来自 watchOS 中 if 条件 Text() 的 SwiftUI 运行时错误

Posted 2023-02-24

【中文标题】来自 watchOS 中 if 条件 Text() 的 SwiftUI 运行时错误

【英文标题】：SwiftUI Runtime Error from if condition Text() in watchOS来自 watchOS 中 if 条件 Text() 的 SwiftUI 运行时错误

【发布时间】：2021-03-07 06:12:27

【问题描述】：

就我所读到的条件视图而言，这段代码应该可以工作。但事实并非如此。

struct Consts 
    static let myCondition = false //no difference if true or false


struct ContentView: View 
    @State var toggle: Bool = false
    var body: some View 
        List() 
            Text("Short Text is in first line")
            Text("Second Line Text is a little longer but not much")
            if Consts.myCondition 
                Text("This is a conditional text. As in: when the user hasn't purchased the option he / she don't need a hint how to use this feature.")
//             else 
//                Text("else doesn't help either.")
            
            Toggle("I also have a toggle but it has nothing to do with this.", isOn: $toggle)
            Text("Here we have a longer Text. Dont know what to type any more.")
            Text("More text which is longer than a few lines.")
            Text("Not so long Text")
        
        .navigationTitle("Hints & Settings")
    

它编译时没有警告或错误。它在模拟器和设备上加载并显示良好。但是每次我从末尾向上滚动列表时，只要这个if condition Text() 变得可见，应用就会崩溃

Fatal error: file SwiftUI, line 0
2021-03-07 06:36:26.548126+0100 WTFif WatchKit Extension[23163:641812] Fatal error: file SwiftUI, line 0

这不仅限于 watchOS。它在 ios 中以相同的方式重现，只是文本必须更长，以便 if condition Text() 在滚动时变得不可见。

我已经用一个数组、条件范围和两个 ForEach() 块解决了这个错误。

struct ContentView: View 
    let myHints = ["Short Text is in first line",
                   "Second Line Text is a little longer but not much",
                   "This is a conditional text. As in: when the user hasn't purchased the option he / she don't need to hint how to use this feature.",
                   "Here we have a longer Text. Dont know what to type any more.",
                   "More text which is longer than a few lines.",
                   "Not so long Text"]
    var myUpperRange: ClosedRange<Int> 
        if Consts.myCondition 
            return 0...1
         else 
            return 0...2
        
    
    var myLowerRange: ClosedRange<Int> 
        return 3...5
    
    @State var toggle: Bool = false
    var body: some View 
        List() 
            ForEach (myUpperRange, id: \.self)  i in
                Text(myHints[i])
            
            Toggle("I also have a toggle but it has nothing to do with this.", isOn: $toggle)
            ForEach (myLowerRange, id: \.self)  i in
                Text(myHints[i])
            
        
        .navigationTitle("Hints & Settings")
    

我的问题基本上是：我没有得到它还是我在 Xcode / SwiftUI 中发现了一个错误？我上面的代码应该工作吗？我可以做些什么不同的事情来让它与简单的文本列表一起工作？

背景：我还有一个带有if condition MyTab() 的 TabView，它可以正常工作而不会崩溃。我是否必须担心这可能会以同样的方式崩溃？我是否也应该在发货前解决这个问题？

PS：我使用的是 Xcode 12.4 (12D4e)

【参考方案1】：

显然，iOS 15 Beta 4 已解决此问题：在我的测试设备上，使用 Xcode 13 Beta 3 编译的测试应用程序在 Beta 4 更新之前出现错误。更新到 iOS 15 Beta 4 后出现错误离开了。 所以我认为有理由说 iOS 15 Beta 4 的更新确实修复了这个错误。