Article

Updating with Notifications

Register to be notified about changes and keep your app up to date.

Overview

It’s possible for another process or app to modify the Calendar database while your app is running. If your app fetches calendar events or reminders, register to be notified about changes to the Calendar database to ensure the calendar and reminder information you display to the user is current.

Register for Notifications

An EKEventStore object posts an EKEventStoreChanged notification whenever it detects changes to the Calendar database. Register for this notification if your app handles event or reminder data.

Listing 1 registers for the EKEventStoreChanged notification.

NotificationCenter.default.addObserver(self, selector: Selector("storeChanged:"), name: .EKEventStoreChanged, object: eventStore)

Respond to Notifications

When you receive an EKEventStoreChanged notification, it’s possible the objects you’ve fetched—such as an EKEventEKReminder, or EKCalendar—have changed. The effect of the changes depends on whether an event was added, modified, or deleted:

  • If an event was added, it does not affect any of your previously fetched events or reminders, but the added event may fall within the date range of events you are displaying to the user.

  • If an event was modified or deleted, properties of EKEvent and EKReminder objects representing that event may become out of date.

Because your local data is often invalidated or incomplete when a change occurs in the Calendar database, you should refetch your current date range of events whenever you receive an EKEventStoreChanged notification. If you are modifying an event and do not want to refetch it unless it is absolutely necessary, call the refreshSourcesIfNecessary() method on the event. If the method returns YES, you can continue to use the event; otherwise, you must refetch it. 

Topics

Receiving a Notification

static let EKEventStoreChanged: NSNotification.Name

A notification posted when changes are made to the Calendar database.

See Also

Events and Reminders

Creating Events and Reminders

Create and modify events and reminders in a user's database.

Retrieving Events and Reminders

Fetch events and reminders from the Calendar database.

class EKEvent

A class that represents an event added to a calendar.

class EKReminder

A class that represents a reminder added to a calendar.