Candidate is not '@objc' but protocol requires it

Question

I have been following this tutorial to learn swift & iOS app development. In the Protocol section, the tutorial defined the following protocol:

@objc protoco         


        

Answer 1

From what I can tell, marking your protocol as @objc means that any classes implementing it also have to be exposed to Objective-C. This can be done either by making Vicki a subclass of NSObject:

class Vicki: NSObject, Speaker {

Or by marking each implemented method as @objc:

class Vicki: Speaker {
    @objc func Speak() {
        print("Hello, I am Vicki!")
    }
    @objc func TellJoke() {
        print("Q: What did Sushi A say to Sushi B?")
    }
}

Update: From Apple's Swift Language Documentation

Optional protocol requirements can only be specified if your protocol is marked with the @objc attribute.

...

Note also that @objc protocols can be adopted only by classes, and not by structures or enumerations. If you mark your protocol as @objc in order to specify optional requirements, you will only be able to apply that protocol to class types.