SwiftUI List: Prevent Empty Selection-CodePudding

I have a SwiftUI list, defined in a typical fashion:

struct SettingsView: View
{
    @State private var selectedCategory: SettingsCategory? = .general

    List(SettingsCategory.allCases, id: \.self, selection: $selectedCategory) { category in
        [...]
    }
}

In this case, the List is a table of "categories" for a settings area in my UI. The SettingsCategory is an enum that defines these categories, and the UI ends up looking like this:

It is not appropriate for this list to have an empty selection; a category should always be selected. In AppKit, it was trivially easy to disable an empty selection on NSTableView. But in SwiftUI, I've been unable to find a way to disable it. Anytime I click in the empty area of the list, the selection is cleared. How can I stop that?

selectedCategory must be an Optional or the compiler vomits all over itself.

I can't use willSet/didSet on selectedCategory because of the @State property wrapper. And I can't use a computed property that never returns nil because the List's selection has to be bound.

I also tried this approach: SwiftUI DatePicker Binding optional Date, valid nil

So, what magical incantation is required to disable empty selection in List?

CodePudding user response：

One solution would be to set the selection back to the original one if the selection becomes nil.

Code:

struct ContentView: View {
    @State private var selectedCategory: SettingsCategory = .general

    var body: some View {
        NavigationView {
            SettingsView(selectedCategory: $selectedCategory)

            Text("Category: \(selectedCategory.rawValue.capitalized)")
                .navigationTitle("App")
        }
    }
}

enum SettingsCategory: String, CaseIterable, Identifiable {
    case destination
    case general
    case speed
    case schedule
    case advanced
    case scripts

    var id: String { rawValue }
}

struct SettingsView: View {
    @Binding private var selectedCategory: SettingsCategory
    @State private var selection: SettingsCategory?

    init(selectedCategory: Binding<SettingsCategory>) {
        _selectedCategory = Binding<SettingsCategory>(
            get: { selectedCategory.wrappedValue },
            set: { newCategory in
                selectedCategory.wrappedValue = newCategory
            }
        )
    }

    var body: some View {
        List(SettingsCategory.allCases, selection: $selection) { category in
            Text(category.rawValue.capitalized)
                .tag(category)
        }
        .onChange(of: selection) { [oldCategory = selection] newCategory in
            if let newCategory = newCategory {
                selection = newCategory
                selectedCategory = newCategory
            } else {
                selection = oldCategory
            }
        }
    }
}

CodePudding user response：

you could try adding .onChange to the List, such as:

.onChange(of: selectedCategory) { val in
    if val == nil {
        selectedCategory = .general // <-- make sure never nil
    }
}