title: Swift - How do you DECIDE the optimal "Deployment Target" for your iOS app
body: <p>On Xcode, you can decide the "Deployment Target" by yourself, but you may choose too old version to run the app stably since some of methods in your code are supported by later version of iOS.
  (e.g. choose Deployment Target 8.0, but when you run the app on a device with iOS version 8.0, the app crashes)</p>
  
  <p>Is there any good way to decide the best Deployment Target, or some tools which can scan the whole code to know the minimum version of iOS?</p>