Create, store, and retrieve a unique iOS device ID using the appropriate technology.

unique ID

    //get a unique ID
    NSString *deviceID = nil;
    UIDevice *device = [UIDevice currentDevice];
    if ([device respondsToSelector:@selector(identifierForVendor)]) {
        deviceID = [[device identifierForVendor] UUIDString];
    }
    else {
        //retrieve an NSDefaults stored UUID
        NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
        NSString *uuidKey = @"UUID";
        deviceID = [defaults stringForKey:uuidKey];
        //nothing stored yet
        if (deviceID == nil) {
            //create a new UUID
            CFUUIDRef cfuuid = CFUUIDCreate(NULL);
            CFStringRef cfDeviceID = CFUUIDCreateString(NULL, cfuuid);
            
            deviceID = (NSString *)cfDeviceID;
            
            CFRelease(cfuuid);
            //autorelease the string after passing the uuid to NSDefaults
            //CFRelease(cfDeviceID);
            
            NSLog(@"creating new UUID: %@", deviceID);
            
            //and store it in NSDefaults
            [defaults setObject:deviceID forKey:uuidKey];
            [deviceID autorelease];
        }
    }