I have tried solving your problem using another approach since using a navigation bar only didn't seem to work out (maybe it's because the AppStore app is using a private api but I'm not knowledgeable enough to tell for sure...)
Anyway I simply used a toolbar placed just underneath the navigation bar on which I added a segmented control, all inside a regular UIViewController.
This is what it looks like in Storyboard:
And this is the result in Simulator:
Just be careful to offset the table view down to account for the vertical space used up by the toolbar.
Hope this helps!
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