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