Dartlang wait more than one future

Question

I want to do something after a lot of future function done,bu I do not know how to write the code in dart? the code like this:

for (var d in data) {
  d.load         


        

Answer 1

Existing answer gives enough information, but I want to add a note/warning. As stated in the docs:

The value of the returned future will be a list of all the values that were produced in the order that the futures are provided by iterating futures.

So, that means that the example below will return 4 as the first element (index 0), and 2 as the second element (index 1).

import 'dart:async';

Future main() async {
  print('start');

  List<int> li = await Future.wait<int>([
    fetchLong(),  // longer (which gives 4) is first
    fetchShort(), // shorter (which gives 2) is second
  ]);

  print('results: ${li[0]} ${li[1]}'); // results: 4 2
}

Future<int> fetchShort() {
  return Future.delayed(Duration(seconds: 4), () {
    print('Short!');
    return 2;
  });
}

Future<int> fetchLong() {
  return Future.delayed(Duration(seconds: 5), () {
    print('Long!');
    return 4;
  });
}

Answer 2

You can use Future.wait to wait for a list of futures:

import 'dart:async';

Future main() async {
  var data = [];
  var futures = <Future>[];
  for (var d in data) {
    futures.add(d.loadData());
  }
  await Future.wait(futures);
}

DartPad example