How to get unique id in iOS device?

Question

I have used mac address to identify iOS devices in server side. When run my application with iOS 7 unable to retrieve the correct mac address. Alternately i used

Answer 1

Getting device ID in

Swift 3

let device_id = UIDevice.currentDevice().identifierForVendor?.UUIDString

Swift 4:

let device_id = UIDevice.current.identifierForVendor!.uuidString