how to identify ios device uniquely

Question

In my current application,i have to let user to login from different iOS devices to their account. Currently i\'m doing user authentication from a token value. but in order

Answer 1

As you already know this using the device's UUID isn't allowed, however, you can generate your own UUID and store it on the devices' UserDefaults.

using the identifierForVendor isn't 100% reliable, as it only works on iOS6 and above, and users have the ability to opt-out of giving it to you, which makes it a bad choice.

Here's some code I copied of the internets sometime ago and still use it till today, will try to find the source and update my answer in a bit. EDIT: Source

This will generate and store a UUID for you in UserDefaults:

- (NSString *)createUUID
{
  CFUUIDRef theUUID = CFUUIDCreate(NULL);
  CFStringRef string = CFUUIDCreateString(NULL, theUUID);
  CFRelease(theUUID);
  [[NSUserDefaults standardUserDefaults] setObject:(__bridge NSString *)string forKey:@"UUID"];
  [[NSUSerDefaults standardUserDefaults] synchronize];
  return (__bridge NSString *)string;
}

And whenever you need to read the generated UUID:

- (NSString*)UUID
{
    return [[NSUserDefaults standardUserDefaults] ObjectForKey:@"UUID"];
}

Now you have the choice to append your own user's ID to that too so you'll be able to know what UUID is linked to which user..

This is just a rough sketch of how it should work