UITableView. Add header to table section programmatically

ViewController.swift

class ViewController: UITableViewController {

    let headerId = "headerId"
 
    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view, typically from a nib.
        
        tableView.sectionHeaderHeight = 50
        tableView.registerClass(MyTableHeader.self, forHeaderFooterViewReuseIdentifier: headerId)
    }
    
    override func tableView(tableView: UITableView, viewForHeaderInSection section: Int) -> UIView? {
        return tableView.dequeueReusableHeaderFooterViewWithIdentifier(headerId)
    }
}

class MyTableHeader: UITableViewHeaderFooterView {
    
    let headerLabel: UILabel = {
        let label = UILabel()
        label.text = "Section"
        label.textAlignment = NSTextAlignment.Center
        
        label.translatesAutoresizingMaskIntoConstraints = false
        
        return label
    }()
    
    override init(reuseIdentifier: String?) {
        super.init(reuseIdentifier: reuseIdentifier)
        
        setupViews()
    }
    
    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    func setupViews() {
        addSubview(headerLabel)
        
        addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("H:|[v0]|", options: NSLayoutFormatOptions(), metrics: nil, views: ["v0": headerLabel]))
        addConstraints(NSLayoutConstraint.constraintsWithVisualFormat("V:|[v0]|", options: NSLayoutFormatOptions(), metrics: nil, views: ["v0": headerLabel]))
    }
}