NAME MooseX::Role::AttributeOverride - Allow roles to modify attributes VERSION This document describes v0.0.8 of MooseX::Role::AttributeOverride - released June 22, 2011 as part of MooseX-Role-AttributeOverride. SYNOPSIS { package MyApp::Role; use Moose::Role; use MooseX::Role::AttributeOverride; has_plus 'fun' => ( default => 'yep', ); has_plus 'alive' => ( default => 'yep', override_ignore_missing => 1, ); } { package MyApp::Trait; use Moose::Role; use MooseX::Role::AttributeOverride; has_plus default => ( default => sub { my $attr = shift; return sub { $attr->name } } ); } { package MyApp; use Moose 1.9900; has nolife => ( is => 'rw', isa => 'Str', traits => ['MyApp::Trait'], ); has 'fun' => ( is => 'rw', isa => 'Str' ); with qw(MyApp::Role); } { package main; use feature 'say'; my $test = MyApp->new(); say "I have " . $test->nolife; # Says I have nolife say "Are you having fun? " . $test->fun; # Says Are you having fun? yep } DESCRIPTION Moose doesn't allow roles to override attributes using the has '+attr' method. There are several good reasons for that. Basically, "that's not what a role is for." A role is a set of requirements with defaults. A class should always be able to override a role. But sometimes you want a role to add features to a class. This is why Moose has method modifiers. This extension adds attribute modifiers. INTERFACE has_plus This has exactly the same syntax as the Moose has command, except you should not use a plus to indicate you are overriding an attribute. has_plus options override_ignore_missing Setting this to a true value will allow your role to have modifications to attributes that may not exist in the class it is applied to. The default is to die in these cases. For example: package MyApp::Role; use Moose::Role; use MooseX::Role::AttributeOverride; has_plus 'alive' => ( default => 'yep', override_ignore_missing => 1, ); package MyApp; use Moose; with qw(MyApp::Role); # I'm not dead yet. The above would not die, even though the MyApp package has no attribute named 'fun.' IMPORTANT NOTE Always apply a role that uses this module after defining attributes. META USAGE This role can be used in traits. For example, the following works: { package MyApp::Trait; use Moose::Role; use MooseX::Role::AttributeOverride; has_plus default => ( default => sub { my $attr = shift; return sub { $attr->name } } ); } { package MyApp; use Moose 1.9900; has nolife => ( is => 'rw', isa => 'Str', traits => ['MyApp::Trait'], ); with qw(MyApp::Role); } { package main; use feature 'say'; my $test = MyApp->new(); say "I have " . $test->nolife; # Says I have nolife } DIAGNOSTICS Can't find attribute $attr required by $role You will see this error if your role has an attribute modification for an attribute that is not in the class. You can squash this by setting the 'override_ignore_missing' option in your 'has_plus' command. Attempt to call has_plus on an invalid object You really should never see this. Please file a bug report if you do. A test case would be nice as well. Illegal inherited options Moose will throw this error if you try to change an accessor option. See the Moose manual for more details. Do not use a plus prefix with the has_plus sugar There is no need for a plus sign on your attribute: # Good has 'children', trait => ['good'] # Bad. Will die. has '+children', trait => ['naughty'] DEPENDENCIES Moose 1.9900 or newer. Older versions may be supported in a future version of this module. INCOMPATIBILITIES I am sure that there are some MooseX modules that will not work with this. Please let me know, and I will at least document them. BUGS AND LIMITATIONS This is not the intended use of roles. As a result, take into account the following: * Order matters! If two roles modify the same attribute in the same way, the second one applied will be the one that is used. This behavior, however, relies on Moose keeping track of order, which it generally does a good job of, but no guarantees. * Currently, the value of the attribute is clobbered when the role is applied. This may change in the future. * This works the same as '+has'. This means that you can't override accessor methods. This is a very sensible Moose limitation. * After having an issue with Moose, clone_and_inherit_options, and traits that use _process_options, I reimplemented clone_and_inherit_optiosn in a way that fixes it. Sort of. A side effect of this is that has_plus will not allow you to override the lazy option, without a default or builder option. * If you try adding this role before adding the attributes, it won't work. I am relatively new to Moose. I had an itch, and wrote this Module to scratch it. Please let me know how to make this module better. For bugs, test cases are great! SEE ALSO Please see those modules/websites for more information related to this module. * Moose * Moose::Manual::Attributes SUPPORT Websites The following websites have more information about this module, and may be of help to you. As always, in addition to those websites please use your favorite search engine to discover more resources. * Search CPAN The default CPAN search engine, useful to view POD in HTML format. * CPAN Testers Dependencies The CPAN Testers Dependencies is a website that shows a chart of the test results of all dependencies for a distribution. * CPANTS The CPANTS is a website that analyzes the Kwalitee ( code metrics ) of a distribution. * CPAN Testers The CPAN Testers is a network of smokers who run automated tests on uploaded CPAN distributions. * CPAN Testers Matrix The CPAN Testers Matrix is a website that provides a visual way to determine what Perls/platforms PASSed for a distribution. Email You can email the author of this module at "EALLENIII at cpan.org" asking for help with any problems you have. Bugs / Feature Requests Please report any bugs or feature requests by email to "bug-moosex-role-attributeoverride at rt.cpan.org", or through the web interface at . You will be automatically notified of any progress on the request by the system. Source Code The code is open to the world, and available for you to hack on. Please feel free to browse it and play with it, or whatever. If you want to contribute patches, please send me a diff or prod me to pull from your repository :) git clone git://github.com/riemann42/MooseX-Role-AttributeOverride.git AUTHOR Edward Allen COPYRIGHT AND LICENSE This software is copyright (c) 2011 by Edward J. Allen III. This is free software; you can redistribute it and/or modify it under the same terms as the Perl 5 programming language system itself. DISCLAIMER OF WARRANTY BECAUSE THIS SOFTWARE IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY FOR THE SOFTWARE, TO THE EXTENT PERMITTED BY APPLICABLE LAW. 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