TableViewCell has grey background after movement out of visible tableView - ios

Question

The following test app displays a simple tableView. The property selectionStyle of the prototype cell is set to default (grey). Since there are more cells than can be displayed, the first cells are visible, the last cells not. The background color of each cell is set to white.
First test:
When one of the cells is selected, its background becomes grey.
In the delegate function, its isSelected property is then set to false, thus the cells background becomes white again. The cell is then moved to row 0, and the data source is updated accordingly.
This works as expected.
Second test:
The tableView is scrolled up so that the last cells become visible.
When a cell is now selected, it is moved again to row 0, which has been moved out of the visible area of the tableView. This works again. However:
If the tableView is then scrolled down so that row 0 becomes visible again, the moved cell has now a grey background, as if it were selected, but it is not. This does not work as expected:
Here is my code:
import UIKit
class ViewController: UIViewController {
#IBOutlet weak var tableView: UITableView!
var tableData = ["00", "01", "02", "03", "04", "05", "06", "07", "08", "09",
"10", "11", "12", "13", "14", "15", "16", "17", "18", "19"]
}
extension ViewController: UITableViewDataSource {
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return tableData.count
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "TableViewCell")!
let row = indexPath.row
cell.textLabel?.text = tableData[row]
cell.backgroundColor = .white
return cell
}
}
extension ViewController: UITableViewDelegate {
func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
let selectedCell = tableView.cellForRow(at: indexPath)!
selectedCell.isSelected = false
let sourceRow = indexPath.row
let destinationRow = 0
let removedElement = tableData.remove(at: sourceRow)
tableData.insert(removedElement, at: 0)
let destinationIndexPath = IndexPath.init(row: destinationRow, section: 0)
tableView.moveRow(at: indexPath, to: destinationIndexPath)
}
}
My question:
Is anything wrong with my code?
Or is this an iOS bug? If so, is there a workaround?
Please note:
It is of course possible to use tableView.reloadData() instead of tableView.moveRow(at:, to:). Then, the moved cell has no grey background. But in this case, the movement is not animated, as I need it in my app under development.
If property selectionStyle of the prototype cell is set to none, the moved cell has neither a grey background, but then one has no visible feedback of the selection.

Answer 1

Instead of set the isSelected property, call the deselectRow(at:animated:) method of UITableView:
func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
tableView.deselectRow(at: indexPath, animated: true)
...
}

Answer 2

I submitted a bug report to Apple and received the following answer:
You should generally always use the deselectRow(at:animated:) method
on UITableView to deselect a row. If you only change the selected
property on the UITableViewCell currently shown for that row directly,
the table view will not be made aware of this, and when a new cell is
reused for that same row during scrolling, the table view will reset
the selected state of the cell to match whether it thinks the row is
selected. The table view’s state is always the source of truth; the
cell state is simply the current visual representation for a
particular row.
Good to know!