The keys that can appear in the change dictionary.
SDKs
Framework
struct NSKeyValueChangeKey
These constants are used as keys in the change dictionary passed to observe.
static let indexesIf the value of the kind entry is NSKey, NSKey, or NSKey, the value of this key is an NSIndex object that contains the indexes of the inserted, removed, or replaced objects.
static let kindAn NSNumber object that contains a value corresponding to one of the NSKey enums, indicating what sort of change has occurred.
static let newIf the value of the kind entry is NSKey, and new was specified when the observer was registered, the value of this key is the new value for the attribute.
static let notificationIf the prior option was specified when the observer was registered this notification is sent prior to a change.
static let oldIf the value of the kind entry is NSKey, and old was specified when the observer was registered, the value of this key is the value before the attribute was changed.