How to implement searchBar on model object

I want to implement a search bar in my app, However I can't access the methods to manipulate strings such filter, lowercase, contain etc. Can anyone provide a suggestion on how can I solve this issue ? I am a beginner.
Here's my model
class Articles: NSObject{

    var author: String?

    var title: String?

    var publishedAt: String?

    var urlImage: String?

    var urlWebsite : String?

}
class LatestNewsViewController: UIViewController, UITableViewDataSource, UITableViewDelegate {

Code Block 
let newsData = Articles() //Model object
let urlRequest = "https://newsapi.org/v2/everything?q=coronavirus&apiKey=" //Website API
var urlSelected = ""
var articles: [Articles]? = [] // holds array of Articles data
var indexOfPageToRequest = 1
@IBOutlet weak var table_view: UITableView!

func parseData(data:Data)-> [Articles] {
var articles: [Articles]? = [] // holds parsed data

Code Block 
		
		do {
				let jsonResult = try JSONSerialization.jsonObject(with: data, options: JSONSerialization.ReadingOptions.mutableContainers) as? NSDictionary
				
				let jsonArticles = jsonResult?["articles"] as? [AnyObject] ?? [] // gets first head of json file and converts it to dictionary
				
				for jsonArticle in jsonArticles{ // captures data and stores it in the model object
						let article = Articles()
						article.author = jsonArticle["author"] as? String
						article.title = jsonArticle["description"] as? String
						article.publishedAt = jsonArticle["publishedAt"] as? String
						article.urlImage = jsonArticle["urlToImage"] as? String
						article.urlWebsite = jsonArticle["url"] as? String
						articles?.append(article) //put article data in the array
				}
				
				print(jsonArticles)
				
				DispatchQueue.main.async {
						
						if(articles!.count > 0)
						{
								self.table_view.reloadData()
						}
				}
				
		} catch {
				print("Nothing my guy\(error)")
		}
		
		return articles ??	[] // returns an array of articles
}
 
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
		return articles?.count ?? 0
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
		
		let cell = tableView.dequeueReusableCell(withIdentifier: "cell1", for: indexPath) as! NewsTableViewCell
		cell.authorName.text = articles?[indexPath.row].author
		cell.headLine.text = articles?[indexPath.row].title
		cell.newsImage.downloadImage(from:(self.articles?[indexPath.item].urlImage ?? "nill"))
		cell.timePublication.text = articles?[indexPath.row].publishedAt
		
		
		return cell
}
func searchBar(_ searchBar: UISearchBar,textDidChange searchText: String){
				filteredData = []
			 
						
		 }