NAME
   Moo - Minimalist Object Orientation (with Moose compatiblity)

SYNOPSIS
    package Cat::Food;

    use Moo;

    sub feed_lion {
      my $self = shift;
      my $amount = shift || 1;

      $self->pounds( $self->pounds - $amount );
    }

    has taste => (
      is => 'ro',
    );

    has brand => (
      is  => 'ro',
      isa => sub {
        die "Only SWEET-TREATZ supported!" unless $_[0] eq 'SWEET-TREATZ'
      },
   );

    has pounds => (
      is  => 'rw',
      isa => sub { die "$_[0] is too much cat food!" unless $_[0] < 15 },
    );

    1;

   And elsewhere:

    my $full = Cat::Food->new(
       taste  => 'DELICIOUS.',
       brand  => 'SWEET-TREATZ',
       pounds => 10,
    );

    $full->feed_lion;

    say $full->pounds;

DESCRIPTION
   This module is an extremely light-weight subset of Moose optimised for
   rapid startup and "pay only for what you use".

   It also avoids depending on any XS modules to allow simple deployments.
   The name "Moo" is based on the idea that it provides almost -- but not
   quite -- two thirds of Moose.

   Unlike Mouse this module does not aim at full compatibility with Moose's
   surface syntax, preferring instead of provide full interoperability via
   the metaclass inflation capabilities described in "MOO AND MOOSE".

   For a full list of the minor differences between Moose and Moo's surface
   syntax, see "INCOMPATIBILITIES WITH MOOSE".

WHY MOO EXISTS
   If you want a full object system with a rich Metaprotocol, Moose is
   already wonderful.

   However, sometimes you're writing a command line script or a CGI script
   where fast startup is essential, or code designed to be deployed as a
   single file via App::FatPacker, or you're writing a CPAN module and you
   want it to be usable by people with those constraints.

   I've tried several times to use Mouse but it's 3x the size of Moo and
   takes longer to load than most of my Moo based CGI scripts take to run.

   If you don't want Moose, you don't want "less metaprotocol" like Mouse,
   you want "as little as possible" -- which means "no metaprotocol", which
   is what Moo provides.

   Better still, if you install and load Moose, we set up metaclasses for
   your Moo classes and Moo::Role roles, so you can use them in Moose code
   without ever noticing that some of your codebase is using Moo.

   Hence, Moo exists as its name -- Minimal Object Orientation -- with a
   pledge to make it smooth to upgrade to Moose when you need more than
   minimal features.

MOO AND MOOSE
   If Moo detects Moose being loaded, it will automatically register
   metaclasses for your Moo and Moo::Role packages, so you should be able
   to use them in Moose code without anybody ever noticing you aren't using
   Moose everywhere.

   Extending a Moose class or consuming a Moose::Role will also work.

   So will extending a Mouse class or consuming a Mouse::Role - but note
   that we don't provide Mouse metaclasses or metaroles so the other way
   around doesn't work. This feature exists for Any::Moose users porting to
   Moo; enabling Mouse users to use Moo classes is not a priority for us.

   This means that there is no need for anything like Any::Moose for Moo
   code - Moo and Moose code should simply interoperate without problem. To
   handle Mouse code, you'll likely need an empty Moo role or class
   consuming or extending the Mouse stuff since it doesn't register true
   Moose metaclasses like Moo does.

   If you want types to be upgraded to the Moose types, use
   MooX::Types::MooseLike and install the MooseX::Types library to match
   the MooX::Types::MooseLike library you're using - Moo will load the
   MooseX::Types library and use that type for the newly created metaclass.

   If you need to disable the metaclass creation, add:

     no Moo::sification;

   to your code before Moose is loaded, but bear in mind that this switch
   is currently global and turns the mechanism off entirely so don't put
   this in library code.

MOO VERSUS ANY::MOOSE
   Any::Moose will load Mouse normally, and Moose in a program using Moose
   - which theoretically allows you to get the startup time of Mouse
   without disadvantaging Moose users.

   Sadly, this doesn't entirely work, since the selection is load order
   dependent - Moo's metaclass inflation system explained above in "MOO AND
   MOOSE" is significantly more reliable.

   So if you want to write a CPAN module that loads fast or has only pure
   perl dependencies but is also fully usable by Moose users, you should be
   using Moo.

   For a full explanation, see the article
   <http://shadow.cat/blog/matt-s-trout/moo-versus-any-moose> which
   explains the differing strategies in more detail and provides a direct
   example of where Moo succeeds and Any::Moose fails.

