Swift Search Bar and Coredata

I added the data from Coredata to the tableview. I also wanted to add a search bar. Whatever I did, only one NSManagedObject is added according to the words written in the search bar. How can I show objects containing the same words?

When the user finishes the search, there is only one object left!

class ViewController: UIViewController {

    @IBOutlet weak var searchBar: UISearchBar!
    @IBOutlet weak var tableView: UITableView!
    
   

    var data = [NSManagedObject]()
    
    var selectedData : NSManagedObject?
    
    
    override func viewDidLoad() {
        super.viewDidLoad()
        
        
        searchBar.delegate = self
        tableView.dataSource = self
        tableView.delegate = self
        getData()
    }
}

extension ViewController: UISearchBarDelegate {
        
    func searchBar(_ searchBar: UISearchBar, textDidChange searchText: String){
                
        // Capitalized ilk harfi büyük diğer harfleri küçük yapıyor
        for word in data {
            
            if let wordy = word.value(forKey: "title") as? String {
                if wordy.capitalized.contains(searchText.capitalized) {
                    data.removeAll(keepingCapacity: false)
                    data.append(word)
                    tableView.reloadData()
                }
            }
        }
    }
}

The issue is that once you find the first word that contains the searchText, you call data.removeAll(keepingCapacity: false). That means you clear the entire array. Then you re-insert the one word that you are currently checking.

Then the for loop immediately stops, because well, there's only one item in the data array now and this one was just handled. The loop is done and you are left with only one item.

What I suggest you do is the following:
Hold a second array of words, but just the ones that you want to show.

var filteredWords = [NSManagedObject]()
...
func searchBar(_ searchBar: UISearchBar, textDidChange searchText: String) {
    filteredWords = []
    for word in data {
        if let wordy = word.value(forKey: "title") as? String {
            if wordy.capitalized.contains(searchText.capitalized) {
                filteredWords.append(word)
            }
        }
    }
    tableView.reloadData()
}

So first you create a new variable to hold the filtertedWords. So you keep the data array always unmodified, so you never lose the words.
Then inside the searchBar(.. textDidChange:) you first clear the filteredWords before adding new items in. To make sure you don't keep entries shown you don't want to show.
You loop over your data entries and each time you find a word that matches, you put it into your filteredWords list.
Also: tableView.reloadData() should only be called when the for loop has finished.

Afterwards you will need to adjust your code in the UITableViewDelegate methods to use filteredData instead of data.

There are further ways to make this nicer like using filteredWords = data.filter { ... } or by simply making new CoreData fetch requests every time the input changes. But using the approach above will fix your issues.