handles => "RoleName" should try to load the module
[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 ? $con->construction_string : undef)
168 : ('$class->'.$target.'::SUPER::new(@_)')
e0e12d16 169 ),
76ab3977 170 subconstructor_handler => (
171 ' if ($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 $_[0] eq 'SWEET-TREATZ'
214 },
215);
216
217 has pounds => (
218 is => 'rw',
c9f73a63 219 isa => sub { die "$_[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 ($foo->does('Some::Role1')) {
382 ...
383 }
384
385Returns true if the object composes in the passed role.
386
387=head1 IMPORTED SUBROUTINES
388
389=head2 extends
390
391 extends 'Parent::Class';
392
2e575bcd 393Declares base class. Multiple superclasses can be passed for multiple
394inheritance (but please use roles instead).
395
396Calling extends more than once will REPLACE your superclasses, not add to
397them like 'use base' would.
8146585e 398
399=head2 with
400
401 with 'Some::Role1';
8146585e 402
f9755246 403or
404
405 with 'Some::Role1', 'Some::Role2';
406
407Composes one or more L<Moo::Role> (or L<Role::Tiny>) roles into the current
408class. An error will be raised if these roles have conflicting methods.
8146585e 409
410=head2 has
411
412 has attr => (
413 is => 'ro',
414 );
415
416Declares an attribute for the class.
417
418The options for C<has> are as follows:
419
420=over 2
421
422=item * is
423
6577509a 424B<required>, may be C<ro>, C<lazy>, C<rwp> or C<rw>.
71db76ce 425
426C<ro> generates an accessor that dies if you attempt to write to it - i.e.
427a getter only - by defaulting C<reader> to the name of the attribute.
428
71db76ce 429C<lazy> generates a reader like C<ro>, but also sets C<lazy> to 1 and
430C<builder> to C<_build_${attribute_name}> to allow on-demand generated
431attributes. This feature was my attempt to fix my incompetence when
432originally designing C<lazy_build>, and is also implemented by
433L<MooseX::AttributeShortcuts>.
434
435C<rwp> generates a reader like C<ro>, but also sets C<writer> to
436C<_set_${attribute_name}> for attributes that are designed to be written
437from inside of the class, but read-only from outside.
438This feature comes from L<MooseX::AttributeShortcuts>.
8146585e 439
6577509a 440C<rw> generates a normal getter/setter by defaulting C<accessor> to the
441name of the attribute.
442
8146585e 443=item * isa
444
52e8f144 445Takes a coderef which is meant to validate the attribute. Unlike L<Moose>, Moo
8146585e 446does not include a basic type system, so instead of doing C<< isa => 'Num' >>,
447one should do
448
c9f73a63 449 isa => sub {
8146585e 450 die "$_[0] is not a number!" unless looks_like_number $_[0]
451 },
452
453L<Sub::Quote aware|/SUB QUOTE AWARE>
454
c4074652 455Since L<Moo> does B<not> run the C<isa> check before C<coerce> if a coercion
456subroutine has been supplied, C<isa> checks are not structural to your code
457and can, if desired, be omitted on non-debug builds (although if this results
458in an uncaught bug causing your program to break, the L<Moo> authors guarantee
459nothing except that you get to keep both halves).
460
71db76ce 461If you want L<MooseX::Types> style named types, look at
462L<MooX::Types::MooseLike>.
463
464To cause your C<isa> entries to be automatically mapped to named
465L<Moose::Meta::TypeConstraint> objects (rather than the default behaviour
466of creating an anonymous type), set:
467
468 $Moo::HandleMoose::TYPE_MAP{$isa_coderef} = sub {
469 require MooseX::Types::Something;
470 return MooseX::Types::Something::TypeName();
471 };
472
473Note that this example is purely illustrative; anything that returns a
474L<Moose::Meta::TypeConstraint> object or something similar enough to it to
475make L<Moose> happy is fine.
476
8146585e 477=item * coerce
478
479Takes a coderef which is meant to coerce the attribute. The basic idea is to
480do something like the following:
481
c9f73a63 482 coerce => sub {
8146585e 483 $_[0] + 1 unless $_[0] % 2
484 },
485
52e8f144 486Note that L<Moo> will always fire your coercion: this is to permit
487C<isa> entries to be used purely for bug trapping, whereas coercions are
c4074652 488always structural to your code. We do, however, apply any supplied C<isa>
489check after the coercion has run to ensure that it returned a valid value.
