Fatal error: @SceneStorage is only for use with SwiftUI App Lifecycle.: file SwiftUI, line 0

Question

我正在尝试为 iOS 14“SceneStorage”使用新的属性包装器，尽管它会产生此错误：

Fatal error: @SceneStorage is only for use with SwiftUI App Lifecycle.: file SwiftUI, line 0

这是我的代码：

struct ContentView: View {
    @SceneStorage("isLoggedIn") var isLoggedIn = true
    
    var body: some View {
        Text("Hello, World!).onAppear {
            print($isLoggedIn)
        }
    }
}

已更新.... 谢谢，@Asperi！确保将 Life Cycle 设置为 SwiftUI App。

Answer 1

适用于 Xcode 12 / iOS 14 / SwiftUI 生命周期

您的项目似乎使用了 SwiftUI 1.0 AppDelegate/SceneDelegate（又名 UIKit 生命周期）

在 SwiftUI 生命周期中，您的应用程序主程序应该像

@main
struct YourAppName: App {
    var body: some Scene {
        WindowGroup {       // << this introduces Scene, needed for SceneStorage
            ContentView()
        }
    }
}

Fatal error: @SceneStorage is only for use with SwiftUI App Lifecycle.: file SwiftUI, line 0

Fatal error: @SceneStorage is only for use with SwiftUI App Lifecycle.: file SwiftUI, line 0

swiftui

ios14

xcode12