title: Swift: convert String to NSTextField
body: <p>When I try to convert a string to an NSTextField using the following code</p>
  
  <pre><code>test?.stringValue = red_str
  </code></pre>
  
  <p>test returns "nil". test is the name of an outlet of type NSTextField! which is connected to an NSTextField in my view. I determined this by single stepping the app past this statement. The quantity "red_str" is a valid string. Thanks for any suggestions.</p>
  
  <p>Here is the function in which the statement is embedded:</p>
  
  <pre><code>@IBAction  func redValue(sender: NSSliderCell) {
      red = Float(sender.doubleValue)
      let red_str = String.localizedStringWithFormat("%6.2f", red)
      test?.stringValue = red_str
      self.needsDisplay = true }
  </code></pre>
  
  <p>The view displays a graph which depends upon the parameter "red" which is updated with the slider. The graph displays (and updates) perfectly; the value of red does not display in the TextView.</p>
  
  <p>For reference, here is the outlet:</p>
  
  <pre><code>@IBOutlet weak var test: NSTextField!
  </code></pre>