Dart Future.wait for multiple futures and get back results of different types

Question

I\'m using Flutter to download 3 different sets of data from a server, then do something with all 3 sets. I could do this:

List foos = await downl         


        

Answer 1

Well, type T is a generic type

You know your types, so you can work with them.

If your are using a FutureBuilder, you can access the different results using this. (same order you put them in the Future.wait method)

snapshot.data[0] // maybe type List<Foo>
snapshot.data[1] // maybe type List<Bar>
snapshot.data[2] // maybe type String

Answer 2

You need to adapt each of your Future<T>s to a common type of Future. You could use Future<void>:

List<Foo> foos;
List<Bar> bars;
List<FooBars> foobars;

await Future.wait<void>([
  downloader.getFoos().then((result) => foos = result),
  downloader.getBars().then((result) => bars = result),
  downloader.getFooBars().then((result) => foobars = result),
]);

processData(foos, bars, foobars);

Or if you prefer await to .then(), the Future.wait call could be:

await Future.wait<void>([
  (() async => foos = await downloader.getFoos())(),
  (() async => bars = await downloader.getBars())(),
  (() async => foobars = await downloader.getFooBars())(),
]);

Answer 3

I think is not possible to do in a super nice fashion. All you can do is something like this:

void main() async {
  List<List<dynamic>> result = await Future.wait<List<dynamic>>([
    getStringData(),
    getIntData(),
  ]);

  print(result[0]);
  print(result[1]);
}

Future<List<String>> getStringData() {
  return Future.value(["a", "b"]);
}

Future<List<int>> getIntData() {
  return Future.value([1, 2]);
}