我的应用程序中有一个通过这种方法发现的错误：
private func createNotifications(dateComponents: DateComponents) {
switch (recurrence) {
case .today:
createNotification(for: dateComponents)
case .tomorrow:
createNotification(for: day(after: dateComponents))
case .daily:
let center = UNUserNotificationCenter.current()
center.getPendingNotificationRequests { (notifications) in
var numberOfCreatableNotifications = 64 - notifications.count
var numberOfCreatedNotifications = 0
var currentDay: DateComponents? = dateComponents
while numberOfCreatableNotifications > 0
&& numberOfCreatedNotifications < self.NUMBER_OF_ALLOWED_NOTIFICATIONS_CREATED_AT_ONE_TIME {
self.createNotification(for: currentDay)
currentDay = self.day(after: currentDay)
numberOfCreatableNotifications -= 1
numberOfCreatedNotifications += 1
}
}
}
}
我正在尝试创建具有某个重复选项（今天，明天或每天）的警报，而每天的案例都无法正常工作。上面的代码在Alarm.swift中。创建警报后，该警报将传递回主视图控制器以保存在Core Data中。我意识到通知没有保存在Core Data中，因为在警报保存到Core Data中时还没有创建通知。这个闭包center.getPendingNotificationRequests（）显然需要一些时间才能返回并运行完成处理程序。
我正在使用getPendingNotificationRequests（）方法，因为我试图确定我可以创建多少个通知（最多64个）。
这是我的问题：我是否应该继续使用此异步方法，并在完成处理程序期间仅在Core Data中进行一些保存？还是应该将保存代码保留在主视图控制器中，而由于某种原因我不再需要此异步方法？
谢谢
顺便说一句，这是我的AlarmVCViewView文件中的大部分代码，这是应用程序中的主要VC：
//MARK: Public properties
var alarms = [AlarmMO]()
let ALARM_CELL_IDENTIFIER = "AlarmTableViewCell"
override func viewDidLoad() {
super.viewDidLoad()
requestUserNotificationsPermissionsIfNeeded()
NotificationCenter.default.addObserver(self, selector: #selector(didBecomeActive), name: UIApplication.didBecomeActiveNotification, object: nil)
loadAlarms()
for alarm in self.alarms {
os_log("There are %d notifications for alarm %d", log: OSLog.default, type: .debug, alarm.notificationUuids.count, alarm.alarmNumber)
}
}
deinit {
NotificationCenter.default.removeObserver(self, name: UIApplication.didBecomeActiveNotification, object: nil)
}
// MARK: - Table view data source
override func numberOfSections(in tableView: UITableView) -> Int {
return 1
}
override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return self.alarms.count
}
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
guard let cell = tableView.dequeueReusableCell(withIdentifier: ALARM_CELL_IDENTIFIER, for: indexPath) as? AlarmTableViewCell else {
fatalError("The dequeued cell is not an instance of AlarmTableViewCell.")
}
guard let alarmMO = self.alarms[safe: indexPath.row] else {
os_log("Could not unwrap alarm for indexPath in AlarmTableViewController.swift", log: OSLog.default, type: .default)
self.tableView.reloadData()
return AlarmTableViewCell()
}
let alarmNumber = alarmMO.value(forKey: "alarmNumber") as! Int
let beginTime = alarmMO.value(forKey: "startTimeInterval") as! Double
let endTime = alarmMO.value(forKey: "endTimeInterval") as! Double
cell.alarmNumberLabel.text = "Alarm " + String(alarmNumber)
let beginTimeHour = Alarm.extractHourFromTimeDouble(alarmTimeDouble: beginTime)
let beginTimeMinute = Alarm.extractMinuteFromTimeDouble(alarmTimeDouble: beginTime)
cell.beginTimeLabel.text = formatTime(hour: beginTimeHour, minute: beginTimeMinute)
let endTimeHour = Alarm.extractHourFromTimeDouble(alarmTimeDouble: endTime)
let endTimeMinute = Alarm.extractMinuteFromTimeDouble(alarmTimeDouble: endTime)
cell.endTimeLabel.text = formatTime(hour: endTimeHour, minute: endTimeMinute)
guard let notificationUuids = self.getNotificationUuidsFromAlarmMO(alarmMO: alarmMO) else {
os_log("Could not get notificationUuids from AlarmMO in tableView(cellForRowAt:) in AlarmTableViewController.swift", log: OSLog.default, type: .debug)
return cell
}
