Calling -[NSFileManager setUbiquitous:itemAtURL:destinationURL:error:] never returns

Question

I have a straightforward NSDocument-based Mac OS X app in which I am trying to implement iCloud Document storage. I'm building with the 10.7 SDK.

I have provisioned my app for iCloud document storage and have included the necessary entitlements (AFAICT). The app builds, runs, and creates the local ubiquity container Documents directory correctly (this took a while, but that all seems to be working). I am using the NSFileCoordinator API as Apple recommended. I'm fairly certain I am using the correct UbiquityIdentifier as recommended by Apple (it's redacted below tho).

I have followed Apple's iCloud Document storage demo instructions in this WWDC 2011 video closely:

Session 107 AutoSave and Versions in Lion

My code looks almost identical to the code from that demo.

However, when I call my action to move the current document to the cloud, I experience liveness problems when calling the -[NSFileManager setUbiquitous:itemAtURL:destinationURL:error:] method. It never returns.

Here is the relevant code from my NSDocument subclass. It is almost identical to Apple's WWDC demo code. Since this is an action, this is called on the main thread (as Apple's demo code showed). The deadlock occurs toward the end when the -setUbiquitous:itemAtURL:destinationURL:error: method is called. I have tried moving to a background thread, but it still never returns.

It appears that a semaphore is blocking while waiting for a signal that never arrives.

When running this code in the debugger, my source and destination URLs look correct, so I'm fairly certain they are correctly calculated and I have confirmed the directories exist on disk.

Am I doing anything obviously wrong which would lead to -setUbiquitous never returning?

- (IBAction)moveToOrFromCloud:(id)sender {
    NSURL *fileURL = [self fileURL];
    if (!fileURL) return;

    NSString *bundleID = [[[NSBundle mainBundle] infoDictionary] objectForKey:@"CFBundleIdentifier"];
    NSString *appID = [NSString stringWithFormat:@"XXXXXXX.%@.macosx", bundleID];

    BOOL makeUbiquitous = 1 == [sender tag];

    NSURL *destURL = nil;
    NSFileManager *mgr = [NSFileManager defaultManager];
    if (makeUbiquitous) {
        // get path to local ubiquity container Documents dir
        NSURL *dirURL = [[mgr URLForUbiquityContainerIdentifier:appID] URLByAppendingPathComponent:@"Documents"];
        if (!dirURL) {
            NSLog(@"cannot find URLForUbiquityContainerIdentifier %@", appID);
            return;
        }

        // create it if necessary
        [mgr createDirectoryAtURL:dirURL withIntermediateDirectories:NO attributes:nil error:nil];

        // ensure it exists
        BOOL exists, isDir;
        exists = [mgr fileExistsAtPath:[dirURL relativePath] isDirectory:&isDir];
        if (!(exists && isDir)) {
            NSLog(@"can't create local icloud dir");
            return;
        }

        // append this doc's filename
        destURL = [dirURL URLByAppendingPathComponent:[fileURL lastPathComponent]];
    } else {
        // get path to local Documents folder
        NSArray *dirs = [mgr URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask];
        if (![dirs count]) return;

        // append this doc's filename
        destURL = [[dirs objectAtIndex:0] URLByAppendingPathComponent:[fileURL lastPathComponent]];
    }

    NSFileCoordinator *fc = [[[NSFileCoordinator alloc] initWithFilePresenter:self] autorelease];
    [fc coordinateWritingItemAtURL:fileURL options:NSFileCoordinatorWritingForMoving writingItemAtURL:destURL options:NSFileCoordinatorWritingForReplacing error:nil byAccessor:^(NSURL *fileURL, NSURL *destURL) {

        NSError *err = nil;
        if ([mgr setUbiquitous:makeUbiquitous itemAtURL:fileURL destinationURL:destURL error:&err]) {
            [self setFileURL:destURL];
            [self setFileModificationDate:nil];
            [fc itemAtURL:fileURL didMoveToURL:destURL];
        } else {
            NSWindow *win = ... // get my window
            [self presentError:err modalForWindow:win delegate:nil didPresentSelector:nil contextInfo:NULL];
        }
    }];
}

Answer 1

I don't know if these are the source of your problems, but here are some things I'm seeing:

• -[NSFileManager URLForUbiquityContainerIdentifier:] may take a while, so you shouldn't invoke it on the main thread. see the "Locating the Ubiquity Container" section of this blog post

• Doing this on the global queue means you should probably use an allocated NSFileManager and not the +defaultManager.

• The block passed to the byAccessor portion of the coordinated write is not guaranteed to be called on any particular thread, so you shouldn't be manipulating NSWindows or presenting modal dialogs or anything from within that block (unless you've dispatched it back to the main queue).

• I think pretty much all of the iCloud methods on NSFileManager will block until things complete. It's possible that what you're seeing is the method blocking and never returning because things aren't configured properly. I'd double and triple check your settings, maybe try to simplify the reproduction case. If it still isn't working, try filing a bug or contacting DTS.