Alternative to switch statement in SwiftUI ViewBuilder block?

Question

⚠️ 23 June 2020 Edit: From Xcode 12, both switch and if let statements will be supported in the ViewBuilder!

I’ve been trying to replicate an app of

Answer 1

Update: SwiftUI 2 now includes support for switch statements in function builders, https://github.com/apple/swift/pull/30174

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Adding to Nikolai's answer, which got the switch compiling but not working with transitions, here's a version of his example that does support transitions.

struct RootView: View {
  @State var containedViewType: ContainedViewType = .home

  var body: some View {
     VStack {
       // custom header goes here
       containedView()
     }
  }

  func containedView() -> some View {
     switch containedViewType {
     case .home: return AnyView(HomeView()).id("HomeView")
     case .categories: return AnyView(CategoriesView()).id("CategoriesView")
     ... 
  }
}

Note the id(...) that has been added to each AnyView. This allows SwiftUI to identify the view within it's view hierarchy allowing it to apply the transition animations correctly.