public function setDirty($key= '') {
        if (empty($key)) {
            foreach (array_keys($this->_fieldMeta) as $fIdx => $fieldKey) {
                $this->setDirty($fieldKey);
            }
        }
        else {
            $key = $this->getField($key, true);
            if ($key !== false) {
                $this->_dirty[$key] = $key;
                if (isset($this->_validated[$key])) unset($this->_validated[$key]);
            }
        }
    }