EventKit & Contacts

Four skills covering calendar events, reminders, and contact access for iOS. Built around the permission models that changed significantly in iOS 17 (EventKit) and iOS 18 (Contacts).

Skills in This Suite

Skill	Type	What It Covers
axiom-eventkit	Discipline	Access tier decision tree, permission model, EventKitUI patterns, reminder patterns, store lifecycle, migration, pressure scenarios
axiom-eventkit-ref	Reference	EKEventStore, EKEvent, EKReminder, EKAlarm, EKRecurrenceRule, EventKitUI controllers, Siri Event Suggestions, virtual conference extensions, error codes
axiom-contacts	Discipline	Access level decision tree, Contact Access Button, picker vs store decisions, key fetching discipline, ContactProvider, pressure scenarios
axiom-contacts-ref	Reference	CNContactStore, CNMutableContact, CNSaveRequest, CNContactFormatter, ContactsUI, ContactProvider, change history sync, error codes

When to Use

EventKit skills when you're:

• Adding events to the user's calendar
• Creating or managing reminders
• Choosing between EventKitUI, write-only, or full access
• Migrating from pre-iOS 17 permission APIs
• Implementing Siri Event Suggestions or virtual conference extensions

Contacts skills when you're:

• Reading or writing contacts
• Choosing between picker, Contact Access Button, or full store access
• Implementing contact search or selection UIs
• Migrating to iOS 18 limited access
• Building a Contact Provider extension

Example Prompts

• "How do I add an event to the user's calendar?"
• "What's the difference between write-only and full Calendar access?"
• "How do I create reminders programmatically?"
• "How do I let users pick a contact in SwiftUI?"
• "What's the Contact Access Button and when should I use it?"
• "How do I implement Siri Event Suggestions for restaurant reservations?"
• "How do I handle iOS 18 limited contact access?"
• "How do I detect contact changes for sync?"

Key Concepts

EventKit: Three Access Tiers

Most apps only need Tier 1 — zero permission prompts.

Tier	Method	Use Case
No access	EKEventEditViewController	Add single events via system UI (iOS 17+ out-of-process)
No access	Siri Event Suggestions	Reservation-style events (restaurant, flight, hotel)
Write-only	requestWriteOnlyAccessToEvents()	Custom UI, batch saves, silent creation
Full access	requestFullAccessToEvents()	Read, modify, delete existing events
Full access	requestFullAccessToReminders()	All reminder operations (no write-only tier)

Contacts: Four Authorization Levels

Most apps should use Contact Access Button or CNContactPickerViewController — no authorization needed.

Level	Behavior
Not Determined	ContactAccessButton works — auto-triggers simplified prompt on tap
Limited (iOS 18+)	App sees only user-selected contacts. Same API surface, different visibility.
Full	Read/write all contacts. Reserve for apps where contacts are the core feature.
Denied	No access to contact data.

Key Pattern: Adding a Calendar Event (Zero Permissions)

let store = EKEventStore()
let event = EKEvent(eventStore: store)
event.title = "Team Standup"
event.startDate = startDate
event.endDate = Calendar.current.date(byAdding: .hour, value: 1, to: startDate) ?? startDate

let editVC = EKEventEditViewController()
editVC.event = event
editVC.eventStore = store
editVC.editViewDelegate = self
present(editVC, animated: true)  // No permission prompt needed

Key Pattern: Contact Access Button (iOS 18+)

ContactAccessButton(queryString: searchText) { identifiers in
    let contacts = await fetchContacts(withIdentifiers: identifiers)
}

Common Mistakes

Mistake	Cost	Fix
Requesting full Calendar access for "add to calendar"	30%+ denial rate	Use EventKitUI (zero permissions)
Calling deprecated requestAccess(to:) on iOS 17	Throws error, no prompt	Use requestFullAccessToEvents()
Missing Info.plist key on iOS 17+	Silent denial	Add NSCalendarsFullAccessUsageDescription
Accessing unfetched key on CNContact	Crash	Always specify keysToFetch
Using CNContactStore for one-time picking	Unnecessary permission prompt	Use CNContactPickerViewController
Ignoring .limited contact status	"Missing contacts" bug	Show ContactAccessButton

Related

• extensions-widgets — If combining calendar data with widgets
• privacy-ux — General iOS privacy and permission UX patterns
• background-processing — If scheduling background calendar sync

Resources

WWDC: 2023-10052, 2024-10121, 2020-10197

Docs: /eventkit, /eventkitui, /contacts, /contactsui, /contactprovider, /technotes/tn3152, /technotes/tn3153, /technotes/tn3149