does app give different device token on re-installing again

Question

I remember, the device token never changes upon re-installing for iPhone.

However these days (especially on iOS 9), I noticed that device token is changing if I re-install the app.

Is this setting is done by Apple or I am missing anything?

I have to know this because this is very important for me as I am sending push based for specific users to inform their updates.

Also for no reason there are un-wanted many device tokens.

Note

I am calling below webservice in App Delegate

- (void)application:(UIApplication*)application didRegisterForRemoteNotificationsWithDeviceToken:(NSData*)deviceToken
{
    // sending it to online database for my record
}

Answer 1

Yes on iOS9 Apple says that Device Token might change each time your app is installed. So the best way is to reregister the Device token on each launch.

Here is a link to Apples documentation about changing device token

Answer 2

You need to find your own way to track user. Here is issues with your approach and suggested vendor identifier:

• Device push token can change at any moment. You can track this change during application launch and ask server to switch tokens, but messages which will be send till this moment on old token will be lost.
• identifierForVendor - also very unreliable source of unique identifier, because it will change in a lot of cases.

  The value in this property remains the same while the app (or another app from the same vendor) is installed on the iOS device. The value changes when the user deletes all of that vendor’s apps from the device and subsequently reinstalls one or more of them. The value can also change when installing test builds using Xcode or when installing an app on a device using ad-hoc distribution. Therefore, if your app stores the value of this property anywhere, you should gracefully handle situations where the identifier changes.

For single device you can use Keychain as source of persistent identifier storage. You can generate for user new unique identifier (for example with NSUUID) and store it in Keychain (if not exist yet). If access group will be configured for stored item and reused with all your application - you will have access to stored unique identifier from your applications on user device. If properly configured, item in Keychain will be stored in encrypted user device backups and even will be restored on his new device.