Judge for yourself.
Here's the file I am working on: [0].
The issue was in this initializer: [1]. In particular, this line was missing: [2]. I had switched to using a UIButton as a custom view, so the callback only got the button, instead of the container UIBarButtonItem. I needed to propagate the tag into the button.
[0] https://github.com/LittleGreenViper/SwipeTabController/blob/...
[1] https://github.com/LittleGreenViper/SwipeTabController/blob/...
[2] https://github.com/LittleGreenViper/SwipeTabController/blob/...