SwiftUI picker driven by an enum: value not updated

Question

According to Apple's documentation regarding Picker in SwiftUI using an Enum, if the enum conforms to the Identifiable protocol in addition to CaseIterable, a picker iterating over all cases should update the bound variable natively.

I tested it, and it does not work as expected.

enum Flavor: String, CaseIterable, Identifiable {
    case chocolate
    case vanilla
    case strawberry

    var id: String { self.rawValue }
}

struct EnumView: View {
    @State private var selectedFlavor = Flavor.chocolate
    var body: some View {
        VStack {
            Picker("Flavor", selection: $selectedFlavor) {
                ForEach(Flavor.allCases) { flavor in
                    Text(flavor.rawValue.capitalized)//.tag(flavor)
                }
            }
        
            Text("Selected flavor: \(selectedFlavor.rawValue)")
        }
    }
}

However, if I pass a tag for each view, it works.

What's happening here? Is the Apple documentation wrong? The selectedFlavor variable expects a value of type Flavor, but the id used in the picker is actually a String.

Thanks.

Answer 1

For a Picker to work properly, its elements need to be identified.

Note that the selectedFlavor variable is of type Flavor. Which means the options in the Picker should be identified as Flavors (not Strings).

However, in your code your id is of type String:

var id: String { self.rawValue }

---

You can either:

• provide a tag (of type Flavor):

Text(flavor.rawValue.capitalized)
    .tag(flavor)

• conform Flavor to Identifiable by providing a custom id of type Flavor:

var id: Flavor { self }

• specify the id parameter (of type Flavor) explicitly in the ForEach:

ForEach(Flavor.allCases, id: \.self) { ... }

• change the selectedFlavor to be a String:

@State private var selectedFlavor = Flavor.chocolate.rawValue

Answer 2

This is an addition to @pawello2222 already awesome answer.

Just to clarify that the solution to conform the enum to Identifiable using the below code works to correctly tag the UI picker without explicitly declaring it within the picker code:

var id: Flavor { self }

The official Apple documentation for the swiftUI picker says to id the enum using var id: String { self.rawValue } and does not work as expected using the rest of the example code.