Make a protocol conform to another protocol

Question

I have two protocols: Pen and InstrumentForProfessional. I\'d like to make any Pen to be an InstrumentForProfessional:

protoc         


        

Answer 1

Here is how you require conformance to protocols in extensions.

extension Pen where Self: InstrumentForProfessional {}

The current way that you are doing makes the compiler think that you are doing inheritance, not protocol conformance.

Also note that let pen = ApplePen() as InstrumentForProfessional doesn't make sense and won't compile.