How do I add an extra separator to the top of a UITableView?

To replicate the standard iOS separator lines, I use a 1 px (not 1 pt) hair line tableHeaderView with the table view’s separatorColor:

// in -viewDidLoad
self.tableView.tableHeaderView = ({
    UIView *line = [[UIView alloc] 
                    initWithFrame:CGRectMake(0, 0,
                    self.tableView.frame.size.width, 1 / UIScreen.mainScreen.scale)];
    line.backgroundColor = self.tableView.separatorColor;
    line;
});

The same in Swift (thanks, Dane Jordan, Yuichi Kato, Tony Merritt):

let px = 1 / UIScreen.main.scale
let frame = CGRect(x: 0, y: 0, width: self.tableView.frame.size.width, height: px)
let line = UIView(frame: frame)
self.tableView.tableHeaderView = line
line.backgroundColor = self.tableView.separatorColor