How to store an object together with a notification so that I can call it when receiving the notification?

Question

I am new to programming and this is my very first project. I am making a pretty simple reminder app; I've created a class reminder with the properties .moreInformation (String), .fireDate (Date), .fromDate (Date), .title (String) and .image(UIImage). You can edit all these properties within in the application. My problem is just: I need a proper solution for storing this object 'reminder'. I am using UserNotifications to register my notification like that:

reminder.fireDate = date
    reminder.image = image
    reminder.description = descriptionTextView.text
    reminder.title = titleTextView.text
    reminder.savedOndate = savedOnDateString

    let center = UNUserNotificationCenter.current()
    let category = UNNotificationCategory(identifier: "General", actions: [], intentIdentifiers: [], options: .customDismissAction)
    center.setNotificationCategories([category])

    let content = UNMutableNotificationContent()
    let contentText = reminder.savedOnDate
    content.title = "Reminder"
    content.body = "Your Reminder from the \(contentText) has arrived!"

    let date2 = reminder.fireDate
    var components = Calendar.current.dateComponents(in: TimeZone.current, from: date2)

    components.hour = 18
    components.minute = 0

    let trigger = UNCalendarNotificationTrigger(dateMatching: components, repeats: false)

    let request = UNNotificationRequest(identifier: "Reminder", content: content, trigger: trigger)


    center.add(request) { (error : Error?) in
        if let theError = error {
            print(theError.localizedDescription)
        }
    }

When the user has received the notification, he should see a pop-up view when starting the app, leading him to a separate view controller that shows the description text, the fromDate etc.

But how do I store the object together with the notification so when the notification has arrived, the other view controller shows the correct description text/ title etc.?

Answer 1

You can use the userInfo dictionary of your UNMutableNotificationContent instance to store custom information. Keep in mind that objects stored in the userInfo dictionary must be property-list types. This means you either need to convert your reminder object to such a type (e.g. NSDictionary) or, and this would be a cleaner solution, implement NSCoding in the class of the reminder object and en/decode it using NSKeyedArchiver/NSKeyedUnarchiver.