public function getField($identifier, $fieldName) {
        $snippetModel = $this->_getSnippetModel();
        $snippet = $snippetModel->fetchByIdentifier($identifier);

        if (!isset($snippet->{$fieldName})) {
            throw new Exception(sprintf(self::EXCEPTION_MISSING_FIELD, $snippet->id, $fieldName));
        }
        return $snippet->{$fieldName};
    }