Question

I would like to schedule a local notification to fire at 7pm everyday IF a certain condition is met (the user hasn’t entered daily data).

How do I go about doing this?

Answer 1

Just break it up into 3 cases:

1. It’s before 7pm, and the user hasn’t entered their daily data yet
2. It’s before 7pm, and the user has entered their daily data
3. It’s after 7pm

In case 1, you set up a notification to go off at 7pm today, and then repeat every day.

In cases 2 and 3, you set up a notification to go off at 7pm tomorrow, and then repeat every day.

The code to create and schedule the notification looks like this:

UILocalNotification *dailyNotification = [[UILocalNotification alloc] init];
dailyNotification.fireDate = nextReminderTime; // set this to 7pm today or tomorrow
dailyNotification.timeZone = [NSTimeZone defaultTimeZone]; 
dailyNotification.repeatInterval = NSDayCalendarUnit;
dailyNotification.soundName = UILocalNotificationDefaultSoundName;
dailyNotification.alertBody = @"You need to enter data for today.";

Of course, if you set up an alert for 7pm today, then the user opens the app and enters data before 7pm, the notification for today needs to be cancelled.

Alternatively (this is what I did in a similar situation), you can cancel all the notifications with [[UIApplication sharedApplication] cancelAllLocalNotifications]; and set them up again from scratch based on the application state every time the app is about to go into the background (i.e., in UIApplication applicationDidEnterBackground:. This is simpler since you don’t have to think about what notifications you set up before.