ios - Passing Data from TableView to ViewController -

i'm trying send data table view viewcontroller keeps crashing. here have done:

in prepare segue

if ([segue.identifier isequaltostring:@"detailsegue"]){     detailview *dv = [segue destinationviewcontroller];     nsindexpath *indexpath = [self.tableview indexpathforselectedrow];     dv.stringforfirstlabel = [_cell.firstarray objectatindex:indexpath.row]  } 

but logs

: unrecognized selector sent instance.

might because call method isequaltostrinf should isequaltostring?