os_log("----- notificationUuids: -----", log: OSLog.default, type: .debug)
for uuid in notificationUuids {
os_log("uuid: %@", log: OSLog.default, type: .debug, uuid)
}
return cell
}
override func tableView(_ tableView: UITableView, canEditRowAt indexPath: IndexPath) -> Bool {
return true
}
override func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCell.EditingStyle, forRowAt indexPath: IndexPath) {
if (editingStyle == .delete) {
guard let alarm = self.alarms[safe: indexPath.row] else {
os_log("Could not get alarm from its indexPath in AlarmTableViewController.swift", log: OSLog.default, type: .default)
self.tableView.reloadData()
return
}
guard let notificationUuids = self.getNotificationUuidsFromAlarmMO(alarmMO: alarm) else {
os_log("Could not get notificationUuids from AlarmMO in tableView(forRowAt:) in AlarmTableViewController.swift", log: OSLog.default, type: .debug)
return
}
self.removeNotifications(notificationUuids: notificationUuids)
guard let appDelegate = UIApplication.shared.delegate as? AppDelegate else {
return
}
let managedContext = appDelegate.persistentContainer.viewContext
managedContext.delete(alarm)
self.alarms.remove(at: indexPath.row)
for (index, alarm) in self.alarms.enumerated() {
let alarmNumber = index + 1
alarm.setValue(alarmNumber, forKey: "alarmNumber")
}
self.saveContext()
self.tableView.reloadData()
}
}
// MARK: Actions
@IBAction func unwindToAlarmList(sender: UIStoryboardSegue) {
if let sourceViewController = sender.source as? AddAlarmViewController, let alarm = sourceViewController.alarm {
let newIndexPath = IndexPath(row: self.alarms.count, section: 0)
os_log("There are %d notificationUuids attached to the alarm created", log: OSLog.default, type: .debug, alarm.notificationUuids.count)
saveAlarm(alarmToSave: alarm)
tableView.insertRows(at: [newIndexPath], with: .automatic)
}
}
// MARK: Private functions
@objc private func didBecomeActive() {
deleteOldAlarms {
DispatchQueue.main.async {
self.tableView.reloadData()
}
}
}
private func deleteOldAlarms(completionHandler: @escaping () -> Void) {
os_log("deleteOldAlarms() called", log: OSLog.default, type: .default)
let notificationCenter = UNUserNotificationCenter.current()
var alarmsToDelete = [AlarmMO]()
guard let appDelegate = UIApplication.shared.delegate as? AppDelegate else {
return
}
let managedContext = appDelegate.persistentContainer.viewContext
notificationCenter.getPendingNotificationRequests(completionHandler: { (requests) in
alarmsToDelete = self.calculateAlarmsToDelete(requests: requests)
os_log("Deleting %d alarms", log: OSLog.default, type: .debug, alarmsToDelete.count)
for alarmMOToDelete in alarmsToDelete {
guard let notificationUuids = self.getNotificationUuidsFromAlarmMO(alarmMO: alarmMOToDelete) else {
os_log("Could not get notificationUuids from AlarmMO in deleteOldAlarms() in AlarmTableViewController.swift", log: OSLog.default, type: .debug)
return
}
self.removeNotifications(notificationUuids: notificationUuids)
managedContext.delete(alarmMOToDelete)
self.alarms.removeAll { (alarmMO) -> Bool in
return alarmMOToDelete == alarmMO
}
}
completionHandler()
})
}
private func calculateAlarmsToDelete(requests: [UNNotificationRequest]) -> [AlarmMO] {
var activeNotificationUuids = [String]()
var alarmsToDelete = [AlarmMO]()
for request in requests {
activeNotificationUuids.append(request.identifier)
}
for alarm in self.alarms {
guard let notificationUuids = self.getNotificationUuidsFromAlarmMO(alarmMO: alarm) else {
os_log("Could not get notificationUuids from AlarmMO in deleteOldAlarms() in AlarmTableViewController.swift", log: OSLog.default, type: .debug)
