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Reading and Writing Reminders

Reminders are tasks that may be tied to a specific time or location. They are similar to calendar events, but can be marked complete and may not necessarily span an exact period of time.

Because EKReminder inherits from EKCalendarItem, you can perform the same methods on a reminder as you would on an event, such as adding an alarm with addAlarm: or setting a recurrence rule with addRecurrenceRule:.

Retrieving Reminders

As with events, you must first establish a connection to the event store to access existing reminders. See Connecting to the Event Store if you have not already done so.

To initialize a connection with access to reminders, pass EKEntityMaskReminder instead of EKEntityMaskEvent.

EKEventStore *store = [[EKEventStore alloc] initWithAccessToEntityTypes:EKEntityMaskReminder];

Just like searching for events, there are two ways to retrieve reminders.

Using Predicates

You can call fetchRemindersMatchingPredicate:completion: to access multiple reminders that match a predicate. Pass a predicate returned by one of the following methods:

predicateForIncompleteRemindersWithDueDateStarting:ending:calendars: finds incomplete reminders within an optional time period
predicateForCompletedRemindersWithCompletionDateStarting:ending:calendars: finds completed reminders within an optional time period
predicateForRemindersInCalendars: finds all reminders

You can iterate across matched reminders by passing a block to the completion argument, as shown in Listing 2-1.

Listing 2-1 Fetching reminders with a predicate

NSPredicate *predicate = [store predicateForRemindersInCalendars:nil];

[store fetchRemindersMatchingPredicate:predicate completion:^(NSArray *reminders) {

    for (EKReminder *reminder in reminders) {

        // do something for each reminder

}];

Using Unique Identifiers

If you know a specific reminder’s unique identifier from previously fetching it with a predicate, you can call the calendarItemWithIdentifier: instance method. calendarItemWithIdentifier: can fetch any calendar item (reminders and events), whereas eventWithIdentifier: fetches only events.

Creating and Editing Reminders

You can create reminders using the reminderWithEventStore: class method. The title and calendar properties are required. The calendar for a reminder is the list with which it is grouped.

Like events, reminders can trigger time-based or location-based alarms to alert the user of a certain task. Read Configuring Alarms for more information on how to attach alarms to calendar items.

To associate a start date or due date with a reminder, use the startDateComponents and dueDateComponents properties. To complete a reminder, set the completed property to YES, which automatically sets completionDate to the current date.

Saving and Removing Reminders

Reminders are saved in a similar fashion to events. To save a reminder to the Calendar database, call the saveReminder:commit:error: method. To remove an event, call the removeReminder:commit:error: method.

Remember, the title and calendar properties must explicitly be set before you save your reminder.

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