Swipe actions in iOS Swift - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a swipe action in iOS apps?

A swipe action lets users swipe a list item left or right to reveal buttons for quick tasks like delete or edit.

beginner

Which UIKit class helps you add swipe actions to table view rows?

UIContextualAction is used to create swipe actions that appear when a user swipes a table view row.

intermediate

How do you specify the style of a swipe action button in Swift?

You set the style property of UIContextualAction to .normal or .destructive to change its look and behavior.

intermediate

What method do you implement to provide swipe actions for a UITableView row?

Implement tableView(_:trailingSwipeActionsConfigurationForRowAt:) or tableView(_:leadingSwipeActionsConfigurationForRowAt:) to return swipe actions.

beginner

Why should swipe actions be accessible?

Making swipe actions accessible ensures all users, including those using VoiceOver or other assistive tech, can use the app easily.

Which class creates a swipe action button in a UITableView?

A UITableViewCell

B UISwipeGestureRecognizer

C UIContextualAction

D UISwipeAction

UIContextualAction is the class used to create swipe action buttons for table view rows.

Which method provides trailing swipe actions in a UITableView?

A tableView(_:trailingSwipeActionsConfigurationForRowAt:)

B tableView(_:cellForRowAt:)

C tableView(_:didSelectRowAt:)

D tableView(_:leadingSwipeActionsConfigurationForRowAt:)

tableView(_:trailingSwipeActionsConfigurationForRowAt:) returns the swipe actions shown when swiping from right to left.

What style makes a swipe action button red and destructive?

A .cancel

B .normal

C .default

D .destructive

The .destructive style colors the button red to indicate a destructive action like delete.

Swipe actions are usually added to which UI element?

A UITableViewCell

B UIButton

C UILabel

D UIImageView

Swipe actions are added to UITableViewCell to allow quick actions on list items.

Why is accessibility important for swipe actions?

A To improve app speed

B To support users with disabilities

C To reduce app size

D To add animations

Accessibility ensures users with disabilities can use swipe actions with assistive technologies.

Explain how to add a delete swipe action to a UITableView row in Swift.

Think about the method that provides swipe actions and how to create a red delete button.

Describe why swipe actions improve user experience in mobile apps.

Consider how users interact with lists and want fast ways to manage items.

Practice

1. What is the main purpose of using UIContextualAction in a swipe action on iOS?

easy

A. To handle tap gestures on the entire screen

B. To create buttons that appear when the user swipes a table cell

C. To change the background color of the app

D. To add animations to buttons outside of swipe actions

Solution

1. Step 1: Understand swipe actions in iOS

   Swipe actions allow users to reveal buttons by swiping on a list item.

2. Step 2: Role of UIContextualAction

   UIContextualAction creates the buttons shown during the swipe gesture.

3. Final Answer:

   To create buttons that appear when the user swipes a table cell -> Option B

4. Quick Check:

   UIContextualAction = Swipe buttons [OK]

Hint: UIContextualAction = swipe buttons on list items [OK]

Common Mistakes:

• Confusing swipe action buttons with general tap gestures
• Thinking UIContextualAction changes app colors
• Assuming it adds animations unrelated to swipe

2. Which of the following is the correct way to create a UIContextualAction for a swipe action in Swift?

easy

A. let action = UIContextualAction(style: .normal, title: "Delete", handler: { _, _, completionHandler in completionHandler(true) })

B. let action = UIContextualAction(style: "normal", title: "Delete", handler: { _, _, completionHandler in completionHandler(true) })

C. let action = UIContextualAction(style: .normal, title: Delete, handler: { _, _, completionHandler in completionHandler(true) })

D. let action = UIContextualAction(style: .normal, title: "Delete")

Solution

1. Step 1: Check UIContextualAction initializer syntax

   The initializer requires a style enum, a String title, and a handler closure with parameters.

2. Step 2: Validate each option

   let action = UIContextualAction(style: .normal, title: "Delete", handler: { _, _, completionHandler in completionHandler(true) }) uses correct enum style, quotes around title, and proper handler closure with completion call.

