clean up docs on default and incompatibility
[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
4b025a84 8our $VERSION = '1.000008'; # 1.0.8
6d71fae7 9$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
191Moo - Minimalist Object Orientation (with Moose compatiblity)
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
a297a9ab 284Extending a L<Moose> class or consuming a L<Moose::Role> will also work.
1fce5bc9 285
a297a9ab 286So will extending a L<Mouse> class or consuming a L<Mouse::Role> - but note
287that we don't provide L<Mouse> metaclasses or metaroles so the other way
288around doesn't work. This feature exists for L<Any::Moose> users porting to
52e8f144 289L<Moo>; enabling L<Mouse> users to use L<Moo> classes is not a priority for us.
c100c04c 290
660f3db2 291This means that there is no need for anything like L<Any::Moose> for Moo
c100c04c 292code - Moo and Moose code should simply interoperate without problem. To
293handle L<Mouse> code, you'll likely need an empty Moo role or class consuming
294or extending the L<Mouse> stuff since it doesn't register true L<Moose>
71bd6a81 295metaclasses like L<Moo> does.
296
297If you want types to be upgraded to the L<Moose> types, use
298L<MooX::Types::MooseLike> and install the L<MooseX::Types> library to
299match the L<MooX::Types::MooseLike> library you're using - L<Moo> will
300load the L<MooseX::Types> library and use that type for the newly created
301metaclass.
660f3db2 302
1fce5bc9 303If you need to disable the metaclass creation, add:
304
305 no Moo::sification;
306
307to your code before Moose is loaded, but bear in mind that this switch is
a297a9ab 308currently global and turns the mechanism off entirely so don't put this
309in library code.
1fce5bc9 310
c687d016 311=head1 MOO VERSUS ANY::MOOSE
312
313L<Any::Moose> will load L<Mouse> normally, and L<Moose> in a program using
314L<Moose> - which theoretically allows you to get the startup time of L<Mouse>
315without disadvantaging L<Moose> users.
316
317Sadly, 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
319significantly more reliable.
320
321So if you want to write a CPAN module that loads fast or has only pure perl
322dependencies but is also fully usable by L<Moose> users, you should be using
323L<Moo>.
324
325For a full explanation, see the article
326L<http://shadow.cat/blog/matt-s-trout/moo-versus-any-moose> which explains
327the differing strategies in more detail and provides a direct example of
328where L<Moo> succeeds and L<Any::Moose> fails.
329
8146585e 330=head1 IMPORTED METHODS
331
332=head2 new
333
334 Foo::Bar->new( attr1 => 3 );
335
336or
337
338 Foo::Bar->new({ attr1 => 3 });
339
2e575bcd 340=head2 BUILDARGS
341
f2eac33e 342 sub BUILDARGS {
a17be455 343 my ( $class, @args ) = @_;
344
345 unshift @args, "attr1" if @args % 2 == 1;
346
f2eac33e 347 return { @args };
a17be455 348 };
349
350 Foo::Bar->new( 3 );
351
352The default implementation of this method accepts a hash or hash reference of
353named parameters. If it receives a single argument that isn't a hash reference
354it throws an error.
355
356You can override this method in your class to handle other types of options
357passed to the constructor.
358
359This method should always return a hash reference of named options.
2e575bcd 360
2d00f3d6 361=head2 BUILD
8146585e 362
2d00f3d6 363Define a C<BUILD> method on your class and the constructor will automatically
364call the C<BUILD> method from parent down to child after the object has
365been instantiated. Typically this is used for object validation or possibly
366logging.
8146585e 367
2d00f3d6 368=head2 DEMOLISH
c2cc003f 369
debb3fcd 370If you have a C<DEMOLISH> method anywhere in your inheritance hierarchy,
371a C<DESTROY> method is created on first object construction which will call
c2cc003f 372C<< $instance->DEMOLISH($in_global_destruction) >> for each C<DEMOLISH>
debb3fcd 373method from child upwards to parents.
374
375Note that the C<DESTROY> method is created on first construction of an object
376of your class in order to not add overhead to classes without C<DEMOLISH>
377methods; this may prove slightly surprising if you try and define your own.
c2cc003f 378
8146585e 379=head2 does
380
381 if ($foo->does('Some::Role1')) {
382 ...
383 }
384
385Returns true if the object composes in the passed role.
386
387=head1 IMPORTED SUBROUTINES
388
389=head2 extends
390
391 extends 'Parent::Class';
392
2e575bcd 393Declares base class. Multiple superclasses can be passed for multiple
394inheritance (but please use roles instead).