IMPORTED METHODS
 new
    Foo::Bar->new( attr1 => 3 );

   or

    Foo::Bar->new({ attr1 => 3 });

 BUILDARGS
    sub BUILDARGS {
      my ( $class, @args ) = @_;

      unshift @args, "attr1" if @args % 2 == 1;

      return { @args };
    };

    Foo::Bar->new( 3 );

   The default implementation of this method accepts a hash or hash
   reference of named parameters. If it receives a single argument that
   isn't a hash reference it throws an error.

   You can override this method in your class to handle other types of
   options passed to the constructor.

   This method should always return a hash reference of named options.

 BUILD
   Define a "BUILD" method on your class and the constructor will
   automatically call the "BUILD" method from parent down to child after
   the object has been instantiated. Typically this is used for object
   validation or possibly logging.

 DEMOLISH
   If you have a "DEMOLISH" method anywhere in your inheritance hierarchy,
   a "DESTROY" method is created on first object construction which will
   call "$instance->DEMOLISH($in_global_destruction)" for each "DEMOLISH"
   method from child upwards to parents.

   Note that the "DESTROY" method is created on first construction of an
   object of your class in order to not add overhead to classes without
   "DEMOLISH" methods; this may prove slightly surprising if you try and
   define your own.

 does
    if ($foo->does('Some::Role1')) {
      ...
    }

   Returns true if the object composes in the passed role.

IMPORTED SUBROUTINES
 extends
    extends 'Parent::Class';

   Declares base class. Multiple superclasses can be passed for multiple
   inheritance (but please use roles instead).

   Calling extends more than once will REPLACE your superclasses, not add
   to them like 'use base' would.

 with
    with 'Some::Role1';

   or

    with 'Some::Role1', 'Some::Role2';

   Composes one or more Moo::Role (or Role::Tiny) roles into the current
   class. An error will be raised if these roles have conflicting methods.

 has
    has attr => (
      is => 'ro',
    );

   Declares an attribute for the class.

   The options for "has" are as follows:

   * is

     required, may be "ro", "lazy", "rwp" or "rw".

     "ro" generates an accessor that dies if you attempt to write to it -
     i.e. a getter only - by defaulting "reader" to the name of the
     attribute.

     "lazy" generates a reader like "ro", but also sets "lazy" to 1 and
     "builder" to "_build_${attribute_name}" to allow on-demand generated
     attributes. This feature was my attempt to fix my incompetence when
     originally designing "lazy_build", and is also implemented by
     MooseX::AttributeShortcuts.

     "rwp" generates a reader like "ro", but also sets "writer" to
     "_set_${attribute_name}" for attributes that are designed to be
     written from inside of the class, but read-only from outside. This
     feature comes from MooseX::AttributeShortcuts.

     "rw" generates a normal getter/setter by defaulting "accessor" to the
     name of the attribute.

   * isa

     Takes a coderef which is meant to validate the attribute. Unlike
     Moose, Moo does not include a basic type system, so instead of doing
     "isa => 'Num'", one should do

      isa => sub {
        die "$_[0] is not a number!" unless looks_like_number $_[0]
      },

     Sub::Quote aware

     Since Moo does not run the "isa" check before "coerce" if a coercion
     subroutine has been supplied, "isa" checks are not structural to your
     code and can, if desired, be omitted on non-debug builds (although if
     this results in an uncaught bug causing your program to break, the Moo
     authors guarantee nothing except that you get to keep both halves).

     If you want MooseX::Types style named types, look at
     MooX::Types::MooseLike.

     To cause your "isa" entries to be automatically mapped to named
     Moose::Meta::TypeConstraint objects (rather than the default behaviour
     of creating an anonymous type), set:

       $Moo::HandleMoose::TYPE_MAP{$isa_coderef} = sub {
         require MooseX::Types::Something;
         return MooseX::Types::Something::TypeName();
       };

     Note that this example is purely illustrative; anything that returns a
     Moose::Meta::TypeConstraint object or something similar enough to it
     to make Moose happy is fine.

   * coerce

     Takes a coderef which is meant to coerce the attribute. The basic idea
     is to do something like the following:

      coerce => sub {
        $_[0] + 1 unless $_[0] % 2
      },

     Note that Moo will always fire your coercion: this is to permit "isa"
     entries to be used purely for bug trapping, whereas coercions are
     always structural to your code. We do, however, apply any supplied
     "isa" check after the coercion has run to ensure that it returned a
     valid value.

