apple-system-integration

Use UNUserNotificationCenter to request authorization, build UNMutableNotificationContent, and attach a UNCalendarNotificationTrigger for wall-clock times or UNTimeIntervalNotificationTrigger for delays. Use a stable identifier so re-scheduling replaces the request instead of duplicating it.

Create an EKEventStore, request write-only access with requestWriteOnlyAccessToEvents for add-only features, then build an EKEvent with title, dates, and calendar, and save it with store.save. Add the matching NSCalendars usage string to Info.plist first.

App Intents is the modern framework for exposing actions to Siri, Shortcuts, Spotlight, and widgets without requiring a Siri entitlement. New Siri and Shortcuts work should use AppIntent and AppShortcutsProvider instead of the legacy Intents framework.

Background tasks fail when the identifier is missing from BGTaskSchedulerPermittedIdentifiers in Info.plist, register is not called before launch finishes, or the handler omits expirationHandler and setTaskCompleted. Tasks are also best-effort and system-throttled, so timing is never guaranteed.

No, widgets run in a separate process and cannot access the app's private container. Share data through an App Group using UserDefaults(suiteName:), a shared file container, or a SwiftData store placed in the group container.

iOS caps each app at 64 pending local notification requests. Schedule a rolling window of upcoming reminders and reconcile against pendingNotificationRequests rather than adding hundreds of requests at once.