iOS - UIStoryboardSegue detecting table cell and opening a viewController?

So I have a UITableView, and the cells are connected to a UIStoryboardSegue in order to open a new UIViewController. After clicking a cell prepareForSegue get's called and everything works fine.

QUESTION: In the follwoing method how can i know what is the indexPath of the selected cell in my TableView?

- (void)prepareForSegue:(UIStoryboardSegue *)segue sender:(id)sender
{
    ObjectDetailViewController *mvc = [segue destinationViewController];
    // PassingObject *obj = [self.array objectAtIndex: ? ];
    mvc.passingObject = obj;
}