Await keyword in iOS Swift - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ ui_behavior

intermediate

Understanding async UI update with await

What will be the visible text on the label after the following Swift async function runs?

iOS Swift

func updateLabel() async {
  label.text = "Loading..."
  let result = await fetchData()
  label.text = result
}

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

A "Data Loaded" is shown after fetchData completes

B "Loading..." remains visible

C The label text is empty

D The app crashes due to missing await

💡 Hint

Remember that await pauses the function until the async call finishes.

The await keyword pauses updateLabel until fetchData returns. So the label first shows "Loading..." then updates to "Data Loaded" after await completes.

❓ lifecycle

intermediate

Await in viewDidLoad lifecycle method

What happens if you call an async function with await inside viewDidLoad in a UIViewController?

iOS Swift

override func viewDidLoad() {
  super.viewDidLoad()
  Task {
    await loadData()
  }
}

func loadData() async {
  // fetch data asynchronously
}

A loadData runs asynchronously without blocking UI

B The UI blocks until loadData finishes

C The app crashes because viewDidLoad cannot be async

D loadData runs synchronously

💡 Hint

Using Task inside viewDidLoad allows async code without blocking.

viewDidLoad cannot be async, but wrapping await calls inside Task runs them asynchronously without blocking the UI.

📝 Syntax

advanced

Identify the syntax error with await usage

Which option contains a syntax error when using await in Swift?

iOS Swift

func fetchUser() async -> String {
  return "User"
}

func showUser() {
  let user = await fetchUser()
  print(user)
}

A

func showUser() async {
  let user = await fetchUser()
  print(user)
}

B

}
)resu(tnirp  
)(resUhctef tiawa = resu tel  
{ cnysa )(resUwohs cnuf

C

func showUser() async {
  let user = fetchUser()
  print(user)
}

D

func showUser() {
  let user = await fetchUser()
  print(user)
}

💡 Hint

Await can only be used inside async functions.

Option D uses await inside a non-async function, causing a syntax error.

🔧 Debug

advanced

Debugging missing await causing runtime issue

What issue arises if you forget to use await when calling an async function?

iOS Swift

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

func process() async {
  let data = fetchData()
  print(data)
}

A data is a String and prints "Data"

B The code causes a compile-time error

C data is a Task<String> and prints the task description

D The app crashes at runtime

💡 Hint

Calling an async function inside an async context requires 'await', otherwise compile error.

Without 'await', the code causes a compile-time error because async functions must be called with 'await' in async contexts.

🧠 Conceptual

expert

Effect of await on concurrency and thread blocking

Which statement best describes what the await keyword does in Swift concurrency?

A await blocks the current thread until the async function finishes

B await runs the async function on a background thread automatically

C await suspends the current async task, allowing other tasks to run without blocking the thread

D await converts an async function into a synchronous one

💡 Hint

Think about how await helps keep the app responsive.

Await suspends the current async task, freeing the thread to run other tasks. It does not block the thread.