     Sub::Quote aware

   * handles

     Takes a string

       handles => 'RobotRole'

     Where "RobotRole" is a role (Moo::Role) that defines an interface
     which becomes the list of methods to handle.

     Takes a list of methods

      handles => [ qw( one two ) ]

     Takes a hashref

      handles => {
        un => 'one',
      }

   * trigger

     Takes a coderef which will get called any time the attribute is set.
     This includes the constructor. Coderef will be invoked against the
     object with the new value as an argument.

     If you set this to just 1, it generates a trigger which calls the
     "_trigger_${attr_name}" method on $self. This feature comes from
     MooseX::AttributeShortcuts.

     Note that Moose also passes the old value, if any; this feature is not
     yet supported.

     Sub::Quote aware

   * "default"

     Takes a coderef which will get called with $self as its only argument
     to populate an attribute if no value is supplied to the constructor -
     or if the attribute is lazy, when the attribute is first retrieved if
     no value has yet been provided.

     Note that if your default is fired during new() there is no guarantee
     that other attributes have been populated yet so you should not rely
     on their existence.

     Sub::Quote aware

   * "predicate"

     Takes a method name which will return true if an attribute has a
     value.

     If you set this to just 1, the predicate is automatically named
     "has_${attr_name}" if your attribute's name does not start with an
     underscore, or <_has_${attr_name_without_the_underscore}> if it does.
     This feature comes from MooseX::AttributeShortcuts.

   * "builder"

     Takes a method name which will be called to create the attribute -
     functions exactly like default except that instead of calling

       $default->($self);

     Moo will call

       $self->$builder;

     If you set this to just 1, the predicate is automatically named
     "_build_${attr_name}". This feature comes from
     MooseX::AttributeShortcuts.

   * "clearer"

     Takes a method name which will clear the attribute.

     If you set this to just 1, the clearer is automatically named
     "clear_${attr_name}" if your attribute's name does not start with an
     underscore, or <_clear_${attr_name_without_the_underscore}> if it
     does. This feature comes from MooseX::AttributeShortcuts.

   * "lazy"

     Boolean. Set this if you want values for the attribute to be grabbed
     lazily. This is usually a good idea if you have a "builder" which
     requires another attribute to be set.

   * "required"

     Boolean. Set this if the attribute must be passed on instantiation.

   * "reader"

     The value of this attribute will be the name of the method to get the
     value of the attribute. If you like Java style methods, you might set
     this to "get_foo"

   * "writer"

     The value of this attribute will be the name of the method to set the
     value of the attribute. If you like Java style methods, you might set
     this to "set_foo".

   * "weak_ref"

     Boolean. Set this if you want the reference that the attribute
     contains to be weakened; use this when circular references are
     possible, which will cause leaks.

   * "init_arg"

     Takes the name of the key to look for at instantiation time of the
     object. A common use of this is to make an underscored attribute have
     a non-underscored initialization name. "undef" means that passing the
     value in on instantiation is ignored.

 before
    before foo => sub { ... };

   See "before method(s) => sub { ... }" in Class::Method::Modifiers for
   full documentation.

 around
    around foo => sub { ... };

   See "around method(s) => sub { ... }" in Class::Method::Modifiers for
   full documentation.

 after
    after foo => sub { ... };

   See "after method(s) => sub { ... }" in Class::Method::Modifiers for
   full documentation.

SUB QUOTE AWARE
   "quote_sub" in Sub::Quote allows us to create coderefs that are
   "inlineable," giving us a handy, XS-free speed boost. Any option that is
   Sub::Quote aware can take advantage of this.

   To do this, you can write

     use Moo;
     use Sub::Quote;

     has foo => (
       is => 'ro',
       isa => quote_sub(q{ die "Not <3" unless $_[0] < 3 })
     );

   which will be inlined as

     do {
       local @_ = ($_[0]->{foo});
       die "Not <3" unless $_[0] < 3;
     }

   or to avoid localizing @_,

     has foo => (
       is => 'ro',
       isa => quote_sub(q{ my ($val) = @_; die "Not <3" unless $val < 3 })
     );

   which will be inlined as

     do {
       my ($val) = ($_[0]->{foo});
       die "Not <3" unless $val < 3;
     }

   See Sub::Quote for more information, including how to pass lexical
   captures that will also be compiled into the subroutine.

