Local Notification every X day - Swift - swift

Question

Before I begin please don't burn me as I know this has been asked hundreds of times on here with no reliable answer but I believe there's a solution using background refresh. https://medisafe.com/ app seems to have solved it!
The goal :
To trigger a local notification at a specified time every x days
My solution
step 1: get timer interval from start date and odd occurrence (this case 2) days from (edited)
step 2: set interval timer on this difference with a repeat
step 3: activate background refresh ( if the app is even terminated it will load the app in the background and give me a small window to perform some tasks)
step 4. set background refresh to trigger once a day
step 5: perform get items api which will refresh all timers and notifications
step 6 sit back and smile with amazement at my solution
but this fails.
so a timer interval
let newTrigger = UNTimeIntervalNotificationTrigger(timeInterval: 172800,repeats: true)
but this will just reset the timer every day when the background fetch is performed and it will trigger 2 days from NOW and not from the start date.
So there must be a way of comparing dates hours and minutes (start date, x date, and current date to work out the timer interval value.
currently im using calendar components. to trigger everyday im doing the following
var triggerType : DateComponents? {
var triggerT : DateComponents?
var cal = Calendar(identifier: .gregorian)
cal.firstWeekday = 2
if let notificationModel = self.notificationModel {
switch notificationModel.reminderType {
case .daily?, .weekly?:
if let date = notificationModel.date {
triggerT = cal.dateComponents([.weekday, .hour, .minute], from:date)
if let weekday = notificationModel.weekday {
triggerT?.weekday = weekday
}
}
case .alternateDays?:
if let date = notificationModel.date {
triggerT = cal.dateComponents([ .hour, .minute], from:date)
// THIS IS WHERE I NEED HELP
}
case .monthly?:
if let date = notificationModel.date {
triggerT = cal.dateComponents([.day,.hour,.minute], from: date)
}
case .yearly?:
triggerT = Calendar.current.dateComponents([.month,.day,.hour,.minute], from: (notificationModel.date)!)
case .oneOff?:
triggerT = Calendar.current.dateComponents([.year,.month,.day,.hour,.minute], from: (notificationModel.date)!)
case .none:
DispatchQueue.main.async {
if let category = self.notificationModel?.category, let title = self.notificationModel?.title {
Toast.down("An error was discovered in \(category). Please change the occurance value for the following \(title)")
}
}
}
} else {
print("NOTIFICATION MODEL IS CORRUPT")
}
return triggerT
}
func add(notification: NotificationModel){
let content = UNMutableNotificationContent()
if let title = notification.title,
let body = notification.body,
let identifier = notification.identifier {
content.title = title
content.body = body
content.sound = UNNotificationSound.default()
content.categoryIdentifier = (notification.category?.rawValue)!
content.setValue("YES", forKeyPath: "shouldAlwaysAlertWhileAppIsForeground")
var trigger : UNCalendarNotificationTrigger?
if let triggerType = self.triggerType {
if let occurance = notification.occurance {
if occurance > 0 {
}
}
trigger = UNCalendarNotificationTrigger(dateMatching: triggerType, repeats: true)
} else {
return
}
let interval = Date().timeIntervalSince1970
let identifierString = "2\(interval)"
var request : UNNotificationRequest!
if notification.reminderType == .alternateDays {
print("ADDING TIMER NOTIFICATION")
print("REMINDER TIME = \(notification.date)")
// 172800 = two days
let newTrigger = UNTimeIntervalNotificationTrigger(timeInterval: 172800,
repeats: true)
request = UNNotificationRequest(identifier: identifierString,
content: content, trigger: newTrigger)
} else {
request = UNNotificationRequest(identifier: identifierString,
content: content, trigger: trigger)
}
center.add(request, withCompletionHandler: { (error) in
if let error = error {
// Something went wrong
print(error.localizedDescription)
} else
{
print("ADDING NOTIDCIATION \(content.title)")
}
})
//SNOOZE OR DELETE NOTIFICATIONS
let snoozeAction = UNNotificationAction(identifier: "Snooze", title: "Snooze", options: [])
let deleteAction = UNNotificationAction(identifier: "UYLDeleteAction",title: "Delete", options: [.destructive])
//Create a category with the actions: This requires another unique identifier (you probably want to define these magic strings in an enum):
let category = UNNotificationCategory(identifier: notification.category!.rawValue,
actions: [snoozeAction,deleteAction],
intentIdentifiers: [], options: [])
//Register the category with the notification center. It is recommended to do this early in the app lifecycle.
center.setNotificationCategories([category])
//To include this action in our notifications we need to set the category in the notification content:
} else {
print("Failed to add notification")
}
}
however, I want every other day and dont want to use the 64 notification limit.
thanks for your time
Thomas

