Scrolling tableview causes checkmark to disappear | addressing reusable cells in Swift 5 - ios

Question

I use the following to mark rows in a tableview as either marked with a checkmark or unselected with no checkmark. The issue that I have stumbled on is when scrolling the tableView seems to reload and cause the checkmark to disappear.
I understand this is caused by reusable cells,
Is there an easy fix I can implement into the code below?
class CheckableTableViewCell: UITableViewCell {
var handler: ((Bool)->())?
override init(style: UITableViewCell.CellStyle, reuseIdentifier: String?) {
super.init(style: style, reuseIdentifier: reuseIdentifier)
self.selectionStyle = .none
}
required init?(coder aDecoder: NSCoder) {
super.init(coder: aDecoder)
}
override func setSelected(_ selected: Bool, animated: Bool) {
super.setSelected(selected, animated: animated)
self.accessoryType = selected ? .checkmark : .none
handler?(selected)
}
}
class TableViewController: UITableViewController {
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath) as! CheckableTableViewCell
cell.handler = {[weak self](selected) in
selected ? self?.selectRow(indexPath) : self?.unselectRow(indexPath)
}
let section = sections[indexPath.section]
let item = section.items[indexPath.row]
cell.textLabel?.textAlignment = .left
cell.selectionStyle = .none
let stringText = "\(item.code)"
cell.textLabel!.text = stringText
return cell
}
UPDATE:
struct Section {
let name : String
var items : [Portfolios]
}
struct Portfolios: Decodable {
let code: String
var isSelected: Bool
enum CodingKeys : String, CodingKey {
case code
}
}

Answer 1

You need to create your data model having a property called isSelected: Bool then use this to decide when a row should be selected or not. Note that you have to toggle this property every time didSelectRowAt(indexPath:) is triggered.
Example
// Declare your model with one of the property called isSelected
class MyModel {
var isSelected: Bool
init(isSelected: Bool) {
self.isSelected = isSelected
}
}
class TableViewController: UITableViewController {
// Dummy data note that it contains array of "MyModel" which have the "isSelected" property.
private var myModels: [MyModel] = [MyModel(isSelected: false),MyModel(isSelected: true),MyModel(isSelected: true),MyModel(isSelected: false) ]
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath) as! CheckableTableViewCell
cell.handler = {[weak self](selected) in
/// Note that I am using selected Property here
myModels[indexPath.row].isSelected ? self?.selectRow(indexPath) : self?.unselectRow(indexPath)
}
let section = sections[indexPath.section]
let item = section.items[indexPath.row]
cell.textLabel?.textAlignment = .left
cell.selectionStyle = .none
let stringText = "\(item.code)"
cell.textLabel!.text = stringText
return cell
override func tableView(tableView: UITableView, didSelectRowAtIndexPath indexPath: NSIndexPath) {
let selectedIndexPath = indexPath
myModels[selectedIndexPath.row].isSelected = true
self.tableView.reloadRows(at: [selectedIndexPath], with: .none)
}
}