如何在nodejs中使用Async瀑布进行API调用

Question

在我的应用程序中，我必须一步一步地执行一系列API调用。我试图使用异步瀑布选项来实现这一点。但在得到第一个API的响应之前，第二个函数正在执行，同样的事情也发生在第二个功能中。那是在得到响应之前，发送最终结果。如果我尝试执行API调用以外的其他任务，则瀑布操作正在正确执行。下面是我尝试过的代码。出于测试目的，从两个函数(myFirstFunction、mySecondFunction(调用相同的API。

const async = require('async');
router.get('/', (req, res) => {
async.waterfall([
myFirstFunction,
mySecondFunction,
],
function (err, result) {
if (err) {
console.log("Error-->" + JSON.stringify(err));
res.status(400).json(err).end();
} else {
console.log(" Result -->" + JSON.stringify(result));
res.status(200).json("Success").end();
}
});
});
const myFirstFunction = (callback) => {
console.log(" ------- myFirstFunction ");
const vehList = callVehicle();
console.log("First Function -->" + JSON.stringify(vehList));
callback(null, vehList);
}
const mySecondFunction = (vehList, callback) => {
console.log("-------- mySecondFunction");
const vehList1 = callVehicle();
const vehList2 = {
"1": vehList,
"2": vehList1
}
console.log("Second Function -->" + JSON.stringify(vehList2));
callback(null, vehList2);
}
const callVehicle = () => {
var options = {
method: "GET",
json: true,
strictSSL: false,
url: `http://localhost:8080/vehicle/make`
};
request(options, function(error, response, body) {
if (body){
console.log("Success REST Response: ", JSON.stringify(body));
return body;
} else {
console.log("Error : ", JSON.stringify(error));
return {"Error": "error"};
}
});
}

获得的输出

F:workSpace_NodeSampleApp>node app.js
server running at 9086
------- myFirstFunction
First Function -->undefined
-------- mySecondFunction
Second Function -->{}
Result -->{}
Success REST Response:  {"vehicleList":[{"make":"Audi","model":"A3","vin":"QVFCFQT7894563214"},{"make":"Audi","model":"A4","vin":"ASECFQT7894563214"},{"make":"Audi","model":"Q7"},{"make":"Audi","model":"Q5","vin":"QWECFQT7894993214"}]}
Success REST Response:  {"vehicleList":[{"make":"Audi","model":"A3","vin":"QVFCFQT7894563214"},{"make":"Audi","model":"A4","vin":"ASECFQT7894563214"},{"make":"Audi","model":"Q7"},{"make":"Audi","model":"Q5","vin":"QWECFQT7894993214"}]}

如何使用async.waterfall实现这一点，或者有没有更好的方法来满足这一要求。

Answer 1

使用Promises和异步函数的最佳方式。

但是，如果你想在没有承诺的情况下完成它，我认为所有异步代码都应该得到一个回调参数。

但是您的callVehicle没有回调参数，所以当call Vehicle收到响应时，无法通知父函数。

const myFirstFunction = (callback) => {
callVehicle(callback);
}
const mySecondFunction = (vehList, callback) => {
const vehList1 = callVehicle((err, res) => callback (err, {
1: vehList,
2: res
}));
}
// We add callback that should be called when we have a result of the api request
const callVehicle = (callback) => {
var options = {
method: "GET",
json: true,
strictSSL: false,
url: `http://localhost:8080/vehicle/make`
};
request(options, function(error, response, body) {
if (!error && body){
console.log("Success REST Response: ", JSON.stringify(body));
callback(null, body)
} else {
console.log("Error : ", JSON.stringify(error));
callback({ Error: error }, null)
});
}

承诺：

const get = (options) => new Promise(
(resolve, reject) => request(
{method: 'GET', ...options},
(err, response, body)=> err ? reject(err) : resolve(body)
)
)
const callVehicle = () => get({
json: true,
strictSSL: false,
url: `http://localhost:8080/vehicle/make`
})
router.get('/', async (req, res) => {
try {
const firstVehicle = await callVehicle()
const secondVehicle = await callVehicle()
res.status(200).json("Success").end();
} (error) {
res.status(400).json(error).end();
}
});