How to identify unique users without using a login system (iOS)

Question

I need to have a way to identify the users of my app, but without having a login system.

I looked into the UUID which gives me part of an answer to my problem, but as it's not the real UDID, it's not "really unique" : if the user re-installs the app, he gets a new UUID, and this can't work for me.

Is there a way I can get the device serial number or something unique like that? Anything of the sort that i could get from the device without having the user to fill any fields.

Answer 1

You can try to use some unique random string that is stored in Key-Value Storage in iCloud of user.

So, when user launches your app for the first time you see that his iCloud stores no value so you generate and store it. And when user will launch app next time you will see this value and will act accordingly.

What is more important even if user will reinstall your app or will make factory reset of device you still be able to identify user by value in his iCloud.