如何处理 Swift UI 版本兼容以支持旧设备？

Question

我正在 Xcode 12 beta WatchOS 7 上开发 Apple Watch 应用程序。

我也打算支持 watchOS 6。

以下代码有错误，不知如何处理，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"))
    }
  }
}

Xcode 注意错误：

'NavigationView' is only available in application extensions for watchOS 7.0 or newer

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)
      }
    }
  }
}

Answer 1

尝试以下方法

  @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)
      }
    }
  }