title: Testing for UIApplicationOpenSettingsURLString existence with Swift
body: <p>On iOS 8 Apple gave us the possibility to go to the App Settings right from our app, using the Constant UIApplicationOpenSettingsURLString</p>
  
  <p><code>UIApplication.sharedApplication().openURL(NSURL.URLWithString(UIApplicationOpenSettingsURLString))</code></p>
  
  <p>There's a code to test if this Constant exists on iOS 7, but it uses ObjC and pointes. Apple did this on their code: <a href="https://developer.apple.com/library/ios/samplecode/AppPrefs/Listings/RootViewController_m.html">https://developer.apple.com/library/ios/samplecode/AppPrefs/Listings/RootViewController_m.html</a></p>
  
  <p>How can I make something like this using Swift?</p>