您好,我是异步调用的新手,希望您能为我提供帮助。
我有一个.then链,我想在链的中间调用一个返回promise的函数,但是我碰巧该链不等待它具有promise函数的结果,并且继续运行而没有等待中
var User = require('../models/user_model');
var mapbox = require('./helper/request_api_mapbox');
findOne_mapbox: (req, res) => {
User.findById(req.params.id)
.then(user => {
...
return user.address;
})
.then(function (adress_to_mapbox)
{
// mapbox.connect_mapbox returns a promise
mapbox.connect_mapbox(adress_to_mapbox)
.then(mapbox_coordinates => {
//inside this console.log is not read it
console.log("2 then mapbox_coordinates ", mapbox_coordinates)
return Promise.resolve(body);
})
})
.then( mapbox_coordinates => {
// in this console.log mapbox_coordinates returns undefined
console.log("last promise mapbox_coordinates",
mapbox_coordinates)
// I want to return mapbox_coordinates
return res.status(200).send({
"response": "I only receive this string "
});
})
}
promise函数为:
'use strict'
const rp = require('request-promise');
const access_token_mapbox = 'bla bla bla private';
function connect_mapbox(adress_to_mapbox) {
return new Promise((resolve, reject) => {
var options = {
method: 'GET',
uri: 'https://api.mapbox.com/geocoding/v5/mapbox.places/' + adress_to_mapbox + '.json?access_token=' + access_token_mapbox,
json: true // Automatically stringifies the body to JSON
};
rp(options)
.then(body => {
if (body.hasOwnProperty('errcode') && body.errcode != 0) {
return Promise.reject(body);
}
console.log("inside connect_mapbox function on mapbox_model 2", body)
return Promise.resolve(body);
})
.catch(err => {
debug(err);
return Promise.reject(err);
})
})
}
module.exports = { connect_mapbox };
在promise函数中,我可以在console.log中看到它使api正确调用并且响应主体正常。
答案 0 :(得分:0)
我正在开始编程,尽管不知道它是否最正确,我还是通过以下方式解决了问题
我通过将connect_mapbox promise函数转换为async await并将.then链转换为async await来解决了这个问题,
'use strict'
const rp = require('request-promise');
const access_token_mapbox = 'bla bla bla private';
async function connect_mapbox(adress_to_mapbox) {
try {
var options = {
method: 'GET',
uri: 'https://api.mapbox.com/geocoding/v5/mapbox.places/' + adress_to_mapbox + '.json?access_token=' + access_token_mapbox,
json: true // Automatically stringifies the body to JSON
};
let response = await rp(options);
console.log("inside connect_mapbox function on mapbox_model", response)
if (response.hasOwnProperty('errcode') && body.errcode != 0) {
return Promise.reject(response);
}
return Promise.resolve(response);
}catch(error) {
return Promise.reject(error);
}
}
module.exports = { connect_mapbox };
.then链像
var User = require('../models/user_model');
var mapbox = require('./helper/request_api_mapbox');
findOne_mapbox: (req, res) => {
User.findById(req.params.id)
.then(user => {
...
return user.address;
})
.then(async function (adress_to_mapbox)
{
console.log("adress_to_mapbox thit could be deleted", adress_to_mapbox)
let mapbox_response = await mapbox.connect_mapbox(adress_to_mapbox)
console.log("async mapbox_response", mapbox_response)
return res.status(200).send({
mapbox_response
});
})
...
}