Dart by Example: Async / Await

  1. import 'dart:async';
  3. const Duration delay = const Duration(milliseconds: 200);
  5. // This function doesn't use async / await; just the
  6. // standard Future API
  7. Future loadLastName(String firstName) {
  8.   return new Future.delayed(delay).then((_) {
  9.     return firstName + 'son';
  10.   });
  11. }
  13. // Marking a function with 'async' will return a future
  14. // that completes with the returned value.
  15. // This function is equivalent to [loadLastName]
  16. Future loadLastName2(String firstName) async {
  17.   await new Future.delayed(delay);
  19.   return firstName + 'son';
  20. }
  22. main() async {
  23.   // 'await' will suspend execution of the function until the
  24.   // future completes:
  25.   var gregsLastName = await loadLastName('greg');
  26.   var stevesLastName = await loadLastName2('steve');
  28.   print('greg $gregsLastName');
  29.   print('steve $stevesLastName');
  30. }
  31.  
  1. $ dart async_await.dart
  2. greg gregson
  3. steve steveson

by @jryanio | source | license