SwiftUI: Reordering with Section crashes app

Question

Goal: Multiple text views visually separated much like what Section{} offers, while also being able to rearrange the items in the list during edit mode. (I am not 100% set on only using section but I haven't found a way to visually distinguish with Form or List.)

The issue: The app crashes on the rearrange when using Section{}.

Error Message: 'Invalid update: invalid number of rows in section 2. The number of rows contained in an existing section after the update (1) must be equal to the number of rows contained in that section before the update (0), plus or minus the number of rows inserted or deleted from that section (0 inserted, 0 deleted) and plus or minus the number of rows moved into or out of that section (0 moved in, 0 moved out).'

Code:

struct SingleItem: Identifiable {
    let id = UUID()
    let item: String
}

class ItemGroup: ObservableObject{
    @Published var group = [SingleItem]()
}

struct ContentView: View {
    @ObservedObject var items = ItemGroup()
    @State private var editMode = EditMode.inactive
    
    var body: some View {
        NavigationView{
            Form {
                Button("Add Item"){
                    addButton()
                }
                ForEach(Array(items.group.enumerated()), id: \.element.id) { index, item in
                    Section{
                        Text(items.group[index].item)
                    }
                }
                .onMove(perform: onMove)
            }
            .navigationBarTitle("List")
            .navigationBarItems(trailing: EditButton())
            .environment(\.editMode, $editMode)
            
        }
    }

    func addButton() {
        let newItem = SingleItem(item: "Word - \(items.group.count)")
        self.items.group.append(newItem)
        
    }

    
    private func onMove(source: IndexSet, destination: Int) {
        items.group.move(fromOffsets: source, toOffset: destination)
    }
}

Asperi Asperi · Accepted Answer · 2020-10-14T04:58:12

Use instead .indices. Tested as worked with no crash on Xcode 12 / iOS 14.

    Form {
        ForEach(items.indices, id: \.self) { i in
            Section {
                Text(items[i].title)
            }
        }
        .onMove(perform: onMove)
    }

SwiftUI: Reordering with Section crashes app

1 Answers