NAME
MooseX::Role::AttributeOverride - Allow roles to modify attributes
VERSION
This document describes v0.0.9 of MooseX::Role::AttributeOverride - released June 29, 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
rride>. 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 :)
AUTHOR
Edward Allen <ealleniii_at_cpan_dot_org>
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.
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