Pull-to-refresh (refreshable) in iOS Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to add a pull-to-refresh modifier to the List.

iOS Swift

List(items, id: \.self) { item in
    Text(item)
}
.[1] {
    print("Refreshing data...")
}

Drag options to blanks, or click blank then click option'

AonTapGesture

BonAppear

ConDisappear

Drefreshable

Attempts:

3 left

💡 Hint

Common Mistakes

Using onAppear instead of refreshable.

Trying to add pull-to-refresh without the refreshable modifier.

The .refreshable modifier adds pull-to-refresh behavior to a List in SwiftUI.

2fill in blank

medium

Complete the async closure to simulate data refresh with a 2-second delay.

iOS Swift

.refreshable {
    await Task.sleep(UInt64([1] * 1_000_000_000))
    print("Data refreshed")
}

Drag options to blanks, or click blank then click option'

A3

B2

C1

D5

Attempts:

3 left

💡 Hint

Common Mistakes

Using 2 without converting to nanoseconds.

Using 2000000000 without multiplying by UInt64.

Task.sleep expects nanoseconds, so 2 seconds is 2 * 1_000_000_000 nanoseconds.

3fill in blank

hard

Fix the error by completing the code to update the items array after refresh.

iOS Swift

.refreshable {
    await Task.sleep(2_000_000_000)
    [1] = ["Apple", "Banana", "Cherry"]
}

Drag options to blanks, or click blank then click option'

Aself.items

Bitems

Cvar items

Dlet items

Attempts:

3 left

💡 Hint

Common Mistakes

Using var or let inside the closure which causes redeclaration errors.

Not using self when required inside closures.

Inside closures, use self.items to update the state variable properly.

4fill in blank

hard

Fill both blanks to declare the items array and bind it to the List.

iOS Swift

@State private var [1] = ["Orange", "Grape"]

var body: some View {
    List([2], id: \.self) { fruit in
        Text(fruit)
    }
}

Drag options to blanks, or click blank then click option'

Aitems

Bfruits

Attempts:

3 left

💡 Hint

Common Mistakes

Using different names for the state variable and List data source.

Forgetting to mark the variable with @State.

The @State variable is named items and the List uses items as its data source.

5fill in blank

hard

Fill all three blanks to create a refreshable List that updates items after a delay.

iOS Swift

@State private var [1] = ["Cat", "Dog"]

var body: some View {
    List([2], id: \.self) { pet in
        Text(pet)
    }
    .refreshable {
        await Task.sleep([3])
        self.[1] = ["Cat", "Dog", "Rabbit"]
    }
}

Drag options to blanks, or click blank then click option'

Apets

Bitems

C2_000_000_000

D1_000_000_000

Attempts:

3 left

💡 Hint

Common Mistakes

Using different names for the state and List data source.

Using 1_000_000_000 for 2 seconds delay.

The state variable and List data source are 'items'. The delay is 2 seconds in nanoseconds.

Practice

1. What does the .refreshable modifier do in a SwiftUI List?

easy

A. Disables scrolling in the list

B. Automatically sorts the list items alphabetically

C. Changes the list background color

D. Allows users to pull down to refresh the list content

Solution

1. Step 1: Understand the purpose of .refreshable

   The .refreshable modifier adds pull-to-refresh functionality to scrollable views like List.

2. Step 2: Identify what pull-to-refresh does

   Pull-to-refresh lets users pull down the list to trigger a data update or refresh action.

3. Final Answer:

   Allows users to pull down to refresh the list content -> Option D

4. Quick Check:

   Pull-to-refresh = update list by pulling down [OK]

Hint: Pull-to-refresh updates list by pulling down [OK]

Common Mistakes:

• Thinking it sorts the list automatically
• Confusing it with disabling scroll
• Assuming it changes UI colors

2. Which of the following is the correct syntax to add pull-to-refresh to a SwiftUI List?

easy

A. List { ... }.refreshable { await loadData() }

B. List { ... }.onRefresh { loadData() }

C. List { ... }.refresh { loadData() }

D. List { ... }.pullToRefresh { await loadData() }

Solution

1. Step 1: Recall the official SwiftUI modifier for pull-to-refresh

   The correct modifier is .refreshable with an async closure.