395
396Calling extends more than once will REPLACE your superclasses, not add to
397them like 'use base' would.
8146585e 398
399=head2 with
400
401 with 'Some::Role1';
8146585e 402
f9755246 403or
404
405 with 'Some::Role1', 'Some::Role2';
406
407Composes one or more L<Moo::Role> (or L<Role::Tiny>) roles into the current
408class. An error will be raised if these roles have conflicting methods.
8146585e 409
410=head2 has
411
412 has attr => (
413 is => 'ro',
414 );
415
416Declares an attribute for the class.
417
1c9916fa 418 package Foo;
419 use Moo;
420 has 'attr' => (
421 is => 'ro'
422 );
d56136b9 423
1c9916fa 424 package Bar;
425 use Moo;
426 extends 'Foo';
d56136b9 427 has '+attr' => (
428 default => sub { "blah" },
429 );
430
431Using the C<+> notation, it's possible to override an attribute.
432
8146585e 433The options for C<has> are as follows:
434
435=over 2
436
437=item * is
438
6577509a 439B<required>, may be C<ro>, C<lazy>, C<rwp> or C<rw>.
71db76ce 440
441C<ro> generates an accessor that dies if you attempt to write to it - i.e.
442a getter only - by defaulting C<reader> to the name of the attribute.
443
71db76ce 444C<lazy> generates a reader like C<ro>, but also sets C<lazy> to 1 and
445C<builder> to C<_build_${attribute_name}> to allow on-demand generated
446attributes. This feature was my attempt to fix my incompetence when
447originally designing C<lazy_build>, and is also implemented by
876b1e94 448L<MooseX::AttributeShortcuts>. There is, however, nothing to stop you
449using C<lazy> and C<builder> yourself with C<rwp> or C<rw> - it's just that
450this isn't generally a good idea so we don't provide a shortcut for it.
71db76ce 451
452C<rwp> generates a reader like C<ro>, but also sets C<writer> to
453C<_set_${attribute_name}> for attributes that are designed to be written
454from inside of the class, but read-only from outside.
455This feature comes from L<MooseX::AttributeShortcuts>.
8146585e 456
6577509a 457C<rw> generates a normal getter/setter by defaulting C<accessor> to the
458name of the attribute.
459
8146585e 460=item * isa
461
52e8f144 462Takes a coderef which is meant to validate the attribute. Unlike L<Moose>, Moo
8146585e 463does not include a basic type system, so instead of doing C<< isa => 'Num' >>,
464one should do
465
c9f73a63 466 isa => sub {
8146585e 467 die "$_[0] is not a number!" unless looks_like_number $_[0]
468 },
469
470L<Sub::Quote aware|/SUB QUOTE AWARE>
471
c4074652 472Since L<Moo> does B<not> run the C<isa> check before C<coerce> if a coercion
473subroutine has been supplied, C<isa> checks are not structural to your code
474and can, if desired, be omitted on non-debug builds (although if this results
475in an uncaught bug causing your program to break, the L<Moo> authors guarantee
476nothing except that you get to keep both halves).
477
71db76ce 478If you want L<MooseX::Types> style named types, look at
479L<MooX::Types::MooseLike>.
480
481To cause your C<isa> entries to be automatically mapped to named
482L<Moose::Meta::TypeConstraint> objects (rather than the default behaviour
483of creating an anonymous type), set:
484
485 $Moo::HandleMoose::TYPE_MAP{$isa_coderef} = sub {
486 require MooseX::Types::Something;
487 return MooseX::Types::Something::TypeName();
488 };
489
490Note that this example is purely illustrative; anything that returns a
491L<Moose::Meta::TypeConstraint> object or something similar enough to it to
492make L<Moose> happy is fine.
493
8146585e 494=item * coerce
495
496Takes a coderef which is meant to coerce the attribute. The basic idea is to
497do something like the following:
498
c9f73a63 499 coerce => sub {
8146585e 500 $_[0] + 1 unless $_[0] % 2
501 },
502
52e8f144 503Note that L<Moo> will always fire your coercion: this is to permit
504C<isa> entries to be used purely for bug trapping, whereas coercions are
c4074652 505always structural to your code. We do, however, apply any supplied C<isa>
506check after the coercion has run to ensure that it returned a valid value.
