我有代码:

import 'dart:async';

Future<int> expensiveCallFromALib(int value) async {
  print('expensiveCall($value)');
  return value + 1;
}

test() {
  Map<String, int>input = {"one":1, "two":2};
  Map result = {};

  print("A");
  input.forEach((String key, int value) {
    expensiveCallFromALib(value).then((int value) {
      result[key] = value;
    });
    print("B");
  });
  print("C");

  print(result);

}

main() {
  test();
}

...与输出
A
B
B
C
{}
expensiveCall(1)
expensiveCall(2)

... 但是我想要
A
B
expensiveCall(1)
B
expensiveCall(2)
C
{one: 2, two: 3}

关键是,我无法更改昂贵的CallFromALib方法。

最佳答案

test() async {
  Map<String, int>input = {"one":1, "two":2};
  Map result = {};

  print("A");
  for(final key in input.keys) {
    int value = await expensiveCallFromALib(input[key]);
      result[key] = value;

    print("B");
  }
  print("C");
  print('result: $result');
}

输出不是您想要的,但是我想它已经足够接近了;-)
HTML OUTPUT
CONSOLE
A
expensiveCall(1)
B
expensiveCall(2)
B
C
result: {one: 2, two: 3}

Plunker example

关于dictionary - 如何使用 map 触发异步请求但获得汇总结果?,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/40530436/

10-10 17:15