2. Step 2: Match syntax with options

   List { ... }.refreshable { await loadData() } uses .refreshable { await loadData() } which is correct syntax.

3. Final Answer:

   List { ... }.refreshable { await loadData() } -> Option A

4. Quick Check:

   Correct modifier = .refreshable [OK]

Hint: Use .refreshable with async closure for pull-to-refresh [OK]

Common Mistakes:

• Using .onRefresh instead of .refreshable
• Missing await keyword in async closure
• Using non-existent modifiers like .pullToRefresh

3. Given this SwiftUI code snippet, what happens when the user pulls down the list?

List(items, id: \.self) { item in
  Text(item)
}
.refreshable {
  await fetchNewItems()
}

medium

A. The list reloads with new items after fetchNewItems completes

B. The list scrolls to the top without changing data

C. Nothing happens because refreshable requires a button

D. The app crashes due to missing completion handler

Solution

1. Step 1: Understand the effect of .refreshable with async closure

   When user pulls down, fetchNewItems() runs asynchronously to update data.

2. Step 2: Identify expected behavior after data fetch

   After fetchNewItems() completes, the list reloads showing updated items.

3. Final Answer:

   The list reloads with new items after fetchNewItems completes -> Option A

4. Quick Check:

   Pull-to-refresh triggers async update = list reload [OK]

Hint: Pull triggers async fetch, then list updates [OK]

Common Mistakes:

• Thinking refreshable needs a button
• Assuming no data change happens
• Believing app crashes without completion

4. What is wrong with this SwiftUI pull-to-refresh code?

List(data) { item in
  Text(item.name)
}
.refreshable {
  fetchData()
}

medium

A. List requires an explicit id parameter

B. refreshable cannot be used on List

C. fetchData() is missing await and async keywords

D. Text cannot display item.name

Solution

1. Step 1: Check the refreshable closure requirements

   The closure must be async and await the async function inside.

2. Step 2: Identify missing async/await usage

   fetchData() is called without await and the closure is not marked async, causing a compile error.

3. Final Answer:

   fetchData() is missing await and async keywords -> Option C

4. Quick Check:

   refreshable closure must be async with await calls [OK]

Hint: Use async closure and await inside refreshable [OK]

Common Mistakes:

• Forgetting to mark closure async
• Calling async functions without await
• Thinking refreshable can't be used on List

5. You want to add pull-to-refresh to a SwiftUI ScrollView that shows a list of messages. Which approach correctly updates the messages asynchronously when pulled?

hard

A. Use .onPull modifier with a synchronous closure

B. Use .refreshable on ScrollView with an async closure that updates the messages array

C. Add a Button inside ScrollView to manually refresh messages

D. Wrap ScrollView in a VStack and call a refresh function onAppear

Solution

1. Step 1: Identify the correct modifier for pull-to-refresh on ScrollView

   The .refreshable modifier works on ScrollView and accepts an async closure.

2. Step 2: Confirm asynchronous update of messages

   The async closure should update the messages array to refresh the UI after pull.

3. Step 3: Evaluate other options

   The other options do not provide pull-to-refresh behavior: using non-existent modifiers, refreshing on appear, or requiring manual buttons.

4. Final Answer:

   Use .refreshable on ScrollView with an async closure that updates the messages array -> Option B

5. Quick Check:

   Pull-to-refresh on ScrollView = .refreshable async closure [OK]

Hint: Use .refreshable with async closure on ScrollView [OK]

Common Mistakes:

• Trying to refresh with onAppear instead of pull
• Using buttons instead of pull-to-refresh
• Using non-existent modifiers like .onPull