8146585e 490
23a3e34e 491L<Sub::Quote aware|/SUB QUOTE AWARE>
2e575bcd 492
e1efec09 493=item * handles
494
495Takes a string
496
69673ca7 497 handles => 'RobotRole'
498
499Where C<RobotRole> is a role (L<Moo::Role>) that defines an interface which
500becomes the list of methods to handle.
e1efec09 501
502Takes a list of methods
503
504 handles => [ qw( one two ) ]
505
506Takes a hashref
507
508 handles => {
509 un => 'one',
510 }
511
8146585e 512=item * trigger
513
6fe5100d 514Takes a coderef which will get called any time the attribute is set. This
515includes the constructor. Coderef will be invoked against the object with the
516new value as an argument.
8146585e 517
71db76ce 518If you set this to just C<1>, it generates a trigger which calls the
519C<_trigger_${attr_name}> method on C<$self>. This feature comes from
520L<MooseX::AttributeShortcuts>.
521
2e575bcd 522Note that Moose also passes the old value, if any; this feature is not yet
523supported.
524
8146585e 525L<Sub::Quote aware|/SUB QUOTE AWARE>
526
52e8f144 527=item * C<default>
8146585e 528
2e575bcd 529Takes a coderef which will get called with $self as its only argument
530to populate an attribute if no value is supplied to the constructor - or
531if the attribute is lazy, when the attribute is first retrieved if no
532value has yet been provided.
533
534Note that if your default is fired during new() there is no guarantee that
535other attributes have been populated yet so you should not rely on their
536existence.
8146585e 537
538L<Sub::Quote aware|/SUB QUOTE AWARE>
539
52e8f144 540=item * C<predicate>
8146585e 541
2e575bcd 542Takes a method name which will return true if an attribute has a value.
8146585e 543
71db76ce 544If you set this to just C<1>, the predicate is automatically named
545C<has_${attr_name}> if your attribute's name does not start with an
546underscore, or <_has_${attr_name_without_the_underscore}> if it does.
547This feature comes from L<MooseX::AttributeShortcuts>.
8146585e 548
52e8f144 549=item * C<builder>
8146585e 550
2e575bcd 551Takes a method name which will be called to create the attribute - functions
552exactly like default except that instead of calling
553
554 $default->($self);
555
556Moo will call
557
558 $self->$builder;
8146585e 559
4752c97b 560The following features come from L<MooseX::AttributeShortcuts>:
561
ba19b6a9 562If you set this to just C<1>, the builder is automatically named
4752c97b 563C<_build_${attr_name}>.
564
565If you set this to a coderef or code-convertible object, that variable will be
566installed under C<$class::_build_${attr_name}> and the builder set to the same
567name.
71db76ce 568
52e8f144 569=item * C<clearer>
8146585e 570
571Takes a method name which will clear the attribute.
572
71db76ce 573If you set this to just C<1>, the clearer is automatically named
574C<clear_${attr_name}> if your attribute's name does not start with an
575underscore, or <_clear_${attr_name_without_the_underscore}> if it does.
576This feature comes from L<MooseX::AttributeShortcuts>.
577
52e8f144 578=item * C<lazy>
8146585e 579
580B<Boolean>. Set this if you want values for the attribute to be grabbed
581lazily. This is usually a good idea if you have a L</builder> which requires
582another attribute to be set.
583
52e8f144 584=item * C<required>
8146585e 585
586B<Boolean>. Set this if the attribute must be passed on instantiation.
587
52e8f144 588=item * C<reader>
1eba910c 589
590The value of this attribute will be the name of the method to get the value of
591the attribute. If you like Java style methods, you might set this to
592C<get_foo>
593
52e8f144 594=item * C<writer>
1eba910c 595
596The value of this attribute will be the name of the method to set the value of
597the attribute. If you like Java style methods, you might set this to
52e8f144 598C<set_foo>.
1eba910c 599
52e8f144 600=item * C<weak_ref>
8146585e 601
602B<Boolean>. Set this if you want the reference that the attribute contains to
603be weakened; use this when circular references are possible, which will cause
604leaks.