8146585e 507
23a3e34e 508L<Sub::Quote aware|/SUB QUOTE AWARE>
2e575bcd 509
e1efec09 510=item * handles
511
512Takes a string
513
69673ca7 514 handles => 'RobotRole'
515
516Where C<RobotRole> is a role (L<Moo::Role>) that defines an interface which
517becomes the list of methods to handle.
e1efec09 518
519Takes a list of methods
520
521 handles => [ qw( one two ) ]
522
523Takes a hashref
524
525 handles => {
526 un => 'one',
527 }
528
cc7ad717 529=item * C<trigger>
8146585e 530
6fe5100d 531Takes a coderef which will get called any time the attribute is set. This
cc7ad717 532includes the constructor, but not default or built values. Coderef will be
533invoked against the object with the new value as an argument.
8146585e 534
71db76ce 535If you set this to just C<1>, it generates a trigger which calls the
536C<_trigger_${attr_name}> method on C<$self>. This feature comes from
537L<MooseX::AttributeShortcuts>.
538
2e575bcd 539Note that Moose also passes the old value, if any; this feature is not yet
540supported.
541
8146585e 542L<Sub::Quote aware|/SUB QUOTE AWARE>
543
52e8f144 544=item * C<default>
8146585e 545
2e575bcd 546Takes a coderef which will get called with $self as its only argument
547to populate an attribute if no value is supplied to the constructor - or
548if the attribute is lazy, when the attribute is first retrieved if no
549value has yet been provided.
550
0e43f98f 551If a simple scalar is provided, it will be inlined as a string. Any non-code
552reference (hash, array) will result in an error - for that case instead use
553a code reference that returns the desired value.
554
2e575bcd 555Note that if your default is fired during new() there is no guarantee that
556other attributes have been populated yet so you should not rely on their
557existence.
8146585e 558
559L<Sub::Quote aware|/SUB QUOTE AWARE>
560
52e8f144 561=item * C<predicate>
8146585e 562
2e575bcd 563Takes a method name which will return true if an attribute has a value.
8146585e 564
71db76ce 565If you set this to just C<1>, the predicate is automatically named
566C<has_${attr_name}> if your attribute's name does not start with an
567underscore, or <_has_${attr_name_without_the_underscore}> if it does.
568This feature comes from L<MooseX::AttributeShortcuts>.
8146585e 569
52e8f144 570=item * C<builder>
8146585e 571
2e575bcd 572Takes a method name which will be called to create the attribute - functions
573exactly like default except that instead of calling
574
575 $default->($self);
576
577Moo will call
578
579 $self->$builder;
8146585e 580
4752c97b 581The following features come from L<MooseX::AttributeShortcuts>:
582
ba19b6a9 583If you set this to just C<1>, the builder is automatically named
4752c97b 584C<_build_${attr_name}>.
585
586If you set this to a coderef or code-convertible object, that variable will be
587installed under C<$class::_build_${attr_name}> and the builder set to the same
588name.
71db76ce 589
52e8f144 590=item * C<clearer>
8146585e 591
592Takes a method name which will clear the attribute.
593
71db76ce 594If you set this to just C<1>, the clearer is automatically named
595C<clear_${attr_name}> if your attribute's name does not start with an
596underscore, or <_clear_${attr_name_without_the_underscore}> if it does.
597This feature comes from L<MooseX::AttributeShortcuts>.
598
52e8f144 599=item * C<lazy>
8146585e 600
601B<Boolean>. Set this if you want values for the attribute to be grabbed
602lazily. This is usually a good idea if you have a L</builder> which requires
603another attribute to be set.
604
52e8f144 605=item * C<required>
8146585e 606
607B<Boolean>. Set this if the attribute must be passed on instantiation.
608
52e8f144 609=item * C<reader>
1eba910c 610
611The value of this attribute will be the name of the method to get the value of
612the attribute. If you like Java style methods, you might set this to
613C<get_foo>
614
52e8f144 615=item * C<writer>
1eba910c 616
617The value of this attribute will be the name of the method to set the value of
618the attribute. If you like Java style methods, you might set this to
52e8f144 619C<set_foo>.
1eba910c 620
52e8f144 621=item * C<weak_ref>
8146585e 622
623B<Boolean>. Set this if you want the reference that the attribute contains to
624be weakened; use this when circular references are possible, which will cause
625leaks.
626
52e8f144 627=item * C<init_arg>
8146585e 628
629Takes the name of the key to look for at instantiation time of the object. A
630common use of this is to make an underscored attribute have a non-underscored
631initialization name. C<undef> means that passing the value in on instantiation
71db76ce 632is ignored.
8146585e 633
634=back
635
636=head2 before
637
638 before foo => sub { ... };
639
640See L<< Class::Method::Modifiers/before method(s) => sub { ... } >> for full
641documentation.
