UNUserNotificationCenter

UNUserNotificationCenter is the central object in the UserNotifications framework responsible for managing notifications for an app. It coordinates the delivery of local and remote notifications and provides an interface to request permission, schedule notifications, and respond to user interactions. The center is accessed via a shared instance and is available across Apple platforms that support UserNotifications.

Access and authorization: An app obtains the shared center with a call to current(). To display alerts, badges, or sounds, the app must request user authorization using requestAuthorization(options:completionHandler:), specifying the desired notification options. The center can also report current settings through getNotificationSettings, enabling the app to adapt behavior based on user preferences.

Scheduling and delivering notifications: Local notifications are created with a content object (UNMutableNotificationContent) and a trigger (such as time interval, calendar date, or location-based triggers). These are bundled into a UNNotificationRequest and submitted with the center’s add(_:withCompletionHandler:) method. The center handles delivery for both local and remote notifications; remote notifications arrive via APNs and may be presented to the user according to the user’s settings and the app’s state.

Managing delivered and pending notifications: The center provides methods to query and modify notifications, including getDeliveredNotifications and getPendingNotificationRequests, and to remove notifications via removeDeliveredNotifications(withIdentifiers:) and removePendingNotificationRequests(withIdentifiers:).

Delegate and user interaction: Implementing UNUserNotificationCenterDelegate allows the app to respond when notifications arrive while the app is in the foreground and to handle user interactions with notification actions.

Categories and actions: Notifications can define categories (UNNotificationCategory) with custom actions (UNNotificationAction), enabling quick user responses directly from the notification interface.

History and scope: Introduced with the UserNotifications framework in iOS 10, UNUserNotificationCenter remains the central API for notification management across supported Apple platforms.