Asynchronous work (Future, async, await)

This lesson covers the basics of asynchronous programming, for work that takes time.

Future is the type representing a value you will get later. Marking a function async lets you use await inside it to wait for asynchronous work to finish.

The sample code simulates a delay with Future.delayed inside Future<String> fetchData() async { ... }, then waits for the result with await before displaying it.

A common early stumble is forgetting to mark the calling function async as well. await can only be used inside an async function.

In professional work, most time-consuming operations — fetching data from a server, reading a file — are written with async and await. It is unavoidable in Flutter development.

📖 Reference code

Future<String> fetchData() async {
  await Future.delayed(Duration(seconds: 1));
  return 'Data loaded';
}

void main() async {
  print('Loading...');
  String result = await fetchData();
  print(result);
}

✍️ Your code

Type your code, then press "Run"

🧪 This site can't compile or run Dart directly, so it checks on the spot whether what you typed matches the reference code (scoring happens entirely in your browser — nothing is sent anywhere).