public function getChangedData($field = null)
    {
        if ($field) {
            return isset($this->changedData[$field]) ? $this->changedData[$field] : null;
        }
        return $this->changedData;
    }
public function getChangedData($field = null)
    {
        if ($field) {
            return isset($this->changedData[$field]) ? $this->changedData[$field] : null;
        }
        return $this->changedData;
    }
public function getChangedData ( $ field = null ) { if ( $ field ) { return isset ( $ this -> changedData [ $ field ] ) ? $ this -> changedData [ $ field ] : null ; } return $ this -> changedData ; }
Return the field data before changed

@param string $field
@return string|array
Return the field data before changed