销毁MainView后如何移除environmentObject并避免崩溃？

我有如下MainView视图结构：

struct MainView: View{
    @EnvironmentObject var appModel: AppDataModel
    @State var localAppDataModel: AppDataModel! = AppDataModel()
    var body: some View{
        VStack {
            ContentView()
        }
        Button(action: {
            appModel.dismissAR()
        },
               label: {
            Text(LocalizedString.close)
                .modifier(VisualEffectRoundedCorner())
        })
        .environmentObject(localAppDataModel)
        .onDisappear{
            localAppDataModel.objectCaptureSession?.cancel()
            localAppDataModel.photogrammetrySession?.cancel()
            localAppDataModel.objectCaptureSession = nil
            localAppDataModel.photogrammetrySession = nil
            localAppDataModel.scanFolderManager = nil
            localAppDataModel.showPreviewModel = false
            localAppDataModel.orbit = .orbit1
            localAppDataModel.orbitState = .initial
            localAppDataModel.isObjectFlipped = false
            localAppDataModel = nil
        }
    }

通过UIKit的如下方法展示该视图：

public static func present(viewC: UIViewController){
    let controller = UIHostingController(rootView: MainView(appModel: .init()))
    mainController = controller
    mainController?.modalPresentationStyle = .fullScreen
    guard let mainController else { return }
    viewC.present(mainController, animated: true, completion: nil)
}
var mainController: UIHostingController<MainView>?

调用以下方法销毁MainView时：

public class AppDataModel: ObservableObject, Identifiable {
    // ...
    func dismissAR(){
        mainController?.dismiss(animated: true)
    }
    // ...
}

应用会崩溃，原因是localAppDataModel变为nil。请问如何在销毁MainView的同时，正确释放/移除localAppDataModel这个environmentObject？

1. 移除onDisappear中直接置空localAppDataModel的代码 #

崩溃核心原因是：调用dismissAR()后视图进入销毁流程，onDisappear触发时，虽然你先清理了模型属性，但最后将localAppDataModel置为nil，此时可能仍有子视图（比如ContentView）在引用该模型，导致野指针访问崩溃。

修改后的onDisappear代码：

.onDisappear{
    localAppDataModel.objectCaptureSession?.cancel()
    localAppDataModel.photogrammetrySession?.cancel()
    localAppDataModel.objectCaptureSession = nil
    localAppDataModel.photogrammetrySession = nil
    localAppDataModel.scanFolderManager = nil
    localAppDataModel.showPreviewModel = false
    localAppDataModel.orbit = .orbit1
    localAppDataModel.orbitState = .initial
    localAppDataModel.isObjectFlipped = false
    // 删除此行：localAppDataModel = nil
}

删除置空代码后，让ARC自动管理模型的内存释放即可。

2. 调整environmentObject的注入范围 #

当前仅给Button注入了localAppDataModel，如果ContentView也依赖该模型，需将注入范围提升至整个VStack，确保所有子视图共享同一模型实例，且生命周期与MainView绑定：

var body: some View{
    VStack {
        ContentView()
        Button(action: {
            appModel.dismissAR()
        },
               label: {
            Text(LocalizedString.close)
                .modifier(VisualEffectRoundedCorner())
        })
    }
    .environmentObject(localAppDataModel) // 将注入移至VStack外部
    .onDisappear{
        // 清理代码...
    }
}

3. 优化dismissAR的内存管理 #

将mainController改为弱引用避免循环引用，并在dismiss完成后清空引用：

// 改为弱引用
weak var mainController: UIHostingController<MainView>?

public static func present(viewC: UIViewController){
    let controller = UIHostingController(rootView: MainView(appModel: .init()))
    mainController = controller
    controller.modalPresentationStyle = .fullScreen
    viewC.present(controller, animated: true, completion: nil)
}

// 在AppDataModel的dismissAR方法中补充完成回调
func dismissAR(){
    mainController?.dismiss(animated: true) {
        mainController = nil // dismiss完成后清空引用
    }
}

4. 可选：用@StateObject替代@State管理本地模型 #

对于ObservableObject类型的本地状态，推荐使用@StateObject，它能更精准地管理ObservableObject的生命周期，避免不必要的重建或内存问题：

// 替换原@State定义
@StateObject var localAppDataModel = AppDataModel()

内容的提问来源于stack exchange，提问作者TheCesco1988