Change local notification’s content using userInfo and custom action
Hello!
In this article I want to share my experience of using one non-obvious (for me at least) hint to send some extra data with UNUserNotificationCenter.
This article will be helpful for the new ones in iOS programming with Swift, I hope. It suppose that you have at least some experience with iOS and Swift. I’m using Swift 5 and Xcode 10.2.1.
The task!
I have an app that shows to user some local notifications. It consist of the main text and a subtext.
So, the idea was to show to user only main text, and, if user wants to know the subtext, he have to hit “Show me” button in notification, which is a custom action.
I’m using next method to show notification (all explanations is below):
- Firts of all we have to define an instance of UNUserNotificationCenter:
class NotificationService: NSObject, UNUserNotificationCenterDelegate {
let notificationCenter = UNUserNotificationCenter.current()
}2. Next, we declare a method that we will use to send notification:
// 1
// We define a method that takes a tuple with two String parameters.
// showBody is a parameter with a Bool type, and it allows us to show or hide the subtext in our notification.
// withAction is also a Bool type parameter, and it uses to hide action button if "Show me" action was hited.
// atDate date - is a Date type parameter, and we use it to schedule a trigger for our notification.func showNotification(with item: (String, String), showBody: Bool, withAction: Bool, atDate date: Date) { // 2
// Here we define our content instance
let content = UNMutableNotificationContent() // 3
// Assigning an identifier for our action
let userActionsIdentifier = “showMe” // 4
// Set our main text to notification.
content.title = item.0 // 5
// For the first call of this method, I set showBody parameter
// to false, so user can't see it in notification.
if showBody { content.body = item.1 } // 6
// Here is the most important part - I assign to content's
// userInfo parameter the item with main text and subtext.
content.userInfo = [item.0: item.1]
content.sound = UNNotificationSound.default // 7
// At first call of this method I set withAction parameter to
// true, to let user be able to hit the "Show me" button.
// To do this, we sets the categoryIdentifier parameter.
if withAction {
content.categoryIdentifier = userActionsIdentifier
} // 8
// Every notification need a unic identifier, so they won't
// replace each othe in the queue.
let notificationID = item.0 // 9
// Define a date parameters to use appropriate trigger in next.
// In this case I'm using only hour, minute and second
// from date.
var dc = DateComponents()
dc.hour = Calendar.current.component(.hour, from: date)
dc.minute = Calendar.current.component(.minute, from: date)
dc.second = Calendar.current.component(.second, from: date) // 10
// Define our trigger. You can use other triggers, but in this
// case I used UNCalendarNotificationTrigger.
let trigger = UNCalendarNotificationTrigger(dateMatching: dc,
repeats: false) // 11
// Define our notification's request with identifier,
// content and trigger.
let request = UNNotificationRequest(identifier: notificationID,
content: content,
trigger: trigger) // 12
// Add our request to notificationCenter, and also
// handling errors.
notificationCenter.add(request) { (error) in
error == nil ?
print(“notifacation request was added at “,
trigger.nextTriggerDate()!) :
print(error.debugDescription)
} // 13
// Define our action. It will create a button that user can
// hit and see our subtext. We define it's identifier and title.
// Options are unused.
let action = UNNotificationAction(identifier: “showMe”,
title: “Show me”,
options: []) // 14
// Define our category for notification, which includes
// our action.
let category = UNNotificationCategory(
identifier:userActionsIdentifier,
actions: [action],
intentIdentifiers: [], options: []) // 15
// Finaly, add our category to notificationCenter.
notificationCenter.setNotificationCategories([category])
}
When we call this method, it will show us notification at specific and time. And if user will pull down notification, the “Show me” button will appear. Next, user have to hit “Show me” to see our subtext. To handle this, we have to use UNUserNotificationCenterDelegate’s method:
func userNotificationCenter(_ center: UNUserNotificationCenter, didReceive response: UNNotificationResponse, withCompletionHandler completionHandler: @escaping () -> Void) { … }So, the code that I’m using in this delegate’s method is as follows:
func userNotificationCenter(_ center: UNUserNotificationCenter, didReceive response: UNNotificationResponse, withCompletionHandler completionHandler: @escaping () -> Void) { print(“didReceive response”) // 1
// With switch operator I'm catching an action's identifier
switch response.actionIdentifier {
case “showMe”:
print(“showMe action”)
// 2
// Here we get our userInfo's data that we passed in
// showNotification method on stage 6 and cast it
// to String type.
let mainText =
response.notification.request.content.userInfo.keys.first! as! String // 3
// Here we again get our userInfo's data that we passed
// in showNotification method on stage 6 and cast it
// to String again.
let subText = response.notification.request.content.userInfo.values.first! as! String // 4
// Here I call our method with new parameters:
// showBody now is true, and withAction is false
// (just because there is no need in action any more).
self.showNotification(with: (mainText, subText),
showBody: true,
withAction: false,
atDate: Date(timeInterval: 3,
since: Date()))
default:
print(“defaul action”)
}
completionHandler()
}
And there you are:
There are some more code inside sample project (that you can download by link below), but the main thing is here in article.
I know that my code needs some refactoring, and more experienced developers can offer more elegant, effective and obvious solution (will be grateful for some advice :) ). But I hope this piece of code will help some one.
Thank you!
p.s. Link to sample project:
