title: Countdown with several decimal slots, using NSTimer in Swift
body: <p>I want to make an app that has a timer starting at 10.0000000 for example, and I want it to countdown perfectly
  Here's my code so far:</p>
  
  <pre><code>import UIKit
  
  class ViewController: UIViewController {
  
      @IBOutlet weak var labelTime: UILabel!
  
      var counter = 10.0000000
  
      var labelValue: Double {
          get {
              return NSNumberFormatter().numberFromString(labelTime.text!)!.doubleValue
          }
          set {
              labelTime.text = "\(newValue)"
          }
      }
  
  
      override func viewDidLoad() {
          super.viewDidLoad()
          // Do any additional setup after loading the view, typically from a nib.
          labelValue = counter
          var timer = NSTimer.scheduledTimerWithTimeInterval(0.0000001, target: self, selector: ("update"), userInfo: nil, repeats: true)
      }
  
      func update(){
          labelValue -= 0.0000001
      }
  
  
  }
  </code></pre>
  
  <p>What happens is that my countdown is really slow, it's just not working and it would take like 1 hour to get to 0 seconds, instead of just 10 seconds. Any ideas? What changes should I make to my code?
  Thanks</p>