605
52e8f144 606=item * C<init_arg>
8146585e 607
608Takes the name of the key to look for at instantiation time of the object. A
609common use of this is to make an underscored attribute have a non-underscored
610initialization name. C<undef> means that passing the value in on instantiation
71db76ce 611is ignored.
8146585e 612
613=back
614
615=head2 before
616
617 before foo => sub { ... };
618
619See L<< Class::Method::Modifiers/before method(s) => sub { ... } >> for full
620documentation.
621
622=head2 around
623
624 around foo => sub { ... };
625
626See L<< Class::Method::Modifiers/around method(s) => sub { ... } >> for full
627documentation.
628
629=head2 after
630
631 after foo => sub { ... };
632
633See L<< Class::Method::Modifiers/after method(s) => sub { ... } >> for full
634documentation.
635
8146585e 636=head1 SUB QUOTE AWARE
637
638L<Sub::Quote/quote_sub> allows us to create coderefs that are "inlineable,"
639giving us a handy, XS-free speed boost. Any option that is L<Sub::Quote>
640aware can take advantage of this.
641
c9f73a63 642To do this, you can write
643
644 use Moo;
645 use Sub::Quote;
646
647 has foo => (
3b4a915a 648 is => 'ro',
649 isa => quote_sub(q{ die "Not <3" unless $_[0] < 3 })
c9f73a63 650 );
651
652which will be inlined as
653
654 do {
655 local @_ = ($_[0]->{foo});
656 die "Not <3" unless $_[0] < 3;
657 }
658
659or to avoid localizing @_,
660
661 has foo => (
3b4a915a 662 is => 'ro',
663 isa => quote_sub(q{ my ($val) = @_; die "Not <3" unless $val < 3 })
c9f73a63 664 );
665
666which will be inlined as
667
668 do {
669 my ($val) = ($_[0]->{foo});
670 die "Not <3" unless $val < 3;
671 }
672
673See L<Sub::Quote> for more information, including how to pass lexical
52e8f144 674captures that will also be compiled into the subroutine.
c9f73a63 675
2e575bcd 676=head1 INCOMPATIBILITIES WITH MOOSE
8146585e 677
52e8f144 678There is no built-in type system. C<isa> is verified with a coderef; if you
8146585e 679need complex types, just make a library of coderefs, or better yet, functions
5902c1fc 680that return quoted subs. L<MooX::Types::MooseLike> provides a similar API
681to L<MooseX::Types::Moose> so that you can write
682
683 has days_to_live => (is => 'ro', isa => Int);
684
685and have it work with both; it is hoped that providing only subrefs as an
686API will encourage the use of other type systems as well, since it's
687probably the weakest part of Moose design-wise.
8146585e 688
2e575bcd 689C<initializer> is not supported in core since the author considers it to be a
f88623a1 690bad idea but may be supported by an extension in future. Meanwhile C<trigger> or
691C<coerce> are more likely to be able to fulfill your needs.
8146585e 692
693There is no meta object. If you need this level of complexity you wanted
2e575bcd 694L<Moose> - Moo succeeds at being small because it explicitly does not
f9755246 695provide a metaprotocol. However, if you load L<Moose>, then
696
697 Class::MOP::class_of($moo_class_or_role)
698
699will return an appropriate metaclass pre-populated by L<Moo>.
8146585e 700
13e41b70 701No support for C<super>, C<override>, C<inner>, or C<augment> - the author
702considers augment to be a bad idea, and override can be translated:
703
704 override foo => sub {
705 ...
706 super();
707 ...
708 };
709
710 around foo => sub {
711 my ($orig, $self) = (shift, shift);
712 ...
713 $self->$orig(@_);
714 ...
715 };
8146585e 716
f2eac33e 717The C<dump> method is not provided by default. The author suggests loading
c96a6326 718L<Devel::Dwarn> into C<main::> (via C<perl -MDevel::Dwarn ...> for example) and
719using C<$obj-E<gt>$::Dwarn()> instead.
720
8146585e 721L</default> only supports coderefs, because doing otherwise is usually a
722mistake anyway.
723
f9755246 724C<lazy_build> is not supported; you are instead encouraged to use the
52e8f144 725C<< is => 'lazy' >> option supported by L<Moo> and L<MooseX::AttributeShortcuts>.
