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# actionIdentifier

The identifier string of the action that the user selected.

```
var actionIdentifier: String { get }
```

## Discussion

This parameter may contain one the identifier of one of your [`UNNotificationAction`](/documentation/UserNotifications/UNNotificationAction) objects or it may contain a system-defined identifier. The system defined identifiers are [`UNNotificationDefaultActionIdentifier`](/documentation/UserNotifications/UNNotificationDefaultActionIdentifier) and [`UNNotificationDismissActionIdentifier`](/documentation/UserNotifications/UNNotificationDismissActionIdentifier), which indicate that the user opened the app or dismissed the notification without any further actions.

For more information about defining custom actions, see [Declaring your actionable notification types](/documentation/UserNotifications/declaring-your-actionable-notification-types).

---

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