Swizzling can't be mentioned with a straight face in an argument about brittleness. But, I'll concede that KVO won't work with arbitrary properties of binary l

Swizzling can't be mentioned with a straight face in an argument about brittleness. But, I'll concede that KVO won't work with arbitrary properties of binary libraries you receive or that Apple builds into the platform, assuming they use swift and choose not to mark them dynamic. So in this sole regard, swift is less dynamic. I guess it remains to be seen whether this actually becomes a problem.