ListPicker.swift

import SwiftUI

protocol PickerEnum: Hashable, Identifiable, CaseIterable where AllCases: RandomAccessCollection {
    var displayName: String { get }
}

struct ListPicker<Selections>: View where Selections: PickerEnum  {
    @Binding var selection: Selections
    var body: some View {
        ForEach(Selections.allCases, id: \.self) { sel in
            ListPickerRow(text: sel.displayName,
                          value: selection,
                          selected: sel == selection)
                .contentShape(Rectangle())
                .onTapGesture {
                    selection = sel
                }
        }
    }
}

fileprivate struct ListPickerRow<Value>: View where Value: Hashable {
    let text: String
    let value: Value
    var selected: Bool

    private let systemImageName = "checkmark"

    var body: some View {
        HStack {
            Text(text)
            Spacer()
            if selected {
                Image(systemName: systemImageName)
            }
        }
    }
}

struct ListPicker_Previews: PreviewProvider {
    enum Hoge: String, PickerEnum {
        var displayName: String { self.rawValue }
        
        var id: String { self.rawValue }
        
        case a
        case b
    }
    static var previews: some View {
        Form {
            ListPicker(selection: .constant(Hoge.a))
        }
    }
}