8146585e 726
2e575bcd 727C<auto_deref> is not supported since the author considers it a bad idea.
8146585e 728
f9755246 729C<documentation> will show up in a L<Moose> metaclass created from your class
c4074652 730but is otherwise ignored. Then again, L<Moose> ignores it as well, so this
f9755246 731is arguably not an incompatibility.
40f3e3aa 732
c4074652 733Since C<coerce> does not require C<isa> to be defined but L<Moose> does
52e8f144 734require it, the metaclass inflation for coerce alone is a trifle insane
c4074652 735and if you attempt to subtype the result will almost certainly break.
736
69673ca7 737Handling of warnings: when you C<use Moo> we enable FATAL warnings. The nearest
738similar invocation for L<Moose> would be:
739
740 use Moose;
741 use warnings FATAL => "all";
742
743Additionally, L<Moo> supports a set of attribute option shortcuts intended to
744reduce common boilerplate. The set of shortcuts is the same as in the L<Moose>
239d4711 745module L<MooseX::AttributeShortcuts> as of its version 0.009+. So if you:
69673ca7 746
747 package MyClass;
748 use Moo;
749
750The nearest L<Moose> invocation would be:
751
752 package MyClass;
753
754 use Moose;
755 use warnings FATAL => "all";
756 use MooseX::AttributeShortcuts;
757
5902c1fc 758or, if you're inheriting from a non-Moose class,
759
760 package MyClass;
761
762 use Moose;
763 use MooseX::NonMoose;
764 use warnings FATAL => "all";
765 use MooseX::AttributeShortcuts;
766
767Finally, Moose requires you to call
768
769 __PACKAGE__->meta->make_immutable;
770
771at the end of your class to get an inlined (i.e. not horribly slow)
772constructor. Moo does it automatically the first time ->new is called
773on your class.
774
6ad9aeab 775An extension L<MooX::late> exists to ease translating Moose packages
776to Moo by providing a more Moose-like interface.
777
660f3db2 778=head1 SUPPORT
779
9836a6ee 780Users' IRC: #moose on irc.perl.org
781
782Development and contribution IRC: #web-simple on irc.perl.org
660f3db2 783
40f3e3aa 784=head1 AUTHOR
785
786mst - Matt S. Trout (cpan:MSTROUT) <mst@shadowcat.co.uk>
787
788=head1 CONTRIBUTORS
789
5da684a2 790dg - David Leadbeater (cpan:DGL) <dgl@dgl.cx>
791
792frew - Arthur Axel "fREW" Schmidt (cpan:FREW) <frioux@gmail.com>
793
794hobbs - Andrew Rodland (cpan:ARODLAND) <arodland@cpan.org>
795
796jnap - John Napiorkowski (cpan:JJNAPIORK) <jjn1056@yahoo.com>
797
798ribasushi - Peter Rabbitson (cpan:RIBASUSHI) <ribasushi@cpan.org>
40f3e3aa 799
11f7a042 800chip - Chip Salzenberg (cpan:CHIPS) <chip@pobox.com>
801
a17be455 802ajgb - Alex J. G. Burzyński (cpan:AJGB) <ajgb@cpan.org>
803
7b8177f8 804doy - Jesse Luehrs (cpan:DOY) <doy at tozt dot net>
805
1fb2de92 806perigrin - Chris Prather (cpan:PERIGRIN) <chris@prather.org>
807
3202e039 808Mithaldu - Christian Walde (cpan:MITHALDU) <walde.christian@googlemail.com>
809
e355471c 810ilmari - Dagfinn Ilmari Mannsåker (cpan:ILMARI) <ilmari@ilmari.org>
811
1d17c7c1 812tobyink - Toby Inkster (cpan:TOBYINK) <tobyink@cpan.org>
813
d092b5ff 814haarg - Graham Knop (cpan:HAARG) <haarg@cpan.org>
815
40f3e3aa 816=head1 COPYRIGHT
817
a958e36d 818Copyright (c) 2010-2011 the Moo L</AUTHOR> and L</CONTRIBUTORS>
40f3e3aa 819as listed above.
820
821=head1 LICENSE
822
823This library is free software and may be distributed under the same terms
824as perl itself.
825
826=cut