C libraries are fine in Swift, but I feel that dealing with a C++ library (and non-CF/system C libraries) is usually a rare exception when "writing an iOS SDK".

C libraries are fine in Swift, but I feel that dealing with a C++ library (and non-CF/system C libraries) is usually a rare exception when "writing an iOS SDK". Most iOS libraries are just written on top of Foundation and the appropriate platform interface kit (if it's a UI library).