Answer 1

Lets say you want to trigger notification 2, 4 and 6 days from now, here is how you can do it:
For my example I added extension to Date
extension Date {
func adding(days: Int) -> Date? {
var dateComponents = DateComponents()
dateComponents.day = days
return NSCalendar.current.date(byAdding: dateComponents, to: self)
}
}
Then you could just create new notifications for dates specified, in this example 2, 4, 6 days from now
let date = Date()
for i in [2, 4, 6] {
if let date = date.adding(days: i) {
scheduleNotification(withDate: date)
}
}
func scheduleNotification(withDate date: Date) {
let notificationContent = UNMutableNotificationContent()
notificationContent.title = "Title"
notificationContent.subtitle = "Subtitle"
notificationContent.body = "Body"
let identifier = "Make up identifiers here"
let dateComponents = Calendar.autoupdatingCurrent.dateComponents([.day, .month, .year, .hour, .minute, .second], from: date)
let trigger = UNCalendarNotificationTrigger(dateMatching: dateComponents, repeats: false)
let notificationReques = UNNotificationRequest(identifier: identifier, content: notificationContent, trigger: trigger)
UNUserNotificationCenter.current().add(notificationReques) { error in
if let e = error {
print("Error \(e.localizedDescription)")
}
}
}
This should schedule 3 notifications - 2, 4, 6 days from now...

Answer 2

So thanks for the directions on here this is the final solution i came up with. Ensure you turn on background modes in app capabilities so the current week is updated. i did mine to every day.
Then the code with comments.
//: Playground - noun: a place where people can play
import UIKit
import UserNotifications
Lets create some helper clases to make it easier to work with dates
// HELPERS
extension Date {
public var weekday: Int {
return Calendar.current.component(.weekday, from: self)
}
public var hour: Int {
get {
return Calendar.current.component(.hour, from: self)
}
set {
let allowedRange = Calendar.current.range(of: .hour, in: .day, for: self)!
guard allowedRange.contains(newValue) else { return }
let currentHour = Calendar.current.component(.hour, from: self)
let hoursToAdd = newValue - currentHour
if let date = Calendar.current.date(byAdding: .hour, value: hoursToAdd, to: self) {
self = date
}
}
}
public var minute: Int {
get {
return Calendar.current.component(.minute, from: self)
}
set {
let allowedRange = Calendar.current.range(of: .minute, in: .hour, for: self)!
guard allowedRange.contains(newValue) else { return }
let currentMinutes = Calendar.current.component(.minute, from: self)
let minutesToAdd = newValue - currentMinutes
if let date = Calendar.current.date(byAdding: .minute, value: minutesToAdd, to: self) {
self = date
}
}
}
}
Then we create our custom notification struct
struct CustomNotification {
static func everyOtherDay(wtihStartDate startDate: Date) -> [Int]? {
//
let currentDate = Date()
// get initial week day from start date to compare dates
let weekDay = startDate.weekday
// Then we need to get week of years for both dates
let cal = Calendar.current
guard let weekA = cal.dateComponents([.weekOfYear], from: startDate).weekOfYear else { return nil}
guard let weekB = cal.dateComponents([.weekOfYear], from: currentDate).weekOfYear else {return nil}
// create two arrays for week days
let weekOne = [1,3,5,7]
let weekTwo = [2,4,6]
// then we create a module to check if we are in week one or week two
let currentWeek = (weekA - weekB) % 2
if currentWeek == 0 {
//week 1
return weekOne.contains(weekDay) ? weekOne : weekTwo
} else {
// week 2
return weekOne.contains(weekDay) ? weekTwo : weekOne
}
}
}
finally in our class where we create the notification. I personally use a notification manager. but to shwo you quickly
class AClass : NSObject {
func setupNotifications() {
let startDate = Date()
let weekDays = CustomNotification.everyOtherDay(wtihStartDate: startDate)
let cal = Calendar.current
let center = UNUserNotificationCenter.current()
if let weekDays = weekDays {
for day in weekDays {
let identifier = "Some Random ID"
let content = UNMutableNotificationContent()
content.title = "title"
content.body = "body"
content.sound = UNNotificationSound.default()
content.categoryIdentifier = "SOME CATEGORY"
content.setValue("YES", forKeyPath: "shouldAlwaysAlertWhileAppIsForeground")
var components = cal.dateComponents([.hour, .minute], from:startDate)
components.weekday = day
let trigger = UNCalendarNotificationTrigger(dateMatching: components, repeats: true)
let request = UNNotificationRequest(identifier: identifier,
content: content, trigger: trigger)
center.add(request, withCompletionHandler: { (error) in
if let error = error {
// Something went wrong
print("ERROR ADDING NOTIFICATION TO CENTER \(error.localizedDescription)")
} else
{
print("ADDING NOTIFCIATION \(content.categoryIdentifier)")
}
})
}
}
}
}
Then we need to setup background fetch in our app and app delegate
// OVER IN APP DELEGATE
func application(_ application: UIApplication, didFinishLaunchingWithOptions launchOptions: [UIApplicationLaunchOptionsKey: Any]?) -> Bool {
// setup background refresh ensuring you turn it on in app capabilities
// trigger back ground refrsh once a day
UIApplication.shared.setMinimumBackgroundFetchInterval(86400)
return true
}
func application(_ application: UIApplication, performFetchWithCompletionHandler completionHandler: #escaping (UIBackgroundFetchResult) -> Void) {
// FETCH DATA and REFRESH NOTIFICATIONS
// We need to do this to ensure the current week value is updated to either 1 or 0
// You will need to delete all notifications with same same category first else your going to be getting both weeks notifications
let aClass = AClass()
aClass.setupNotifications()
}
Hope this helps somebody :D Thomas