iCloud UIDocumentPicker crashes intermittently and hangs

Question

Issue:

When choosing a document from iCloud the application randomly crashes, for most of the time the following code will work, but on rare occasions it will fail.

I have enabled iCloud entitlement in the app and can't seem to find the reason why it intermittently fails. Is there a check that I'm missing?

It's also hanging for a noticeable 5 or so seconds on occasions (usually in the run up to crashing)

Code:

#pragma mark - iCloud =======================================================================================================
- (void)documentPicker:(UIDocumentPickerViewController *)controller didPickDocumentAtURL:(NSURL *)url {

BOOL fileUrlAuthozied = [url startAccessingSecurityScopedResource];
NSURL *ubiquityURL = [[NSFileManager defaultManager] URLForUbiquityContainerIdentifier:nil];
NSLog(@"ubiquityURL - %@",ubiquityURL);

if(fileUrlAuthozied){
    NSFileCoordinator *fileCoordinator = [[NSFileCoordinator alloc] init];
    NSError *error;

    [fileCoordinator coordinateReadingItemAtURL:url options:0 error:&error byAccessor:^(NSURL *newURL) {

        NSData *data = [NSData dataWithContentsOfURL:newURL];
        //Do something with data
        selectedDocumentToUpload = [[UploadDocumentObj alloc] initWithiCloudDocument:data];
        [self performSegueWithIdentifier:@"goToRename" sender:nil];

    }];
    [url stopAccessingSecurityScopedResource];
}else{
     //Error handling
    [Lib showErrorMessageWithTitle:@"Alert" message:@"E-Sign could not retrive the document!\nPlease try again." delegate:self];

}
}

Error:

2015-03-18 16:22:15.955 E-Sign[6338:1860982] *** Assertion failure in -[UIDocumentPickerViewController _commonInitWithCompletion:], /SourceCache/UIKit/UIKit-3318.93/UIDocumentPickerViewController.m:66
2015-03-18 16:22:15.960 E-Sign[6338:1860982] *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Application initializing document picker is missing the iCloud entitlement. Is com.apple.developer.icloud-container-identifiers set?'

Other errors:

2015-03-18 16:33:45.884 E-Sign[6357:1864309] plugin com.apple.UIKit.fileprovider.default interrupted
2015-03-18 16:33:45.885 E-Sign[6357:1864309] plugin com.apple.UIKit.fileprovider.default invalidated

Anyone come across this before?

Answer 1

I recently stumpled opon the same problem:

*** Assertion failure in -[UIDocumentPickerViewController _commonInitWithCompletion:]

is caused due to lacking App-Capabilities. Go to your Build and choose Capabilities -> iCloud

Activate it via the switch on the right hand side and toggle iCloud Documents and CloudKit ON. (Notice: This will only work with a payed developer account)

Rebuild->Run

Also have in mind:

iCloud entitlements are available only to apps submitted to the App Store or to the Mac App Store. (Source)