Moos(3)

NAME
Moos - Moo s{imple,peedy,ingle}

SYNOPSIS
    package Foos;
    use Moos;

    extends 'Boos';
    with 'Cloos';

    has this => ();
    has that => 42;
    has other => (
        builder => 'build_other',
        lazy => 1,
    );

    sub BUILD {
        my $self = shift;
        # build, build, build
    }

    sub BUILDARGS {
        my ($self, @args) = @_;
        # munge, munge, munge
        return {%munged_args};
    }

DESCRIPTION
Moos completes the M to Moose sequence of Perl OO modules.

This one is pure Perl, single file and mostly Moose compatible (for what it does). Moos has no non-core dependencies, but certain features (roles, debugging functions, legacy Perl support) do require additional modules. If you steer away from those features, you don't need those additional modules.

FEATURES
Here's a quick list of the Moose compatible features that are supported by Moos.

  strict/warnings
Turns on "strict" and "warnings" for you.

  Helpful exports
The ever useful "blessed" (from Scalar::Util) and "confess" (from Carp) are exported to your namespace.

  extends
For inheritance. "Moos::Object" is the default base class.

    package MyClass;
    extends 'MyBaseClass';

Supports multiple inheritance, by allowing multiple classes on a single invocation.

  with
Moos can consume roles using the "with" keyword. Using this feature requires Role::Tiny to be installed.

    with 'ThisClass', 'ThatClass';

  has
Accessor generator. Supports the "is", "default", "build", "lazy", "clearer", "predicate", "required", "handles" and "trigger" options, described below. The supported options are about the same as Moose. Other arguments (e.g. "isa" and "coerce") are currently ignored.

    has this => ();

NOTE: Class::XSAccessor will be used for simple accessors if it is installed.
      This can be disabled by setting $Moos::CAN_HAZ_XS to false or by setting
      the PERL_MOOS_XS_DISABLE to true.

is  Specify which type of attribute accessor to provide. The default is "rw", a read-write accessor. Read-only "ro" accessors are also supported.

        has this => ( is => "ro" );
        has 'this';                   # read-write
        has that => ();               # read-write

    Unlike Moose, Moos cannot generate differently named getters and setters. If you want your setter named something different (e.g. a private method), then you could do something like:

        has this => ( is => 'ro' );
        sub _set_this { $_[0]{this} = $_[1] }

required
    Require that a value for the attribute be provided to the constructor or generated during object construction.

        has this => ( required => 1 );

lazy
    Don't generate defaults during object construction.

        has this => ( builder => '_build_this', lazy => 1 );

trigger
    A coderef which will be called when the attribute is assigned to via a method call or the constructor. (But not when an attribute is implicitly given a value via a default or builder.) The coderef is called with the instance as the first parameter, the new value as the second parameter, and the old value (if any) as the third parameter.

        has age => ( trigger => sub {
            croak "non-numeric age" unless looks_like_number($_[1]);
        } );

    Triggers can be used to emulate Moose's type constraints, coercion and weakened reference features, but if you find yourself doing this frequently then you should consider upgrading to Moo or Moose.

handles
    Delegated method calls.

        has wheels => (handles => [qw/ roll /]);

    This accepts a hashref or arrayref, but not the other possibilities offered by Moose.

builder
    Specify the method name to generate a default value.

        has this => ( builder => '_build_this' );
        has that => ( builder => 1 );  # accept default name for method

default
    Specify the sub to generate a default value.

        has this => ( default => sub { 42 } );

    Moos provides a shortcut for specifying the default. If the number of arguments (after the name) is an odd number, then the first argument is the default. The following forms are valid:

        has a => 42;
        has b => 'string' => (lazy => 1);
        has c => {};
        has d => [1, 2, 3, 4];

    These all result in creating a Moos "default" argument. If the default is an array or hash reference, a shallow copy is made.

clearer
    Creates a clearer method.

        has this => ( clearer => "clear_this" );
        has that => ( clearer => 1 );  # accept default name for method

predicate
    Creates a predicate method, which can be used to check if the attribute is set or unset.

        has this => ( predicate => "has_this" );
        has that => ( predicate => 1 );  # accept default name for method

  Class and Object Methods

new A constructor class method.

        my $object = MyClass->new(this => 'nice', that => 2);

BUILD
    Custom object construction. If you define BUILD, it is passed the value of the new object during construction. You can modify the object. Any value you return is ignored.

        sub BUILD { my $self = shift; ... }

BUILDARGS
    Custom constructor argument processing. If you define BUILDARGS, you can control how the constructor's arguments are built into the object hashref.

