public function custom($name) {
        if ($this->_exist) {
            $class = 'Controller\Request\Custom\\' . ucfirst($name);

            if (class_exists($class)) {
                array_push($this->_constraints, ['type' => self::CUSTOM, 'value' => new $class($this->_field, $this->_label, $this->_data[$this->_field])]);
            }
            else {
                throw new MissingClassException('The custom validation class "' . $class . '" was not found');
            }
        }

        return $this;
    }