title: Nil cannot be assigned to type 'Timer'?
body: <p>Hi there I am completing some research for Alzheimers Disease - I want to be able to record the time it takes to complete a drawing (it should only take a few seconds for the patient to draw). I want to record both the time spent with apple pencil on tablet and the time spent overall to complete a drawing (time on tablet plus time in between strokes).</p>
  
  <p>I have created this application so far but can't get the timer to work.</p>
  
  <p>I have the drawing/scribble board down pat.</p>
  
  <p>I have tried many different approaches but I am just not experienced enough in code to work out why it is not starting the timer when the apple pencil hits the tablet. The code below is for the ViewController script.</p>
  
  <p>Only one of the timers for = time spent drawing, has been created so far. But I can't even get that to work.</p>
  
  <p>Tried changing the script, tried asking friends. Im quite new to swift so any help is much appreciated.</p>
  
  <pre><code>
  import UIKit
  
  class ViewController: UIViewController {
  
  
      @IBOutlet weak var canvasView: CanvasView!
      override func viewDidLoad() {
          super.viewDidLoad()
          // Do any additional setup after loading the view, typically from a nib.
      }
  
      @IBAction func clearCanvas(_ sender: Any) {
          canvasView.clearCanvas()
          timer.invalidate()
  
          seconds = 0    
          timeDrawing.text = "\(seconds)"
      }
      @IBOutlet weak var timeDrawing: UILabel!
  
      var seconds = 0 
      var timer = Timer()
      var isTimerRunning = false //This will be used to make sure only one timer is created at a time.
      var resumeTapped = false
      var touchPoint:CGPoint!
      var touches:UITouch!
  
      func runTimer() {
          timer = Timer.scheduledTimer(timeInterval: 1, target: self,   selector: (#selector(ViewController.updateTimer)), userInfo: nil, repeats: true)
      }
      private(set) var from: Date?
  
      @objc func updateTimer() {
          let to = Date()
          let timeIntervalFrom = (from ?? to).timeIntervalSince1970
          let time = to.timeIntervalSince1970 - timeIntervalFrom
          timeDrawing.text = "\(round(time))" //This will update the label.
      }
  
      override func touchesBegan(_ touches: Set&lt;UITouch&gt;, with event: UIEvent?) {
          super.touchesBegan(touches, with: event)
          guard let touch = touches.first else { return }
          let touches = touch.location(in: canvasView) // or maybe ...(in: self)
  
          if touch.type == .pencil  {
              if !isTimerRunning {
                  from = Date()
                  runTimer()
              }
          }
      }
  
      override func touchesEnded(_ touches: Set&lt;UITouch&gt;, with event: UIEvent?) {
          super.touchesEnded(touches, with: event)
          if !isTimerRunning {
              timer.invalidate()
              timer = nil
              from = nil
              timeDrawing.text = "0"
          }
  }
  }
  </code></pre>
  
  <p>I was hoping when the apple pencil touched the tablet it would start the timer. And then when the pencil left the tablet it would stop one timer and start one of the timers (yet to be implemented). (i have yet to add another timer for the time in between strokes, any help with that would be appreciated too.)</p>