Let's say you have a Picker in SwiftUI and want the ability to set its value to nil. In order for the optional binding to work correctly, you can tag each item with the value casted as the optional type.

struct ContentView: View {
    @State var selection: String?

    var body: some View {
        Picker("Select:", selection: $selection) {
            Text("None").tag(nil as String?)
            Divider()
            Text("Red").tag("R" as String?)
            Text("Green").tag("G" as String?)
            Text("Blue").tag("B" as String?)
        }
    }
}

This is great for things like user preferences, which we use it extensively in all of our apps at Neat Software.