這是我的控制器：
const rssService = require('../services/rss.service');
async function parser() {
const result = await rssService.rssParser('someurl');
return result;
};
const parse = async function (req, res) {
const p = new Promise((resolve, reject) => {
const t = parser();
if (t === undefined) {
resolve(t);
} else {
// eslint-disable-next-line prefer-promise-reject-errors
reject('something bad happened');
}
});
p.then((result) => res.send(result)).catch((message) => console.log(`ERROR ${message}`));
};
module.exports = {
parse,
};
在函式：parser() 上面，我試圖呼叫我有邏輯的 rss.service.js 檔案。該檔案是一個 rss 決議器，它嘗試決議提要并進行一些計算（需要 promise 和異步），然后回傳 json 物件。
這是我的 rss.service 的樣子：
const rssParser = async function parseRssFeed(url) {
const parser = new Parser();
const appRoot = process.env.PWD;
const downloadDir = `${appRoot}/downloads/`;
if (!fs.existsSync(downloadDir)) {
fs.mkdirSync(downloadDir);
}
try {
const feed = await parser.parseURL('someurl');
const processedFeedItems = await Promise.all(feed.items.map(async (currentItem) => {
const {
fileUrl,
downloadPath,
} = await downloadFile(currentItem);
const hashValue = calculateHash(downloadPath)
return {
title: currentItem.title,
hash: hashValue,
url: mp3FileUrl,
};
}));
return (JSON.stringify(processedFeedItems));
} catch (error) {
console.error(error);
return 'error';
}
};
當我除錯我的代碼時，我可以驗證是否使用正確的資料創建了 Json 物件，但結果不會回傳給被呼叫者（控制器）。
uj5u.com熱心網友回復：
因為你提到你是新人，所以我會更深入一點：
const rssService = require('../services/rss.service');
// This is an async function (always returns a promise)
async function parser() {
const result = await rssService.rssParser('someurl');
return result;
};
const parse = async function (req, res, next) {
// In await/async, you should use try/catch/throw instead of .then and .catch
// It does the same thing, but it's the preferred syntax and is "easier" to read IMO
// Out in "the community" people will complain if you mix await/async with promises like that
try {
// Adding await to ensure left-assign works.
// This is necessary because parser is an async function (so returns a promise)
const result = await parser();
// here, since you used `await` you get the value instead of the promise
if (result === undefined) throw new Error('something bad happened')
return res.send(result)
} catch (error) {
console.log(`ERROR ${error.message}`;
// Do you need to do anything else with this error? I assume something like:
return next(error);
}
};
module.exports = {
parse,
};
uj5u.com熱心網友回復：
快速看一下，您似乎忘記等待決議決議器的承諾。
...
const p = new Promise(async(resolve, reject) => {
const t = await parser();
...
轉載請註明出處，本文鏈接：https://www.uj5u.com/gongcheng/323861.html
標籤：节点.js