Attaching and Removing Alarms

You can add an alarm to an event with the addAlarm: method. Alarms can be created with an absolute date or with an offset relative to the start date of the event. Alarms created with a relative offset must occur before or at the start date of the event.

In OS X, you can trigger an action alongside the alarm; for example, set:

• The emailAddress property to send an email

• The soundName property to play a sound

• The url property to open a URL

You can remove an alarm from an event with the removeAlarm: method.

Setting Geofences

A geofence is a virtual border surrounding a geographic location that, when crossed, can trigger an alarm for an event. Geofences are a useful way to remind users of tasks they need to do when entering or exiting a certain region. For example, when a user leaves their workplace, an alarm can fire that reminds them to stop by the grocery store. As a developer, you have control over specifying the latitude and longitude of the center, as well as the radius of the geofence.

Configure a geofence for an event by creating an alarm and setting its structured location and proximity. Call the locationWithTitle: method to create a structured location. To set longitude and latitude coordinates, pass a CLLocation to the geoLocation property of the structured location returned. A value of 0 for the radius property will use the system’s default radius; to choose a radius of your own, specify a value in meters.

While geofence-enabled alarms can be applied to events, they are more practical for reminders.