title: Device UUID not unique when user uninstall and re-install
body: <p>I have a system where each user allowed to install apps for two devices only. The issue is happened when user uninstall and reinstall again on the same device. So it will generate new UUID and when the apps check to web service.</p>
  
  <p>The apps will send UUID and login id in order to check if the user with that login id has installed in more than two devices. I am using real iPhone and iPad device, not using simulator. I am not sure for production environment. Currently the apps is distributed using Apple TestFlight using AppStore Distribution profile.</p>
  
  <p>I generate the uuid using this </p>
  
  <pre><code>let uuid = UIDevice.currentDevice().identifierForVendor!.UUIDString
  </code></pre>
  
  <p>Thanks.</p>