Continue operation when app did enter background on iOS

Question

in my app i have some NSOperation that update some core data element from a online database, sometime the update require some minute, and when the screen of iPhone lock, the

Answer 1

That's not how you do this. Any code that you want to run in the background must be wrapped properly. Something like this:

- (void)someMethodToKeepRunningInBackground {
    UIBackgroundTaskIdentifier taskId = [[UIApplication sharedApplication] beginBackgroundTaskWithExpirationHandler:^(void) {
        // Uh-oh - we took too long. Stop task.
    }];

    // Perform task here        

    if (taskId != UIBackgroundTaskInvalid) {
        [[UIApplication sharedApplication] endBackgroundTask:taskId];
    }
}

You don't do anything in the UIApplicationDelegate applicationDidEnterBackground: method.

Any task that is wrapped inside the "background task" calls will be allowed to keep running when the app enters the background.

Here's the really important part - the task only gets 10 minutes maximum. If it is still running after 10 minutes your app will be terminated. The expiration handler gives you a few seconds to cleanly end the task before the app is terminated uncleanly.