Re: Adding traits at runtime

On Jun 9, 2008, at 4:40 PM, Dan Harbin wrote:

> Stevan,
>
> Thanks for the help.  I am getting the following exception:
>
> Can't locate object method "excludes_role" via package  
> "Class::MOP::Class" at lib/Moose/Meta/Role/Application/ToClass.pm  
> line 25.
>
> I'm building a class from a YAML spec, and I want to add a trait to  
> every attribute I pull from the YAML file:
>
> use YAML;
> use Moose;
> use My::Super;
> use My::Trait;
>
> my $file = shift @ARGV;
> my $yaml = YAML::LoadFile($file);
>
> my $rowclass = Moose::Meta::Class->create(
>     "My::Class",
>     superclasses => ['My::Super'],
> );
>
> my %columns = @{ $yaml->{columns} };
> while (my ($name, $params) = each %columns) {
>   my $attr = Moose::Meta::Attribute->new($name, %$params);
>   My::Trait->meta->apply($attr);
>   $rowclass->add_attribute($attr);
> }
>
> Am I doing something wrong?

No, sorry I gave bad advice, the metaclass of the  
Moose::Meta::Attribute instance is a Class::MOP::Class an therefore  
does not know know about roles.

Why not do:

     $rowclass->add_attribute($name, %$params, traits =>  
[ 'My::Trait' ]);

This should work as expected.

- Stevan





>
>
> On Mon, Jun 9, 2008 at 3:24 PM, Stevan Little  
> <[email protected]> wrote:
> Dan,
>
> Something like this maybe?
>
> My::Trait->meta->apply(My::Class->meta->get_attribute('foo'));
>
> - Stevan
>
>
> On Jun 9, 2008, at 4:21 PM, Dan Harbin wrote:
>
> Is there a way to add a trait to an attribute at runtime?  I know  
> it can be
> done through the "new" method of Moose::Meta::Attribute, but what  
> about
> adding one after it's been initialized?
>
> Thanks,
> Dan
>
>