Swift UNNotification - Repeat Interval after Fire Date

Question

I'm sending a local notification to the user with a UNUserNotification. I want to first send a notification at a starting time I'm calculating from a Time Picker. After this first notification, I want to send a reminder every 15 minutes. Is there any way to set the Trigger for a Calendar and a time interval?

let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "HH"
    let hour = dateFormatter.string(from: _notificationTime)

    dateFormatter.dateFormat = "mm"
    let minutes = dateFormatter.string(from: _notificationTime)

    var dateComponents = DateComponents()
    dateComponents.hour = Int(hour)
    dateComponents.minute = Int(minutes)
    let trigger = UNCalendarNotificationTrigger(dateMatching: dateComponents, repeats: true)

    let content = UNMutableNotificationContent()
    content.body = "Hi " + settings.username + ".\nHast du deine Pille schon genommen?"
    content.categoryIdentifier = "takePill"
    content.userInfo = ["customData": "takePill"]
    content.sound = UNNotificationSound.default()

    if let path = Bundle.main.path(forResource: "DontForget", ofType: "PNG") {
        let url = URL(fileURLWithPath: path)

        do {
            let attachment = try UNNotificationAttachment(identifier: "DontForget", url: url, options: nil)
            content.attachments = [attachment]
        } catch {
            print("The attachment was not loaded.")
        }
    }

    let pillTakenAction = UNNotificationAction(identifier: "pillTakenAction", title: "Pille eingenommen", options: [])
    let pillTakenCategory = UNNotificationCategory(identifier: "pillTakenCategory", actions: [pillTakenAction], intentIdentifiers: [], options: [])

    center.setNotificationCategories([pillTakenCategory])

    content.categoryIdentifier = "pillTakenCategory"

    let request = UNNotificationRequest(identifier: UUID().uuidString, content: content, trigger: trigger)
    center.add(request)

Answer 1

UNNotificationTrigger has a property repeats which determine if the the notification should be repeated or not. By setting that property to true, you specify that the notification needs to be repeated at the given date.

In your code above :

var dateComponents = DateComponents()
    dateComponents.hour = Int(hour)
    dateComponents.minute = Int(minutes)
    let trigger = UNCalendarNotificationTrigger(dateMatching: dateComponents, repeats: true)

You have specified the property as true, which will repeat the notification at the particular time dateComponents.

To achieve this you can use UNTimeIntervalNotificationTrigger. First, schedule the UNCalanderNotificationTrigger at your specified time. When this notification gets called, in the userNotificationCenter(_ center:, didReceive response:, withCompletionHandler completionHandler:) function you can schedule a UNTimeIntervalNotificationTrigger to repeat every 15 minutes.

Your code will look like

func userNotificationCenter(_ center: UNUserNotificationCenter, didReceive response: UNNotificationResponse, withCompletionHandler completionHandler: @escaping () -> Void) {

let trigger = UNTimeIntervalNotificationTrigger(timeInterval: (15*60), repeats: true)

    let content = UNMutableNotificationContent()
    content.body = "Hi " + settings.username + ".\nHast du deine Pille schon genommen?"
    content.categoryIdentifier = "takePill"
    content.userInfo = ["customData": "takePill"]
    content.sound = UNNotificationSound.default()

    if let path = Bundle.main.path(forResource: "DontForget", ofType: "PNG") {
        let url = URL(fileURLWithPath: path)

        do {
            let attachment = try UNNotificationAttachment(identifier: "DontForget", url: url, options: nil)
            content.attachments = [attachment]
        } catch {
            print("The attachment was not loaded.")
        }
    }

    let pillTakenAction = UNNotificationAction(identifier: "pillTakenAction", title: "Pille eingenommen", options: [])
    let pillTakenCategory = UNNotificationCategory(identifier: "pillTakenCategory", actions: [pillTakenAction], intentIdentifiers: [], options: [])

    center.setNotificationCategories([pillTakenCategory])

    content.categoryIdentifier = "pillTakenCategory"

    let request = UNNotificationRequest(identifier: UUID().uuidString, content: content, trigger: trigger)
    center.add(request)
}

Hope this helps. :)