如何使用异步/等待内部的承诺

Question

我想在此诺言中使用异步/等待，以获取一些API或数据库存储的货币率来转换货币。

就像我想在这里使用这样的等待，但不确定要放置异步。

arrcars["price_client"] = await forexService.convertCurrency(item.regular_price, "EUR", userCurrency);

我发布了整个代码。这里需要一些指导。

这是控制器

    const httpStatus = require('http-status');
    const pick = require('../utils/pick');
    const catchAsync = require('../utils/catchAsync');
    const async = require('async');
    const axios = require('axios');
    const { talixoService } = require('../services');
    const { iwayService } = require('../services');
    const { forexService } = require('../services');
    
        const searchCars = function (req, res) {
            const talixoData = talixoService.findTalixoCars(req.body) //call talixo api in services
            const iwayData = iwayService.findiWayCars(req.body) //call iwaytransfers api in services
        
            if (req.query.usercurrency) {
                var userCurrency = req.query.usercurrency;
            } else {
                var userCurrency = "INR";
            }
        
            return Promise.allSettled([talixoData, iwayData]).then(([restalixo, resiway]) => {
                const taxiresults = [];
                if (restalixo.status === "fulfilled") {
                    //console.log(restalixo.value.data);
                    if (restalixo.value.data.taxis.length) {
                        restalixo.value.data.taxis.forEach(function (item) {
                            arrcars = {};
                            arrcars["carname"] = item.car_model;
                            arrcars["originprice"] = item.regular_price;
                            arrcars["price_client"] = forexService.convertCurrency(item.regular_price, "EUR", userCurrency);
                            arrcars["discountprice_client"] = forexService.convertCurrency(item.discount_price, "EUR", userCurrency);
                            arrcars["packageId"] = item.id;
                            arrcars["image"] = item.image_url;
                            arrcars["freewaittime"] = item.included_waiting_time;
                            arrcars["maxluggage"] = item.luggage;
                            arrcars["maxpassengers"] = item.seats;
                            arrcars["discountprice"] = item.discount_price;
                            arrcars["vehicletype"] = item.vehicle_type;
                            arrcars["vendor"] = "Talixo";
                            arrcars["vehicleremarks"] = "Or Similar";
                            taxiresults.push(arrcars);
                        });
                    }
                    if (restalixo.value.data.limousines.length) {
                        restalixo.value.data.limousines.forEach(function (item) {
                            arrcars = {};
                            arrcars["carname"] = item.car_model;
                            arrcars["originprice"] = item.regular_price;
                            arrcars["price_client"] = forexService.convertCurrency(item.regular_price, "EUR", userCurrency);
                            arrcars["discountprice_client"] = forexService.convertCurrency(item.discount_price, "EUR", userCurrency);
                            arrcars["packageId"] = item.id;
                            arrcars["image"] = item.image_url;
                            arrcars["freewaittime"] = item.included_waiting_time;
                            arrcars["maxluggage"] = item.luggage;
                            arrcars["maxpassengers"] = item.seats;
                            arrcars["discountprice"] = item.discount_price;
                            arrcars["vehicletype"] = item.vehicle_type;
                            arrcars["vendor"] = "Talixo";
                            arrcars["vehicleremarks"] = "Or Similar";
                            taxiresults.push(arrcars);
                        });
                    }
                }
                //iwaytransfers supplier data
                if (resiway.status === "fulfilled") {
                    //console.log(resiway.value.data);
                    if (resiway.value.data.result.length) {
                        resiway.value.data.result.forEach(function (item) {
                            var imgsrc = "https://iwayex.com/images/cars/";
                            arrcars = {};
                            arrcars["carname"] = item.car_class.models[0];
                            arrcars["originprice"] = item.price;
                            arrcars["price_client"] = forexService.convertCurrency(item.price, "EUR", userCurrency);
                            arrcars["discountprice_client"] = forexService.convertCurrency(item.price, "EUR", userCurrency);
                            arrcars["packageId"] = item.price_uid;
                            arrcars["image"] = imgsrc + item.car_class.photo;
                            arrcars["freewaittime"] = item.allowable_time;
                            arrcars["maxluggage"] = "";
                            arrcars["maxpassengers"] = item.car_class.capacity;
                            arrcars["discountprice"] = item.price;
                            arrcars["vehicletype"] = item.vehicle_type;
                            arrcars["vendor"] = "iway Transfers";
                            arrcars["vehicleremarks"] = "Or Similar";
                            taxiresults.push(arrcars);
                        });
                    }
                }
        
                if (taxiresults.length) {
                    sortedresult = taxiresults.sort(function (a, b) {
                        return a.discountprice - b.discountprice;
                    });
                    res.status(200).send(sortedresult)
                }else{
                    res.status(200).send({})
                }
            });
        }

module.exports = {
    searchCars
}

这是我得到的结果样本。

{
carname: "Toyota Prius"
discountprice: 27.5
discountprice_client: {}
freewaittime: 45
image: "https://static.talixo.de/images/vehicles/economy.png"
maxluggage: 3
maxpassengers: 3
originprice: 27.5
packageId: "16021"
price_client: {}
vehicleremarks: "Or Similar"
vehicletype: "limo"
vendor: "Talixo"
}

