public function execute()
 {
     $code = waRequest::post('code', '', waRequest::TYPE_STRING_TRIM);
     $rate = (double) waRequest::post('rate', 0);
     if (!$code) {
         $this->errors[] = _w("Error when change currency");
         return;
     }
     if ($rate <= 0) {
         $this->errors[] = _w("Error when change currency");
     }
     $currency_model = new shopCurrencyModel();
     if (!$currency_model->changeRate($code, $rate)) {
         $this->errors[] = _w("Error when change currency");
         return;
     }
 }