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

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)

   }

}