DrawView.swift

class ViewController: UIViewController {    
    override func viewDidLoad() {
        super.viewDidLoad()
        let draw = DrawView(frame: self.view.bounds)
        view.addSubview(draw)
    }
}

class DrawView: UIView {
    override init(frame: CGRect) {
        super.init(frame: frame)
    }
    
    required init?(coder aDecoder: NSCoder) {
        fatalError("init(coder:) has not been implemented")
    }
    
    override func draw( _ rect: CGRect) {
    }
    
    func drawLine(x:Int, y:Int, width:Int, height:Int) {
    }
}