Why modern concurrency matters in Swift - Test Your Understanding

Practice - 5 Tasks

1fill in blank

easy

Complete the code to start a simple asynchronous task in Swift.

Swift

Task [1] {
    print("Hello from async task!")
}

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

Astart

Binit

Cdetached

Drun

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'start' or 'run' which are not valid Task methods.

In Swift, Task.detached starts a new asynchronous task detached from the current context.

2fill in blank

medium

Complete the code to await an asynchronous function call.

Swift

func fetchData() async -> String {
    return "Data"
}

func load() async {
    let result = [1] fetchData()
    print(result)
}

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

Async

Basync

Cdefer

Dawait

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'async' instead of 'await' when calling async functions.

The await keyword is used to wait for an asynchronous function to complete in Swift concurrency.

3fill in blank

hard

Fix the error in the code to correctly define an async function.

Swift

func process() [1] -> String {
    return "Done"
}

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

Aasync

Bawait

Casync throws

Dthrows

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'await' in the function signature instead of 'async'.

To define an asynchronous function in Swift, add the async keyword before the return type.

4fill in blank

hard

Fill both blanks to create a Task that returns a value asynchronously.

Swift

let task = Task [1] {
    return [2]
}

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

A.detached

B42

C"Hello"

D.init

Attempts:

3 left

💡 Hint

Common Mistakes

Using .init instead of .detached for creating a detached task.

Task.detached creates a new detached task, and the task returns the string "Hello".

5fill in blank

hard

Fill all three blanks to define and call an async function correctly.

Swift

func greet() [1] -> String {
    return "Hi!"
}

Task [2] {
    let message = [3] greet()
    print(message)
}

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

Aasync

Bdetached

Cawait

Dthrows

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to mark the function async or missing the await keyword when calling it.

The function is marked async, the task is created with detached, and the call uses await to wait for the result.

Practice

1. What is the main benefit of using modern concurrency with async and await in Swift?

easy

A. It makes your app use more memory.

B. It allows your app to do many tasks at the same time without freezing.

C. It slows down your app to avoid errors.

D. It removes the need for functions.

Solution

1. Step 1: Understand what concurrency means

   Concurrency means doing multiple tasks at once, which helps apps stay responsive.

2. Step 2: Connect concurrency with async and await

   These keywords let Swift run tasks without waiting and freezing the app.

3. Final Answer:

   It allows your app to do many tasks at the same time without freezing. -> Option B

4. Quick Check:

   Modern concurrency = smooth multitasking [OK]

Hint: Remember: async/await = multitasking without freezing [OK]

Common Mistakes:

• Thinking concurrency slows the app down
• Confusing concurrency with more memory use
• Believing async/await removes functions

2. Which of the following is the correct way to declare an asynchronous function in Swift?

easy

A. func fetchData() async -> String

B. async func fetchData() -> String

C. func async fetchData() -> String

D. func fetchData() -> async String

Solution

1. Step 1: Recall Swift async function syntax

   In Swift, async comes after the function parentheses.

2. Step 2: Check each option's syntax

   Only func fetchData() async -> String places async correctly after the parentheses.

3. Final Answer:

   func fetchData() async -> String -> Option A

4. Quick Check:

   async keyword after () = correct syntax [OK]

Hint: Put async right after () in function declaration [OK]

Common Mistakes:

• Placing async before func
• Inserting async inside parameter list
• Putting async before return type

3. What will be printed by this Swift code using async/await?

func fetchNumber() async -> Int {
    return 10
}

Task {
    let number = await fetchNumber()
    print(number)
}

medium

A. Nothing prints

B. await fetchNumber()

C. Error: missing await

D. 10

Solution

1. Step 1: Understand async function behavior

   The function fetchNumber() returns 10 asynchronously.

2. Step 2: Check how Task and await work

   The Task runs the async code, and await waits for the result before printing.

3. Final Answer:

   10 -> Option D

4. Quick Check:

   await fetchNumber() returns 10 [OK]

Hint: await waits for async result before printing [OK]

Common Mistakes:

• Forgetting to use await
• Expecting print before result is ready
• Thinking async functions run instantly

4. Identify the error in this Swift async code:

func loadData() async -> String {
    return "Data"
}

func printData() {
    let result = await loadData()
    print(result)
}

medium

A. loadData should not be async

B. await cannot be used inside printData

C. Missing async keyword in printData function declaration

D. printData should return String

Solution

1. Step 1: Check where await is used

   The function printData() uses await inside its body.

2. Step 2: Confirm async requirement for await

   Any function using await must be marked async.

3. Final Answer:

   Missing async keyword in printData function declaration -> Option C

4. Quick Check:

   await requires async function [OK]

Hint: Add async to any function using await [OK]

Common Mistakes:

• Not marking function async when using await
• Thinking await can be used in normal functions
• Confusing async with return type

5. You want to fetch user data and user posts concurrently in Swift using async/await. Which approach best uses modern concurrency to improve speed?

hard

A. Use async let to start both fetchUser() and fetchPosts() at the same time, then await both results.

B. Run fetchUser() synchronously, then fetchPosts() asynchronously.

C. Call fetchUser() and fetchPosts() one after another with await each time.

D. Use DispatchQueue without async/await to run both tasks.

Solution

1. Step 1: Understand sequential vs concurrent calls

   Calling await one after another waits for the first to finish before starting the second.

2. Step 2: Use async let for concurrency

   Using async let starts both tasks simultaneously, improving speed.

3. Final Answer:

   Use async let to start both fetchUser() and fetchPosts() at the same time, then await both results. -> Option A

4. Quick Check:

   async let = concurrent tasks [OK]

Hint: Use async let to run tasks together, then await results [OK]

Common Mistakes:

• Awaiting tasks one by one causing delay
• Mixing synchronous and asynchronous calls incorrectly
• Using old concurrency methods instead of async/await