3. Final Answer:

   let action = UIContextualAction(style: .normal, title: "Delete", handler: { _, _, completionHandler in completionHandler(true) }) -> Option A

4. Quick Check:

   Correct initializer syntax = let action = UIContextualAction(style: .normal, title: "Delete", handler: { _, _, completionHandler in completionHandler(true) }) [OK]

Hint: Use .normal enum and quoted title with handler closure [OK]

Common Mistakes:

• Using string instead of enum for style
• Missing quotes around title string
• Omitting handler closure or completion call

3. Given this code snippet inside a UITableViewDelegate method, what happens when the user swipes the cell?

let deleteAction = UIContextualAction(style: .destructive, title: "Delete") { _, _, completionHandler in
    print("Deleted")
    completionHandler(true)
}
let configuration = UISwipeActionsConfiguration(actions: [deleteAction])
return configuration

medium

A. A red "Delete" button appears; tapping it prints "Deleted" and closes swipe

B. The cell immediately deletes without user interaction

C. Nothing happens because completionHandler is not called

D. The swipe gesture is disabled

Solution

1. Step 1: Analyze swipe action setup

   A destructive style button labeled "Delete" is created with a handler that prints and calls completionHandler(true).

2. Step 2: Understand user interaction

   Swiping reveals the button; tapping it triggers the handler, printing "Deleted" and ending the swipe.

3. Final Answer:

   A red "Delete" button appears; tapping it prints "Deleted" and closes swipe -> Option A

4. Quick Check:

   Swipe button tap triggers handler = A red "Delete" button appears; tapping it prints "Deleted" and closes swipe [OK]

Hint: Completion handler true ends swipe and triggers action [OK]

Common Mistakes:

• Thinking swipe deletes immediately without tap
• Forgetting to call completionHandler(true)
• Assuming swipe gesture disables without code

4. Identify the error in this swipe action handler code:

let editAction = UIContextualAction(style: .normal, title: "Edit") { action, view, _ in
    print("Edit tapped")
}

medium

A. Title string should be lowercase

B. Incorrect style enum used for edit action

C. Missing call to completionHandler inside the closure

D. Closure parameters are in wrong order

Solution

1. Step 1: Review UIContextualAction handler requirements

   The handler closure must call the completionHandler to signal action completion.

2. Step 2: Check the given code

   The closure ignores the third parameter (completionHandler) and does not call it, causing swipe to hang.

3. Final Answer:

   Missing call to completionHandler inside the closure -> Option C

4. Quick Check:

   Always call completionHandler in swipe action handler [OK]

Hint: Always call completionHandler(true/false) in handler closure [OK]

Common Mistakes:

• Ignoring completionHandler call
• Using wrong style enum (normal is valid here)
• Thinking title case matters
• Mixing closure parameter order

5. You want to add two swipe actions: "Flag" (normal style) and "Delete" (destructive style) to a table cell. Which code correctly creates and returns the swipe configuration?

hard

A. let flag = UIContextualAction(style: .normal, title: "Flag") { _, _, completion in completion(true) }
let delete = UIContextualAction(style: .destructive, title: "Delete") { _, _, completion in completion(true) }
return UISwipeActionsConfiguration(actions: [flag, delete])

B. let flag = UIContextualAction(style: .normal, title: "Flag") { _, _, completionHandler in completionHandler(true) }
let delete = UIContextualAction(style: .destructive, title: "Delete") { _, _, completionHandler in completionHandler(true) }
return UISwipeActionsConfiguration(actions: [flag, delete])

C. let flag = UIContextualAction(style: .normal, title: "Flag") { _, _, completionHandler in completionHandler(false) }
let delete = UIContextualAction(style: .destructive, title: "Delete") { _, _, completionHandler in completionHandler(true) }
return UISwipeActionsConfiguration(actions: [flag, delete])

D. let flag = UIContextualAction(style: .normal, title: "Flag") { _, _, completionHandler in completionHandler(true) }
let delete = UIContextualAction(style: .destructive, title: "Delete") { _, _, completionHandler in completionHandler(true) }
return UISwipeActionsConfiguration(actions: [delete, flag])

Solution

1. Step 1: Confirm action creation and completion calls

   Both actions use correct styles and call completionHandler(true) to indicate success.

2. Step 2: Check order of actions in configuration

   Swipe actions appear in order given; "Delete" usually placed first for prominence, then "Flag".

3. Final Answer:

   Actions created with correct styles and completion calls; configuration returns [delete, flag] -> Option D

4. Quick Check:

   Correct styles, completion calls, and order = let flag = UIContextualAction(style: .normal, title: "Flag") { _, _, completionHandler in completionHandler(true) } let delete = UIContextualAction(style: .destructive, title: "Delete") { _, _, completionHandler in completionHandler(true) } return UISwipeActionsConfiguration(actions: [delete, flag]) [OK]

Hint: Call completionHandler(true) and order destructive before normal [OK]

Common Mistakes:

• Calling completionHandler(false) which cancels action
• Using wrong variable name for completionHandler
• Incorrect order of actions in array
• Omitting completionHandler call