title: Draw lines in swift 3.0
body: <p>I used the following code to no avail in Swift 3.0 - it gives me a blank screen on the simulator - I don't know what's happening.</p>
  
  <pre><code>import UIKit
  
  class DrawExample: UIView {
  
          override func draw( _ rect: CGRect) {
  
          let context = UIGraphicsGetCurrentContext()
          context!.setLineWidth(3.0)
          context!.setStrokeColor(UIColor.purple.cgColor)
  
          //make and invisible path first then we fill it in
          context!.move(to: CGPoint(x: 50, y: 60))
          context!.addLine(to: CGPoint(x: 250, y:320))
          context!.strokePath()
      }
  </code></pre>