这里的问题是， 我希望

discountprice_client: Converted Number, 

我能在那里得到空白的对象，如上所述样本中可以看出。 我一直在与异步的另一个函数中使用此功能，然后它可以正常工作。但是在这种情况下，我不确定如何放置异步/等待。

这在内部

forex.service.js内部

    const convertCurrency = async (amount, basecurrency, reqCurrency) => {
        if (basecurrency === reqCurrency) {
            let result = Math.round(amount) + ' ' + reqCurrency;
            return result;
        } else {
            const reqForexData = await getForexbyISO(reqCurrency);
            const baseForexData = await getForexbyISO(basecurrency);
            const amountInUSD = amount / baseForexData.forexRate;
            const amountInreqC = amountInUSD * reqForexData.forexRate;
            let result = Math.round(amountInreqC) + ' ' + reqCurrency;
            return result;
        }
    }

module.exports = {
    convertCurrency
}

Answer 1

您可以做：

// notice the `async` before `function`
resiway.value.data.result.forEach(async function (item) {
  // ...
  arrcars = {};
  arrcars["price_client"] = await forexService.convertCurrency(item.price, "EUR", userCurrency);
  arrcars["discountprice_client"] = await forexService.convertCurrency(item.price, "EUR", userCurrency);
  // ...
});

但是它可能导致意外的行为，

我会这样做

// add missing `async`
return Promise.allSettled([talixoData, iwayData]).then(async ([restalixo, resiway]) => {
  // ...
  // await for all loop at once to avoid odd side effects
  await Promise.all(resiway.value.data.result.map(async function (item) {
    // ...
    arrcars = {};
    arrcars["price_client"] = await 
  forexService.convertCurrency(item.price, "EUR", userCurrency);
    arrcars["discountprice_client"] = await 
  forexService.convertCurrency(item.price, "EUR", userCurrency);
    // ...
  }));
  // ...
});

Answer 2

简化您的服务

您正在编写Talixo和Iway服务，但是使用结果很困难。而不是返回整个响应，而是将重要的字段返回给您的消费者 -

// services/talixo_service.js

async function findTalixoCars(query) {
  const result = await // ... perform request
  return result.value.data ?? [] // <- return relevant data
}

请注意，我们使用返回_____ ?? []为确保数组始终返回 -

// services/iway_service.js

async function findiWayCars(query) {
  const result = await // ... perform request
  return result.value.data.result ?? [] // <- return relevant data
}

searchCars

使用简化的服务，我们编写了searchcars的高级实现。而不是使用Promise.allsettled我们可以使用.catch（_ =＆gt; []）潜在的失败以保证我们具有数组结果。这减少了对逻辑检查和代码分支的需求，以使代码更具声明性，并且不容易出现错误 -

async function searchCars(req, res) {
  const [talixo, iway] = await Promise.all([
    talixoService.findTalixoCars(req.body).catch(_ => []),
    iwayService.findiWayCars(req.body).catch(_ => [])
  ])

  const userCurrency = req.query.usercurrency ?? "INR"

  const taxis = [
    ...await Promise.all(talixo.taxis.map(item => fromTalixo(item, userCurrency))),
    ...await Promise.all(talixo.limousines.map(item => fromTalixo(item, userCurrency))),
    ...await Promise.all(iway.map(item => fromIway(item, userCurrency)))
  ]
  
  res.status(200).send(
    taxis.sort((a,b) => a.discountprice - b.discountprice)
  )
}

数据映射

上面的搜索功能取决于fromtalixo 和。这些映射功能降低了代码的复杂性和重新定位，并为我们提供了一个良好的概念模型，以从远程服务映射到我们本地数据 -

async function fromTalixo(data, userCurrency) {
  return {
    carname: data.car_model,
    originprice: data.regular_price,
    price_client: await forexService.convertCurrency(data.regular_price, "EUR", userCurrency),
    discountprice_client: await forexService.convertCurrency(data.discount_price, "EUR", userCurrency),
    packageId: data.id,
    image: data.image_url,
    freewaittime: data.included_waiting_time,
    maxluggage: data.luggage,
    maxpassengers: data.seats,
    discountprice: data.discount_price,
    vehicletype: data.vehicle_type,
    vendor: "Talixo",
    vehicleremarks: "Or Similar",
  }
}

async function fromIway(data, userCurrency) {
  return {
    carname: data.car_class.models[0],
    originprice: data.price,
    price_client: await forexService.convertCurrency(data.price, "EUR", userCurrency),
    discountprice_client: await forexService.convertCurrency(data.price, "EUR", userCurrency),
    packageId: data.price_uid,
    image: `https://iwayex.com/images/cars/${data.car_class.photo}`,
    freewaittime: data.allowable_time,
    maxluggage: "",
    maxpassengers: data.car_class.capacity,
    discountprice: data.price,
    vehicletype: data.vehicle_type,
    vendor: "iway Transfers",
    vehicleremarks: "Or Similar",
  }
}