gistfile1.m

// Do I miss something obvious or is this the best way to detect if UIDocumentInteractionController is still open or not? 

// (BOOL _isShowingOpenInMenu is in the class)

- (void)openInAction:(id)sender {
    // do we need to dismiss a popover?
    if ([self checkAndDismissPopoverForViewControllerClass:[UIDocumentInteractionController class] animated:YES]) {
        return;
    }
    
    if (self.document.fileUrl) {
        _isShowingOpenInMenu = NO;
        documentInteractionController_ = [UIDocumentInteractionController interactionControllerWithURL:self.document.fileUrl];
        documentInteractionController_.delegate = self;
        if (PSIsIpad()) {
            [documentInteractionController_ presentOptionsMenuFromBarButtonItem:sender animated:YES];
        }else {
            [documentInteractionController_ presentPreviewAnimated:YES];
        }
    }
}

- (void)documentInteractionControllerDidDismissOpenInMenu:(UIDocumentInteractionController *)controller {
    documentInteractionController_.delegate = nil;
    documentInteractionController_ = nil;
    _isShowingOpenInMenu = NO;
}

- (void)documentInteractionControllerWillPresentOpenInMenu:(UIDocumentInteractionController *)controller {
    _isShowingOpenInMenu = YES;
}

- (void)documentInteractionControllerDidDismissOptionsMenu:(UIDocumentInteractionController *)controller {
    dispatch_async(dispatch_get_main_queue(), ^{
        if (!_isShowingOpenInMenu) {
            documentInteractionController_.delegate = nil;
            documentInteractionController_ = nil;    
        }
    });
}