Gpf_Rpc_Form::addValidator PHP Method

        public function addValidator(Gpf_Rpc_Form_Validator_Validator $validator, $fieldName, $fieldLabel = null)
        {
            $this->validator->addValidator($validator, $fieldName, $fieldLabel);
        }

 /**
  * @anonym
  * @service custom_separator write
  * @param Gpf_Rpc_Params $params
  * @return Gpf_Rpc_Form
  */
 public function save(Gpf_Rpc_Params $params) {
     $form = new Gpf_Rpc_Form($params);
     $form->addValidator(new Gpf_Rpc_Form_Validator_MandatoryValidator(), self::COMMISSION_KEY);
     $form->addValidator(new Gpf_Rpc_Form_Validator_NumberRangeValidator(0, 100), self::COMMISSION_KEY);
     $form->validate();
     if($form->isSuccessful()){
         Gpf_Settings::set(self::COMMISSION_KEY, $form->getFieldValue(self::COMMISSION_KEY));
         $form->setInfoMessage($this->_('Plugin configuration saved'));
     }
     return $form;
 }