I never thought that I'd become "sharp edges guy" but the last couple of days at work I've run into doozies.

1. The AVCaptureMetadataOutput.rectOfInterest rectangle has to be transformed into the coordinate space of the output itself - meaning that you can't give it a CGRect from your view and have it work. Instead it must be converted to the coordinate space using AVCaptureVideoPreviewLayer.metadataOutputRectConverted(fromLayerRect:).
2. When adding a custom view to a UIBarButtonItem you need to have that view handle the tap on the item itself. Assigning a UIImageView, for example, negates the bar button item's target and action properties for some reason. Of course it's not documented.

I wonder what I'll run into tomorrow 🙂