Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Duplicate states in queue'

Question

I'm working on a project that use UISlideViewController. I know that this may be a duplicate question but non of the posts before about this topic helped me. I have a specific problem, as I managed to understand. My app crashes on this block. I have read before, it's important to put all work with the UI in the main thread. This is the code:

pageViewController.setViewControllers([viewController],
                    direction: direction,
                    animated: animated,
                    completion: { completed in
                        dispatch_async(dispatch_get_main_queue()) {
 ...

The error that I get is next:

*** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Duplicate states in queue'
*** First throw call stack:
(0x183fd1900 0x18363ff80 0x183fd17d0 0x18494499c 0x1894dc9f4 0x1894dcdec...)

Testing it further I also get this error on the same line of code:

    *** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'No view controller managing visible view <UITableView: 0x12744aa00;
frame = (0 0; 375 515);
    clipsToBounds = YES; autoresize = W+H; 
    gestureRecognizers = <NSArray: 0x12836cf60>; 
    layer = <CALayer: 0x1286226b0>;
    contentOffset: {0, 0}; contentSize: {375, 291}>'

The bug is very hard to reproduce. One literally needs to touch and scroll multiple times on UIPageViewController to get this crash.
Thanks for your time and help.

Answer 1

You should put the setViewControllers:direction:animated:completion: code inside of a dispatch_async block. It worked for me. https://stackoverflow.com/a/24749239