// Trigger a segue programmatically
performSegue(withIdentifier: "showDetail", sender: self)

1// Storyboard has identifier "ShowDetail" (capital S)
2// Code uses "showDetail" (lowercase s) — DOES NOT MATCH
3performSegue(withIdentifier: "showDetail", sender: self)
4// Crash: has no segue with identifier 'showDetail'
5
6// Fix: match the exact string from the storyboard
7performSegue(withIdentifier: "ShowDetail", sender: self)
8
9// Better: use a constant to prevent typos
10enum Segue {
11    static let showDetail = "ShowDetail"
12    static let showSettings = "ShowSettings"
13    static let showProfile = "ShowProfile"
14}
15
16performSegue(withIdentifier: Segue.showDetail, sender: self)

1// The segue exists in the storyboard but is connected to a different view controller
2// Or the segue was deleted and recreated without updating the identifier
3
4// Verify in Xcode:
5// 1. Open Main.storyboard
6// 2. Click on the source view controller
7// 3. Open the Connections Inspector (right panel)
8// 4. Check that the segue appears under "Triggered Segues"
9// 5. Verify the identifier in the Attributes Inspector

1class MyViewController: UIViewController {
2
3    override init(nibName: String?, bundle: Bundle?) {
4        super.init(nibName: nibName, bundle: bundle)
5        // WRONG: view is not loaded yet, no navigation stack
6        performSegue(withIdentifier: "ShowDetail", sender: self)
7    }
8
9    override func viewDidLoad() {
10        super.viewDidLoad()
11        // RISKY: view is loaded but may not be in the window hierarchy
12        // performSegue may silently fail
13    }
14
15    override func viewDidAppear(_ animated: Bool) {
16        super.viewDidAppear(animated)
17        // CORRECT: view is fully visible and in the navigation stack
18        performSegue(withIdentifier: "ShowDetail", sender: self)
19    }
20}

1// Segue is connected FROM ViewControllerA TO ViewControllerB
2// But you are calling performSegue from ViewControllerC
3
4class ViewControllerC: UIViewController {
5    func goToDetail() {
6        // This fails because ViewControllerC has no segue named "ShowDetail"
7        performSegue(withIdentifier: "ShowDetail", sender: self)
8    }
9}
10
11// Fix: ensure the segue is connected from the correct source view controller

1class ListViewController: UIViewController {
2
3    var items: [Item] = []
4    var selectedItem: Item?
5
6    func tableView(_ tableView: UITableView, didSelectRowAt indexPath: IndexPath) {
7        selectedItem = items[indexPath.row]
8        performSegue(withIdentifier: "ShowDetail", sender: self)
9    }
10
11    override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
12        if segue.identifier == "ShowDetail" {
13            if let detailVC = segue.destination as? DetailViewController {
14                detailVC.item = selectedItem
15            }
16        }
17    }
18}

1// Instead of storyboard segues, navigate programmatically
2class ListViewController: UIViewController {
3
4    func showDetail(item: Item) {
5        let detailVC = DetailViewController()
6        detailVC.item = item
7        navigationController?.pushViewController(detailVC, animated: true)
8    }
9
10    // Or instantiate from storyboard without segues
11    func showDetailFromStoryboard(item: Item) {
12        let storyboard = UIStoryboard(name: "Main", bundle: nil)
13        if let detailVC = storyboard.instantiateViewController(
14            withIdentifier: "DetailVC"
15        ) as? DetailViewController {
16            detailVC.item = item
17            navigationController?.pushViewController(detailVC, animated: true)
18        }
19    }
20}

1// 1. Print all segues to verify they exist
2override func prepare(for segue: UIStoryboardSegue, sender: Any?) {
3    print("Segue triggered: \(segue.identifier ?? "nil")")
4    print("Destination: \(type(of: segue.destination))")
5}
6
7// 2. Check if the view controller is in the hierarchy
8print("Parent: \(String(describing: parent))")
9print("Navigation: \(String(describing: navigationController))")
10print("Is in window: \(view.window != nil)")
11
12// 3. Override shouldPerformSegue to prevent invalid transitions
13override func shouldPerformSegue(withIdentifier identifier: String, sender: Any?) -> Bool {
14    if identifier == "ShowDetail" && selectedItem == nil {
15        print("Cannot show detail: no item selected")
16        return false
17    }
18    return true
19}