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9
Custom Actions Written by Scott Grosch

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At this point, you’ve implemented as much of push notifications as most app developers will ever want or need to do. Don’t give up now! There are still some really amazing features you can add to your app to make it shine, should you so desire.

In the previous chapter, you built an app that triggers an action when the user taps on a received notification. Sometimes, a simple tap is not enough. Maybe your friend is asking you to grab coffee and you want an easy way to accept the offer. Or maybe another friend posted a funny tweet and you want to favorite it right from the notification.

Thankfully, iOS gives you a way to attach buttons to a push notification so that the user can provide a meaningful response to the received notification without having to open your app! In this chapter, you’ll learn how to make your notifications actionable.

After opening up the starter project for this chapter, remember to turn on the Push Notifications capability as discussed in Chapter 4, “Xcode Project Setup”, and set the team signing as discussed in Chapter 7, “Expanding the Application”.

Categories

Notification categories allow you to specify up to four custom actions per category that will be displayed with your push notification. Keep in mind that the system will only display the first two actions if your notification appears in a banner, so you always want to configure the most relevant actions first.

Note: The simulator does not currently display categories. Be sure to test on a physical device.

To enable the user to decide what action to take, you’ll add Accept and Reject buttons to your push notifications.

You’ll first add an enum to the top of AppDelegate.swift, right below the import statements, to identify your buttons.

public let categoryIdentifier = "AcceptOrReject"

public enum ActionIdentifier: String {
  case accept, reject
}

Use an enum to ensure you aren’t hardcoding strings for identifiers as you won’t ever display them to an end user.

Once that’s done, add a method at the bottom of AppDelegate to perform the registration.

private func registerCustomActions() {
  let accept = UNNotificationAction(
    identifier: ActionIdentifier.accept.rawValue,
    title: "Accept")

  let reject = UNNotificationAction(
    identifier: ActionIdentifier.reject.rawValue,
    title: "Reject")

  let category = UNNotificationCategory(
    identifier: categoryIdentifier,
    actions: [accept, reject],
    intentIdentifiers: [])

  UNUserNotificationCenter.current().setNotificationCategories([category])
}

Here, you create a notification category with two buttons. When a push notification arrives with a category set to AcceptOrReject, your custom actions will be triggered, and iOS will include the two buttons at the bottom of your push notification.

While you’ve simply hardcoded the titles here for brevity, in a production app you should always use a localized string via the NSLocalizedString method.

Note: Even if you don’t think you’re going to localize your app, it’s better to get in the habit now than have to go back and find every single user visible string later if plans change!

You only need to register your actions if you’re actually accepting push notifications, so add a call to registerCustomActions() at the end of application(_:didRegisterForRemoteNotificationsWithDeviceToken:)

registerCustomActions()

Build and run your app. Now, go back into the push notification tester app (as described in Chapter 5, “Apple Push Notifications Servers”) and use the following payload:

{
  "aps": {
    "alert": {
      "title": "Long-press this notification"
    },
    "category": "AcceptOrReject",
    "sound": "default"
  }
}

The critical part of the payload is making sure the category value exactly matches what you specified during your registration with UNUserNotificationCenter. Send another push to yourself now.

See your action buttons? No? Don’t worry, you didn’t mess anything up!

The trick is you need to long press the notification to reveal the buttons.

Once you do that, the custom buttons appear and you can select one.

Go back into your NotificationDelegate.swift and the following statements to the end of userNotificationCenter(_:didReceive:withCompletionHandler:):

let identity = response.notification.request.content.categoryIdentifier
guard identity == categoryIdentifier,
  let action = ActionIdentifier(rawValue: response.actionIdentifier) else {
  return
}

print("You pressed \(response.actionIdentifier)")

Note: You can safely ignore the warning about action not being used as you’ll use it in just a moment.

Remember that this method will be called when you tap on the notification, so you need to do a quick check to make sure you’re handling your own category, and then you can grab the button that was pressed. This method will be called even when your app is not in the foreground, so be careful of what you do here!

Build and run your code again, and send yourself another notification from the Tester app. Long press the notification and select one of the buttons; you should see a similar message in Xcode’s console:

You pressed accept

Tracking the notification with Combine

The NotificationDelegate is not where you want to take action when a push notification is acted upon, unless it’s a simple data storage operation. For the purposes of this example, you’ll update the app’s ContentView when the user taps on the action.

import Combine

// 1
final class Counter: ObservableObject {
  // 2
  @Published public var accepted = 0
  @Published public var rejected = 0

  // 3
  static let shared = Counter()
  
  private init() {}
}

Responding to the action

Head back over to the NotificationDelegate.swift file and replace the print statement with the following code:

switch action {
case .accept: Counter.shared.accepted += 1
case .reject: Counter.shared.rejected += 1
}
@ObservedObject var counter = Counter.shared
ColoredCounter(
  count: $counter.accepted,
  backgroundColor: .green,
  text: "Accepted")
ColoredCounter(
  count: $counter.rejected,
  backgroundColor: .red,
  text: "Rejected")

Key points

  • You can make a push notification actionable by attaching a button to a notification.
  • Notification categories allow you to specify up to four custom actions per category that will be displayed with your push notification.
  • Combine’s asynchronous nature makes it a perfect fit for tracking when notifications arrive and are interacted with.

Where to go from here?

If you’re interested in learning more about the Combine framework, you can check out any of these great resources, depending on your preferred learning style:

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