public struct PropertyChange
Information about a specific property which changed in an
Object change notification.
The name of the property which changed.
public let name: String
Value of the property before the change occurred. This is not supplied if the change happened on the same thread as the notification and for
For object properties this will give the object which was previously linked to, but that object will have its new values and not the values it had before the changes. This means that
previousValuemay be a deleted object, and you will need to check
isInvalidatedbefore accessing any of its properties.
public let oldValue: Any?