You cannot get the unique identifier directly in iOS7.
In app delegate, there is a method called "application:didRegisterForRemoteNotificationsWithDeviceToken:", Use this method you can get the deviceToken in NSData, then you can use NSRegularExpression with pattern "[><]" to replace with "" for NSData's description. Then that will be the "unique identifier" you are looking for.
我们现在不能直接得到唯一表示用
[[UIDevice currentDevice] uniqueIdentifier]
但是我们可以使用"application:didRegisterForRemoteNotificationsWithDeviceToken:"来得到。