INCOMPATIBILITIES WITH MOOSE
   There is no built-in type system. "isa" is verified with a coderef; if
   you need complex types, just make a library of coderefs, or better yet,
   functions that return quoted subs. MooX::Types::MooseLike provides a
   similar API to MooseX::Types::Moose so that you can write

     has days_to_live => (is => 'ro', isa => Int);

   and have it work with both; it is hoped that providing only subrefs as
   an API will encourage the use of other type systems as well, since it's
   probably the weakest part of Moose design-wise.

   "initializer" is not supported in core since the author considers it to
   be a bad idea but may be supported by an extension in future. Meanwhile
   "trigger" or "coerce" are more likely to be able to fulfill your needs.

   There is no meta object. If you need this level of complexity you wanted
   Moose - Moo succeeds at being small because it explicitly does not
   provide a metaprotocol. However, if you load Moose, then

     Class::MOP::class_of($moo_class_or_role)

   will return an appropriate metaclass pre-populated by Moo.

   No support for "super", "override", "inner", or "augment" - the author
   considers augment to be a bad idea, and override can be translated:

     override foo => sub {
       ...
       super();
       ...
     };

     around foo => sub {
       my ($orig, $self) = (shift, shift);
       ...
       $self->$orig(@_);
       ...
     };

   The "dump" method is not provided by default. The author suggests
   loading Devel::Dwarn into "main::" (via "perl -MDevel::Dwarn ..." for
   example) and using "$obj->$::Dwarn()" instead.

   "default" only supports coderefs, because doing otherwise is usually a
   mistake anyway.

   "lazy_build" is not supported; you are instead encouraged to use the "is
   => 'lazy'" option supported by Moo and MooseX::AttributeShortcuts.

   "auto_deref" is not supported since the author considers it a bad idea.

   "documentation" will show up in a Moose metaclass created from your
   class but is otherwise ignored. Then again, Moose ignores it as well, so
   this is arguably not an incompatibility.

   Since "coerce" does not require "isa" to be defined but Moose does
   require it, the metaclass inflation for coerce alone is a trifle insane
   and if you attempt to subtype the result will almost certainly break.

   Handling of warnings: when you "use Moo" we enable FATAL warnings. The
   nearest similar invocation for Moose would be:

     use Moose;
     use warnings FATAL => "all";

   Additionally, Moo supports a set of attribute option shortcuts intended
   to reduce common boilerplate. The set of shortcuts is the same as in the
   Moose module MooseX::AttributeShortcuts as of its version 0.009+. So if
   you:

       package MyClass;
       use Moo;

   The nearest Moose invocation would be:

       package MyClass;

       use Moose;
       use warnings FATAL => "all";
       use MooseX::AttributeShortcuts;

   or, if you're inheriting from a non-Moose class,

       package MyClass;

       use Moose;
       use MooseX::NonMoose;
       use warnings FATAL => "all";
       use MooseX::AttributeShortcuts;

   Finally, Moose requires you to call

       __PACKAGE__->meta->make_immutable;

   at the end of your class to get an inlined (i.e. not horribly slow)
   constructor. Moo does it automatically the first time ->new is called on
   your class.

SUPPORT
   Users' IRC: #moose on irc.perl.org

   Development and contribution IRC: #web-simple on irc.perl.org

AUTHOR
   mst - Matt S. Trout (cpan:MSTROUT) <[email protected]>

CONTRIBUTORS
   dg - David Leadbeater (cpan:DGL) <[email protected]>

   frew - Arthur Axel "fREW" Schmidt (cpan:FREW) <[email protected]>

   hobbs - Andrew Rodland (cpan:ARODLAND) <[email protected]>

   jnap - John Napiorkowski (cpan:JJNAPIORK) <[email protected]>

   ribasushi - Peter Rabbitson (cpan:RIBASUSHI) <[email protected]>

   chip - Chip Salzenberg (cpan:CHIPS) <[email protected]>

   ajgb - Alex J. G. Burzyński (cpan:AJGB) <[email protected]>

   doy - Jesse Luehrs (cpan:DOY) <doy at tozt dot net>

   perigrin - Chris Prather (cpan:PERIGRIN) <[email protected]>

   Mithaldu - Christian Walde (cpan:MITHALDU)
   <[email protected]>

   ilmari - Dagfinn Ilmari Mannsåker (cpan:ILMARI) <[email protected]>

   tobyink - Toby Inkster (cpan:TOBYINK) <[email protected]>

COPYRIGHT
   Copyright (c) 2010-2011 the Moo "AUTHOR" and "CONTRIBUTORS" as listed
   above.

LICENSE
   This library is free software and may be distributed under the same
   terms as perl itself.

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