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

Just shared this on Twitter with you, but I believe when using NSDocument you don't need to do any of the NSFileCoordinator stuff - just make the document ubiquitous and save.

Answer 2

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.

Answer 3

Hmm,

did you try not using a ubiquity container identifier in code (sorry - ripped out of a project so I've pseudo-coded some of this):

NSFileManager *fm = [NSFileManager defaultManager];
NSURL *iCloudDocumentsURL = [[fm URLForUbiquityContainerIdentifier:nil] URLByAppendingPathComponent:@"Documents"];
NSURL *iCloudFileURL = [iCloudDocumentsURL URLByAppendingPathComponent:[doc.fileURL lastPathComponent]];
ok = [fm setUbiquitous:YES itemAtURL:doc.fileURL destinationURL:iCloudRecipeURL error:&err];
NSLog(@"doc moved to iCloud, result: %d (%@)",ok,doc.fileURL.fileURL);

And then in your entitlements file:

<key>com.apple.developer.ubiquity-container-identifiers</key>
<array>
    <string>[devID].com.yourcompany.appname</string>
</array>

Other than that, your code looks almost identical to mine (which works - except I'm not using NSDocument but rolling it all myself).

Answer 4

If this is the first place in your code that you are accessing iCloud look in Console.app for a message like this:

taskgated: killed yourAppID [pid 13532] because its use of the com.apple.developer.ubiquity-container-identifiers entitlement is not allowed

Anytime you see this message delete your apps container ~/Library/Containers/<yourAppID> There may also be other useful messages in Console.app that will help you solve this issue. I have found that deleting the app container is the new Clean Project when working with iCloud.

Answer 5

Ok, So I was finally able to solve the problem using Dunk's advice. I'm pretty sure the issue I was having is as follows:

• Sometime after the WWDC video I was using as a guide was made, Apple completed the ubiquity APIs and removed the need to use an NSFileCoordinator object while saving from within an NSDocument subclass.

So the key was to remove both the creation of the NSFileCoordinator and the call to -[NSFileCoordinator coordinateWritingItemAtURL:options:writingItemAtURL:options:error:byAccessor:]

I also moved this work onto a background thread, although I'm fairly certain that was not absolutely required to fix the issue (although it was certainly a good idea).

I shall now submit my completed code to Google's web crawlers in hopes of assisting future intrepid Xcoders.

Here's my complete solution which works:

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

    BOOL makeUbiquitous = 1 == [sender tag];

    if (makeUbiquitous) {
        [self displayMoveToCloudDialog];
    } else {
        [self displayMoveFromCloudDialog];
    }

    dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0), ^{
        [self doMoveToOrFromCloud:makeUbiquitous];
    });
}


- (void)doMoveToOrFromCloud:(BOOL)makeUbiquitous {
    NSURL *fileURL = [self fileURL];
    if (!fileURL) return;

    NSURL *destURL = nil;
    NSFileManager *mgr = [[[NSFileManager alloc] init] autorelease];
    if (makeUbiquitous) {
        NSURL *dirURL = [[MyDocumentController instance] ubiquitousDocumentsDirURL];
        if (!dirURL) return;

        destURL = [dirURL URLByAppendingPathComponent:[fileURL lastPathComponent]];
    } else {
        // move to local Documentss folder
        NSArray *dirs = [mgr URLsForDirectory:NSDocumentDirectory inDomains:NSUserDomainMask];
        if (![dirs count]) return;

        destURL = [[dirs firstObject] URLByAppendingPathComponent:[fileURL lastPathComponent]];
    }

    NSError *err = nil;
    void (^completion)(void) = nil;

    if ([mgr setUbiquitous:makeUbiquitous itemAtURL:fileURL destinationURL:destURL error:&err]) {
        [self setFileURL:destURL];
        [self setFileModificationDate:nil];

        completion = ^{
            [self hideMoveToFromCloudDialog];
        };

    } else {
        completion = ^{
            [self hideMoveToFromCloudDialog];
            NSWindow *win = [[self canvasWindowController] window];
            [self presentError:err modalForWindow:win delegate:nil didPresentSelector:nil contextInfo:NULL];
        };
    }

    dispatch_async(dispatch_get_main_queue(), completion);
}