Add a Searchbar on TableView but no response - ios

Question

Referring to shrikar's work - ://shrikar.com/swift-ios-tutorial-uisearchbar-and-uisearchbardelegate/, I try to build a searchbar in table view. The tableview works fine when no adding search text. The problem is no response and error message when add search text.
I wonder something wrong. Could anybody help us? Thanks.
import UIKit
import SDWebImage
class ArticleListViewController: UITableViewController, UISearchBarDelegate{
#IBOutlet weak var searchBar: UISearchBar!
var searchActive : Bool = false
var filtered = [Article]()
var articles = [Article](){
didSet{
DispatchQueue.main.async{
self.tableView.reloadData()
}
}
}
override func viewDidLoad() {
super.viewDidLoad()
searchBar.delegate = self
downLoadLatestArticles()
}
func downLoadLatestArticles(){
Article.downLoadItem { (articles, error) in
if let error = error {
print("fail \(error)")
return
}
if let articles = articles {
self.articles = articles
}
}
}
func searchBarTextDidBeginEditing(searchBar: UISearchBar) {
searchActive = true;
}
func searchBarTextDidEndEditing(searchBar: UISearchBar) {
searchActive = false;
}
func searchBarCancelButtonClicked(searchBar: UISearchBar) {
searchActive = false;
}
func searchBarSearchButtonClicked(searchBar: UISearchBar) {
searchActive = false;
}
func searchBar(searchBar: UISearchBar, textDidChange searchText: String) {
if(searchText == " "){
searchActive = false
}else{
filtered = articles.filter ({ (article_f) -> Bool in
let tmp: String = article_f.name
let range = tmp.range(of:searchText, options: String.CompareOptions.caseInsensitive)
return range != nil
})
if(filtered.count == 0){
searchActive = false;
} else {
searchActive = true;
}
}
self.tableView.reloadData()
}
override func didReceiveMemoryWarning() {
super.didReceiveMemoryWarning()
}
override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
if(searchActive) {
return filtered.count
}
return articles.count
}
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "ListTableCell", for: indexPath) as! ListTableCell
var article : Article
if(searchActive){
article = filtered[indexPath.row]
}
else{
article = articles[indexPath.row]
}
cell.nameLabel?.text = article.name
cell.locationLabel?.text = article.location
cell.photoView?.sd_setImage(with: article.image_URL)
return cell
}
}