NAME

MooseX::LazyRequire - Required attributes which fail only when trying to use them

SYNOPSIS

    package Foo;

    use Moose;
    use MooseX::LazyRequire;

    has foo => (
        is            => 'ro',
        lazy_required => 1,
    );

    has bar => (
        is      => 'ro',
        builder => '_build_bar',
    );

    sub _build_bar { shift->foo }


    Foo->new(foo => 42); # succeeds, foo and bar will be 42
    Foo->new(bar => 42); # succeeds, bar will be 42
    Foo->new;            # fails, neither foo nor bare were given

DESCRIPTION

This module adds a lazy_required option to Moose attribute declarations.

The reader methods for all attributes with that option will throw an exception unless a value for the attributes was provided earlier by a constructor parameter or through a writer method.

CAVEATS

Apparently Moose roles don't have an attribute metaclass, so this module can't easily apply its magic to attributes defined in roles. If you want to use lazy_required in role attributes, you'll have to apply the attribute trait yourself:

    has foo => (
        traits        => ['LazyRequire'],
        is            => 'ro',
        lazy_required => 1,
    );

AUTHOR

Florian Ragwitz <rafl@debian.org>

COPYRIGHT AND LICENSE

This software is copyright (c) 2010 by Florian Ragwitz.

This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself.