Delete Core Data Row When Long Pressing

Question

I have created a new Mac OS xcode application with core data and was playing around with the default code that generates that allows you to add items.

But I wanted to change the way in which the rows are deleted. With using a long press gesture to trigger the delete.

View:

var body: some View {
    List {
        ForEach(items) { item in
            Text("Item at \(item.timestamp!, formatter: itemFormatter)")
                
        }
        //.onDelete(perform: deleteItems) Want to change this command to the one below
          .onLongPressGesture(minimumDuration: 1.5, perform: deleteItems)

    }
    .toolbar {
        Button(action: addItem) {
            Label("Add Item", systemImage: "plus")
        }
    }
}

Delete Item Function

private func deleteItems(offsets: IndexSet) {
    withAnimation {
        offsets.map { items[$0] }.forEach(viewContext.delete)

        do {
            try viewContext.save()
        } catch {
            // Replace this implementation with code to handle the error appropriately.
            // fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
            let nsError = error as NSError
            fatalError("Unresolved error \(nsError), \(nsError.userInfo)")
        }
    }

But I get the following error

Cannot convert value of type '(IndexSet) -> ()' to expected argument type '() -> Void'

workingdog support Ukraine · Accepted Answer · 2021-07-07 12:52:23Z

2

".onDelete(perform action: ((IndexSet) -> Void)?)" and ".onLongPressGesture(minimumDuration: Double = 1.5, perform action: @escaping () -> Void)" as you can see have different signatures. So what you are doing is not working.

You could try something like this:

List {
    ForEach(items, id: \.self) { item in
        Text("Item at \(item)")
            .onLongPressGesture(minimumDuration: 1.5, perform: {deleteItems2(item)})
    }
   // .onDelete(perform: deleteItems)
}
    
private func deleteItems2(_ item: Item) {
    if let ndx = items.firstIndex(of: item) {
        viewContext.delete(items[ndx])
    do {
        try viewContext.save()
    } catch {
        // Replace this implementation with code to handle the error appropriately.
        // fatalError() causes the application to generate a crash log and terminate. You should not use this function in a shipping application, although it may be useful during development.
        let nsError = error as NSError
        fatalError("Unresolved error \(nsError), \(nsError.userInfo)")
    }
  }
}

edited Jul 7, 2021 at 12:52

answered Jul 7, 2021 at 1:20

workingdog support Ukraine

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4 Comments

marcus Over a year ago

I tried this but I get the following error Value of type 'FetchedResults<item>' has no member 'remove'

workingdog support Ukraine Over a year ago

this is just an example, since you don't show us the Items code. You have to adjust it to your particular condition. Probably using "viewContext.delete" on the item or items.

workingdog support Ukraine Over a year ago

I've updated the answer using a guess at what items are.

marcus Over a year ago

Thank you so much! I managed to get it working :)

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