does NSMetadataQueryDidUpdateNotification can work with NSFileManager setUbiquitous - icloud

Question

i am trying to track my icloud upload progress using NSMetadataQueryDidUpdateNotification..but it can't work... i don't know what the problem is..
here is my code for upload to icloud
dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^(void) {
NSFileCoordinator* fileCoordinator = [[NSFileCoordinator alloc] initWithFilePresenter:nil];
[fileCoordinator coordinateReadingItemAtURL:backupUrl options:NSFileCoordinatorReadingWithoutChanges error:nil byAccessor:^(NSURL *newURL) {
NSFileManager* fm = [NSFileManager defaultManager];
NSError *theError = nil;
BOOL success =[fm setUbiquitous:YES itemAtURL:backupUrl destinationURL:[[ubiq URLByAppendingPathComponent:#"Documents" isDirectory:true] URLByAppendingPathComponent:bName] error:&theError];
if (!(success)) {
[progView dismiss];
UIAlertView* alertFail=[[UIAlertView alloc]initWithTitle:#"Backup Error" message:#"Could not backup to iCloud." delegate:Nil cancelButtonTitle:#"OK" otherButtonTitles:nil, nil];
[alertFail show];
NSLog(#"iCloud error: %#", [theError localizedDescription]);
}
else{
[self loadNotes:bName];
}
}];
});
and this code for tracing my upload progress
- (void)loadNotes:(NSString *)bname {
self.alertQuery = [[NSMetadataQuery alloc] init];
[self.alertQuery setPredicate:[NSPredicate predicateWithFormat:#"%K LIKE %#", NSMetadataItemFSNameKey, bname]];
[self.alertQuery setSearchScopes:#[NSMetadataQueryUbiquitousDataScope]];
[[NSNotificationCenter defaultCenter]addObserver:self selector:#selector(liveupdate:) name:NSMetadataQueryDidUpdateNotification object:self.alertQuery];
[self.alertQuery startQuery];
}
-(void)liveupdate:(NSNotification *)note {
NSMetadataQuery* query=[note object];
if ([query resultCount]==0){
return;
}
NSMetadataItem* item=[query resultAtIndex:0];
float progress=[[item valueForAttribute:NSMetadataUbiquitousItemPercentUploadedKey]floatValue];
[progView.progBar setProgress:progress animated:NO];
if ([[item valueForAttribute:NSMetadataUbiquitousItemIsUploadedKey] boolValue]){
[query stopQuery];
[query disableUpdates];
_alertQuery=nil;
[progView dismiss];
}
}
what is the wrong with code...
can somebody tell me what is the best way to track icloud upload progress in NSFileManager setUbiquitous....
thank you...

Answer 1

You will probably want to observe the NSMetadataQueryDidFinishGatheringNotification notification, which fires first, with the initial set of results.
But even then, you may not get what you want, because the update notification will only fire if the set of results changes. You are searching for a particular file, and since that file is not being deleted or anything like that, your set of results will remain the same, even if the file uploads or downloads.
In my experience, NSMetadataQuery is not very effective for monitoring upload and download progress. You can hack it to almost work, but it is never exactly what you want.
Probably the best you can do is fire the metadata query, observe the finished-gathering notification, stop the query, and start the query again. Do this at regular intervals of a second or so, and you should be able to track the progress.
You should also consider whether you really want to track progress of an individual file. It will depend how large your files are. In many cases, you may be better to track the number of files to upload/download, or the total bytes remaining.
If this is the case, you can try to setup a metadata that includes a predicate with the uploaded/downloaded status included. This will continually fire notifications when a file finishes uploading/downloading. You can find an example of this here. Look for the method startMonitoringMetadata.