg@cpan.org>
855
80fd66d7 856mattp - Matt Phillips (cpan:MATTP) <mattp@cpan.org>
857
40f3e3aa 858=head1 COPYRIGHT
859
a958e36d 860Copyright (c) 2010-2011 the Moo L</AUTHOR> and L</CONTRIBUTORS>
40f3e3aa 861as listed above.
862
863=head1 LICENSE
864
865This library is free software and may be distributed under the same terms
072d158f 866as perl itself. See L<http://dev.perl.org/licenses/>.
40f3e3aa 867
868=cut