Summary - Async

Combine async/await, Future.wait and Completer to write a parallel downloader.

Summary - Async

In this group we learned the basics of asynchronous programming: Future represents an async result; async/await writes code synchronously; .then/.catchError builds chains; Future.wait runs in parallel; Completer enables manual completion.

Together these tools form the foundation of async code in Dart. They are used for network requests, file reads, timers and similar operations. They manage long tasks without blocking the main thread.

Now let's do an exercise that uses two tools together: run two Futures in parallel with Future.wait and print their sum.

Exercise Sum of parallel Futures

void main() async is already written. Create two Future.value (1 and 2). Run them in parallel with Future.wait and wait with await. Print the sum of the two elements of the result list; for example print('Total: ${results[0] + results[1]}').

Show example solution

void main() async {
  var f1 = Future.value(1);
  var f2 = Future.value(2);
  var results = await Future.wait([f1, f2]);
  print('Total: ${results[0] + results[1]}');
}

Test yourself

Match the async concepts

Future

Async result
await

Waiting
Future.wait

Parallel wait
Completer

Manual completion
What is used to run multiple Futures in parallel?
- Completer
- then
- Future.wait
- await
Show answer

Future.wait — Future.wait runs multiple Futures in parallel.

Next lesson: What are streams?

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