I am in the process of rewriting my app from objective c to Swift and I noticed that UIActionSheet behaves differently in Swift version than in obj-c version.
Obj-c
Turns out this was yet another case of finding answer right after asking the question.
All I had to do was add Cancel button as another button and then specify its index:
var sheet = UIActionSheet(title: nil, delegate: self, cancelButtonTitle: nil, destructiveButtonTitle: nil)
sheet.addButtonWithTitle("Camera")
sheet.addButtonWithTitle("Photo Library")
sheet.addButtonWithTitle("Cancel")
sheet.cancelButtonIndex = 2
sheet.showInView(self.controller.view)
Not sure if they changed the way how UIActionSheet is supposed to work in Swift or if it's bug that nobody cares to fix since it's deprecated in iOS 8 anyway