async await multiple 自分の使う言語まとめ

コンパイラの言うがままにasync awaitして結局同期的じゃんと言うコードを死ぬほどみてきた。
いいかげんそこそこ使いこなせる程度には知っておきたいね。

JavaScript

https://qiita.com/im36-123/items/c0678a46ee0f8e44e150
await Promise.all使う

function get(url) {
  return fetch(url);
}

async function fn() {
  const results = [];
  const urls = ['https://hoge/api', 'https://fuga/api'];
  for (const url of urls) {
    results.push(get(url));
  }
  console.log(await Promise.all(results));
}

Kotlin

https://stackoverflow.com/a/62966043/5598088
awaitAll使う

viewModelScope.launch {
    val a = async { firstUseCase.execute() }
    val b = async { secondUseCase.execute() }

    val (resA, resB) = awaitAll(a, b)

    //Use results 'resA' and 'resB' here
}

Python

asyncio.gather使う
https://stackoverflow.com/questions/34377319/combine-awaitables-like-promise-all

Dart

  final results = await Future.wait([
    task2(),
    task2(),
    task2(),
    task2(),
  ]);
  print(results);

Future<String> task2() async {
  String result;
  Duration sec3 = Duration(seconds: 3);
  await Future.delayed(sec3, () {
    result = 'task 2 data';
    print('Task 2 complete');
  });
  return result;
}

[task 2 data, task 2 data, task 2 data, task 2 data]