Следующий код работает до тех пор, пока операция удаления не будет выполнена для элементов списка. Но это происходит не каждый раз при запуске кода. Он вылетает с кодом ошибки потока EXC_BAD_ACCESS:
Then I realized, this error is occurring after a certain time after delete operation if the app is kept running
This is why this error is very confusing to figure out. But it started appearing when I added DispatchQueue.main.async method to tasks in Model.swift.
The purpose of this code is to reload updated results from core data using self.fetchAll() method when there is any change happened in the list.
Another problem I noticed is the red lines appearing after deleting.
Questions:
- How to update content view struct with least code when a core data list is updated? (This ссылка имеет другой подход, поскольку метод выборки вызывается каждый раз явно в коде.)
- Как оптимизировать этот код с меньшим количеством кода и большей стабильностью?
- Является ли проблема с красной линией на картинке частью существующей ошибки macOS?
macOS : 10.15.4
XCode: 11.5
Целевой: 10.15
Model.swift
import Foundation
import CoreData
class Model: ObservableObject {
@Published var context: NSManagedObjectContext
@Published var tasks: [Task] = [Task]() {
didSet {
DispatchQueue.main.async {
self.fetchAll()
}
}
}
init(_ viewContext: NSManagedObjectContext) {
context = viewContext
}
}
// MARK: Methods
extension Model {
func fetchAll() {
let req = Task.fetchRequest() as NSFetchRequest<Task>
req.sortDescriptors = [NSSortDescriptor(keyPath: \Task.name, ascending: true)]
do {
self.tasks = try self.context.fetch(req)
} catch let error as NSError {
print(error.localizedDescription)
}
}
func addTask(_ text: String) {
let name = text.trimmingCharacters(in: .whitespacesAndNewlines)
if (name != "") {
let task = Task(context: self.context)
task.id = UUID()
task.name = name
task.creationTimestamp = Date()
task.updatedTimestamp = Date()
self.context.insert(task)
self.save()
}
}
func save() {
guard self.context.hasChanges else { return }
do {
try self.context.save()
print("Saved changes")
} catch let error as NSError {
print(error.localizedDescription)
}
}
}
AppDelegate.swift
import Cocoa
import SwiftUI
@NSApplicationMain
class AppDelegate: NSObject, NSApplicationDelegate {
var window: NSWindow!
var model: Model!
func applicationShouldTerminateAfterLastWindowClosed(_ sender: NSApplication) -> Bool {
return true
}
func applicationDidFinishLaunching(_ aNotification: Notification) {
model = Model(persistentContainer.viewContext)
let contentView = ContentView().environmentObject(model)
window = NSWindow(
contentRect: NSRect(x: 0, y: 0, width: 480, height: 300),
styleMask: [.titled, .closable, .miniaturizable, .resizable, .fullSizeContentView],
backing: .buffered, defer: false)
window.center()
window.setFrameAutosaveName("Main Window")
window.contentView = NSHostingView(rootView: contentView)
window.makeKeyAndOrderFront(nil)
}
func applicationWillTerminate(_ aNotification: Notification) { }
// MARK: - Core Data stack
lazy var persistentContainer: NSPersistentCloudKitContainer = {
let container = NSPersistentCloudKitContainer(name: "Todo_List")
container.loadPersistentStores(completionHandler: { (storeDescription, error) in
if let error = error {
fatalError("Unresolved error \(error)")
}
})
container.viewContext.mergePolicy = NSMergeByPropertyObjectTrumpMergePolicy
container.viewContext.undoManager = nil
container.viewContext.shouldDeleteInaccessibleFaults = true
container.viewContext.automaticallyMergesChangesFromParent = true
return container
}()
// MARK: - Core Data Saving and Undo support
@IBAction func saveAction(_ sender: AnyObject?) {
let context = persistentContainer.viewContext
if !context.commitEditing() {
NSLog("\(NSStringFromClass(type(of: self))) unable to commit editing before saving")
}
if context.hasChanges {
do {
try context.save()
} catch {
let nserror = error as NSError
NSApplication.shared.presentError(nserror)
}
}
}
func windowWillReturnUndoManager(window: NSWindow) -> UndoManager? {
return persistentContainer.viewContext.undoManager
}
func applicationShouldTerminate(_ sender: NSApplication) -> NSApplication.TerminateReply {
let context = persistentContainer.viewContext
if !context.commitEditing() {
NSLog("\(NSStringFromClass(type(of: self))) unable to commit editing to terminate")
return .terminateCancel
}
if !context.hasChanges {
return .terminateNow
}
do {
try context.save()
} catch {
let nserror = error as NSError
let result = sender.presentError(nserror)
if (result) {
return .terminateCancel
}
let question = NSLocalizedString("Could not save changes while quitting. Quit anyway?", comment: "Quit without saves error question message")
let info = NSLocalizedString("Quitting now will lose any changes you have made since the last successful save", comment: "Quit without saves error question info");
let quitButton = NSLocalizedString("Quit anyway", comment: "Quit anyway button title")
let cancelButton = NSLocalizedString("Cancel", comment: "Cancel button title")
let alert = NSAlert()
alert.messageText = question
alert.informativeText = info
alert.addButton(withTitle: quitButton)
alert.addButton(withTitle: cancelButton)
let answer = alert.runModal()
if answer == .alertSecondButtonReturn {
return .terminateCancel
}
}
return .terminateNow
}
}
ContentView.swift
import SwiftUI
struct ContentView: View {
@EnvironmentObject var model: Model
@State var taskName: String = ""
var body: some View {
VStack{
ZStack{
TaskList()
.padding(.top,31)
VStack(spacing:0){
TextField("New Task", text: self.$taskName, onCommit: {
self.model.addTask(self.taskName)
self.taskName = ""
})
.padding(5)
Divider().offset(y:-1)
Spacer()
}
if model.tasks.isEmpty {
Text("Nothing To Do\nPlease add something To Do.")
.multilineTextAlignment(.center)
.font(.headline)
.padding(.horizontal)
.frame(maxWidth: .infinity, maxHeight: .infinity)
}
}
}
.frame(minWidth: 200, maxWidth: .infinity, maxHeight: .infinity)
.onAppear{
self.model.fetchAll()
}
}
}
TaskList.swift
import SwiftUI
struct TaskList: View {
@EnvironmentObject var model: Model
@State var selection: Task?
var body: some View {
List(selection: self.$selection){
ForEach(self.model.tasks, id: \.self) { task in
TaskRow(task: task).tag(task)
}
.onDelete(perform: onDelete)
}
}
private func onDelete(with indexSet: IndexSet) {
indexSet.forEach { index in
let task = self.model.tasks[index]
self.model.context.delete(task)
}
self.model.save()
}
}
TaskRow.swift
struct TaskRow: View {
@ObservedObject var task: Task
@EnvironmentObject var model: Model
var dateString: String {
if let timestamp = task.updatedTimestamp {
let formatter = DateFormatter()
formatter.dateStyle = .long
formatter.timeStyle = .medium
return formatter.string(from: timestamp)
} else {
return "No date recorded"
}
}
var body: some View {
HStack {
Toggle(isOn: Binding<Bool>(get: { () -> Bool in
return self.task.checked
}, set: { (enabled) in
self.task.checked = enabled
self.task.updatedTimestamp = Date()
self.model.save()
})){
Text("")
}
VStack {
HStack {
Text(task.name ?? "Unknown Task").font(.system(size: 20))
Spacer()
}
HStack {
Text(dateString).font(.system(size: 10)).bold()
Spacer()
}
}
}
}
}