how can i save checked rows of tableview in userdefault?

Question

I'm facing the same issue as asked in this question:

how can i store selected rows of tableview in nsuserdefaults in swift 3

However, I'm interested in knowing how to repopulate with the saved rows that have been checkmarked?

Thank you!

Answer 1

Create a variable with didSet so that we can reload table once the value is assigned to it.

var selectedRows: [Int] = [] {
    didSet {
        myTableView.reloadData()
    }
}

On viewDidLoad() assign value to selectedRows from userDefaults

override func viewDidLoad() {
    super.viewDidLoad()        
    selectedRows = UserDefaults.standard.value(forKey: "selectedRows") as? [Int] ?? []
}

Use this code to update cell.

func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
    let cell = UITableViewCell(style: .default, reuseIdentifier: "myCell")
    cell.textLabel?.text = "\(indexPath.row)"
    cell.accessoryType = selectedRows.contains(indexPath.row) ? .checkmark : .none
    
    return cell
}

Finally in didSelectRowAt use this logic to update selectedRows variable and store it to userDefaults.

func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
    if selectedRows.contains(indexPath.row) {
        self.selectedRows = selectedRows.filter{$0 != indexPath.row}
    }else{
        self.selectedRows.append(indexPath.row)
    }
    UserDefaults.standard.set(selectedRows, forKey: "selectedRows")
}

---

If you want to store selected index in userdefault on button click, you can use following example.

//
// Within SMViewController.swift file.
//
class SMViewController: UIViewController, UITableViewDataSource {
    
    @IBOutlet weak var myTableView: UITableView!
    
    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return 1
    }
    
    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell: SMCell = tableView.smDequeueReusableCell(forIndexPath: indexPath)
        cell.delegate = self
        return cell
    }
    
}

extension SMViewController: MyCellDelegate {
    func didClickButton(cell: SMCell) {
        if let indexPath = self.myTableView.indexPath(for: cell) {
            // 1) Get all indexes
            var allIndexes = UserDefaults.standard.array(forKey: "myIndexes") as? [Int] ?? []
            // 2) Append current selected index
            allIndexes.append(indexPath.row)
            // 3) Store updated indexes in user defaults.
            UserDefaults.standard.setValue(allIndexes, forKey: "myIndexes")
        }
    }
}

//
// Within SMCell.swift file.
//
protocol MyCellDelegate: AnyObject {
    func didClickButton(cell: SMCell)
}

class SMCell: UITableViewCell {
    weak var delegate: MyCellDelegate?
    @IBOutlet weak var myButton: UIButton!
    
    /// Link this button to your `TableViewCell`
    @IBAction func smButtonHandler(_ sender: UIButton) {
        self.delegate?.didClickButton(cell: self)
    }
}

I hope this is helpful. Let me know if you do have any confusion.

Thanks