开发者问题收集

如何修复:“无法读取未定义的属性‘then’”

2019-01-08
571

当我尝试从函数获取响应时遇到问题,我刚开始使用 Promises,所以也许我做错了什么。 当我启动我的应用程序时,我收到错误: 无法读取未定义的属性“then” 。 我做错了什么? 在我开始使用 Promises 之前,一切都运行良好,在我尝试更改应用程序逻辑后,它崩溃了。 我的主要文件如下:

/app.js

const request = require('request');
const yargs = require('yargs');

const geocode = require('./geocode/geocode')

const argv = yargs
    .options({
        a: {
            demand: true,
            alias: 'address',
            string: true,
            describe: 'Address to fetch weather for'
        }
    })
    .help()
    .alias('help', 'h')
    .argv;

geocode.geocodeAddress(argv.a)
.then((res) => {
    console.log(res);
},
(error) => {
    console.log(error);
})

我的地理编码文件:

/geocode/geocode.js
const request = require('request');

const geocodeAddress = (address) => {
    const encodedAddress = encodeURIComponent(address);

    request({
        url: `https://maps.googleapis.com/maps/api/geocode/json?key=myKey&address=${encodedAddress}`,
        json: true
    }, (err, res, body) => {
        return new Promise((resolve, reject) => {
            if(err){
                reject('Unable to connect to Google servers.')
            } else if (body.status === 'ZERO_RESULTS') {
                reject('Unable find any address.')
            } else if (body.status === 'OK') {
                const lat = body.results[0].geometry.location.lat;
                const lon = body.results[0].geometry.location.lng;
                const adrs = body.results[0].formatted_address;
                const answer = {
                    lat: lat,
                    lon: lon,
                    address: adrs
                };
                resolve(answer);
            }
        })
    })
};

module.exports.geocodeAddress = geocodeAddress;
2个回答

可能是因为您的 geocodeAddress 是一个常量,而不是一个异步函数。

盲拍尝试:

async geocodeAddress (address) {

就像@liam说的,尝试:

return request({...})
Joel Rodrigues
2019-01-08

为我解决问题的代码:

const request = require('request');

const geocodeAddress = (address) => {
    const encodedAddress = encodeURIComponent(address);

    return new Promise((resolve, reject) => { 
        request({
        url: `https://maps.googleapis.com/maps/api/geocode/json?key=myKey&address=${encodedAddress}`,
        json: true
    }, (err, res, body) => {
            if(err){
                reject('Unable to connect to Google servers.')
            } else if (body.status === 'ZERO_RESULTS') {
                reject('Unable find any address.')
            } else if (body.status === 'OK') {
                const lat = body.results[0].geometry.location.lat;
                const lon = body.results[0].geometry.location.lng;
                const adrs = body.results[0].formatted_address;
                const answer = {
                    lat: lat,
                    lon: lon,
                    address: adrs
                };
                resolve(answer);
            }
        })
    })
};

module.exports.geocodeAddress = geocodeAddress;
Valentin Mohis
2019-01-08