Best practice for removePendingNotificationRequests with CoreData

Question

Created Feb ’21

Replies 17

Boosts 0

Views 2.4k

Participants 2

Hello all,

I have a question regarding how to use the removePendingNotificationRequests when implemented in CoreData.

Currently, I have an app that lets users save meeting URLs. Each meeting the user creates is stored as a CoreData entity. They can set a time for these meetings, and the app will schedule a local notification for a few minutes before the meeting. The way I'm doing this is passing the meeting time the user selected into a sendNotification function and using that time as a trigger (UNCalendarNotificationTrigger).

Problem is -- once a user creates a meeting and the notification is set, the notification will happen even if the user deletes the meeting before the scheduled time. I want to use removePendingNotificationRequests to solve this problem. My question is: removePendingNotificationRequests accepts a string as the identifier for which notification request to remove. But, how do I pass this string to the request? And which string should I use? The meeting's name? I've been thinking about creating a new UUID attribute for my meeting entity so I'll always have a unique string, and passing that UUID to the onDelete function of the meetings.

Here's how I'm passing the meeting time to the notification function (this is inside a "Create" button in a AddNewMeeting view):

Code Block self.notificationManager.sendNotification(title: "Upcoming Meeting", subtitle: nil, body: "\(meetingName) will start in 5 minutes. Tap here to get meeting information.", time: meetingTime, meetingName: "\(meetingName)")

This is my current code for the list of meetings:

Code Block ForEach(items, id: \.self) { item in
       OneTimeRow(meeting: item)
}
.onDelete(perform: deleteItems)

And this is the delete function:

Code Block     private func deleteItems(offsets: IndexSet) {
        withAnimation {
            offsets.map { items[$0] }.forEach(viewContext.delete)
            do {
                try viewContext.save()
            } catch {
                print("There was an error deleting items")
            }
        }
     removePendingNotificationRequests(withIdentifiers identifiers: [String]) // <-- Is this how to put the function in?
    }

And this is the code for scheduling notifications:

Code Block     func sendNotification(title: String, subtitle: String?, body: String, time: Date, meetingName: String) {
            let content = UNMutableNotificationContent()
            content.title = title
            if let subtitle = subtitle {
                content.subtitle = subtitle
            }
            content.body = body
            let triggerDate = time - 5 * 60
                let trigger = UNCalendarNotificationTrigger(
                            dateMatching: Calendar.current.dateComponents([.timeZone, .year, .month, .day, .hour, .minute], from: triggerDate),
                            repeats: true
                )
        let request = UNNotificationRequest(identifier: "\(meetingName)", content: content, trigger: trigger)
                UNUserNotificationCenter.current().add(request, withCompletionHandler: nil)
        }

Thank you!

Answered by Claude31 in 663611022

That is what you should use.

Of course, pass the actual Strings, with the exact meeting identifier

Code Block      removePendingNotificationRequests(withIdentifiers identifiers: [meetingID])

Note also :

This method executes asynchronously, removing the pending notification requests on a secondary thread.

Answer 1

Hu is I OP

Feb ’21

Anyone have any ideas? Basically, I need a way to pass the meeting name of the meeting that is being deleted to the delete function.

Code Block ForEach(items, id: \.self) { item in       
     OneTimeRow(meeting: item)}
.onDelete(perform: deleteItems)

I'm going to include the following in the delete function:

Code Block removePendingNotificationRequests(withIdentifiers identifiers: [String]

Answer 2

Claude31 OP

Feb ’21

Accepted Answer

That is what you should use.

Of course, pass the actual Strings, with the exact meeting identifier

Code Block      removePendingNotificationRequests(withIdentifiers identifiers: [meetingID])

Note also :

This method executes asynchronously, removing the pending notification requests on a secondary thread.

