} func login(userName: String, password: String) { precondition(!userName.isEmpty, "User name must be non-empty string.") precondition(!password.isEmpty, "Password must be non-empty string.") precondition(state == .none, "App state must be non-login state.") // ϩάΠϯॲཧ assert(state != .superUser, "Cannot become super-user immediately.") } લఏ݅ Ϣʔβʔ໊ɾύεϫʔυඞਢ ঢ়ଶະϩάΠϯͰͳ͚Ε͍͚ͳ͍