Symfony: exclude empty values from form save - forms

Question

I have a many to many relation between Product and Properties. I'm using embedRelation() in my Product form to edit a Product and it's Properties. Properties includes images which causes my issue. Every time I save the form the updated_at column is updated for file properties even when no file is uploaded.
Therefore, I want to exclude empty properties when saving my form.
I'm using Symfony 1.4 and Doctrine 1.2.
I'm thinking something like this in my ProductForm.class.php, but I need some input on how to make this work.
Thanks
class ProductForm extends BaseProductForm
{
public function configure()
{
unset($this['created_at'], $this['updated_at'], $this['id'], $this['slug']);
$this->embedRelation('ProductProperties');
}
public function saveEmbeddedForms($con = null, $forms = null)
{
if (null === $forms)
{
$properties = $this->getValue('ProductProperties');
$forms = $this->embeddedForms;
foreach($properties as $p)
{
// If property value is empty, unset from $forms['ProductProperties']
}
}
}
}

Answer 1

I ended up avoiding Symfony's forms and saving models instead of saving forms. It can be easier when playing with embedded forms. http://arialdomartini.wordpress.com/2011/04/01/how-to-kill-symfony%E2%80%99s-forms-and-live-well/

Answer 2

Solved it by checking if posted value is a file, and if both filename and value_delete is null I unset from the array. It might not be best practice, but it works for now.
Solution based on http://www.symfony-project.org/more-with-symfony/1_4/en/06-Advanced-Forms
class ProductPropertyValidatorSchema extends sfValidatorSchema
{
protected function configure($options = array(), $messages = array())
{
// N0thing to configure
}
protected function doClean($values)
{
$errorSchema = new sfValidatorErrorSchema($this);
foreach($values as $key => $value)
{
$errorSchemaLocal = new sfValidatorErrorSchema($this);
if(array_key_exists('value_delete', $values))
{
if(!$value && !$values['value_delete'])
{
unset($values[$key]);
}
}
// Some error for this embedded-form
if (count($errorSchemaLocal))
{
$errorSchema->addError($errorSchemaLocal, (string) $key);
}
}
// Throws the error for the main form
if (count($errorSchema))
{
throw new sfValidatorErrorSchema($this, $errorSchema);
}
return $values;
}
}