One of the three alternative methods for the unique ID of iOS devices

[UIDeviceUniqueIdentifier] One of the alternative methods specified in the document (there are three alternative methods in total ):

UniqueIdentifierProperty Available in iOS 2.0 through iOS 6.1
UniqueIdentifierAttribute can be used for iOS 2.0 to iOS 6.1

UniqueIdentifier

An alphanumeric string unique to each device based on various hardware details. (read-only) (Available in iOS 2.0 through iOS 6.1.
A combination of numbers and letters that are unique to each device based on multiple hardware information. (Read-only) (available for iOS 2.0 to iOS 6.1)

Alternative method:

UseTheIdentifierForVendOr property of this class
UseIdentifierForVendorAttribute

OrTheAdvertisingIdentifierProperty ofASIdentifierManagerClass instead, as appropriate,
Or replace itASIdentifierManagerClassAdvertisingIdentifierAttribute

OrUseUUIDMethod ofNSUUIDClass to createUUIDAnd write it to theuser defaults database .)

Or use NSUUIDClass UUIDMethod To create a UUID and write it into the user's default database, that is UserDefault.

- (NSString *)generateUuidString {      CFUUIDRef uuid = CFUUIDCreate(kCFAllocatorDefault);      NSString *uuidString = (NSString*)CFUUIDCreateString(kCFAllocatorDefault, uuid);      [uuidString autorelease];      CFRelease(uuid);          return uuidString;  }