关于 ios：NSCalendarDayChanged 发布时没有更改日期

NSCalendarDayChanged is posting without the day changing

应用程序委托中的以下代码应该每天一次向 assignments 数组添加一个新分配。问题是，每次打开应用程序时都会添加一个新任务，即使日期没有改变。似乎每次打开应用程序时 NSCalendarDayChanged 都会发布。

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var assignments = [Assignment]()

func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {

if let _ = loadHW(){
assignments = loadHW()!
}

if let assignment = NSKeyedUnarchiver.unarchiveObject(withFile: Assignment.ArchiveURL.path) as? [Assignment]{
assignments = assignment
}

// Define identifier
let notificationName = Notification.Name("NSNotification.Name.NSCalendarDayChanged")

// Register to receive notification
NotificationCenter.default.addObserver(self, selector: #selector(calendarDayDidChange(notification:)), name: notificationName, object: nil)

// Post notification
NotificationCenter.default.post(name: notificationName, object: nil)

// Override point for customization after application launch.NSNotification.Name.NSCalendarDayChanged
return true
}
func calendarDayDidChange(notification : NSNotification)
{
let currentDate = Date()
let dateFormatter = DateFormatter()

let dayOfTheWeek = Calendar(identifier: Calendar.Identifier.gregorian).component(.weekday, from: Date())
print(dayOfTheWeek)

dateFormatter.dateFormat ="M/dd/YY"
let convertedCurrentDate = dateFormatter.string(from: currentDate)
print(convertedCurrentDate)

//Adds an assignment based on date comparisons
if let dates = NSKeyedUnarchiver.unarchiveObject(withFile: SettingsViewController.datesURL.path) as? [Date] {
print(1)
if currentDate >= dates[0] && currentDate <= dates[1] {
print(2)
if let weekendHW = NSKeyedUnarchiver.unarchiveObject(withFile: SettingsViewController.weekendURL.path) as? Bool {
print(3)
if(weekendHW || (!weekendHW && dayOfTheWeek != 1 && dayOfTheWeek != 7)){
print(4)
if assignments.count > 0{
assignments.insert(Assignment(hw: assignments[0].hw, date: convertedCurrentDate)!, at: 0)
print(5)
}else if assignments.count == 0 {
assignments.append(Assignment(hw:"", date: convertedCurrentDate)!)
print(6)
}
saveHW()
print("save complete")
}
}
}
}

//adds assignment on first launch of app
if assignments.count == 0 {
assignments.append(Assignment(hw:"", date: convertedCurrentDate)!)
saveHW()
}

}
func saveHW() {
let isSuccessfulSave = NSKeyedArchiver.archiveRootObject(assignments, toFile: Assignment.ArchiveURL.path) //saves array grades to file defined in Assignment class

if !isSuccessfulSave { //Diagnostic
print("Save failed")
}
}

func loadHW() -> [Assignment]? {
return NSKeyedUnarchiver.unarchiveObject(withFile: Assignment.ArchiveURL.path) as? [Assignment] //gets array grades from file where saved, defined in Assignment class

}

我可以进行哪些更改以确保每天只创建一个作业？