EventKit Integration (System Calendar) in iOS App
EventKit — a framework for reading and writing events to the system calendar on iOS and macOS. Technically straightforward to integrate, but there are several places where developers consistently lose time.
Permissions and typical mistakes
Before iOS 17, EventKit used one key to request Calendar access: NSCalendarsUsageDescription in Info.plist. Since iOS 17, Apple split access into two levels: write-only (NSCalendarsWriteOnlyAccessUsageDescription) and full access (NSCalendarsFullAccessUsageDescription). An app built for iOS 17 SDK without NSCalendarsWriteOnlyAccessUsageDescription will crash when trying to create an event — even if the old key is present.
Access request via EKEventStore.requestFullAccessToEvents returns asynchronously. Common mistake — calling EKEventStore.save immediately after requestAccess without waiting for the user's response. Result: EKErrorCalendarAccessDenied in release build, because simulator sometimes grants access automatically without a dialog.
Implementation approach
Working with EKEventStore — it's a heavyweight object, create once and reuse through a singleton or injectable service. Creating a new instance for each request — memory leak and performance hit.
To create an event:
let store = EKEventStore()
let event = EKEvent(eventStore: store)
event.title = "Meeting"
event.startDate = startDate
event.endDate = endDate
event.calendar = store.defaultCalendarForNewEvents
event.addAlarm(EKAlarm(relativeOffset: -600)) // -10 minutes
do {
try store.save(event, span: .thisEvent)
} catch {
// EKErrorNoCalendar, EKErrorEventNotMutable — handle separately
}
EKSpan.thisEvent vs EKSpan.futureEvents — important parameter when working with recurring events. Client wants to change one specific event in a series — use thisEvent. Wants to change everything from that date onward — use futureEvents. Can't mix them up.
Subscribe to calendar changes via EKEventStoreChangedNotification if the app displays an event list: user might have changed an event directly through system Calendar.app, and UI needs updating.
What's included in the work
- Setting up
Info.plistfor iOS 16 and iOS 17+ - Requesting permissions with correct handling of all states (denied, restricted, fullAccess, writeOnly)
- CRUD operations with events: create, edit, delete
- Working with recurring events and reminders
- Subscribing to storage changes
- Handling multiple calendars (iCloud, local, Exchange)
Timeline
2–3 days including real device testing under iOS 16 and 17. Cost calculated individually.