堆棧內存溢出
  簡體   English   中英

我應該在這里使用完成處理程序嗎？ 如果是這樣，怎么做最好？

[英]Should I use a completion handler here? If so, how best to do it?

 原文  2018-12-09 17:34:08  7   1    ios/ swift/ closures/ completionhandler

問題描述

我的應用程序中有一個通過以下方法發現的錯誤： 

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
            }
        }
    }
}

我正在嘗試創建具有某個重復選項（今天，明天或每天）的警報，而日常情況卻不起作用。 上面的代碼在Alarm.swift中。 創建警報后，該警報將傳遞回主視圖控制器以保存在Core Data中。 我意識到通知沒有保存在Core Data中，因為在警報保存到Core Data中時還沒有創建通知。 這個閉包center.getPendingNotificationRequests（）顯然需要一些時間才能返回並運行完成處理程序。

我正在使用getPendingNotificationRequests（）方法，因為我試圖確定我可以創建多少個通知（最多64個）。

這是我的問題：我是否應該繼續使用此異步方法，並在完成處理程序期間僅在Core Data中進行一些保存？ 還是應該將保存代碼保留在主視圖控制器中，並且由於某種原因我不需要它，所以我只是停止使用此異步方法？

謝謝

順便說一句，這是我的AlarmTableViewController文件中的大部分代碼，AlarmTableViewController文件是應用程序中的主要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

}

1 個解決方案

解決方案1
 1  2018-12-09 22:27:18

如果此方法始終異步運行並始終調用完成處理程序，則可能是最簡單的方法。 因此，您的調用代碼將在調用此方法時將其交給完成處理程序，然后停止。 稍后，此方法將在完成處理程序上回調調用方，從而通知它我們創建了一些通知。 一個可能的草圖： 

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)
        }
    }
}

暫無
暫無

聲明:本站的技術帖子網頁，遵循CC BY-SA 4.0協議，如果您需要轉載，請注明本站網址或者原文地址。任何問題請咨詢:yoyou2525@163.com.

相關問題 我如何在自己的完成處理程序中使用變量 如何在完成處理程序塊中檢查NSURLSessionDownloadTask的狀態？ 如何使用以下完成處理程序調用 function？ 如何在帶有Swift的dismissViewControllerAnimated中使用完成處理程序？ 如何將 PushKit 的完成處理程序用於 reportNewIncomingCallWithUUID 僅在設置了數據后如何調用完成處理程序？ Swift：如何通過完成處理程序（關閉）中的引用存儲對象數組？ 如何創建自己的完成處理程序作為方法參數的一部分 在初始化單元格之前，如何從完成處理程序中運行代碼？ swift 5 ios：如何從 session.dataTask 完成處理程序中獲取數據
相關標簽
 
粵ICP備18138465號  © 2020-2024 STACKOOM.COM