[html-formfu] Validating unique names

Ton Voon ton.voon at altinity.com
Wed May 14 17:45:34 BST 2008

On 14 May 2008, at 15:46, Andreas Marienborg wrote:

> On May 14, 2008, at 4:39 PM, Ton Voon wrote:
>> We've just starting playing with FormFu with new Catalyst  
>> application and am impressed with how it works. However, one thing  
>> which I find hard is how to define a field as unique across all the  
>> existing rows.
>> For instance, we have a list of hosts and we need to ensure that  
>> the host name given in the form is unique. Obviously if the host is  
>> being edited and the name is the same, then the validator should  
>> pass.
>> It looks like a validator callback is the best way to do that, but  
>> I can't see how to integrate this with DBIx::Class. How do others  
>> do this?
> We do this by setting something in the form stash before processing,  
> then the validator can reach this trough the $form->stash method (I  
> think). This might only work if you implement it as a constraint or  
> validator class, not as a validator or constraint callback (too long  
> since I worked with formfu :/)
> Anyway, once you have the object beeing worked on, you can check  
> that the ID or whatever is the same, and return "AOK" then
> hope that made some sense


Thanks. I was thinking that the stash maybe one option. However, after  
a bit of playing, I think I might have hit on something where it might  
integrate better with DBIx::Class using object methods instead.

I've got a new class called HTML::FormFu::Validator::Object, which is  


package HTML::FormFu::Validator::Object;

use strict;
use base 'HTML::FormFu::Validator';

__PACKAGE__->mk_accessors(qw/ object /);

sub validate_value {
     my ( $self, $value ) = @_;
     $self->$object->validate_value( $self, $value );



then I've added this method to DBIx::Class::HTML::FormFu:

sub validate_value {
         my ($self, $field, $new_value) = @_;
         if ($self->name ne $new_value) {
                 return $self->result_source->resultset- 
 >count( { $field->name => $new_value } ) == 0;
         return 1;


which is a component of my DBIx::Class objects:

__PACKAGE__->load_components( qw/HTML::FormFu Core/ );

so you can now define $field with:
$field->validator('Object')->object( $object );

When validation occurs, it will call validate_value in  
H::F::V::Object.pm, which in turn calls $object- 
 >validate_value( $field, $new_value) which now has all the  
information it needs to do the validation (new value, the object and  
the field information).

Is this a suitable, general solution? I can provide patches if this is  


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