dequeueReusableCell 问题。 当我选择一个单元格时，正在选择另一个单元格

Question

I want when I select a cell, to put another image, and go back to old image when I click it again. It works but when I select multiple cells and scroll down, it gets messy and selects some cells I didnt select.
What to reset?
What to add in prepareForReuse()?

Here is my tableviewcell:

import Foundation
import UIKit

class DownloadTableViewCell: UITableViewCell {


    @IBOutlet weak var downloadImage: UIImageView!

    @IBOutlet weak var cardSetLabel: UILabel!

    func configureCell(label: String) {
        cardSetLabel.text = label
       downloadImage.image = UIImage(named: "circle_blank")
    }
    func changeImage() {
        if(downloadImage.image == UIImage(named: "circle_download")){
            downloadImage.image = UIImage(named: "circle_blank")
            self.backgroundColor = #colorLiteral(red: 1, green: 1, blue: 1, alpha: 1)
        }
        else {
            downloadImage.image = UIImage(named: "circle_download")
            self.backgroundColor = #colorLiteral(red: 0.6000000238, green: 0.6000000238, blue: 0.6000000238, alpha: 1)
        }
    }
    override func prepareForReuse() {

        super.prepareForReuse()

           isHidden = false
           isSelected = false
           isHighlighted = false

    }
}

And here are my tableView methods

  func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "DownloadTableViewCell", for: indexPath) as! DownloadTableViewCell       
        cell.cardSetLabel.text = cardsets[indexPath.row].title

        return cell
    }
    func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
        let cell = self.tableView.cellForRow(at: indexPath) as! DownloadTableViewCell

        cell.changeImage()
//        self.tableView.indexPathsForSelectedRows?.forEach { index in
//            debugPrint("Selected rows", index.row)
//        }
        tableView.reloadData()
    }

Answer 1

you have to keep a state of an image to display outside of a cell due to fact that a cell can be dequeued. In the example below the state is stored in cellSelectedImage property. In tableView(_ :, didSelectRowAt:) you have to add a logic of changing an image for a given row and reload a cell.

enum DownloadImage: String {
    case circle_blank, circle_download
}

class ViewController: UIViewController {

    @IBOutlet var tableView: UITableView!

    var data = Array(repeating: "Test", count: 20)
    var cellSelectedImage = Array(repeating: DownloadImage.circle_blank.rawValue, count: data.count)

    override func viewDidLoad() {
        super.viewDidLoad()
        // Do any additional setup after loading the view.
    }


}

class CustomCell: UITableViewCell {

    @IBOutlet weak var downloadImage: UIImageView!

    @IBOutlet weak var cardSetLabel: UILabel!

    func configureCell(label: String, imageName: String) {
        cardSetLabel.text = label
        downloadImage.image = UIImage(named: imageName)
        if imageName == DownloadImage.circle_download.rawValue {
            self.backgroundColor = #colorLiteral(red: 0.6000000238, green: 0.6000000238, blue: 0.6000000238, alpha: 1)

        } else {
            self.backgroundColor = #colorLiteral(red: 1, green: 1, blue: 1, alpha: 1)
        }
    }
}

extension ViewController: UITableViewDataSource {

    func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
        return data.count
    }

    func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
        let cell = tableView.dequeueReusableCell(withIdentifier: "cell") as! CustomCell
        cell.configureCell(label: data[indexPath.row], imageName: cellSelectedImage[indexPath.row])
        return cell
    }

}

extension ViewController: UITableViewDelegate {
    func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {

        let imgName = cellSelectedImage[indexPath.row] == DownloadImage.circle_blank.rawValue ? DownloadImage.circle_download.rawValue : DownloadImage.circle_blank.rawValue
        cellSelectedImage[indexPath.row] = imgName
        tableView.reloadRows(at: [indexPath], with: .automatic)
    }
}

Answer 2

Release downloaded image in prepareforReuse

override func prepareForReuse() {

    super.prepareForReuse()

       isHidden = false
       isSelected = false
       isHighlighted = false
       downloadImage.image = nil

}