UITableView How to call a function after reordering cells - ios

Question

In my project I wanted to implement moving rows as well as deleting them but not with stock "Delete" button but by tapping the image that is within my custom UITableViewCell called QueueCell. I delete rows in function deleteByTap2 which uses the sender.tag (which is the cell.indexPath.row) to recognise which cell should be removed. Both moving and deleting work great on their own but when you move, for example, 6th row to 2nd it still carries the tag = 6 and because of that when I tap on image to delete the row, incorrect row gets deleted. I created a function reTag which is supposed to update tags of all cells within the sections and it works great after being called in deleteByTap2 function but when called at the end of
func tableView(_ tableView: UITableView, moveRowAt sourceIndexPath: IndexPath, to destinationIndexPath: IndexPath)
it seems to not know the state of tableView after moving row. I searched the forum and I found that there was undocumented UITableViewDelegate function
- (void)tableView:(UITableView *)tableView didEndReorderingRowAtIndexPath:(NSIndexPath *)indexPath;
but I tried calling it and it seems it was removed (or maybe name changed)
When should I call the reTag function so it would work properly? So it would know the order of tableView after reordering it?
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "cell", for: indexPath) as! QueueCell
let item = sungs[indexPath.section].songsIn[indexPath.row]
cell.setup(item: item)
if indexPath.section == 2{
let tap = UITapGestureRecognizer(target: self, action: #selector(deleteByTap2(_:)))
tap.numberOfTapsRequired = 1
tap.numberOfTouchesRequired = 1
cell.artwork.addGestureRecognizer(tap)
cell.artwork.isUserInteractionEnabled = true
cell.artwork.tag = indexPath.row
}
return cell
}
override func tableView(_ tableView: UITableView, moveRowAt sourceIndexPath: IndexPath, to destinationIndexPath: IndexPath) {
var toMove: MPMediaItem
tableView.beginUpdates()
if sourceIndexPath.section == 2{
if player.isShuffle{
toMove = player.shufQueue[player.shufIndex + sourceIndexPath.row + 1]
player.shufQueue.remove(at: player.shufIndex + sourceIndexPath.row + 1)
if destinationIndexPath.section == 2{
player.shufQueue.insert(toMove, at: player.shufIndex + destinationIndexPath.row + 1)
}
}else{
toMove = player.defQueue[player.defIndex + sourceIndexPath.row + 1]
player.defQueue.remove(at: player.defIndex + sourceIndexPath.row + 1)
if destinationIndexPath.section == 2{
player.defQueue.insert(toMove, at: player.defIndex + destinationIndexPath.row + 1)
}
}
}
tableView.endUpdates()
reTag(section: destinationIndexPath.section)
}
//the beginUpdates()-endUpdates() doesn't do much good here, actually it messes some of my cells
func reTag(section: Int){
var indexPath: IndexPath
for row in 0 ..< tableView.numberOfRows(inSection: section){
indexPath = IndexPath(row: row, section: section)
if let cell = tableView.cellForRow(at: indexPath) as? QueueCell{
cell.artwork.tag = row
}
}
}
func deleteByTap2(_ sender: UITapGestureRecognizer){
let tag = (sender.view?.tag)!
if player.isUsrQueue{
player.usrQueue.remove(at: player.usrIndex + tag + 1)
player.usrQueueCount! -= 1
sungs[2].songsIn.remove(at: tag)
}else{
player.defQueue.remove(at: player.defIndex + tag + 1)
sungs[2].songsIn.remove(at: tag)
player.defQueueCount! -= 1
}
let indexPath = IndexPath(row: tag, section: 2)
tableView.deleteRows(at: [indexPath], with: .fade)
reTag(section: 2)
}

Answer 1

This is a good example of why it's a bad idea to use .tag on objects to try and track them in this way.
I'd suggest that you move the tap gesture inside your cell class, and add a "call back" closure. This sample is, of course, missing your data class and cell.setup() code, but you should be able to see what needs to be changed:
// cell class
class QueueCell: UITableViewCell {
#IBOutlet weak var artwork: UIImageView!
var tapCallback: ((QueueCell) -> ())?
func addTap() {
if artwork.gestureRecognizers == nil {
// cells are reused, so only add this once
let tap = UITapGestureRecognizer(target: self, action: #selector(artworkTap(_:)))
tap.numberOfTapsRequired = 1
tap.numberOfTouchesRequired = 1
artwork.addGestureRecognizer(tap)
artwork.isUserInteractionEnabled = true
}
}
func artworkTap(_ sender: UITapGestureRecognizer) -> Void {
tapCallback?(self)
}
}
// table view class
override func tableView(_ tableView: UITableView, moveRowAt sourceIndexPath: IndexPath, to destinationIndexPath: IndexPath) {
// all you have to do is manage your data,
// no need to reload() or "re-tag" anything
}
override func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "QueueCell", for: indexPath) as! QueueCell
// your cell configuration
//let item = sungs[indexPath.section].songsIn[indexPath.row]
//cell.setup(item: item)
if indexPath.section == 2 {
// tell the cell to add the gesture recognizer
cell.addTap()
// set the "call back" closure
cell.tapCallback = {
theCell in
if let iPath = tableView.indexPath(for: theCell) {
self.deleteByTap2(tableView, indexPath: iPath)
}
}
}
return cell
}
func deleteByTap2(_ tableView: UITableView, indexPath: IndexPath) -> Void {
print("Tapped on artwork at:", indexPath)
// you now have a reference to the table view and the indexPath for the cell that
// contained the artwork image view that was tapped
}
Now your deleteByTap2() function will match the familiar didSelectRowAt function, and you can handle your deleting there.