Structured concurrency in iOS Swift - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to start an asynchronous task using Swift's structured concurrency.

iOS Swift

Task {
    await [1]()
}

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

Aprint

Bsleep

CfetchData

Drun

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to use await before the async function call.

Using a synchronous function inside Task without await.

The Task initializer creates a new asynchronous task. Inside it, you call await fetchData() to run the async function.

2fill in blank

medium

Complete the code to define an async function that returns a string after a delay.

iOS Swift

func fetchData() async -> String {
    try? await Task.sleep(nanoseconds: 1_000_000_000)
    return [1]
}

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

ATask.sleep

B"Done"

Cawait "Done"

DDone

Attempts:

3 left

💡 Hint

Common Mistakes

Returning a bare word without quotes causes an error.

Trying to await a string literal.

The function returns the string "Done". It must be a string literal with quotes.

3fill in blank

hard

Fix the error in the code by choosing the correct keyword to mark the function as asynchronous.

iOS Swift

func loadData() [1] -> String {
    return "Loaded"
}

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

Aasynchronous

Bawait

Casync await

Dasync

Attempts:

3 left

💡 Hint

Common Mistakes

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

Writing 'async await' together which is invalid.

The correct keyword to mark a function as asynchronous is async. It goes after the parameter list.

4fill in blank

hard

Fill both blanks to create a task group that runs two async functions concurrently and collects their results.

iOS Swift

await withTaskGroup(of: String.self) { group in
    group.[1] {
        await fetchData1()
    }
    group.[2] {
        await fetchData2()
    }
}

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

AaddTask

BrunTask

CstartTask

DlaunchTask

Attempts:

3 left

💡 Hint

Common Mistakes

Using methods that do not exist on TaskGroup.

Using different methods for each task.

The method to add a new task to the group is addTask. Both blanks need this method to add tasks.

5fill in blank

hard

Fill all three blanks to create a dictionary that maps task results to their lengths, filtering only results longer than 3 characters.

iOS Swift

let results = ["apple", "bat", "carrot"]
let lengths = results.reduce(into: [String: Int]()) { lengths, [1] in
    if [2] > 3 {
        lengths[[3]] = [2]
    }
}

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

Aword

Bword.count

Dcount

Attempts:

3 left

💡 Hint

Common Mistakes

Using undefined variables.

Mixing up keys and values in the dictionary.

The reduce(into:) uses word as key, word.count as value, and iterates with word over results.