How can I know when UNUserNotificationCenter's removeAllPendingNotificationRequests() has completed? - ios

Question

The iOS docs say that UNUserNotificationCenter's removeAllPendingNotificationRequests() is asynchronous.
What I want to do is this:
Call removeAllPendingNotificationRequests() to get rid of all my scheduled notifications
Schedule a bunch of new notifications, some of which may or may not have the same IDs as what was there previously
But since the documentation says that the method is asynchronously running on another thread (and there is no completion callback parameter) I'm worried that sometimes, depending on the vagaries of threads and timing and whatnot, that step #1 will still be going as I am creating things in step 2 and therefore it will also kill some of the new notifications I'm making.
This kind of stuff is a little tricky to test manually, since it depends on timing. So I'm curious is anyone knows if this is something I should be worried about or not...

Answer 1

In documentation for add notification I found this:
Calling -addNotificationRequest: will replace an existing notification
request with the same identifier.
Maybe the solution would be something like this:
Create new notification requests
Get all pending and filter out only the ones that will not be replaced
Delete not replaced
Add all new notifications
let center = UNUserNotificationCenter.current()
// Create new requests
let newRequests: [UNNotificationRequest] = [...]
let identifiersForNew: [String] = newRequests.map { $0.identifier }
center.getPendingNotificationRequests { pendingRequests in
// Get all pending notification requests and filter only the ones that will not be replaced
let toDelete = pendingRequests.filter { !identifiersForNew.contains($0.identifier) }
let identifiersToDelete = toDelete.map { $0.identifier }
// Delete notifications that will not be replaced
center.removePendingNotificationRequests(withIdentifiers: identifiersToDelete)
// Add all new requests
for request in newRequests {
center.add(request, withCompletionHandler: nil)
}
}

Answer 2

I have the same case as you and up to know I don't have a problem with this code:
center.getPendingNotificationRequests(completionHandler: { notifications in
var notificationIds:[String] = []
for notification in notifications {
if notification.identifier != "something_taht_I_dont_dismiss"{
notificationIds.append(notification.identifier)
}
}
self.center.removePendingNotificationRequests(withIdentifiers: notificationIds)
createAllNewNotifications()
})
If you want to double check all if the pending notifications are removed you can create simple recursion method for checking.
func removeAllNotificationsSafe() {
center.removeAllPendingNotificationRequests()
checkNotificationsAreRemoved()
}
func checkNotificationsAreRemoved() {
center.getPendingNotificationRequests(completionHandler: { notifications in
if notifications.count > 0 {
self.checkNotificationsAreRemoved()
} else {
self.doWhathverYouWant()
}
}
}
I don't believe this is needed, because all the actions of UNUserNotificationCenter will be synchronized between each other.