POPExample.swift

//: Playground - noun: a place where people can play

import UIKit

class Developer {
    var name: String?
    
    init(name: String) {
        self.name = name
    }
}

protocol DevelopableInSwift { }
protocol DevelopableInKotlin { }

class iOSDeveloper:Developer, DevelopableInSwift { }
class AndroidDeveloper:Developer, DevelopableInKotlin { }

extension DevelopableInSwift where Self: iOSDeveloper {
    func useGuard() { }
}

extension DevelopableInKotlin where Self: AndroidDeveloper {
    func isNullSafe() -> Bool { return true }
}

class ViewController: UIViewController {
    
    var developer: Developer { return AndroidDeveloper(name: "Lawrey") }
    
    override func viewDidLoad() {
        if developer is DevelopableInSwift,
            let iOSDev = developer as? iOSDeveloper {
            print("I am an iOS Developer!")
            iOSDev.useGuard()
        }else if developer is DevelopableInKotlin,
            let androidDev = developer as? AndroidDeveloper {
            print("I am an Android Developer!")
            androidDev.isNullSafe()
        }
    }
}

let viewController = ViewController()
viewController.viewDidLoad()