I won’t teach Swift here, but Google is your friend. You can start by studying all the languages differences with regards to extending existing protocols, and how optional protocol conformance and methods are handled. Swift in many ways (not just with protocols) is like a fix for many headaches that objc provided in these areas. It’s partly why Apple encourages “protocol oriented” programming in swift over “object oriented” because of how rich the feature set is compared to objc.
Quite a lot has changed in objc since the nextstep days! And a lot more changed as Apple learned from that and built swift. My guess is you don’t know these languages as well as you think if you’re not clear about these differences.
