async.parallel中的async等待，回调未定义

Question

我正在尝试在async.parallel中进行异步/等待，但无法调用回调。 但是，如果我删除异步/等待，则可以调用该回调。 下面是代码

let parallelFunc = listCamId.map(camId => {
    return async function (callback) {
      let insertRuleTransParam = {
        rule_id: ruleId,
        camera_id: camId,
        vas_id: vasId,
        additional_parameter: additionalParameter
      }

      let configParamCamera = { where: { id: camId } };
      let configParamRule = { where: { id: ruleId } };

      try {
        let ruleTrans = await createRuleTransaction(insertRuleTransParam);
        let rule = await ruleService.find(configParamRule, "one");
        let cam = await cameraService.find(configParamCamera, "one");
        let uri = await constructCamUri(cam.protocol, cam.user_access, cam.password, cam.ip_address, cam.port, cam.path);
        let visionParam = await startVasRule(vasId, ruleTrans.id, camId, rule.rule_path, rule.rule_exec, uri);
        let updateRuleParam = {
          port_stream: visionParam.port,
          url_stream: visionParam.url,
          mmap_in: visionParam.mmap_in,
          mmap_out: visionParam.mmap_out
        }
        await updateRuleTransaction(updateRuleParam);
        callback(null);
      } catch (e) {
        callback(e);
      }
    }
  })

  return new Promise((resolve, reject) => {
    async.parallel(parallelFunc, function (err, results) {
      if (err) {
        reject(err);
      } else {
        resolve('success');
      }
    })
  });

有人可以指出代码有什么问题吗？

Answer 1

不要将async.js库用于async.js代码，也不要使用回调参数。 只需使用Promise.all等待多件事：

let promises = listCamId.map(async function(camId) {
  let insertRuleTransParam = {
    rule_id: ruleId,
    camera_id: camId,
    vas_id: vasId,
    additional_parameter: additionalParameter
  }

  let configParamCamera = { where: { id: camId } };
  let configParamRule = { where: { id: ruleId } };

  let ruleTrans = await createRuleTransaction(insertRuleTransParam);
  let rule = await ruleService.find(configParamRule, "one");
  let cam = await cameraService.find(configParamCamera, "one");
  let uri = await constructCamUri(cam.protocol, cam.user_access, cam.password, cam.ip_address, cam.port, cam.path);
  let visionParam = await startVasRule(vasId, ruleTrans.id, camId, rule.rule_path, rule.rule_exec, uri);
  let updateRuleParam = {
    port_stream: visionParam.port,
    url_stream: visionParam.url,
    mmap_in: visionParam.mmap_in,
    mmap_out: visionParam.mmap_out
  }
  await updateRuleTransaction(updateRuleParam);
  return null;
});
return Promise.all(promises);

Answer 2

您可以在async.js中使用async / await

您的代码中存在一个主要错误：

return async function (callback) {}

异步函数不需要或不需要callback ，它们是Promises简写

这是一个将在async.js中运行的async function的简单示例：

async function forAsync() {
  try {
    let user = await db.findOne({});
    return user // this is equivalent to resolve(user)
  } catch (e) {
    throw(e) // this is equivalent to reject(err)
  }
}

作为一个Promise它将如下：

function forAsync() {
  return new Promise((resolve,reject) => {
    db.findOne({}, (err,res) => {
      if (err) reject(err)
      let user = res;
      resolve(user);
    });
  }
}

作为callback ，如下所示：

function forAsync(callback) {
  db.findOne({}, (err,res) => {
    if (err) callback(err)     
    let user = res;     
    callback(null, user);
  });
}