Why use class only protocols in Swift?

Question

Can anyone please explain class only protocols to me in Swift. I understand what protocols are and why we use them. I also understand that its recommended to use class only protocols when we use reference type objects in it and want to limit the protocol conformation to classes only. However, I can't find any good answer to support that recommendation. Why is it recommended? What is the drawbacks of using normal protocols in that case.

Answer 1

One use case:

• You have a "delegate" protocol and someone wants to have a weak property of that protocol type. weak can only be used on reference types; therefore, the protocol must be class-only.