javascript - Sails.js 控制器从 Promise 中获取数据
问题描述
我正在尝试使用sails.js(使用node.js)。我有一个控制器如下。Thsi 控制器解析在 url 参数中传递的 ical url ical_url
,我正在尝试解析它并根据需要构建一个规范化的 json objetc。我有一个parse
仅在此控制器之外公开的功能。它使用 node-ical npm 包 ( https://www.npmjs.com/package/node-ical ) 来解析 ical 内容。在该ical.fromURL
方法中,我有一个回调函数,我用它初始化了一个变量normalized_data
并将数据存储在其中。我打算使用该数据并调用decorate
方法进行一些处理并取回 json。请查看以开头的行//>>>>>>
,根据我的愿望,我无法访问normalized_data
As perhttps://github.com/jens-maus/node-ical/blob/HEAD/index.js#L87 ical.fromURL
正在返回一个承诺,但我很难理解如何使用作为该承诺一部分的数据。有人可以帮我在这个文件(尤其是方法)中进行所需的更改parse
以满足我的期望吗?提前致谢。
/**
* IcalsController
*/
const ical = require('node-ical');
const months = ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec'];
const days = ['Sun', 'Mon', 'Tue', 'Wed', 'Thur', 'Fri', 'Sat'];
function normalize(ev_obj) {
return {
"uid": ev_obj.uid,
"start": ev_obj.start.toDateString(),
"end": ev_obj.end.toDateString(),
"start_ts": ev_obj.start,
"end_ts": ev_obj.end,
"user": ev_obj.organizer.val.split("mailto:")[1].split("@")[0], //TODO - use regex for extraction
"summary": ev_obj.summary,
"categories": ev_obj.categories,
"all_day": (ev_obj["event-allday"] == "true")
}
}
function decorate(data) {
//do something here and return a json object
//return json_object;
}
module.exports = {
parse: function (req, res) {
if (req.param("ical_url") == undefined) {
return res.status(400).send("ical_url is missing");
}
ical.fromURL( //refer - https://github.com/jens-maus/node-ical/blob/HEAD/index.js#L87
req.param("ical_url"),
{},
function (err, data) {
let normalized_data = [];
for (let k in data) {
if (data.hasOwnProperty(k)) {
if (data[k].type == 'VEVENT') {
normalized_data.push(normalize(data[k]));
}
}
}
}
);
//>>>>>> Here I want to call decorate function and pass normalized_data as parameter
let result = decorate(normalized_data)
return res.send(result);
},
};
解决方案
问题在于没有考虑方法的异步性质fromURL
。
代码正在调用fromURL
,这将导致在将来某个时间方法完成时调用回调,然后立即尝试将尚未收到的数据作为响应发送给客户端。
您需要在异步操作完成后发送响应,并且您实际上已经收到了一些数据,更像这样:
parse: function (req, res) {
if (req.param("ical_url") == undefined) {
return res.status(400).send("ical_url is missing");
}
ical.fromURL( //refer - https://github.com/jens-maus/node-ical/blob/HEAD/index.js#L87
req.param("ical_url"),
{},
function (err, data) {
let normalized_data = [];
for (let k in data) {
if (data.hasOwnProperty(k)) {
if (data[k].type == 'VEVENT') {
normalized_data.push(normalize(data[k]));
}
}
}
res.send(decorate(normalized_data)); << Response moved inside the callback.
}
);
}
虽然我实际上会建议,但您可以使用async/await
关键字作为更清洁的解决方案。
parse: async function (req, res) { << Mark method as async
if (req.param("ical_url") == undefined) {
return res.status(400).send("ical_url is missing");
}
// Await keyword lets us use data from a promise more like it were simpler synchronous code
const raw_data= await ical.fromURL( //refer - https://github.com/jens-maus/node-ical/blob/HEAD/index.js#L87
req.param("ical_url"),
{});
let normalized_data = [];
// Do your normalization of raw_data here
return res.send(decorate(noramlized_data));}