swift - 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 mine using SwiftUI. It has a RootViewController which, depending on an enum value, shows a different child view controller. As in SwiftUI we use views instead of view controllers, my code looks like this:

struct RootView : View {
   @State var containedView: ContainedView = .home

   var body: some View {
      // custom header goes here
      switch containedView {
         case .home: HomeView()
         case .categories: CategoriesView()
         ...
      }
   }
}

Unfortunately, I get a warning:

Closure containing control flow statement cannot be used with function builder ViewBuilder.

So, are there any alternatives to switch so I can replicate this behaviour?

Answer 1

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

Thanks for the answers, guys. I’ve found a solution on Apple’s Dev Forums. It’s answered by Kiel Gillard. The solution is to extract the switch in a function as Lu_, Linus and Mo suggested, but we have to wrap the views in AnyView for it to work – like this:

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

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

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