Have you ever needed to determine which version of your app users are updating from for data migration purposes? Or perhaps you want to determine the time at which the user opened your app for the first time for analytics purposes? Well, there is an app, er… library for that: AppUpdateTracker.

AppUpdateTracker was created initially as some cobbled code I hastily added within the source of Appirater while working on the UCD Mobile project. I needed the ability to determine not only when the user updated the app, but from which version they are upgrading for in order to perform data migrations within the Core Data store.

I extracted that code into an isolated project and thus, AppUpdateTracker was born. It detects the following events:

• when the user launches the app for the first time, provides:
  • timestamp of when user opened app for the first time, in seconds since epoch
  • installation count representing the number of times the user has opened the app for the first time on the same device
• when the user opens the app for the first time after updating, provides:
  • the previous version the user updated from
  • the current version of the app (provided for convenience)
• when the user brings the app to the foreground, provides:
  • usage count representing how many times the app has been opened (includes bringing app to foreground after resigning active, not only cold start)

It works by persisting a small amount information within NSUserDefaults, all of which are directly accessible via getters in the interface. It broadcasts an NSNotification whenever one of the 3 aforementioned events occurs. It is important to note that only 1 event can happen during any given app session, so you needn’t worry about handling the case where an app update notification is broadcast, followed by that of a use count incremented. (The use count is reset to 1 in this case.)

Additionally, I have recently added block support, making usage trivial:

[AppUpdateTracker registerForAppUpdatesWithBlock:^(NSString *previousVersion, NSString *currentVersion) {
        NSLog(@"app updated from: %@ to: %@", previousVersion, currentVersion);
}];
[AppUpdateTracker registerForFirstInstallWithBlock:^(NSTimeInterval installTimeSinceEpoch, NSUInteger installCount) {
        NSLog(@"first install detected at: %f amount of times app was (re)installed: %lu", installTimeSinceEpoch, (unsigned long)installCount);
}];
[AppUpdateTracker registerForIncrementedUseCountWithBlock:^(NSUInteger useCount) {
        NSLog(@"incremented use count to: %lu", (unsigned long)useCount);
}];

Which you are free to call anywhere or anytime within your app (although it is recommended you call these within application:didFinishLaunchingWithOptions:), resulting in one and only one of the 3 blocks being called during any given session (with the exception of registerForIncrementedUseCountWithBlock: being called every time the app is foregrounded).

So there you have it! Easy app update/install tracking for your iOS app. Enjoy!