1 + (NSString *)uuidString 2 { 3 CFUUIDRef uuid_ref = CFUUIDCreate(NULL); 4 CFStringRef uuid_string_ref= CFUUIDCreateString(NULL, uuid_ref); 5 NSString *uuid = [NSString stringWithString:(__bridge NSString *)uuid_string_ref]; 6 CFRelease(uuid_ref); 7 CFRelease(uuid_string_ref); 8 return [uuid lowercaseString]; 9 }