Replacing UIDevice uniqueIdentifier

Since uniqueIdentifier is now deprecated (back from the iOS 5 days) and Apple no longer accepts apps that use this method (the latest Xcode, it seems, does not even build a project that uses this function).

I googled what to replace it with and assembled one solution from several different ones:

NSString *uuid = @"";

if ([[UIDevice currentDevice] respondsToSelector:@selector(identifierForVendor)]) {
    // This is will run if it is iOS6 or later
    uuid = [[[UIDevice currentDevice] identifierForVendor] UUIDString];
} else {
    NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
    id uuidId = [defaults objectForKey:@"deviceUuid"];
    if (uuidId)
        uuid = (NSString *)uuidId;
else {
        // Create universally unique identifier (object)
        CFUUIDRef uuidObject = CFUUIDCreate(kCFAllocatorDefault);

        // Get the string representation of CFUUID object.
        uuid = (__bridge_transfer NSString *)CFUUIDCreateString(kCFAllocatorDefault, uuidObject);
        CFRelease(uuidObject);
        [defaults setObject:uuid forKey:@"deviceUuid"];
    }
}

Apple now suggests using the identifierForVendor method. This identifier will be unique for each device, but the same across all of your apps on that device. That is, if you install 2 apps from one vendor on the same phone, this id will be the same in both apps. It appeared in iOS 6 and, as far as I understood, on iOS 6 it changes if the app is deleted and installed again. In iOS 7, judging by what people write, it will already be tied to the MAC address and will always stay the same.

The identifierForVendor method had a bug in iOS 6.0: on devices updated over the air it returned a value full of zeros. In 6.0.1 and later that was fixed.

identifierForVendor appeared only in iOS 6, so if you support iOS 5 you need something else. This is where CFUUIDCreate comes in handy. An ID created with it will also change after the app is removed and installed again if you store it somewhere like NSUserDefaults, as in the code above. If you store it in KeyChain, you can avoid it changing after installation. Although how necessary that is is not very clear to me personally. But once generated, the identifier has to be stored somewhere, otherwise this code will generate a different one every time.

That is the cheat sheet.