A collection of interchangeable classes that notify you when a given file or folder changes. You can register for notifications, or register as a delegate.
UKKQueue - Uses the Unix kqueue mechanism in the background. This gives the most immediate change notifications, whether your application is in the foreground or background. However, it also is the most low-level and requires your application to be running or it will miss changes. Also, as safe-saves in modern Cocoa apps generally work by writing to a new file, then deleting the old file and giving the new one the original's name, it may report files as deleted that have just been saved, forcing you to unregister and re-register for change notifications.
UKFSEventsWatcher - Uses FSEvents under the hood. This is the same mechanism as Spotlight and Time Machine use. It can remember changes across restarts, but will sometimes report a large number of changes in the same folder as a vague "something in this folder changed". It is geared towards watching when folder contents change, but that luckily includes changes to those files' contents.
UKFNSubscribeFileWatcher - This is the mechanism the Finder used for a long time. It is the least resource-intensive as it coalesces updates that happen while your application is in the background, or repeated updates to the same file. It was deprecated in Mac OS X 10.8.
UKFileWatcher - A protocol that all the above classes conform to, allowing you to try each of them out easily and pick the one you like most.
Copyright 2003-2014 by Uli Kusterer.
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