public static let KingfisherDidCleanDiskCache
This notification will be sent when the disk cache got cleaned either there are cached files expired or the
total size exceeding the max allowed size. The manually invoking of
clearDiskCache method will not trigger
object of this notification is the
ImageCache object which sends the notification.
A list of removed hashes (files) could be retrieved by accessing the array under
KingfisherDiskCacheCleanedHashKey key in
userInfo of the notification object you received.
By checking the array, you could know the hash codes of files are removed.