How to pass indexPath value from performSegue() to prepareForSegue() - ios

Question

I have a tableView in a SubMenuViewController, when a user taps (using didSelectRowAt) on a cell and segues, I need to pass that cell to the next UserInputViewController,
Here is my code:
class SubMenuViewController: UIViewController {
//MARK: - Properties and outlets
var node: Node?
#IBOutlet weak var tableView: UITableView!
//MARK: - View controller methods
override func viewDidLoad() {
super.viewDidLoad()
self.navigationController?.isNavigationBarHidden = false
self.navigationItem.title = node?.value.rawValue
let nib = UINib(nibName: "SubMenuTableViewCell", bundle: nil)
tableView.register(nib, forCellReuseIdentifier: "SubMenuCell")
}
override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
if segue.identifier == "userInput" {
let vc = segue.destination as! UserInputViewController
let indexPath = sender as! IndexPath
vc.node = node?.childenNode[indexPath.row]
}
}
}
//MARK: UITableViewDataSource methods
extension SubMenuViewController: UITableViewDataSource {
func tableView(_ tableView: UITableView, numberOfRowsInSection section: Int) -> Int {
return node!.childCount
}
func tableView(_ tableView: UITableView, cellForRowAt indexPath: IndexPath) -> UITableViewCell {
let cell = tableView.dequeueReusableCell(withIdentifier: "SubMenuCell", for: indexPath) as! SubMenuTableViewCell
let desciptionModule = node?.childenNode[indexPath.row].value
let description = Modules.description(module: desciptionModule!)
cell.title.text = description.main
cell.subtitle.text = description.sub
return cell
}
}
//MARK: - UITableViewDelegate methods
extension SubMenuViewController: UITableViewDelegate {
func tableView(_ tableView: UITableView, heightForRowAt indexPath: IndexPath) -> CGFloat {
return 68
}
func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
tableView.deselectRow(at: indexPath, animated: true)
guard let selectedNode = node?.childenNode[indexPath.row] else {
return
}
if selectedNode.isLeaveNode() {
performSegue(withIdentifier: "userInput", sender: indexPath)
} else {
let subMenuViewController = self.storyboard!.instantiateViewController(withIdentifier: "subMenu") as! SubMenuViewController
subMenuViewController.node = selectedNode
//let subMenuViewController = SubMenuViewController(node: selectedNode)
self.navigationController?.pushViewController(subMenuViewController, animated: true)
}
}
}
Right now, in my performSegue, I passed in my indexPath into the sender, and I should expect to get it back in prepareForSegue, but I can't. Any suggestions guys?
Thanks

Answer 1

In my opinion it isn't very good practice to pass the index path (or any other value that counts a s "data") as the sender argument; as its name suggests, it is intended for passing the object that sent the message (i.e., called the action method), in this case self (you could "relay" the original sender if your action method calls another action method instead, but that's off-topic here).
As #sCha kindly pointed out in the comments, the Apple documentation on this method in particular, though, seems to leave room for doubt nevertheless. The parameter name sender clearly comes from the homonimous argument in all control actions that follow Cocoa's target/action pattern.
My suggestion:
The best you can do I think is to store the index path in a property of your view controller:
var selectedIndexPath: IndexPath?
...set it on tableView(_:didSelectRowAt:):
if selectedNode.isLeaveNode() {
self.selectedIndexPath = indexPath
performSegue(withIdentifier: "userInput", sender: indexPath)
} else {
self.selectedIndexPath = nil
// ...
...and retrieve it (while resetting the property) in the prepareForSegue(_:sender:) implementation of the target view controller:
if let vc = segue.source as? SubmenuViewController {
if let indexPath = vc.selectedIndexPath {
vc.selectedIndexPath = nil // (reset it, just to be safe)
// Use indexPath...
}
}