如何为任务设置每日本地通知，但在用户之前完成任务时不显示

Question

I know similar questions appeared before but I think I need more clarification since i still don't know how to make it done. I'm a beginner programmer so please forgive me any mistakes.

I'm trying to have daily reminders for daily tasks from my app IF user didn't complete it yet, so how can i make it not show up when he had already done the task?

Solutions i found so far suggest to remove pending notification and setting up new one for future date in the same time.

I successfully set up daily notifications using this code:

    func sendDailyReminder() {
        let content = UNMutableNotificationContent()
        content.title = "Daily reminder"
        content.body = "You still have task to complete today."
        content.sound = UNNotificationSound.default
        var dateComponents = DateComponents()
        dateComponents.hour = 20
        dateComponents.minute = 00
        let trigger = UNCalendarNotificationTrigger(dateMatching: dateComponents, repeats: true)
        let request = UNNotificationRequest(identifier: "dailyTrigger", content: content, trigger: trigger)

        center.add(request) { (error) in
            if let error = error {
                print("Notification Error: ", error)
            }
        }
    }

i can also successfully remove pending notification with removePendingNotificationRequest method but how can I set it up trigger for tomorrow using dateComponents here?

Or is there any other way to achieve that? Maybe using background fetch to check if its done just before sending notification?

Some replies i found suggest that its actually impossible but then how any task or to-do app can achieve something like that?

Answer 1

I ended up using multiple notifications for each weekday but set it up in little different way:

First set up daily reminder using weekday Int as identifier

func setWeekdayReminder(weekday: Int) {
        let center = UNUserNotificationCenter.current()
        let content = UNMutableNotificationContent()
        content.title = "Daily reminder"
        content.body = "You still have some tasks to complete today."
        content.sound = UNNotificationSound.default
        var dateComponents = DateComponents()
        dateComponents.hour = 18
        dateComponents.minute = 35
        dateComponents.weekday = weekday
        let trigger = UNCalendarNotificationTrigger(dateMatching: dateComponents, repeats: true
        let request = UNNotificationRequest(identifier: String(weekday), content: content, trigger: trigger)

        center.add(request) { (error) in
            if let error = error {
                print("Notification Error: ", error)
            }
        }
    }

then i made a function to check if there is any missing day after users launches app (except today, so i won't request todays notification again even after removing it earlier when user completes the task)

func checkDailyReminder() {

       let currentWeekday = Calendar.current.component(.weekday, from: Date())

       center.getPendingNotificationRequests { (requests) in
            var weekdayArray : [Int] = []

            for each in requests {
               weekdayArray.append(Int(each.identifier)!)
            }
            for number in 1...7 {
                if weekdayArray.contains(number) {
                    print("weekdayArray contains weekday \(number)")
                } else {
                    print("weekdayArray doesnt contain weekday \(number)")
                    if number != currentWeekday {
                          self.setWeekdayReminder(weekday: number)
                    }
                }
            }

        }
    }

Of course it's kind of a hack and when user completes the task and somehow won't go back for a week and open it again on the same weekday then he won't get notification that day but it works for rest of the time.

Answer 2

Here is what I came up with. Basically everyday the app runs, i'll run this function, to setup local notifications. It sets them up for the next 14 days. Everyday it runs, its always going to be setting up the 14th day from now. It will skip the others, they are already pending. There is also a function for canceling the notification today, once the task is completed.

func setupLocalNotifications() {
    let center = UNUserNotificationCenter.current()
    center.getNotificationSettings { setting in
        guard setting.authorizationStatus == .authorized else {
            print("Not authorized for local push notifications")
            return
        }
        
        let dateFormatter = DateFormatter()
        dateFormatter.dateFormat = "yyyyMMdd"
        dateFormatter.timeZone = TimeZone(abbreviation: "UTC")
        
        let calendar = Calendar.current
        var date = calendar.date(bySettingHour: 14, minute: 0, second: 0, of: Date())!
        center.getPendingNotificationRequests { [weak self] notificationRequests in
            (1...14).forEach { _ in
                //Capture this date.
                let thisDate = date
                
                //Prepare the next date.
                date = calendar.date(byAdding: .day, value: 1, to: date)!
                
                let identifier = dateFormatter.string(from: thisDate)
                
                guard thisDate.isPastDate == false else {
                    Log.d(TAG, "Task Date is in the past - Skipping \(identifier)")
                    return
                }
                
                // Check if we've already scheduled this identifier
                guard notificationRequests.first(where: { $0.identifier == identifier }) == nil else {
                    print("Task Already Scheduled - Skipping \(identifier)")
                    return
                }
                
                // Check if we'e already done our task for the day.
                /*
                 TODO: Special Code Guard that checks if we've already completed the task today. (I took this out because it had project specific code, but you should check your core data or whatever, to see if the task is finished for today.
                 */
                
                let content = UNMutableNotificationContent()
                
                content.title = "Title"
                content.body = "Body"
                
                let dateComponents = Calendar.current.dateComponents([.year, .month, .day, .hour, .minute], from: thisDate)
                
                let trigger = UNCalendarNotificationTrigger(dateMatching: dateComponents, repeats: false)
                
                let request = UNNotificationRequest(identifier: identifier, content: content, trigger: trigger)
                
                let notificationCenter = UNUserNotificationCenter.current()
                notificationCenter.add(request) { (error) in
                    if error != nil {
                        Log.e(TAG, error)
                    }
                    print("Successfully scheduled: \(identifier)")
                }
            }
        }
    }
}

Here is the cancel task function.

func cancelTodaysNotification() {
    let center = UNUserNotificationCenter.current()
    let calendar = Calendar.current
    let dateFrom = calendar.startOfDay(for: Date())
    
    let dateFormatter = DateFormatter()
    dateFormatter.dateFormat = "yyyyMMdd"
    dateFormatter.timeZone = TimeZone(abbreviation: "UTC")
    
    let identifier = dateFormatter.string(from: dateFrom)

    center.removePendingNotificationRequests(withIdentifiers: [identifier])
    
    print("Removed Local Notification for Date: \(identifier)")
    
}