SwiftUI中修改子对象属性后退后视图不更新问题求助

我已经将代码精简到最小复现版本：当修改数组中某个对象的属性时，数据已变更但SwiftUI视图无法可靠更新。

操作步骤：

• 创建新Schedule
• 点击该Schedule进入编辑页
• 修改其名称
• 返回列表页

此时列表视图不会更新，除非新增一个Schedule才会触发List刷新。请问如何实现名称修改后立即更新视图？

原代码 #

Views #

import SwiftUI
import CoreData

struct ContentView: View {
    
    @ObservedObject var allSchedules:AllSchedules = AllSchedules.shared
 
    var body: some View {
        NavigationView {
            List {
                ForEach (allSchedules.schedules) { s in
                    NavigationLink(destination: EditView(schedule: s), label: {Text(s.name)} )
                }
                
                Button("Add a Schedule") { allSchedules.schedules.append(Schedule()) }
                
            }
        }
    }
}


struct EditView: View {
 
    @State var schedule:Schedule
 
    var body: some View {
        List {
            TextField("Change Name", text: $schedule.name, prompt: Text("Change Name"))
        }
    }
}

Classes #

class AllSchedules:ObservableObject {

    @Published var schedules:Array<Schedule> = []
    
    static let shared = AllSchedules()
    
    private init() {}
    
}

class Schedule: ObservableObject, Identifiable {

    let id = UUID()
    
    @Published var name:String = "New Schedule"
    
}

项目模板代码（无此代码无法运行） #

import CoreData

@main
struct Timer3App: App {
    let persistenceController = PersistenceController.shared

    var body: some Scene {
        WindowGroup {
            ContentView()
                .environment(\.managedObjectContext, persistenceController.container.viewContext)
        }
    }
}

struct PersistenceController {
    static let shared = PersistenceController()

    static var preview: PersistenceController = {
        let result = PersistenceController(inMemory: true)
        let viewContext = result.container.viewContext
        for _ in 0..<10 {
            let newItem = Item(context: viewContext)
            newItem.timestamp = Date()
        }
        do {
            try viewContext.save()
        } catch {
            let nsError = error as NSError
            fatalError("Unresolved error \(nsError), \(nsError.userInfo)")
        }
        return result
    }()

    let container: NSPersistentContainer

    init(inMemory: Bool = false) {
        container = NSPersistentContainer(name: "Timer3")
        if inMemory {
            container.persistentStoreDescriptions.first!.url = URL(fileURLWithPath: "/dev/null")
        }
        container.loadPersistentStores(completionHandler: { (storeDescription, error) in
            if let error = error as NSError? {
                fatalError("Unresolved error \(error), \(error.userInfo)")
            }
        })
        container.viewContext.automaticallyMergesChangesFromParent = true
    }
}

核心问题：AllSchedules里的@Published var schedules只会在数组本身增删元素时发送更新通知，但数组内的Schedule对象是引用类型，其内部属性变化不会触发AllSchedules的更新信号，导致ContentView无法刷新。

下面提供两种实用解决方法：

方法一：将Schedule改为值类型（struct） #

值类型的属性修改会生成新实例，数组能检测到元素变化，触发@Published更新，是最简洁的方案。

修改后的代码 #

Classes部分

class AllSchedules: ObservableObject {
    @Published var schedules: Array<Schedule> = []
    
    static let shared = AllSchedules()
    
    private init() {}
}

struct Schedule: Identifiable {
    let id = UUID()
    var name: String = "New Schedule"
}

Views部分

调整EditView使用@Binding传递值类型，ContentView的ForEach绑定数组元素：

struct ContentView: View {
    @ObservedObject var allSchedules: AllSchedules = AllSchedules.shared
 
    var body: some View {
        NavigationView {
            List {
                // 使用$绑定数组元素
                ForEach ($allSchedules.schedules) { $s in
                    NavigationLink(destination: EditView(schedule: $s), label: {Text(s.name)} )
                }
                
                Button("Add a Schedule") { 
                    allSchedules.schedules.append(Schedule()) 
                }
            }
        }
    }
}

struct EditView: View {
    // 使用@Binding接收值类型
    @Binding var schedule: Schedule
 
    var body: some View {
        List {
            TextField("Change Name", text: $schedule.name, prompt: Text("Change Name"))
        }
    }
}

方法二：手动监听子对象变化（保留类类型） #

如果必须用引用类型的Schedule，可以在AllSchedules中监听每个Schedule的属性变化，手动触发父对象的更新。

修改后的代码 #

Classes部分

import Combine

class AllSchedules: ObservableObject {
    @Published var schedules: Array<Schedule> = []
    
    static let shared = AllSchedules()
    
    private init() {}
    
    // 封装添加方法，同时监听子对象变化
    func addSchedule() {
        let newSchedule = Schedule()
        // 监听子对象的更新信号，触发当前对象的刷新
        let cancellable = newSchedule.objectWillChange.sink { [weak self] _ in
            self?.objectWillChange.send()
        }
        // 保存监听对象，防止被提前释放
        newSchedule.cancellable = cancellable
        schedules.append(newSchedule)
    }
}

class Schedule: ObservableObject, Identifiable {
    let id = UUID()
    @Published var name: String = "New Schedule"
    // 保存监听的生命周期对象
    var cancellable: AnyCancellable?
}

Views部分

修改添加按钮调用封装的方法：

Button("Add a Schedule") { allSchedules.addSchedule() }

内容的提问来源于stack exchange，提问作者user1933275