如何在async / await语法中拒绝？ [英] How to reject in async/await syntax?

问题描述

如何拒绝async / await函数返回的承诺？

How can I reject a promise that returned by an async/await function?

例如。最初

foo(id: string): Promise<A> {
  return new Promise((resolve, reject) => {
    someAsyncPromise().then((value)=>resolve(200)).catch((err)=>reject(400))
  });
}

转换为async / await

Translate into async/await

async foo(id: string): Promise<A> {
  try{
    await someAsyncPromise();
    return 200;
  } catch(error) {//here goes if someAsyncPromise() rejected}
    return 400; //this will result in a resolved promise.
  });
}

那么，在这种情况下我怎么能正确拒绝这个承诺？

So, how could I properly reject this promise in this case?

推荐答案

你最好的选择是抛出一个错误包装该值，导致被拒绝的承诺，错误包装值：

Your best bet is to throw an Error wrapping the value, which results in a rejected promise with an Error wrapping the value:

} catch (error) {
    throw new Error(400);
}

你也可以抛出值，但是没有堆栈跟踪信息：

You can also just throw the value, but then there's no stack trace information:

} catch (error) {
    throw 400;
}

或者，返回一个被拒绝的承诺，其中包含错误包装值：

Alternately, return a rejected promise with an Error wrapping the value:

} catch (error) {
    return Promise.reject(new Error(400));
}

（或者只是返回Promise.reject（400） ; ，但是再次没有上下文信息。）

(Or just return Promise.reject(400);, but again, then there's no context information.)

（在您的情况下，因为您正在使用 TypeScript 和 foo 的后续值是 Promise< A> ，你会用返回Promise.reject< A>（400 / *或错误* /）; ）

(In your case, as you're using TypeScript and foo's retrn value is Promise<A>, you'd use return Promise.reject<A>(400 /*or error*/);)

在 async / await 情况，最后一点可能是语义不匹配，但确实有效。

In an async/await situation, that last is probably a bit of a semantic mis-match, but it does work.

如果你抛出一个错误，这对消费你的 foo 的结果等待语法：

If you throw an Error, that plays well with anything consuming your foo's result with await syntax:

try {
    await foo();
} catch (error) {
    // Here, `error` would be an `Error` (with stack trace, etc.).
    // Whereas if you used `throw 400`, it would just be `400`.
}

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