List view basics in iOS Swift

Introduction

A list view shows many items in a scrollable column. It helps users see and pick from multiple things easily.

Showing a list of contacts in a phone app.

Displaying messages in a chat app.

Listing songs in a music player.

Showing tasks in a to-do list app.

Displaying settings options in an app.

Syntax

iOS Swift

import SwiftUI

struct ContentView: View {
  let items = ["Apple", "Banana", "Cherry"]

  var body: some View {
    List(items, id: \.self) { item in
      Text(item)
    }
  }
}

The List view creates a scrollable list of rows.

Use id: \.self when your data items are simple and identifiable by themselves.

Examples

A simple list of color names.

iOS Swift

List(["Red", "Green", "Blue"], id: \.self) { color in
  Text(color)
}

A list with fixed rows written directly inside the List.

iOS Swift

List { 
  Text("First item")
  Text("Second item")
  Text("Third item")
}

A list with custom data type using Identifiable protocol.

iOS Swift

struct Fruit: Identifiable {
  let id = UUID()
  let name: String
}

let fruits = [Fruit(name: "Mango"), Fruit(name: "Peach")]

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

Sample App

This app shows a scrollable list of fruit names with a title on top.

iOS Swift

import SwiftUI

struct ContentView: View {
  let fruits = ["Apple", "Banana", "Cherry", "Date"]

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

@main
struct MyApp: App {
  var body: some Scene {
    WindowGroup {
      ContentView()
    }
  }
}

Important Notes

List automatically scrolls if items don't fit on screen.

Use id: \.self only for simple, unique data like strings.

For complex data, use Identifiable protocol to help SwiftUI track items.

Summary

List shows many items vertically and scrolls if needed.

Use List(data, id: \.self) for simple lists.

Use Identifiable for custom data types in lists.

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