- (NSString *)createUUID  {    // Create universally unique identifier (object)    CFUUIDRef uuidObject = CFUUIDCreate(kCFAllocatorDefault);      // Get the string representation of CFUUID object.    NSString *uuidStr = [(NSString *)CFUUIDCreateString(kCFAllocatorDefault, uuidObject) autorelease];      // If needed, here is how to get a representation in bytes, returned as a structure    // typedef struct {    //   UInt8 byte0;    //   UInt8 byte1;    //   ...    //   UInt8 byte15;    // } CFUUIDBytes;    CFUUIDBytes bytes = CFUUIDGetUUIDBytes(uuidObject);      CFRelease(uuidObject);      return uuidStr;  }