.swift

private var searchTimer: Timer?

func searchBar(_ searchBar: UISearchBar, textDidChange searchText: String) {
    if let searchTimer = searchTimer {
        searchTimer.invalidate()
    }
    searchTimer = Timer.scheduledTimer(timeInterval: 0.4, target: self, selector: #selector(self.reload(timer:)), userInfo: searchText, repeats: false)
}

func reload(timer: Timer) {
    print(timer.userInfo ?? "")
}