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

dump
    Returns a textual dump of the object.

meta
    Returns a Moos::Meta::Class object for the class. This has a very limited subset of Moose::Meta::Class' functionality, including implementations of the following methods: "name", "attribute_metaclass", "add_attribute", "add_method", "superclasses", "linearized_isa", "new_object", "get_all_attributes", "get_attribute" and "find_attribute_by_name".

    The attribute introspection methods return Moos::Meta::Attribute objects which provide a very limited subset of Moose::Meta::Attribute's functionality, including implementations of the following methods: "name", "associated_class", "predicate", "clearer", "default", "builder", "trigger", "required", "lazy" and "documentation".

does/DOES
    Methods to check whether the classobject performs a particular role. The methods differ in that "does" checks roles only in the MooseMoo/Role::Tiny sense; "DOES" also takes into account UNIVERSAL::DOES.

  Roles
If you need roles, then Moos classes have experimental support for Role::Tiny, Moo::Role and Moose::Role roles. (Moos provides a "with" command that uses Role::Tiny to do the work.)

    {
        package Local::Class;
        use Moos;
        with "Local::Role";
        ...;
    }

Limitations: Note that Moo and Moose each allow type constraints for attributes; Moos does not. This means that if you compose, say, a Moose::Role into a Moos class, you end up with a strange situation where the accessor methods will enforce type constraints (because they were generated by Moose) but the constructor will not (because it is inherited from Moos::Object).

See also Moos::Role.

  Method Modifiers
If you need method modifiers, then try Class::Method::Modifiers.

  Development Options
Moos has a couple of builtin dev options. They are controlled by environment variables.

PERL_MOOS_ACCESSOR_CALLS
    By setting this environment variable, Moos will warn everytime an accessor method is called.

PERL_MOOS_XXX
    By setting the environment variable, Moos will export the XXX debugging keywords.

WHENCE MOOS
I(ngy) created Moos during Pegex development. Pegex uses a clone of Moos called Pegex::Base. (Moos ships with a commandline utility called "remoos" that does this cloning.)

Pegex is a parser framework and needs to be fast. While looking into speed issues I noted that accessor calling was the biggest hit. I tried all the various Mo* solutions and Mouse was the fastest.

I was happy until I remembered that Mouse uses XS, and for various reasons this broke my toolchain (TestML, Module::Install, etc).

So I made a single module/file Moose clone and it worked out well. I've shared Pegex::Base as Moos in case any other projects want it.

Later on, Toby Inkster added a bunch of low-cost but very handy features from Moose.

The name Moos was chosen because it was the only name left between M and Moose. (Thus adding to the epic confusion that we embrace as Perl Mongers! :)

ON SPEED
In the end, I got Pegex to run even faster with Moos than it originally did with Mouse. I'll tell you my secret...

Accessors (usually) do not need to be method calls.

Replace these:

    my $foo = $self->foo;
    $self->foo($foo);

with:

    my $foo = $self->{foo};
    $self->{foo} = $foo;

And your code will be faster (and a bit uglier).

The only time that you need to call an accessor method is when you are accessing a property and it might invoke a "lazy" "builder", "default" or "trigger" method. Otherwise you are just wasting time. At least with the minimal feature set offered by Moos.

The PERL_MOOS_ACCESSOR_CALLS feature described above is for finding these method calls.

Note that third parties can still use your module's accessor methods like they would expect to.

I'm sure I've missed some subtleties, and would be glad to hear opinions, but in the meantime I'm happy that my code is faster and pure Perl.

SEE ALSO

•   M

•   Mo

•   Moo

•   Moos

•   Moose

•   Mouse

•   Mousse

AUTHORS
Ingy döt Net <ingy@cpan.org>

Toby Inkster <tobyink@cpan.org>

COPYRIGHT AND LICENSE
Copyright 2012-2014. Ingy döt Net.

This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.

See <http://www.perl.com/perl/misc/Artistic.html>