Start a counter at 10 and decrement when tapped (no lower than 0). Remembers value between runs of the app. https://www.reddit.com/r/swift/comments/3lbk2v/stuck_with_saving_a_number_and_decreasing_it_with/

ViewController.swift

class ViewController: UIViewController {
  let clicksKey = "clicksKey"
  let maxClicks = 10
  
  @IBOutlet weak var clicksLabel: UILabel!
  
  override func viewDidLoad() {
    super.viewDidLoad()
    updateLabel()
  }
  
  func updateLabel() {
    let clicks = getClicksRemaining()
    if (clicks > 0) {
      clicksLabel.text = "You have \(clicks) remaining"
    } else {
      clicksLabel.text = "You have no remaining"
    }
  }

  func getClicksRemaining() -> Int {
    let defaults = NSUserDefaults.standardUserDefaults()

    // do we have a click count saved?
    if defaults.objectForKey(clicksKey) != nil {
      return defaults.integerForKey(clicksKey)
    } else {
      return maxClicks
    }
  }


  @IBAction func tappedButton(sender: AnyObject) {
    var currentCount = getClicksRemaining()
    if (currentCount > 0) {
      currentCount = currentCount - 1
      let defaults = NSUserDefaults.standardUserDefaults()
      defaults.setInteger(currentCount, forKey: clicksKey)
    
      updateLabel()
    }
  }

}