Answer 3

Hu is I OP

Feb ’21

Thank you, I'm now having trouble because I want to use the .onDelete(perform: ) to call two functions, the actual delete function then the delete notification function. I don't know how to call two functions, though:

Code Block .onDelete(perform: deleteItems)

Here are my two functions:

Code Block     private func deleteItems(offsets: IndexSet) {
        withAnimation {
            offsets.map { items[$0] }.forEach(viewContext.delete)
            do {
                try viewContext.save()
            } catch {
                print("There was an error deleting items")
            }
        }
    }
    private func removeSingleNotification(meetingID: String) {
        notificationManager.removePendingNotificationRequests(meetingID: meetingID)
    }

So I want to call both of these with the onDelete but I don't know how to include both functions because when I do, I get a compiler error that it can't type check in a reasonable amount of time. Thank you.

Answer 4

Claude31 OP

Feb ’21

Did you try to include both functions inside deleteItems ?

Answer 5

Hu is I OP

Feb ’21

Yes, I tried:

Code Block .onDelete(perform: deleteItems, removeSingleNotification(meetingID: "\(item.meetingLink)"))

But it's giving me a "cannot type check in reasonable time" error.

Answer 6

Hu is I OP

Feb ’21

Ok, actually, the error is that the 'items' is not in the scope of the function.

Code Block ForEach(items, id: \.self) { item in   
    OneTimeRow(meeting: item)
}
   .onDelete(perform: deleteItems, removeSingleNotification(meetingID: "\(item.meetingLink)"))

Any ideas about how to pass the specific item to the function? Thanks.

Answer 7

Claude31 OP

Feb ’21

Where is items defined ?

Answer 8

Hu is I OP

Feb ’21

Items is defined in a fetch request at the top of this view.

Code Block     @FetchRequest(
        entity: Item.entity(),
        sortDescriptors: [NSSortDescriptor(keyPath: \Item.time, ascending: true)],
        animation: .default)
    private var items: FetchedResults<Item>

Answer 9

Claude31 OP

Feb ’21

That would help to see the complete file, to understand why it is out of scope, and which function it is.

Answer 10

Hu is I OP

Feb ’21

Code for content view:

Code Block 
@Environment(\.managedObjectContext) private var viewContext
@FetchRequest(
        entity: Item.entity(),
        sortDescriptors: [NSSortDescriptor(keyPath: \Item.time, ascending: true)],
        animation: .default)
    private var items: FetchedResults<Item>
NavigationView {
                List {
                    Section(header:
                        Text("One-Time Meetings")
                            .textCase(nil)
                            .font(.headline)
                            .onAppear {
                                checkForUpdate()
                            }
                    ) {
                        ForEach(items, id: \.self) { item in
                            OneTimeRow(meeting: item)
                        }
                        .onDelete(perform: deleteItems, removeSingleNotification(meetingID: "\(item.meetingLink)"))
                    }
    private func deleteItems(offsets: IndexSet) {
        withAnimation {
            offsets.map { items[$0] }.forEach(viewContext.delete)
            do {
                try viewContext.save()
            } catch {
                print("There was an error deleting items")
            }
        }
    }
    private func removeSingleNotification(meetingID: String) {
        notificationManager.removePendingNotificationRequests(meetingID: meetingID)
        print("Deleted notification scheduled for meeting with identifier \(meetingID)")
    }

Answer 11

Claude31 OP

Feb ’21

That's not the complete file.

I do not see the

Code Block struct xxxx: View {

declaration for instance.

So please provide the complete file.

Answer 12

Hu is I OP

Feb ’21

Github link

Answer 13

Claude31 OP

Feb ’21

Is this your exact and complete project in the link ? Or a model from which you built your project ?

Answer 14

Hu is I OP

Feb ’21

Yes. It's content view and the notifications file.

Answer 15

Claude31 OP

Feb ’21

I downloaded and tried to run.

There is an error in Notifications:

Code Block     var meetings: Item?

Item is not defined.

Answer 16

Hu is I OP

Feb ’21

Oh, you want to run it. Let me give you the complete source code. Here

Answer 17

Claude31 OP

Feb ’21

Thanks. But you sent only the .xcodeproj file, without any content file.
You have to link to a zip of the complete project folder.