642
643=head2 around
644
645 around foo => sub { ... };
646
647See L<< Class::Method::Modifiers/around method(s) => sub { ... } >> for full
648documentation.
649
650=head2 after
651
652 after foo => sub { ... };
653
654See L<< Class::Method::Modifiers/after method(s) => sub { ... } >> for full
655documentation.
656
8146585e 657=head1 SUB QUOTE AWARE
658
659L<Sub::Quote/quote_sub> allows us to create coderefs that are "inlineable,"
660giving us a handy, XS-free speed boost. Any option that is L<Sub::Quote>
661aware can take advantage of this.
662
c9f73a63 663To do this, you can write
664
665 use Moo;
666 use Sub::Quote;
667
668 has foo => (
3b4a915a 669 is => 'ro',
670 isa => quote_sub(q{ die "Not <3" unless $_[0] < 3 })
c9f73a63 671 );
672
673which will be inlined as
674
675 do {
676 local @_ = ($_[0]->{foo});
677 die "Not <3" unless $_[0] < 3;
678 }
679
680or to avoid localizing @_,
681
682 has foo => (
3b4a915a 683 is => 'ro',
684 isa => quote_sub(q{ my ($val) = @_; die "Not <3" unless $val < 3 })
c9f73a63 685 );
686
687which will be inlined as
688
689 do {
690 my ($val) = ($_[0]->{foo});
691 die "Not <3" unless $val < 3;
692 }
693
694See L<Sub::Quote> for more information, including how to pass lexical
52e8f144 695captures that will also be compiled into the subroutine.
c9f73a63 696
2e575bcd 697=head1 INCOMPATIBILITIES WITH MOOSE
8146585e 698
52e8f144 699There is no built-in type system. C<isa> is verified with a coderef; if you
8146585e 700need complex types, just make a library of coderefs, or better yet, functions
5902c1fc 701that return quoted subs. L<MooX::Types::MooseLike> provides a similar API
702to L<MooseX::Types::Moose> so that you can write
703
704 has days_to_live => (is => 'ro', isa => Int);
705
706and have it work with both; it is hoped that providing only subrefs as an
707API will encourage the use of other type systems as well, since it's
708probably the weakest part of Moose design-wise.
8146585e 709
2e575bcd 710C<initializer> is not supported in core since the author considers it to be a
0e43f98f 711bad idea and Moose best practices recommend avoiding it. Meanwhile C<trigger> or
f88623a1 712C<coerce> are more likely to be able to fulfill your needs.
8146585e 713
714There is no meta object. If you need this level of complexity you wanted
2e575bcd 715L<Moose> - Moo succeeds at being small because it explicitly does not
f9755246 716provide a metaprotocol. However, if you load L<Moose>, then
717
718 Class::MOP::class_of($moo_class_or_role)
719
720will return an appropriate metaclass pre-populated by L<Moo>.
8146585e 721
13e41b70 722No support for C<super>, C<override>, C<inner>, or C<augment> - the author
723considers augment to be a bad idea, and override can be translated:
724
725 override foo => sub {
726 ...
727 super();
728 ...
729 };
730
731 around foo => sub {
732 my ($orig, $self) = (shift, shift);
733 ...
734 $self->$orig(@_);
735 ...
736 };
8146585e 737
f2eac33e 738The C<dump> method is not provided by default. The author suggests loading
c96a6326 739L<Devel::Dwarn> into C<main::> (via C<perl -MDevel::Dwarn ...> for example) and
740using C<$obj-E<gt>$::Dwarn()> instead.
741
0e43f98f 742L</default> only supports coderefs and plain scalars, because passing a hash
743or array reference as a default is almost always incorrect since the value is
744then shared between all objects using that default.
8146585e 745
f9755246 746C<lazy_build> is not supported; you are instead encouraged to use the
52e8f144 747C<< is => 'lazy' >> option supported by L<Moo> and L<MooseX::AttributeShortcuts>.
8146585e 748
0e43f98f 749C<auto_deref> is not supported since the author considers it a bad idea and
750it has been considered best practice to avoid it for some time.
8146585e 751
f9755246 752C<documentation> will show up in a L<Moose> metaclass created from your class
c4074652 753but is otherwise ignored. Then again, L<Moose> ignores it as well, so this
f9755246 754is arguably not an incompatibility.
40f3e3aa 755
c4074652 756Since C<coerce> does not require C<isa> to be defined but L<Moose> does
52e8f144 757require it, the metaclass inflation for coerce alone is a trifle insane
c4074652 758and if you attempt to subtype the result will almost certainly break.
