/ 
MooseX-Declare-0.10
River stage two • 42 direct dependents • 49 total dependents
/ MooseX::Declare

NAME

MooseX::Declare - Declarative syntax for Moose

SYNOPSIS

use MooseX::Declare;

class BankAccount {
    has 'balance' => ( isa => 'Num', is => 'rw', default => 0 );

    method deposit (Num $amount) {
        $self->balance( $self->balance + $amount );
    }

    method withdraw (Num $amount) {
        my $current_balance = $self->balance();
        ( $current_balance >= $amount )
            || confess "Account overdrawn";
        $self->balance( $current_balance - $amount );
    }
}

class CheckingAccount extends BankAccount {
    has 'overdraft_account' => ( isa => 'BankAccount', is => 'rw' );

    before withdraw (Num $amount) {
        my $overdraft_amount = $amount - $self->balance();
        if ( $self->overdraft_account && $overdraft_amount > 0 ) {
            $self->overdraft_account->withdraw($overdraft_amount);
            $self->deposit($overdraft_amount);
        }
    }
}

DESCRIPTION

This module provides syntactic sugar for Moose, the postmodern object system for Perl 5. When used, it sets up the class and role keywords.

KEYWORDS

class

class Foo { ... }

my $anon_class = class { ... };

Declares a new class. The class can be either named or anonymous, depending on whether or not a classname is given. Within the class definition Moose and MooseX::Method::Signatures are set up automatically in addition to the other keywords described in this document. At the end of the definition the class will be made immutable. namespace::clean is injected to clean up Moose for you.

Because of the way the options are parsed, you cannot have a class named "is", "with" or "extends".

It's possible to specify options for classes:

extends
class Foo extends Bar { ... }

Sets a superclass for the class being declared.

with
class Foo with Role { ... }

Applies a role to the class being declared.

is mutable
class Foo is mutable { ... }

Causes the class not to be made immutable after its definition.

Options can also be provided for anonymous classes using the same syntax:

my $meta_class = class with Role;

role

role Foo { ... }

my $anon_role = role { ... };

Declares a new role. The role can be either named or anonymous, depending on wheter or not a name is given. Within the role definition Moose::Role and MooseX::Method::Signatures are set up automatically in addition to the other keywords described in this document. Again, namespace::clean is injected to clean up Moose::Role and for you.

It's possible to specify options for roles:

with
role Foo with Bar { ... }

Applies a role to the role being declared.

before / after / around / override / augment

before   foo ($x, $y, $z) { ... }
after    bar ($x, $y, $z) { ... }
around   baz ($x, $y, $z) { ... }
override moo ($x, $y, $z) { ... }
augment  kuh ($x, $y, $z) { ... }

Add a method modifier. Those work like documented in Moose, except for the slightly nicer syntax and the method signatures, which work like documented in MooseX::Method::Signatures.

For the around modifier an additional argument called $orig is automatically set up as the invocant for the method.

clean

When creating a class with MooseX::Declare like:

use MooseX::Declare;
class Foo { ... }

What actually happens is something like this:

{
    package Foo;
    use Moose;
    use namespace::clean -except => 'meta';
    ...
    __PACKAGE__->meta->mate_immutable();
    1;
}

So if you declare imports outside the class, the symbols get imported into the main:: namespace, not the class' namespace. The symbols then cannot be called from within the class:

use MooseX::Declare;
use Data::Dump qw/dump/;
class Foo {
    method dump($value) { return dump($value) } # Data::Dump::dump IS NOT in Foo::
    method pp($value)   { $self->dump($value) } # an alias for our dump method
}

Furthermore, any imports will not be cleaned up by namespace::clean after compilation since the class knows nothing about them! The temptation to do this may stem from wanting to keep all your import declarations in the same place.

The solution is two-fold. First, only import MooseX::Declare outside the class definition (because you have to). Make all other imports inside the class definition and clean up with the clean keyword:

use MooseX::Declare;
class Foo {
    use Data::Dump qw/dump/;
    clean;
    method dump($value) { return dump($value) } # Data::Dump::dump IS in Foo::
    method pp($value)   { $self->dump($value) } # an alias for our dump method
}

Foo->new->dump($some_value);
Foo->new->pp($some_value);

NOTE that the import Data::Dump::dump() and the method Foo::dump(), although having the same name, do not conflict with each other.

SEE ALSO

Moose

Moose::Role

MooseX::Method::Signatures

namespace::clean

AUTHOR

Florian Ragwitz <rafl@debian.org>

With contributions from:

Ash Berlin <ash@cpan.org>
Hans Dieter Pearcey <hdp@cpan.org>
Nelo Onyiah <nelo.onyiah@gmail.com>
Piers Cawley <pdcawley@bofh.org.uk>
Tomas Doran <bobtfish@bobtfish.net>
Yanick Champoux <yanick@babyl.dyndns.org>

COPYRIGHT AND LICENSE

Copyright (c) 2008, 2009 Florian Ragwitz

Licensed under the same terms as perl itself.