Question

I have loaded some values into local documents in my application. When the application is running app writes, say, 50 records.

Now, when the user force-closes the app and starts it again: The files only write the new records 50+existing 50.

How to handle this issue?

Answer 1

If your application is force-quit completely, you do not have an opportunity to write out additional data. No more of your code is run.

If you are talking about the force quit that happens when your app is in the background and the OS wants to free up memory, you must implement a callback in your application delegate (you can use notifications too but let’s keep it simple) and observe when the OS places your app in the background. At that point, write your data to disk:

@implementaton MyAppDelegate
- (void)applicationDidEnterBackground: (UIApplication *)application {
    [myDatabase commit];
    [myFiles save];
    [myWhatever doWhatever];
    // etc.
}
@end