gistfile1.m

//http://mobiledevelopertips.com/core-services/create-universally-unique-identifier-uuid-the-ios-6-way.html

//The class NSUUID implements RFC 4122 creating values that are 128 bits long and guaranteed to be unique across space and time by using a unique value on the device as well as a value representing the elapsed time since October 15, 1582 at 00:00:00.

// iOS 6
NSUUID  *uuid = [NSUUID UUID];
NSLog(@"UUID: %@", [uuid UUIDString]);

// Output: UUID: A84AFC3C-B3A7-31C7-B3E9-234AF423C6B1

// iOS < 6
CFUUIDRef uuid = CFUUIDCreate(NULL);
CFStringRef identifier = CFUUIDCreateString(NULL, uuid);
CFRelease(uuid);
NSString *uuidString = CFBridgingRelease(identifier);