Why modern concurrency matters in Swift - See It in Action

Why Modern Concurrency Matters

📖 Scenario: Imagine you are building a simple app that fetches user data from the internet and then processes it. Without concurrency, the app waits for the data to load before doing anything else, making it slow and unresponsive. Modern concurrency helps your app stay fast and smooth by doing tasks at the same time.

🎯 Goal: You will create a Swift program that uses modern concurrency features to fetch and process user data asynchronously, showing why concurrency makes apps faster and more responsive.

📋 What You'll Learn

Create an array of user IDs

Create a delay time variable

Use async/await to fetch user data concurrently

Print the fetched user data

💡 Why This Matters

🌍 Real World

Modern apps often need to fetch data from the internet or perform tasks without freezing the screen. Using concurrency lets apps do many things at once, making them faster and smoother.

💼 Career

Understanding modern concurrency in Swift is essential for iOS developers to build responsive apps that handle network calls, animations, and user interactions efficiently.

1

Create an array of user IDs

Create a constant array called userIDs with these exact values: [101, 102, 103]

Swift

# Create a constant array called userIDs with values [101, 102, 103]
# Your code here

Need a hint?

Use let to create a constant array named userIDs with the numbers 101, 102, and 103 inside square brackets.

2

Create a delay time variable

Create a constant called delaySeconds and set it to 2 to simulate network delay

Swift

let userIDs = [101, 102, 103]
# Create a constant delaySeconds and set it to 2
# Your code here

Need a hint?

Use let delaySeconds = 2 to create a constant that holds the number 2.

3

Fetch user data concurrently using async/await

Write an async function called fetchUserData that takes an Int parameter userID and returns a String. Inside, use Task.sleep with delaySeconds to simulate delay, then return a string like "User data for ID \(userID)". Then, create an async function called loadAllUsers that uses await and async let to fetch data for all userIDs concurrently and collects the results into an array called results.

Swift

let userIDs = [101, 102, 103]
let delaySeconds = 2

// Write async function fetchUserData(userID: Int) -> String
// Write async function loadAllUsers() to fetch all user data concurrently
# Your code here

Need a hint?

Use async and await keywords. Use Task.sleep to pause inside fetchUserData. Use async let to start multiple fetches at the same time.

4

Print the fetched user data

Call loadAllUsers() inside a Task and print each string in the returned array results on its own line

Swift

let userIDs = [101, 102, 103]
let delaySeconds = 2

func fetchUserData(userID: Int) async -> String {
    try? await Task.sleep(nanoseconds: UInt64(delaySeconds) * 1_000_000_000)
    return "User data for ID \(userID)"
}

func loadAllUsers() async -> [String] {
    async let first = fetchUserData(userID: userIDs[0])
    async let second = fetchUserData(userID: userIDs[1])
    async let third = fetchUserData(userID: userIDs[2])
    let results = await [first, second, third]
    return results
}

// Call loadAllUsers() inside Task and print each result
# Your code here

Need a hint?

Use Task { ... } to run async code at the top level. Use a for loop to print each string in the results array.