I have a really strange behaviour when trying to add a MPVolumeView to my current view. Without adding constraints in the interfacebuilder to the wrapper uiview, everything works fine. But when I add constraints to the wrapper view in interface builder I am not able to change the volume anymore.
self.volumeView = MPVolumeView(frame: self.volumeSliderWrapper.bounds)
self.volumeView?.autoresizingMask = [.FlexibleHeight, .FlexibleWidth];
OK for everybody having the same problem. I ended with setting the type of the wrapper UIView to MPVolumeView, so I don't have a wrapper anymore. Seems the best way to get rid of the problem.