List view basics in iOS Swift - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ ui_behavior

intermediate

What will this SwiftUI List display?

Consider this SwiftUI code snippet. What will the list show when the app runs?

iOS Swift

struct ContentView: View {
  let fruits = ["Apple", "Banana", "Cherry"]
  var body: some View {
    List(fruits, id: \.self) { fruit in
      Text(fruit)
    }
  }
}

A A list showing Apple, Banana, and Cherry as separate rows

B A list showing numbers 0, 1, 2 instead of fruit names

C An empty list with no rows

D A single row showing all fruits concatenated as "AppleBananaCherry"

💡 Hint

Think about how List uses the array and the id parameter to create rows.

The List uses the fruits array and creates a row for each fruit string. The id: \.self means each string is unique and used as an identifier.

📝 Syntax

intermediate

Identify the syntax error in this List code

Which option correctly fixes the syntax error in this SwiftUI List code?

iOS Swift

struct ContentView: View {
  let numbers = [1, 2, 3]
  var body: some View {
    List(numbers) { number in
      Text("Number: \(number)")
    }
  }
}

A Change List to VStack: VStack(numbers) { number in ... }

B Add id: \.self to List: List(numbers, id: \.self) { number in ... }

C Remove the closure: List(numbers)

D Replace Text with Button: List(numbers) { number in Button("(number)") {} }

💡 Hint

List needs a way to identify each item uniquely when the data is not identifiable by default.

The List initializer requires an id parameter when the data elements do not conform to Identifiable. Adding id: \.self fixes the syntax error.

❓ lifecycle

advanced

What happens when the data array changes in a SwiftUI List?

Given this code, what will happen if the fruits array changes after the view appears?

iOS Swift

struct ContentView: View {
  @State var fruits = ["Apple", "Banana"]
  var body: some View {
    VStack {
      List(fruits, id: \.self) { fruit in
        Text(fruit)
      }
      Button("Add Cherry") {
        fruits.append("Cherry")
      }
    }
  }
}

A The app crashes because fruits is modified inside the view

B The List stays the same and does not show Cherry

C The List updates to show Apple, Banana, and Cherry after tapping the button

D The button does nothing because fruits is a constant

💡 Hint

Think about how @State works in SwiftUI and how views update.

Using @State allows the view to update when fruits changes. Adding Cherry triggers the view to refresh and show the new item.

❓ navigation

advanced

How to navigate to a detail view from a List row?

Which code snippet correctly navigates to a DetailView when a list row is tapped?

iOS Swift

struct ContentView: View {
  let items = ["One", "Two"]
  var body: some View {
    NavigationView {
      List(items, id: \.self) { item in
        // What goes here?
      }
    }
  }
}

A ListRow(item: item).navigate(to: DetailView(item: item))

B Button(action: { DetailView(item: item) }) { Text(item) }

C Text(item).onTapGesture { NavigationLink(destination: DetailView(item: item)) }

D NavigationLink(destination: DetailView(item: item)) { Text(item) }

💡 Hint

NavigationLink wraps the row content to enable navigation.

NavigationLink creates a tappable row that navigates to the destination view when tapped.

🔧 Debug

expert

Why does this List crash with 'Index out of range'?

This code crashes when tapping the Delete button. Why?

iOS Swift

struct ContentView: View {
  @State var fruits = ["Apple", "Banana", "Cherry"]
  var body: some View {
    List {
      ForEach(0..<fruits.count, id: \.self) { index in
        Text(fruits[index])
      }
      .onDelete { indices in
        fruits.remove(atOffsets: indices)
      }
    }
  }
}

A Using a range 0..<fruits.count in ForEach causes index mismatch after deletion

B fruits array is immutable and cannot be modified

C onDelete is not supported inside List

D The id: \.self is missing in ForEach

💡 Hint

Think about how ForEach with a range behaves when the array changes size.

Using a range for ForEach means indices are fixed at creation. After deletion, indices may be invalid causing crash. Using ForEach over the array elements directly avoids this.