List view basics in iOS Swift - Mini App: Build & Ship

Build: Simple List Screen

This screen shows a list of fruits. Each fruit name is shown in a row. The list is scrollable if needed.

Target UI

---------------------
| Simple List Screen |
---------------------
| Apple             |
| Banana            |
| Cherry            |
| Date              |
| Elderberry        |
| Fig               |
| Grape             |
---------------------

Use SwiftUI List to display a list of fruit names

Show at least 7 fruit names as rows

Each row should show the fruit name as text

The list should be scrollable if the content is longer than the screen

Starter Code

iOS Swift

import SwiftUI

struct SimpleListScreen: View {
    let fruits = ["Apple", "Banana", "Cherry", "Date", "Elderberry", "Fig", "Grape"]

    var body: some View {
        // TODO: Add your List view here
        Text("Replace this with a List")
    }
}

struct SimpleListScreen_Previews: PreviewProvider {
    static var previews: some View {
        SimpleListScreen()
    }
}

Task 1

Task 2

Task 3

Solution

iOS Swift

import SwiftUI

struct SimpleListScreen: View {
    let fruits = ["Apple", "Banana", "Cherry", "Date", "Elderberry", "Fig", "Grape"]

    var body: some View {
        NavigationView {
            List(fruits, id: \.self) { fruit in
                Text(fruit)
            }
            .navigationTitle("Simple List Screen")
        }
    }
}

struct SimpleListScreen_Previews: PreviewProvider {
    static var previews: some View {
        SimpleListScreen()
    }
}

We use a List view to show a scrollable list of items. The fruits array holds the fruit names. We pass this array to the List and provide an identifier using id: \.self because the items are strings and unique. Each row shows the fruit name inside a Text view. Wrapping the list in a NavigationView allows us to add a title at the top with navigationTitle. This creates a simple, scrollable list screen.

Final Result

Completed Screen

---------------------
| Simple List Screen |
---------------------
| Apple             |
| Banana            |
| Cherry            |
| Date              |
| Elderberry        |
| Fig               |
| Grape             |
---------------------

User can scroll up and down if the list is longer than the screen

Each row shows the fruit name clearly

Stretch Goal

Add a navigation bar button labeled 'Add' that prints 'Add tapped' to the console when tapped.

💡 Hint

Use the .toolbar modifier on the NavigationView and add a Button with an action that calls print("Add tapped")

Practice

1. What does the List view in SwiftUI primarily do?

easy

A. Displays multiple items vertically and allows scrolling if needed

B. Creates a horizontal stack of buttons

C. Shows a single image on the screen

D. Plays a video in full screen

Solution

1. Step 1: Understand the purpose of List

   The List view is designed to show many items arranged vertically.

2. Step 2: Recognize scrolling behavior

   If the items exceed the screen height, List allows vertical scrolling automatically.

3. Final Answer:

   Displays multiple items vertically and allows scrolling if needed -> Option A

4. Quick Check:

   List shows vertical scrollable items = B [OK]

Hint: List shows vertical scrollable items [OK]

Common Mistakes:

• Confusing List with horizontal stacks
• Thinking List shows only one item
• Assuming List plays media content

2. Which of the following is the correct syntax to create a simple list from an array of strings named fruits?

easy

A. List { fruits }

B. List(fruits) { fruit in Text(fruit) }

C. List(fruits, id: fruit) { Text(fruit) }

D. List(fruits, id: \.self) { fruit in Text(fruit) }

Solution

1. Step 1: Identify correct List initializer

   For simple arrays, use List(data, id: \.self) to uniquely identify each item.

2. Step 2: Check closure syntax

   The closure receives each item and returns a Text view displaying it.

3. Final Answer:

   List(fruits, id: \.self) { fruit in Text(fruit) } -> Option D

4. Quick Check:

   Use id: \.self for simple arrays = C [OK]

Hint: Use id: \.self for simple array lists [OK]

Common Mistakes:

• Omitting id: \.self causes errors
• Passing id: fruit instead of id: \.self
• Using List without closure for data

3. Given this code snippet, what will be displayed?

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

medium

A. Number: 1, Number: 4, Number: 9

B. Number: 1, Number: 2, Number: 3

C. Number: 2, Number: 4, Number: 6

D. Number: 0, Number: 1, Number: 2

Solution

1. Step 1: Understand the data and transformation

   The array contains 1, 2, 3. Each number is multiplied by 2 in the Text view.

2. Step 2: Calculate displayed values

   1*2=2, 2*2=4, 3*2=6, so the list shows "Number: 2", "Number: 4", "Number: 6".

3. Final Answer:

   Number: 2, Number: 4, Number: 6 -> Option C

4. Quick Check:

   Multiply each number by 2 = A [OK]

Hint: Check how data transforms inside Text closure [OK]

Common Mistakes:

• Ignoring the multiplication inside the string
• Confusing array values with displayed text
• Assuming original numbers are shown

4. What is wrong with this SwiftUI List code?

struct ContentView: View {
  let items = ["A", "B", "C"]
  var body: some View {
    List(items) { item in
      Text(item)
    }
  }
}

medium

A. Missing id parameter for simple array causes a compile error

B. Text view cannot display strings directly

C. List requires items to be Int type

D. Closure syntax is incorrect

Solution

1. Step 1: Check List initializer requirements

   When using List with simple arrays like [String], you must provide an id parameter to identify each element uniquely.

2. Step 2: Identify missing id parameter

   The code omits id: \.self, so it will cause a compile-time error.

3. Final Answer:

   Missing id parameter for simple array causes a compile error -> Option A

4. Quick Check:

   Simple arrays need id: \.self in List = D [OK]

Hint: Always add id: \.self for simple arrays in List [OK]

Common Mistakes:

• Assuming List infers id automatically
• Thinking Text can't display strings
• Believing List only works with Int arrays

5. You have a custom struct Person conforming to Identifiable with a unique id. How do you create a List to display each person's name?

hard

A. List(people, id: \.name) { person in Text(person.name) }

B. List(people) { person in Text(person.name) }

C. List(people, id: \.self) { person in Text(person.name) }

D. List(people) { Text(person.name) }

Solution

1. Step 1: Understand Identifiable protocol usage

   If Person conforms to Identifiable, List can use the id property automatically without specifying id parameter.

2. Step 2: Use List with closure accessing person.name

   Simply pass people array and provide closure to show Text with person.name.

3. Final Answer:

   List(people) { person in Text(person.name) } -> Option B

4. Quick Check:

   Identifiable lets List infer id automatically = A [OK]

Hint: Use List(people) if Person is Identifiable [OK]

Common Mistakes:

• Adding redundant id parameter when Identifiable is used
• Using wrong key path for id
• Omitting closure parameter name