GET request with async/await in iOS Swift - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ ui_behavior

intermediate

What is the output of this Swift async GET request code?

Consider this Swift code that fetches JSON data asynchronously. What will be printed if the request succeeds and the JSON contains {"message": "Hello"}?

iOS Swift

import Foundation

func fetchMessage() async {
  guard let url = URL(string: "https://example.com/api/message") else { return }
  do {
    let (data, _) = try await URLSession.shared.data(from: url)
    if let json = try? JSONSerialization.jsonObject(with: data) as? [String: String],
       let message = json["message"] {
      print(message)
    } else {
      print("No message found")
    }
  } catch {
    print("Request failed")
  }
}

Task {
  await fetchMessage()
}

A Request failed

B No message found

C Hello

D Compilation error

💡 Hint

Look at how the JSON is parsed and the key accessed.

The code fetches data from the URL, parses it as JSON dictionary, then prints the value for key "message". Since the JSON contains {"message": "Hello"}, it prints "Hello".

❓ lifecycle

intermediate

When is the async GET request executed in this SwiftUI view?

Given this SwiftUI view, when does the fetchData() async function run?

iOS Swift

import SwiftUI

struct ContentView: View {
  @State private var text = ""

  var body: some View {
    Text(text)
      .task {
        await fetchData()
      }
  }

  func fetchData() async {
    // async GET request code here
    text = "Data loaded"
  }
}

A Immediately when the app launches

B When the view appears on screen

C Only when the user taps the Text

D When the view disappears

💡 Hint

The .task modifier runs code related to the view's lifecycle.

The .task modifier runs its async code when the view appears on screen, so fetchData() runs then.

🔧 Debug

advanced

What error does this async GET request code produce?

Identify the error in this Swift async GET request code snippet.

iOS Swift

func loadData() async {
  let url = URL(string: "https://example.com/data")!
  let (data, response) = try await URLSession.shared.data(from: url)
  print(String(data: data, encoding: .utf8) ?? "No data")
}

A Missing await keyword before URLSession.shared.data call

B Missing try keyword before URLSession.shared.data call

C No error, code runs fine

D URL is optional and not unwrapped safely

💡 Hint

Check how async functions are called with await.

URLSession.shared.data(from:) is async and must be called with await. Missing await causes a compile error.

🧠 Conceptual

advanced

Which statement about async GET requests in Swift is true?

Choose the correct statement about using async/await for GET requests in Swift.

A Async/await requires manually creating completion handlers

B Async/await can only be used with POST requests

C Async/await blocks the main thread until the request finishes

D Async/await allows writing asynchronous code that looks like synchronous code

💡 Hint

Think about how async/await changes code style.

Async/await lets you write asynchronous code in a clear, linear style without callbacks.

📝 Syntax

expert

What is the value of 'result' after this Swift async GET request code runs?

Given this code snippet, what will be the value of 'result' after execution?

iOS Swift

import Foundation

func fetchNumber() async throws -> Int {
  let url = URL(string: "https://example.com/number")!
  let (data, _) = try await URLSession.shared.data(from: url)
  let numberString = String(data: data, encoding: .utf8) ?? "0"
  return Int(numberString) ?? 0
}

var result = 0

Task {
  do {
    result = try await fetchNumber()
  } catch {
    result = -1
  }
}

A All of the above depending on server response

B 0 if the server returns invalid data

C 0 if the server returns empty data

D 42 if the server returns "42" as plain text

💡 Hint

Consider how the code handles different server responses and errors.

The code returns the integer parsed from server data, or 0 if parsing fails, or -1 if the request throws an error. So result depends on server response.