Swipe actions in iOS Swift - Mini App: Build & Ship

Build: Swipe Actions List

A simple list where each item can be swiped left to reveal Delete and Edit actions.

Target UI

-------------------------
| Swipe Actions List     |
-------------------------
| Item 1                |
| Item 2                |
| Item 3                |
| Item 4                |
| Item 5                |
-------------------------

Swipe left on any item to show buttons:
[Delete] [Edit]

Display a list of 5 items labeled 'Item 1' to 'Item 5'.

Enable swipe left gesture on each list item.

Reveal two swipe actions: Delete (red) and Edit (gray).

Delete action removes the item from the list with animation.

Edit action prints 'Edit tapped on Item X' to the console.

Starter Code

iOS Swift

import SwiftUI

struct SwipeActionsListView: View {
    @State private var items = ["Item 1", "Item 2", "Item 3", "Item 4", "Item 5"]

    var body: some View {
        NavigationView {
            List {
                ForEach(items, id: \.self) { item in
                    Text(item)
                        // TODO: Add swipe actions here
                }
            }
            .navigationTitle("Swipe Actions List")
        }
    }
}

struct SwipeActionsListView_Previews: PreviewProvider {
    static var previews: some View {
        SwipeActionsListView()
    }
}

Task 1

Task 2

Task 3

Solution

iOS Swift

import SwiftUI

struct SwipeActionsListView: View {
    @State private var items = ["Item 1", "Item 2", "Item 3", "Item 4", "Item 5"]

    var body: some View {
        NavigationView {
            List {
                ForEach(items, id: \.self) { item in
                    Text(item)
                        .swipeActions(edge: .trailing) {
                            Button(role: .destructive) {
                                withAnimation {
                                    items.removeAll { $0 == item }
                                }
                            } label: {
                                Label("Delete", systemImage: "trash")
                            }
                            .tint(.red)

                            Button {
                                print("Edit tapped on \(item)")
                            } label: {
                                Label("Edit", systemImage: "pencil")
                            }
                            .tint(.gray)
                        }
                }
            }
            .navigationTitle("Swipe Actions List")
        }
    }
}

struct SwipeActionsListView_Previews: PreviewProvider {
    static var previews: some View {
        SwipeActionsListView()
    }
}

This solution uses SwiftUI's swipeActions modifier on each list item to add swipe gestures.

The Delete button has a destructive role and red tint. When tapped, it removes the item from the list with animation.

The Edit button has a gray tint and prints a message to the console identifying which item was tapped.

The list updates dynamically because the items array is marked with @State.

Final Result

Completed Screen

-------------------------
| Swipe Actions List     |
-------------------------
| Item 1                |
| Item 2                |
| Item 3                |
| Item 4                |
| Item 5                |
-------------------------

Swipe left on an item reveals:
[Delete (red)] [Edit (gray)]

Swipe left on any item to reveal Delete and Edit buttons.

Tap Delete to remove the item with a smooth animation.

Tap Edit to print 'Edit tapped on Item X' in the console.

Stretch Goal

Add a confirmation alert before deleting an item.

💡 Hint

Use the .alert modifier with a state variable to show a confirmation dialog before removing the item.

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