node.js - 错误: Callback was already called in loopback

Question

我有以下代码:

"use strict";
const Raven = require("raven");
Raven.config(
    "test"
).install();

module.exports = function(Reservation) {
  function dateValidator(err) {
    if (this.startDate >= this.endDate) {
      err();
    }
  }

  function sendEmail(campground) {
    return new Promise((resolve, reject) => {
      Reservation.app.models.Email.send(formEmailObject(campground), 
        function(
          err,
          mail
        ) {
           if (err) {
            console.log(err);
            Raven.captureException(err);
            reject(err);
           } else {
             console.log(mail);
             console.log("email sent!");
             resolve(mail);
           }
       });
   });
} 

  function formEmailObject(campground) {
    return {
      to: "loopbackintern@yopmail.com",
      from: "noreply@optis.be",
      subject: "Thank you for your reservation at " + campground.name,
      html:
        "<p>We confirm your reservation for <strong>" +
        campground.name +
        "</strong></p>"
    };
   }

Reservation.validate("startDate", dateValidator, {
 message: "endDate should be after startDate"
});

Reservation.observe("after save", async function(ctx, next) {
 try {
  const campground = await Reservation.app.models.Campground.findById(
    ctx.instance.campgroundId
  );
  const mail = await sendEmail(campground);
  next();
 } catch (e) {
  Raven.captureException(e);
  next(e);
 }
});
};

抱歉，格式不正确。当流程完成后，我收到此错误:

( Node :3907)UnhandledPromiseRejectionWarning:未处理的 promise 拒绝(拒绝 ID:1):错误:回调已被调用。

我在两个地方调用 next() 回调，一处在 try 代码中，一处在 catch 代码中。我假设当一切顺利时，下一个回调仅被调用一次，当出现问题时也是如此。但好像被调用了两次，不知道为什么。

我还尝试在 try/catch 代码之外调用 next，但它会导致相同的错误。如果我只留下捕获代码中调用的下一个，则不会引发错误。

有什么想法吗？谢谢!

Answer 1

如果您使用异步函数，则不应显式调用 next，它会自动调用。

check out this github issue for loopback async/await

所以你的钩子(Hook)可以像下面这样。

 Reservation.observe("after save", async ctx => {
  try {
    const campground = await Reservation.app.models.Campground.findById(
      ctx.instance.campgroundId
    );
    const mail = await sendEmail(campground);
  } catch (e) {
    Raven.captureException(e);
    throw e;
  }
});

注意:除非您想修改/处理错误，否则不需要将其包装在 try catch 中。