[html-formfu] How to best pass the resultset object to DBIC validator callbacks?

[Dan Dascalescu]

[ Possibly related but old thread:
http://thread.gmane.org/gmane.comp.lang.perl.modules.html-formfu.general/415/ ]

In a Catalyst application, I'm trying to implement a validator
callback that does a database lookup. Normally, I would do this:

In the form config file, have:

     "validators" : [
       { "type": "Callback",
         "callback": "MyApp::Schema::ResultSet::Urls::validator_unique_url",
         "message": "This URL already exists"
       }
     ]

Then in MyApp::Schema::ResultSet::Urls,

use base qw/MyApp::Schema::Base::ResultSet/;
sub validator_unique_url {
   my $value = shift;
   .... how do I get at the DB?
}

The problem here is that I don't have $elf and I can't call
__PACKAGE__->find or other resultset methods. That would generate this
error:

Can't use string ("MyApp::Schema::ResultSet::Urls") as a HASH ref
while "strict refs" in use at
C:/strawberry/perl/site/lib/Class/Accessor/Grouped.pm line 246.

The workaround that I found was to add the callback programmatically
and pass it an anonymous sub which in turn calls the real validator
MyApp::Schema::ResultSet::Urls::validator_unique_url. Here's the code:

sub index :Path :Args(0) :FormConfig {
   my ( $self, $c ) = @_;
   my $form = $c->stash->{form};

   my $field = $form->get_all_element({name => 'url'});
   $field->validator('Callback')->callback(sub{
       my $value = shift;
       return $c->model('DBIC::Urls')->validator_unique_url($value);
   });


1. Is this the best way to achieve the goal of doing some DB-related
validation in a callback? If so, I'll be happy to document this in the
Validator::Callback.pm, which is painfully empty at the moment.

2. Is it best practice to put the callback information in the form
config file, or to modify the form in the controller code?

Thanks,
Dan

PS: after an hour of working with this, the anonymous sub approach
feels very natural and almost not worth documenting - but when I hit
it the first time, I wish there were some documentation