Always get a unique device id in iOS 7

Question

Our iOS application is for specific users. So, we used device unique identifier for user identification. This approach works fine till iOS 6, because we are

Answer 1

From the UIDevice Class reference for identifierForVendor:

The value changes when the user deletes all of that vendor’s apps from the device and subsequently reinstalls one or more of them. The value can also when installing test builds using Xcode or when installing an app on a device using ad-hoc distribution. Therefore, if your app stores the value of this property anywhere, you should gracefully handle situations where the identifier changes.