Are FSEvents available on iOS?

Question

In my application, I need to be able to control the directory for file changes (add / remove). I read that FSEvents is available in iOS 5 but cannot find more information about this. Does anyone know they are available? and if so, are there any examples?

Answer 1

I ended up with a FileMonitor class that used kevents

#import <Foundation/Foundation.h> @protocol FileMonitorDelegate <NSObject> @required -(void) dirChanged:(NSString*) aDirName; @end @interface FileMonitor : NSObject - (void) monitorDir:(NSString*) aDir delegate:(id<FileMonitorDelegate>) aDelegate; @end 

And implementation

 #import <fcntl.h> #import <unistd.h> #import <sys/event.h> #import "FileMonitor.h" #import "LogMacros.h" @interface FileMonitor () @property (nonatomic, assign, readonly) CFFileDescriptorRef _fileDes; @property (nonatomic, retain) NSArray* fns; @end @implementation FileMonitor static int _dirFD; static CFFileDescriptorRef _fileDes; static id<FileMonitorDelegate> _delegate; static NSString *_watchedDir; static void KQCallback(CFFileDescriptorRef kqRef, CFOptionFlags callBackTypes, void *info){ LOG(@"KQCallback called !!"); if(_delegate){ [_delegate dirChanged:_watchedDir]; } // Pull the native FD around which the CFFileDescriptor was wrapped int kq = CFFileDescriptorGetNativeDescriptor(_fileDes); if (kq < 0){ return; } // If we pull a single available event out of the queue, assume the directory was updated struct kevent event; struct timespec timeout = {0, 0}; if (kevent(kq, NULL, 0, &event, 1, &timeout) == 1){ if( _delegate ){ [_delegate dirChanged:_watchedDir]; }else{ LOG_ERROR(@"Callback with NO delegate set"); } } // issue callback request CFFileDescriptorEnableCallBacks(_fileDes, kCFFileDescriptorReadCallBack); } #pragma mark - #pragma mark View lifecycle - (void) monitorDir:(NSString*) aDir delegate:(id<FileMonitorDelegate>) aDelegate{ ASSERT(aDir); ASSERT(aDelegate); _watchedDir = aDir; _delegate = aDelegate; NSError *error; self.fns = [[NSFileManager defaultManager] contentsOfDirectoryAtPath:aDir error:&error]; LOG_IF_NSERROR(error); [self startMonitor]; } - (void)startMonitor { // One ping only if (_fileDes != NULL){ LOG_ERROR(@"kernel queue was null"); return; } // Open an event-only file descriptor associated with the directory int dirFD = open([ _watchedDir fileSystemRepresentation], O_EVTONLY); if (dirFD < 0) { LOG_ERROR(@"could not open file descriptor"); return; } // Create a new kernel event queue int kq = kqueue(); if (kq < 0){ LOG_ERROR(@"could not open kernel queue"); close(dirFD); return; } // Set up a kevent to monitor struct kevent eventToAdd; // Register an (ident, filter) pair with the kqueue eventToAdd.ident = dirFD; // The object to watch (the directory FD) eventToAdd.filter = EVFILT_VNODE; // Watch for certain events on the VNODE spec'd by ident eventToAdd.flags = EV_ADD | EV_CLEAR; // Add a resetting kevent eventToAdd.fflags = NOTE_WRITE; // The events to watch for on the VNODE spec'd by ident (writes) eventToAdd.data = 0; // No filter-specific data eventToAdd.udata = NULL; // No user data // Add a kevent to monitor if (kevent(kq, &eventToAdd, 1, NULL, 0, NULL)){ close(kq); close(dirFD); return; } // Wrap a CFFileDescriptor around a native FD CFFileDescriptorContext context = {0, (__bridge void *)(self), NULL, NULL, NULL}; _fileDes = CFFileDescriptorCreate(NULL, // Use the default allocator kq, // Wrap the kqueue true, // Close the CFFileDescriptor if kq is invalidated KQCallback, // Fxn to call on activity &context); // Supply a context to set the callback "info" argument if (_fileDes == NULL){ close(kq); close(dirFD); return; } // Spin out a pluggable run loop source from the CFFileDescriptorRef // Add it to the current run loop, then release it CFRunLoopSourceRef rls = CFFileDescriptorCreateRunLoopSource(NULL, _fileDes, 0); if (rls == NULL){ CFRelease(_fileDes); _fileDes = NULL; close(kq); close(dirFD); return; } CFRunLoopAddSource(CFRunLoopGetCurrent(), rls, kCFRunLoopDefaultMode); CFRelease(rls); // Store the directory FD for later closing _dirFD = dirFD; // issue callback request CFFileDescriptorEnableCallBacks(_fileDes, kCFFileDescriptorReadCallBack); } - (void)stopMonitor{ if (_fileDes) { close(_dirFD); CFFileDescriptorInvalidate(_fileDes); CFRelease(_fileDes); _fileDes = NULL; } } - (void)restartMonitor{ [self stopMonitor]; [self startMonitor]; } - (void)dealloc{ [self stopMonitor]; } @end 

Answer 2

Pay attention to a higher level (and more powerful than FSEvents) in any case NSFileCoordinator and NSFilePresenter.

NSFilePresenter: http://developer.apple.com/library/ios/#documentation/Foundation/Reference/NSFilePresenter_protocol/Reference/Reference.html

NSFileCoordinator: http://developer.apple.com/library/ios/#documentation/Foundation/Reference/NSFileCoordinator_class/Reference/Reference.html

In 2011, a WWDC session “Using the Benefits of File Coordination” was held, which gives you an overview of the API in 2011, which is worth checking out.