return []
}
let activeNotificationUuidsSet: Set<String> = Set(activeNotificationUuids)
let alarmUuidsSet: Set<String> = Set(notificationUuids)
let union = activeNotificationUuidsSet.intersection(alarmUuidsSet)
if union.isEmpty {
alarmsToDelete.append(alarm)
}
}
return alarmsToDelete
}
private func removeNotifications(notificationUuids: [String]) {
os_log("Removing %d alarm notifications", log: OSLog.default, type: .debug, notificationUuids.count)
let notificationCenter = UNUserNotificationCenter.current()
notificationCenter.removePendingNotificationRequests(withIdentifiers: notificationUuids)
}
private func loadAlarms() {
os_log("loadAlarms() called", log: OSLog.default, type: .debug)
guard let appDelegate = UIApplication.shared.delegate as? AppDelegate else {
return
}
let managedContext = appDelegate.persistentContainer.viewContext
let fetchRequest = NSFetchRequest<AlarmMO>(entityName: "Alarm")
do {
if self.alarms.count == 0 {
self.alarms = try managedContext.fetch(fetchRequest)
os_log("Loading %d alarms", log: OSLog.default, type: .debug, self.alarms.count)
} else {
os_log("Didn't need to load alarms", log: OSLog.default, type: .debug)
}
} catch let error as NSError {
print("Could not fetch alarms. \(error), \(error.userInfo)")
}
}
private func saveAlarm(alarmToSave: Alarm) {
guard let appDelegate = UIApplication.shared.delegate as? AppDelegate else {
return
}
let managedContext = appDelegate.persistentContainer.viewContext
let entity = NSEntityDescription.entity(forEntityName: "Alarm", in: managedContext)!
let alarmMO = AlarmMO(entity: entity, insertInto: managedContext)
alarmMO.setValue(alarmToSave.alarmTime, forKeyPath: "alarmTime")
alarmMO.setValue(alarmToSave.alarmNumber, forKeyPath: "alarmNumber")
alarmMO.setValue(alarmToSave.alarmIntervalBeginTimeDouble, forKeyPath: "startTimeInterval")
alarmMO.setValue(alarmToSave.alarmIntervalEndTimeDouble, forKeyPath: "endTimeInterval")
alarmMO.setValue(alarmToSave.recurrence.hashValue, forKeyPath: "recurrence")
alarmMO.setValue(alarmToSave.notificationUuids, forKeyPath: "notificationUuids")
if managedContext.hasChanges {
do {
try managedContext.save()
self.alarms.append(alarmMO)
} catch let error as NSError {
print("Could not save alarm to CoreData. \(error), \(error.userInfo)")
}
} else {
os_log("No changes to the context to save", log: OSLog.default, type: .debug)
}
}
private func getNotificationUuidsFromAlarmMO(alarmMO: AlarmMO) -> [String]? {
guard let notificationUuids = alarmMO.value(forKey: "notificationUuids") as! [String]? else {
os_log("Found nil when attempting to unwrap notificationUuids in getNotificationUuidsFromAlarmMO() in AlarmTableViewController.swift, returning nil",
log: OSLog.default, type: .default)
return nil
}
return notificationUuids
}
答案 0 :(得分：1)
如果此方法始终异步运行并且始终调用完成处理程序，则可能是最简单的方法。因此，您的调用代码将在调用此方法时将其交给完成处理程序，然后停止。稍后，此方法将在完成处理程序上回调调用方，从而通知它我们创建了一些通知。可能的草图：
private func createNotifications(dateComponents: DateComponents, completion: (Int) -> Void) {
let center = UNUserNotificationCenter.current()
center.getPendingNotificationRequests { (notifications) in
switch (recurrence) {
// this is wrong, you should not be looking outside this method for the recurrence value...
// ... but it's just a sketch
case .today:
createNotification(for: dateComponents)
completion(1)
case .tomorrow:
createNotification(for: day(after: dateComponents))
completion(1)
case .daily:
// ... decide whether to create the notifications or not ...
// ... and create however many you decide to ...
let howManyWeCreated = // however many we created
completion(howManyWeCreated)
}
}
}