When a file is changed in iCloud (whether added, deleted, or the content changed), I would like to call a method I created ([self methodName]) so that I can update my table view with the names of the new files. How am I notified of the file change? Do I need to listen for a NSNotification (if so, what is it?) or do I have to check manually? Thanks.
The name of the NSNotification I have to listen for is NSMetadataQueryDidUpdateNotification. This is how I did it:
[[NSNotificationCenter defaultCenter] addObserver:self selector:@selector(queryDidUpdate:) name:NSMetadataQueryDidUpdateNotification object:query];
...
-(void)queryDidUpdate:(NSNotification *)notification {
//something changed, reload (NSMetadataQuery, create NSPredicate, rerun the query, etc.)
}
This section of the Apple developer website contains a great tutorial for setting up document-based iCloud apps.
To answer your questions, though: as long as your document is a UIDocument you can register for a notification. Just search that page for "Monitoring Document-State Changes and Handling Errors" - there is tons of source code to help you out.
来源：https://stackoverflow.com/questions/11287294/how-do-you-detect-when-a-file-is-changed-in-icloud