Swiftui 如何处理兼容Swift UI版本以支持旧设备？

我正在Xcode 12 beta WatchOS 7上开发一款apple watch应用程序

我也打算支持watchOS 6

下面的代码有错误，我不知道如何处理，它属于SwiftUI问题：

struct CompactStockListView: View {
  var body: some View {
    NavigationView {
      List(getStocks(), id: \.id) { stock in
        CompactStockRowView(stock: stock)
          .padding(.vertical, 6)
      }
      .navigationBarTitle(Text("Landmarks"))
    }
  }
}

请注意错误：

“NavigationView”仅在watchOS 7.0或更高版本的应用程序扩展中可用

下一步： 尝试此解决方案但未成功：

struct CompactStockListView: View {
  var body: some View {
    getListSafe() // Error
  }
  
  func getListSafe() -> View {  // Error tooo
    if #available(watchOSApplicationExtension 7.0, *) {
      return NavigationView {
        List(getStocks(), id: \.id) { stock in
          CompactStockRowView(stock: stock)
            .padding(.vertical, 6)
        }
        .navigationBarTitle(Text("Landmarks"))
      }
    } else {
      // Fallback on earlier versions
      return List(getStocks(), id: \.id) { stock in
        CompactStockRowView(stock: stock)
          .padding(.vertical, 6)
      }
    }
  }
}

试试下面的方法

  @ViewBuilder
  func getListSafe() -> some View {
    if #available(watchOSApplicationExtension 7.0, *) {
      NavigationView {
        List(getStocks(), id: \.id) { stock in
          CompactStockRowView(stock: stock)
            .padding(.vertical, 6)
        }
        .navigationBarTitle(Text("Landmarks"))
      }
    } else {
      // Fallback on earlier versions
      List(getStocks(), id: \.id) { stock in
        CompactStockRowView(stock: stock)
          .padding(.vertical, 6)
      }
    }
  }