determine prereqs automatically

[gitmo/MooseX-UndefTolerant.git] / README

NAME
    MooseX::UndefTolerant - Make your attribute(s) tolerant to undef
    initialization

SYNOPSIS
      package My::Class;

      use Moose;
      use MooseX::UndefTolerant;

      has 'name' => (
        is => 'ro',
        isa => 'Str',
        predicate => 'has_name'
      );

      # Meanwhile, under the city...

      # Doesn't explode
      my $class = My::Class->new(name => undef);
      $class->has_name # False!

    Or, if you only want one attribute to have this behaviour:

      package My:Class;
      use Moose;

      use MooseX::UndefTolerant::Attribute;

      has 'bar' => (
          traits => [ qw(MooseX::UndefTolerant::Attribute)],
          is => 'ro',
          isa => 'Num',
          predicate => 'has_bar'
      );

DESCRIPTION
    Loading this module in your Moose class makes initialization of your
    attributes tolerant of undef. If you specify the value of undef to any
    of the attributes they will not be initialized, effectively behaving as
    if you had not provided a value at all.

MOTIVATION
    I often found myself in this quandry:

      package My:Class;
      use Moose;

      has 'foo' => (
        is => 'ro',
        isa => 'Str',
      );

      # ... then

      my $foo = ... # get the param from something

      my $class = My:Class->new(foo => $foo, bar => 123);

    What if foo is undefined? I didn't want to change my attribute to be
    Maybe[Str] and I still want my predicate ("has_foo") to work. The only
    real solution was:

      if(defined($foo)) {
        $class = My:Class->new(foo => $foo, bar => 123);
      } else {
        $class = My:Class->new(bar => 123);
      }

    Or some type of codemulch using ternarys. This module allows you to make
    your attributes more tolerant of undef so that you can keep the first
    example: have your cake and eat it too!

PER ATTRIBUTE
    See MooseX::UndefTolerant::Attribute.

CAVEATS
    This extension does not currently work in immutable classes when
    applying the trait to some (but not all) attributes in the class. This
    is because the inlined constructor initialization code currently lives
    in Moose::Meta::Method::Constructor, not Moose::Meta::Attribute. The
    good news is that this is expected to be changing shortly.

ACKNOWLEDGEMENTS
    Many thanks to the crew in #moose who talked me through this module:

    Hans Dieter Pearcey (confound)

    Jesse Luehrs (doy)

    Tomas Doran (t0m)

    Dylan Hardison (dylan)

    Jay Shirley (jshirley)

    Mike Eldridge (diz)

AUTHOR
    Cory G Watson <gphat at cpan.org>

COPYRIGHT AND LICENSE
    This software is copyright (c) 2011 by Cory G Watson.

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