Method check

/**
 * Checks that the object is valid and able to be stored.
 *
 * This method checks that the parent_id is non-zero and exists in the database.
 * Note that the root node (parent_id = 0) cannot be manipulated with this class.
 *
 * @return  boolean  True if all checks pass.
 *
 * @since   1.7.0
 */
public function check()
{
    try {
        parent::check();
    } catch (\Exception $e) {
        $this->setError($e->getMessage());
        return false;
    }
    $this->parent_id = (int) $this->parent_id;
    // Set up a mini exception handler.
    try {
        // Check that the parent_id field is valid.
        if ($this->parent_id == 0) {
            throw new \UnexpectedValueException(sprintf('Invalid `parent_id` [%1$d] in %2$s::check()', $this->parent_id, \get_class($this)));
        }
        $query = $this->_db->getQuery(true)->select('1')->from($this->_tbl)->where($this->_tbl_key . ' = ' . $this->parent_id);
        if (!$this->_db->setQuery($query)->loadResult()) {
            throw new \UnexpectedValueException(sprintf('Invalid `parent_id` [%1$d] in %2$s::check()', $this->parent_id, \get_class($this)));
        }
    } catch (\UnexpectedValueException $e) {
        // Validation error - record it and return false.
        $this->setError($e);
        return false;
    }
    return true;
}