Re: Why doesn't the data save in TableView?

I'm a beginner, please help me to understand why it happens?

I have two TableViewCotrollers - dynamic and static. When I add or edit item in static TVC it pass to the dynamis TVC. This data is visible in the table. But after that it is not saved. When i open the app again these changes are missing and if I roll the wheel of the pickerView these changes disappear.

I put the function of saving to file on disk wherever possible, but it still does not work. What is my mistake?

TVC 1 - Dynamic

import UIKit

class StudentsTableViewController: UITableViewController, UIPickerViewDataSource, UIPickerViewDelegate {
    
    @IBOutlet weak var pickerViewStudents: UIPickerView!
    var classesObject = [ClassUnit]()
    var classSelected: String = ""
    var studentsSelected: [String] = [] {
        didSet {
            tableView.reloadData()
        }
    }

    override func viewDidLoad() {
        super.viewDidLoad()
        
        self.pickerViewStudents.delegate = self
        self.pickerViewStudents.dataSource = self
        
        classesObject = ClassUnit.loadFromFile()
        navigationItem.leftBarButtonItem = editButtonItem
    }

    func numberOfComponents(in pickerView: UIPickerView) -> Int {
        return 1
    }

    func pickerView(_ pickerView: UIPickerView, numberOfRowsInComponent component: Int) -> Int {
        return classesObject.count
    }

    func pickerView(_ pickerView: UIPickerView, titleForRow row: Int, forComponent component: Int) -> String? {        
        classesObject = ClassUnit.loadFromFile()
        return classesObject[row].classTitle
    }
    
    override func viewWillAppear(_ animated: Bool) {
        classesObject = ClassUnit.loadFromFile()
        pickerViewStudents.reloadAllComponents()
        tableView.reloadData()
    }
    
    func pickerView(_ pickerView: UIPickerView, didSelectRow row: Int, inComponent component: Int) {
        classSelected = classesObject[row].classTitle
        studentsSelected = classesObject[row].classStudents
        ClassUnit.saveToFile(classes: classesObject)
    }

    // MARK: - Table view data source//

    override func numberOfSections(in tableView: UITableView) -> Int {
        return 1
    }

    override func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return studentsSelected.count
    }
    
    override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "ClassTitleStudents", for: indexPath)
        cell.textLabel?.text = studentsSelected[indexPath.row]
        cell.showsReorderControl = true
        ClassUnit.saveToFile(classes: classesObject)
        return cell
    }

    override func tableView(_ tableView: UITableView, editingStyleForRowAt indexPath: IndexPath) ->
        UITableViewCellEditingStyle {
            return .delete
    }

    override func tableView(_ tableView: UITableView, commit editingStyle: UITableViewCellEditingStyle, forRowAt indexPath: IndexPath) {
        if editingStyle == .delete {
            studentsSelected.remove(at: indexPath.row)
            tableView.deleteRows(at: [indexPath], with: .automatic)
            ClassUnit.saveToFile(classes: classesObject)
        }
    }

    override func tableView(_ tableView: UITableView, moveRowAt fromIndexPath: IndexPath, to: IndexPath) {
        let moveStudent = studentsSelected.remove(at: fromIndexPath.row)
        studentsSelected.insert(moveStudent, at: to.row)
        tableView.reloadData()
        ClassUnit.saveToFile(classes: classesObject)
    }

    // MARK: - Navigation

    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {

        if segue.identifier == "EditStudentSegue" {
            let indexPath = tableView.indexPathForSelectedRow!
            let student = studentsSelected[indexPath.row]
            let nav = segue.destination as! UINavigationController
            let  editStudentName = nav.topViewController as! AddEditStudentTableViewController
            editStudentName.student = student
            ClassUnit.saveToFile(classes: classesObject)
        }
    }
    
    @IBAction func unwindToStudentsTableView(segue: UIStoryboardSegue) {
        guard segue.identifier == "saveUnwindStudents" else { return }
        let sourceViewController = segue.source as! AddEditStudentTableViewController        
        let student = sourceViewController.student
        if let selectedIndexPath = tableView.indexPathForSelectedRow {
            studentsSelected[selectedIndexPath.row] = student
            tableView.reloadRows(at: [selectedIndexPath], with: .none)
            ClassUnit.saveToFile(classes: classesObject)
        } else {
            let newIndexPath = IndexPath(row: studentsSelected.count, section: 0)
            studentsSelected.append(student)
            //tableView.insertRows(at: [newIndexPath], with: .automatic)
            ClassUnit.saveToFile(classes: classesObject)
        }
    }
}

TVC 2 - Static

import UIKit

class AddEditStudentTableViewController: UITableViewController {
    
    @IBOutlet weak var nameStudent: UITextField!
    
    @IBOutlet weak var saveButton: UIBarButtonItem!
    
    var classesObject = [ClassUnit]()
    
    var student = ""

    override func viewDidLoad() {
        super.viewDidLoad()
        
        nameStudent.text = student
        updateSveButton()
        classesObject = ClassUnit.loadFromFile()
    }

    func updateSveButton() {
        let nameOfStudent = nameStudent.text ?? ""
        saveButton.isEnabled = !nameOfStudent.isEmpty
        ClassUnit.saveToFile(classes: classesObject)
    }
    
    @IBAction func textEditingChanged(_ sender: UITextField) {
        updateSveButton()
    }


    // MARK: - Navigation

    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
        
        guard segue.identifier == "saveUnwindStudents" else { return }
        
        let nameOfStudent = nameStudent.text ?? ""
        
        student = nameOfStudent
        
        ClassUnit.saveToFile(classes: classesObject)
    }
}