Downcast.swift

protocol AssotiatedTypeProtocol {
    func bar()
}

class BaseClass: AssotiatedTypeProtocol {
    func bar() {
        print("BaseClass")
    }
}

class Class1: BaseClass {
    override func bar() {
        print("Class1")
    }
}

class Class2: BaseClass {
    override func bar() {
        print("Class2")
    }
}

var objs: [BaseClass] = [Class1(), Class2()]
objs[0].bar()
objs[1].bar()

var objs: [AssotiatedTypeProtocol] = [Class1(), Class2()]
objs[0].bar()
objs[1].bar()