/**
* Method to move a row in the ordering sequence of a group of rows defined by an SQL WHERE clause.
* Negative numbers move the row up in the sequence and positive numbers move it down.
*
* @param integer $delta The direction and magnitude to move the row in the ordering sequence.
* @param string $where WHERE clause to use for limiting the selection of rows to compact the
* ordering values.
*
* @return mixed Boolean True on success.
*
* @throws UnexpectedValueException
*/
public function move($delta, $where = '')
{
if (!$this->onBeforeMove($delta, $where)) {
return false;
}
// If there is no ordering field set an error and return false.
$ordering_field = $this->getColumnAlias('ordering');
if (!in_array($ordering_field, $this->getKnownFields())) {
throw new UnexpectedValueException(sprintf('%s does not support ordering.', $this->_tbl));
}
// If the change is none, do nothing.
if (empty($delta)) {
$result = $this->onAfterMove();
return $result;
}
$k = $this->_tbl_key;
$row = null;
$query = $this->_db->getQuery(true);
// If the table is not loaded, return false
if (empty($this->{$k})) {
return false;
}
// Select the primary key and ordering values from the table.
$query->select(array($this->_db->qn($this->_tbl_key), $this->_db->qn($ordering_field)));
$query->from($this->_tbl);
// If the movement delta is negative move the row up.
if ($delta < 0) {
$query->where($this->_db->qn($ordering_field) . ' < ' . $this->_db->q((int) $this->{$ordering_field}));
$query->order($this->_db->qn($ordering_field) . ' DESC');
} elseif ($delta > 0) {
$query->where($this->_db->qn($ordering_field) . ' > ' . $this->_db->q((int) $this->{$ordering_field}));
$query->order($this->_db->qn($ordering_field) . ' ASC');
}
// Add the custom WHERE clause if set.
if ($where) {
$query->where($where);
}
// Select the first row with the criteria.
$this->_db->setQuery($query, 0, 1);
$row = $this->_db->loadObject();
// If a row is found, move the item.
if (!empty($row)) {
// Update the ordering field for this instance to the row's ordering value.
$query = $this->_db->getQuery(true);
$query->update($this->_tbl);
$query->set($this->_db->qn($ordering_field) . ' = ' . $this->_db->q((int) $row->{$ordering_field}));
$query->where($this->_tbl_key . ' = ' . $this->_db->q($this->{$k}));
$this->_db->setQuery($query);
$this->_db->execute();
// Update the ordering field for the row to this instance's ordering value.
$query = $this->_db->getQuery(true);
$query->update($this->_tbl);
$query->set($this->_db->qn($ordering_field) . ' = ' . $this->_db->q((int) $this->{$ordering_field}));
$query->where($this->_tbl_key . ' = ' . $this->_db->q($row->{$k}));
$this->_db->setQuery($query);
$this->_db->execute();
// Update the instance value.
$this->{$ordering_field} = $row->{$ordering_field};
} else {
// Update the ordering field for this instance.
$query = $this->_db->getQuery(true);
$query->update($this->_tbl);
$query->set($this->_db->qn($ordering_field) . ' = ' . $this->_db->q((int) $this->{$ordering_field}));
$query->where($this->_tbl_key . ' = ' . $this->_db->q($this->{$k}));
$this->_db->setQuery($query);
$this->_db->execute();
}
$result = $this->onAfterMove();
return $result;
}