UI赢得了带有Coredata的实时更改

Question

我有一个Swiftui + Coredata简单的TODO应用程序，一切正常，但是我的UpdateTodo函数应该可以处理单击todo的单击并从完成转换为撤消，反之亦然，但无法正常工作。 当我单击UI中什么都没发生时，但是当我回到屏幕回到Todos屏幕上时，我可以看到UI更改，也可以持续存在，因此当我关闭并打开应用程序时，更改为反映在应用程序中。 因此，我的问题是“ ISDONE”属性并未实时在UI中切换，并且只有当视图重新出现时，它实际上显示了已进行的更改。

ViewModel（Coredata）：

class TodoViewModel:ObservableObject {
    
    let container: NSPersistentContainer
    
    @Published var categories = [CategoryTodo]()
    @Published var todos = [Todo]()
    
    init() {
        container = NSPersistentContainer(name: "UniversityProject")
        container.loadPersistentStores { (description, error) in
            if let error = error {
                fatalError("Error: \(error.localizedDescription)")
            }
        }
    }
    
    //MARK: - Todos
    func getTodos() {
        let request = NSFetchRequest<Todo>(entityName: "Todo")
        let sort = NSSortDescriptor(key: #keyPath(Todo.dateCreated), ascending: false)
        request.sortDescriptors = [sort]
        do {
            try todos = container.viewContext.fetch(request)
        } catch {
            print("Error getting data. \(error)")
        }
    }
    
    
    func addTodo(todo text: String, category categoryName:String) {
        let newTodo = Todo(context: container.viewContext)
        newTodo.todo = text
        newTodo.category = categoryName
        newTodo.id = UUID().uuidString
        newTodo.isDone = false
        newTodo.dateCreated = Date()
        saveTodo()
    }
    
    func saveTodo() {
        do {
            try container.viewContext.save()
            getTodos()
        } catch let error {
            print("Error: \(error)")
        }
    }
    
    func deleteTodo(indexSet: IndexSet) {
        let todoIndex = indexSet[indexSet.startIndex]
        let object = todos[todoIndex]
        container.viewContext.delete(object)
        saveTodo()
    }
    
    func updateTodo(item: Todo) {
            item.setValue(!item.isDone, forKey: "isDone")
            saveTodo()
    }
    
}

TodoSview：

struct TodosView: View {
    @EnvironmentObject var viewModel: TodoViewModel
    
    let categoryName:String
    
    var body: some View {
        List {
            ForEach(viewModel.todos.filter{$0.category == categoryName}) { item in
                TodoItem(item: item)
                    .onTapGesture {
                        withAnimation(.linear) {
                            viewModel.updateTodo(item: item)
                        }
                    }
            }
            .onDelete(perform: viewModel.deleteTodo)
            
        }.onAppear { viewModel.getTodos() }
        
            .navigationBarTitle(categoryName)
            .navigationBarTitleDisplayMode(.inline)
            .toolbar {
                ToolbarItem(placement: .navigationBarTrailing) {
                    HStack {
                        EditButton()
                        NavigationLink(destination: AddTodoView(category: categoryName)) {
                            Image(systemName: "plus.circle")
                                .resizable()
                                .foregroundColor(.blue)
                                .frame(width: 25, height: 25)
                        }
                    }
                }
            }
        
    }
}

Answer 1

没有所有相关代码，我只能猜测并建议您尝试类似的事情：

func updateTodo(item: Todo) {
    if let ndx = todos.firstIndex(where: {$0.id == item.id}) {
        todos[ndx].isDone = !item.isDone
        saveTodo()
    }
}

或

func updateTodo(item: Todo) {
    objectWillChange.send()
    item.setValue(!item.isDone, forKey: "isDone")
    saveTodo()
}