pass row number outside "did select" function

The way to pass data through a segue is using prepare(segue:)

Your desttination is a viewController class is DestViewController

Inside, define a property

var rowSelected : Int?

In the source controller, declare a var to hold the selection

fileprivate var selectedRow: Int?

that you set in didSelectRow

    func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
        rowSelected = indexPath.row
        print(rowSelected)     //just for testing
        performSegue(withIdentifier: "ToObjectSearch", sender: self)
    }

   override func prepare(for segue: UIStoryboardSegue, sender: Any?) {

        // Get the destination  view controller in destVC.
        // Pass the selected object to the new view controller.
        if let destVC = segue.destination as? DestViewController {
            destVC.rowSelected = rowSelected
        }
    }

Note: in the prepare, you should test it is the right segue, so that, if you define other vsegues you know which one to prepare

  override func prepare(for segue: UIStoryboardSegue, sender: Any?) {

        // Get the destination  view controller in destVC.
        // Pass the selected object to the new view controller.
         if segue.identifier == "ToObjectSearch" 
             if let destVC = segue.destination as? DestViewController {
                 destVC.rowSelected = rowSelected
          }
        }
    }