Tells your object that the presented item’s contents or attributes changed.
- iOS 5.0+
- macOS 10.7+
- tvOS 9.0+
- watchOS 2.0+
You can use this method to update your internal data structures to reflect the changes to the presented item. This method reports both changes to the file’s contents, such as the data in a file or the files in a directory, or the attributes of the item, such as whether the Hide extension checkbox of a file was toggled.
Because this method notifies you of both attribute and content changes, you might want to check the modification date before needlessly rereading the contents of a file. To do that, you must store the date when your object last made changes to the file and compare that date with the item’s current modification date. Use the
coordinate(reading method of a file coordinator to ensure exclusive access to the file when reading the current modification date.