Is it possible to implement optional methods in protocol definition?

In Swift, protocols can contain optional methods, but only if the protocol is declared with @objc and restricted to classes (i.e., inheriting from AnyObject). This is because optional methods are implemented through the Objective-C runtime mechanism.

Example:

@objc protocol MyProtocol {
    @objc optional func optionalMethod()
    func requiredMethod()
}

class MyClass: NSObject, MyProtocol {
    func requiredMethod() {
        print("Required method")
    }
    // optionalMethod is not mandatory to implement
}

If the protocol is not marked with @objc, all methods are considered mandatory and must be implemented.

Thus, implementing optional methods in protocols is possible but with restrictions related to the use of the Objective-C runtime.