title: Error: Cannot find an overload for 'Init' that supplied arguments
body: <p>I am unable to fix this issue, I'm using Xcode6.    </p>
  
  <pre><code>var numbersOnscreen:Double = 0;                 
          @IBOutlet var displabel: UILabel!
  
          @IBAction func numbers(sender: UIButton) {
              displabel.text = displabel.text + String(sender.tag-1)
              numbersOnscreen = Double(displabel.text)  //error line
          }
  </code></pre>