Why do NSFilePresenter protocol methods never get called? - macos

Question

I am trying to monitor file changes in local and iCloud directories and have implemented the NSFilePresenter protocol methods but the only method that gets called is presentedItemAtURL.
Am I correct in assuming that I should be able to monitor a local or an iCloud directory and get notified any time any process adds, modifies or deletes a file in the directory.
Here is the basic code for the OS X App:
- (void)awakeFromNib {
_presentedItemURL = myDocumentsDirectoryURL;
_presentedItemOperationQueue = [[NSOperationQueue alloc] init];
[_presentedItemOperationQueue setMaxConcurrentOperationCount: 1];
_fileCoordinator = [[NSFileCoordinator alloc] initWithFilePresenter:self];
}
- (NSURL*) presentedItemURL {
FLOG(#" called %#", _presentedItemURL);
return _presentedItemURL;
}
- (NSOperationQueue*) presentedItemOperationQueue {
FLOG(#" called");
return _presentedItemOperationQueue;
}
- (void)presentedItemDidChange {
FLOG(#" called");
dispatch_async(dispatch_get_main_queue(), ^{
[self reloadData];
});
}
-(void)accommodatePresentedItemDeletionWithCompletionHandler:(void (^)(NSError *errorOrNil))completionHandler
{ FLOG(#" called");
[[NSOperationQueue mainQueue] addOperationWithBlock:^{
[self reloadData];
}];
completionHandler(nil);
}
-(void)presentedSubitemDidChangeAtURL:(NSURL *)url {
FLOG(#" called");
dispatch_async(dispatch_get_main_queue(), ^{
[self reloadData];
});
}
-(void)presentedSubitemDidAppearAtURL:(NSURL *)url {
FLOG(#" called");
dispatch_async(dispatch_get_main_queue(), ^{
[self reloadData];
});
}

Answer 1

Long time ago, I know, but perhaps this will still help. NSFilePresenter will only notify you about changes made by another process that makes changes to a directory or file USING AN NSFileCoordinator. If another process (eg: iTunes file sharing) makes changes without an NSFileCoordinator, you won't be notified.

Answer 2

This is in no way my final implementation and I will edit/update as I improve. But since there is nil examples on how to do this, i figured i'd share something that works!!! That's right, it works. I am able to read the file in my app, and at the same time make a change in textedit and the changes propagate to my app. Hope this helps bud.
PBDocument.h
#interface PBDocument : NSObject <NSFilePresenter>
#property (nonatomic, strong) NSTextView *textView;
#pragma mark - NSFilePresenter properties
#property (readonly) NSURL *presentedItemURL;
#property (readonly) NSOperationQueue *presentedItemOperationQueue;
- (instancetype)initWithContentsOfURL:(NSURL *)url error:(NSError *__autoreleasing *)outError textView:(NSTextView*)textView;
#end
PBDocument.m
#interface PBDocument ()
#property (readwrite) NSURL *presentedItemURL;
#property (readwrite) NSOperationQueue *presentedItemOperationQueue;
#property (readwrite) NSFileCoordinator *fileCoordinator;
#end
#implementation PBDocument
- (instancetype)initWithContentsOfURL:(NSURL *)url error:(NSError *__autoreleasing *)outError textView:(NSTextView*)textView {
self = [super init];
if (self) {
_textView = textView;
_presentedItemURL = url;
_presentedItemOperationQueue = [NSOperationQueue mainQueue];
[NSFileCoordinator addFilePresenter:self];
_fileCoordinator = [[NSFileCoordinator alloc] initWithFilePresenter:self];
[self readWithCoordination];
}
return self;
}
- (void)readWithCoordination {
NSError *error = nil;
[self.fileCoordinator coordinateReadingItemAtURL:_presentedItemURL options:NSFileCoordinatorReadingWithoutChanges error:&error byAccessor:^(NSURL *newURL) {
NSLog(#"Coordinating Read");
NSError *error = nil;
NSFileWrapper *wrapper = [[NSFileWrapper alloc] initWithURL:newURL options:0 error:&error];
if (!error) {
[self readFromFileWrapper:wrapper ofType:[self.presentedItemURL pathExtension] error:&error];
}
if (error) #throw [NSException exceptionWithName:NSInternalInconsistencyException reason:[NSString stringWithFormat:#"%#", error] userInfo:nil];
}];
if (error) #throw [NSException exceptionWithName:NSInternalInconsistencyException reason:[NSString stringWithFormat:#"%#", error] userInfo:nil];
}
- (void)presentedItemDidChange {
[self readWithCoordination];
}
#end

Answer 3

If it's any help to anyone this is the approach (FSEvents) I ended up using recently for a file sync solution and it seems to work for any file system. I have not done any research recently on NSFileCoordinator to see whether this is better worse or what the use cases are as a comparison.
I also did not test every use case so your mileage may vary.
https://github.com/eonil/FSEvents