Swipe actions in iOS Swift - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ ui_behavior

intermediate

Swipe action behavior in a UITableView

What happens when you swipe a table view cell to the left and implement the following code in trailingSwipeActionsConfigurationForRowAt?

iOS Swift

func tableView(_ tableView: UITableView, trailingSwipeActionsConfigurationForRowAt indexPath: IndexPath) -> UISwipeActionsConfiguration? {
  let deleteAction = UIContextualAction(style: .destructive, title: "Delete") { _, _, completionHandler in
    print("Deleted row at \(indexPath.row)")
    completionHandler(true)
  }
  return UISwipeActionsConfiguration(actions: [deleteAction])
}

A A red "Delete" button appears when swiping left, and tapping it prints the deleted row index.

B A green "Delete" button appears when swiping left, but tapping it does nothing.

C Swiping left does nothing because the method is for right swipe only.

D Swiping right triggers the delete action instead of left swipe.

💡 Hint

Trailing swipe actions appear when swiping left on a cell.

The method trailingSwipeActionsConfigurationForRowAt defines actions shown when swiping left. The action style .destructive shows a red button. The completion handler confirms the action was performed.

❓ lifecycle

intermediate

Swipe action completion handler importance

What is the effect of not calling completionHandler(true) inside a swipe action handler?

iOS Swift

let editAction = UIContextualAction(style: .normal, title: "Edit") { _, _, completionHandler in
  print("Edit tapped")
  // Missing completionHandler call
}

A The swipe action closes immediately without performing the action.

B The swipe action triggers twice because completion is not called.

C The app crashes due to missing completion handler call.

D The swipe action button stays visible and the swipe does not close automatically.

💡 Hint

The completion handler tells the system the action finished.

If you do not call the completion handler, the system thinks the action is still running and keeps the swipe action visible, preventing the swipe from closing.

📝 Syntax

advanced

Correct syntax for adding multiple swipe actions

Which option correctly creates two swipe actions "Flag" and "More" for trailing swipe in a UITableView?

iOS Swift

func tableView(_ tableView: UITableView, trailingSwipeActionsConfigurationForRowAt indexPath: IndexPath) -> UISwipeActionsConfiguration? {
  let flagAction = UIContextualAction(style: .normal, title: "Flag") { _, _, completionHandler in
    completionHandler(true)
  }
  let moreAction = UIContextualAction(style: .normal, title: "More") { _, _, completionHandler in
    completionHandler(true)
  }
  // Return configuration here
}

A return UISwipeActionsConfiguration(actions: flagAction, moreAction)

B return UISwipeActionsConfiguration(actions: [flagAction, moreAction])

C return UISwipeActionsConfiguration(actions: flagAction + moreAction)

D return UISwipeActionsConfiguration(actions: [flagAction & moreAction])

💡 Hint

The actions parameter expects an array of UIContextualAction objects.

The actions parameter must be an array. Option B correctly passes an array with two actions. Other options have syntax errors or wrong types.

❓ navigation

advanced

Swipe action triggering navigation

You want a swipe action to navigate to a detail screen when tapped. Which code snippet correctly performs this navigation inside the swipe action handler?

iOS Swift

let detailAction = UIContextualAction(style: .normal, title: "Details") { [weak self] _, _, completionHandler in
  // Navigate to detail screen
  completionHandler(true)
}

A self?.navigationController?.pushViewController(DetailViewController(), animated: true)

B present(DetailViewController(), animated: true)

C navigationController.pushViewController(DetailViewController(), animated: true)

D self.navigationController.pushViewController(DetailViewController(), animated: true)

💡 Hint

Use optional chaining with self inside closures to avoid retain cycles.

Inside closures, use [weak self] and optional chaining to safely access navigationController. Option A correctly uses self? and optional chaining. Options C and D cause errors because self is optional or missing ?. Option A is invalid because present() is not called on self or a view controller.

🔧 Debug

expert

Why does swipe action not appear on iOS 15+?

You implemented leadingSwipeActionsConfigurationForRowAt but the swipe action does not appear on iOS 15 and later. What is the most likely cause?

iOS Swift

func tableView(_ tableView: UITableView, leadingSwipeActionsConfigurationForRowAt indexPath: IndexPath) -> UISwipeActionsConfiguration? {
  let pinAction = UIContextualAction(style: .normal, title: "Pin") { _, _, completionHandler in
    completionHandler(true)
  }
  return UISwipeActionsConfiguration(actions: [pinAction])
}

A The method <code>leadingSwipeActionsConfigurationForRowAt</code> is deprecated and replaced by a delegate property.

B Swipe actions are disabled by default on iOS 15 and require explicit enabling in Info.plist.

C The table view's <code>separatorInset</code> or <code>layoutMargins</code> prevent swipe actions from showing.

D The swipe action style .normal is not supported on iOS 15 and must be .destructive.

💡 Hint

Check the table view cell layout and margins if swipe actions do not appear.

On iOS 15+, if the cell's separatorInset or layoutMargins are set incorrectly, swipe actions may not appear. This is a common layout issue. Swipe actions are not disabled by default and the method is not deprecated. Style .normal is supported.