     var pingHelper: PingHelper?
     
     @IBAction func intervalTextFieldChanged(sender: NSTextField) {
-        if let helper = pingHelper {
-            helper.interval = intervalTextField.doubleValue
-            helper.start()
-            savePrefs(fromPingHelper: helper)
+        guard let helper = pingHelper else {
+            return
         }
+        helper.interval = intervalTextField.doubleValue
+        helper.start()
+        savePrefs(fromPingHelper: helper)
     }
     
     @IBAction func quit(sender: AnyObject) {

    
    var currentStatus: Status? {
        didSet {
            if let status = currentStatus {
                statusTextField.stringValue = status.rawValue
                switch status {
                case .Success:
                    statusTextField.textColor = NSColor(calibratedRed: 0, green: 149/255.0, blue: 0, alpha: 1)
                case .Failure:
                    statusTextField.textColor = NSColor.orangeColor()
                case .Error:
                    statusTextField.textColor = NSColor.redColor()
                default:
                    statusTextField.textColor = NSColor.blackColor()
                }
            }
        }
    }

    }
    
    @IBAction func saveHostButtonPressed(sender: NSButton) {
        guard let helper = pingHelper else {
            return
        }
        
        statusTextField.stringValue = "Starting…"
        statusTextField.textColor = NSColor.blackColor()
        helper.host = targetHostTextField.stringValue
        helper.start()
        savePrefs(fromPingHelper: helper)
    }
    
    @IBAction func startStopButtonPressed(sender: NSButtonCell) {
        guard let helper = pingHelper else {
            return
        }
        
        if helper.running {
            helper.stop()
        } else {
            helper.start()
        }
    }
    
