sorting - Yii2 GridView default order by CASE WHEN -

i using gridview display data. need add default sorting 2 columns follows:

(case     when (inbound_datetime null , outbound_datetime < now()) or (inbound_datetime not null , inbound_datetime < now())         9999     when (inbound_datetime not null , outbound_datetime < now())         inbound_datetime         else outbound_datetime end) asc 

if add code in order by clause in data provider query, of other sorting options don't work because condition applied query itself.

i tried apply default sorting other grid, not working (the method searches attribute name):

'sort' => [     'defaultorder' => [         '(case             when (inbound_datetime null , outbound_datetime < now()) or (inbound_datetime not null , inbound_datetime < now())                 9999             when (inbound_datetime not null , outbound_datetime < now())                 inbound_datetime                 else outbound_datetime         end)' => sort_asc,     ], ], 

is there way make default sorting work , still keep ability use grid sorting column names correctly?

i did more thinking , have come solution problem.

i define query in controller method opens view. added condition checks if sort parameter passed request. if passed, create query without order by clause. if sort parameter not passed (no column sorting done), create query order by clause. in controller method:

if (yii::$app->request->get('sort')) {     $query = travel::find(); } else {     $query = travel::find()         ->orderby('(case             when (inbound_datetime null , outbound_datetime < now()) or (inbound_datetime not null , inbound_datetime < now())                 9999             when (inbound_datetime not null , outbound_datetime < now())                 inbound_datetime                 else outbound_datetime         end) asc');      }