Cell stays highlighted and interactively unhighlights as we swipe - ios

Question

After we tap on the table view cells to push and pop to the detail view, if we swipe back to the previous table view, you'll notice that the cell stays highlighted and interactively unhighlights as we swipe.
How can this be programmatically implemented in UIKit?
The following reference illustrates the behaviour:
WWDC20 Introduction to SwiftUI: https://developer.apple.com/videos/play/wwdc2020-10119/?time=630

Answer 1

First, if you haven't already, you need to mark your "selected" when you tap on it:
func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
guard let cell = tableView.cellForRow(at: indexPath) as? SubclassedCell else {
return
}
//`setSelected(:animated:) is built into `UITableViewCell`
cell.setSelected(true, animated: true)
...
Then in viewWillAppear(_:) you're going to coordinate the deselection animation with the edge swipe animation:
override func viewWillAppear(_ animated: Bool) {
super.viewWillAppear(animated)
//1
guard let selectedIndexPath = tableView.indexPathForSelectedRow else {
return
}
//2
if let transitionCoordinator = self.transitionCoordinator {
transitionCoordinator.animate(alongsideTransition: { (context) in
self.tableView.deselectRow(at: selectedIndexPath, animated: true)
}, completion: nil)
//3
transitionCoordinator.notifyWhenInteractionChanges { (context) in
if context.isCancelled {
self.tableView.selectRow(at: selectedIndexPath, animated: true, scrollPosition: .none)
}
}
} else {
//4
tableView.deselectRow(at: selectedIndexPath, animated: animated)
}
}
That's a LOT of code, here are the highlights:
Only run this if there's a selected index path. There's no selection if you’re on this screen for the first time. (Btw, the table view keeps track of its own selected index path(s). You just need to mark cells selected or not selected).
Coordinate the row deselection animation with the current animation "context" (i.e. the edge swipe animation context).
You might change your mind mid-swipe! If this happens, you want to re-select the thing you were deselecting.
Back in the day, before transition coordinators, you only had to add this one line. This else case is there in case there's no transition coordinator (old version of iOS, going back in the stack without animation, etc).
Ok..before you give up on UIKit, know there's a shortcut.
Shortcut: Use UITableViewController instead of UIViewController
Instead of subclassing UIViewController and adding a table view, just subclass UITableViewController. You still have to mark your cell selected, but that's it.
This works because UITableViewController has a property called clearsSelectionOnViewWillAppear, which is set to true by default. It takes care of everything for you.