建立将NSURL.scheme转换为SecProtocolType的方法？

I my Mac Swift application, I need to use a C API that requires a SecProtocolType value. I have a valid NSURL, with a scheme string, for example "http" or "ftp". I can do string searching with the raw values in SecProtocolType, but that looks like an invitation for "unexpected behavior" :) Is there a better or standard way? TY!I my Mac Swift application, I need to use a C A