759
69673ca7 760Handling of warnings: when you C<use Moo> we enable FATAL warnings. The nearest
761similar invocation for L<Moose> would be:
762
763 use Moose;
764 use warnings FATAL => "all";
765
766Additionally, L<Moo> supports a set of attribute option shortcuts intended to
767reduce common boilerplate. The set of shortcuts is the same as in the L<Moose>
239d4711 768module L<MooseX::AttributeShortcuts> as of its version 0.009+. So if you:
69673ca7 769
770 package MyClass;
771 use Moo;
772
773The nearest L<Moose> invocation would be:
774
775 package MyClass;
776
777 use Moose;
778 use warnings FATAL => "all";
779 use MooseX::AttributeShortcuts;
780
5902c1fc 781or, if you're inheriting from a non-Moose class,
782
783 package MyClass;
784
785 use Moose;
786 use MooseX::NonMoose;
787 use warnings FATAL => "all";
788 use MooseX::AttributeShortcuts;
789
790Finally, Moose requires you to call
791
792 __PACKAGE__->meta->make_immutable;
793
794at the end of your class to get an inlined (i.e. not horribly slow)
795constructor. Moo does it automatically the first time ->new is called
796on your class.
797
6ad9aeab 798An extension L<MooX::late> exists to ease translating Moose packages
799to Moo by providing a more Moose-like interface.
800
660f3db2 801=head1 SUPPORT
802
cb21f16e 803Users' IRC: #moose on irc.perl.org
9836a6ee 804
cb21f16e 805=for html <a href="http://chat.mibbit.com/#moose@irc.perl.org">(click for instant chatroom login)</a>
806
807Development and contribution IRC: #web-simple on irc.perl.org
808
809=for html <a href="http://chat.mibbit.com/#web-simple@irc.perl.org">(click for instant chatroom login)</a>
072d158f 810
811Bugtracker: L<http://rt.cpan.org/NoAuth/Bugs.html?Dist=Moo>
812
813Git repository: L<git://git.shadowcat.co.uk/gitmo/Moo.git>
814
815Git web access: L<http://git.shadowcat.co.uk/gitweb/gitweb.cgi?p=gitmo/Moo.git>
660f3db2 816
40f3e3aa 817=head1 AUTHOR
818
819mst - Matt S. Trout (cpan:MSTROUT) <mst@shadowcat.co.uk>
820
821=head1 CONTRIBUTORS
822
5da684a2 823dg - David Leadbeater (cpan:DGL) <dgl@dgl.cx>
824
825frew - Arthur Axel "fREW" Schmidt (cpan:FREW) <frioux@gmail.com>
826
827hobbs - Andrew Rodland (cpan:ARODLAND) <arodland@cpan.org>
828
829jnap - John Napiorkowski (cpan:JJNAPIORK) <jjn1056@yahoo.com>
830
831ribasushi - Peter Rabbitson (cpan:RIBASUSHI) <ribasushi@cpan.org>
40f3e3aa 832
11f7a042 833chip - Chip Salzenberg (cpan:CHIPS) <chip@pobox.com>
834
a17be455 835ajgb - Alex J. G. Burzyński (cpan:AJGB) <ajgb@cpan.org>
836
7b8177f8 837doy - Jesse Luehrs (cpan:DOY) <doy at tozt dot net>
838
1fb2de92 839perigrin - Chris Prather (cpan:PERIGRIN) <chris@prather.org>
840
3202e039 841Mithaldu - Christian Walde (cpan:MITHALDU) <walde.christian@googlemail.com>
842
e355471c 843ilmari - Dagfinn Ilmari Mannsåker (cpan:ILMARI) <ilmari@ilmari.org>
844
1d17c7c1 845tobyink - Toby Inkster (cpan:TOBYINK) <tobyink@cpan.org>
846
d092b5ff 847haarg - Graham Knop (cpan:HAARG) <haarg@cpan.org>
848
80fd66d7 849mattp - Matt Phillips (cpan:MATTP) <mattp@cpan.org>
850
40f3e3aa 851=head1 COPYRIGHT
852
a958e36d 853Copyright (c) 2010-2011 the Moo L</AUTHOR> and L</CONTRIBUTORS>
40f3e3aa 854as listed above.
855
856=head1 LICENSE
857
858This library is free software and may be distributed under the same terms
072d158f 859as perl itself. See L<http://dev.perl.org/licenses/>.
40f3e3aa 860
861=cut