javascript - 类型错误 : Cannot read property 'rows' of undefined

Question

关注 Getting started with Postgres in your React app 时，在处理和导出 getMerchants、createMerchant 和 deleteMerchant 函数时，我收到此错误 -- 类型错误:无法读取未定义的属性“行”，这是怎么回事？这可能是我所缺少的非常小的东西。 getMerchants 和 resolve(results.rows) 发生错误

const Pool = require('pg').Pool
const pool = new Pool({
    user: 'my_user',
    host: 'localhost',
    database: 'my_database',
    password: 'root',
    port: 5432,
});

const getMerchants = () => {
    return new Promise(function(resolve, reject) {
        pool.query('SELECT * FROM userIds ORDER BY id ASC', (error, results) => {
            if (error) {
                reject(error)
            }
            resolve(results.rows);
        })
    })
}
const createMerchant = (body) => {
    return new Promise(function(resolve, reject) {
        const { name, email } = body
        pool.query('INSERT INTO userIds (name, email) VALUES ($1, $2) RETURNING *', [name, email], (error, results) => {
            if (error) {
                reject(error)
            }
            resolve(`A new merchant has been added added: ${results.rows[0]}`)
        })
    })
}
const deleteMerchant = () => {
    return new Promise(function(resolve, reject) {
        const id = parseInt(Request.params.id)
        pool.query('DELETE FROM userIds WHERE id = $1', [id], (error, results) => {
            if (error) {
                reject(error)
            }
            resolve(`Merchant deleted with ID: ${id}`)
        })
    })
}

module.exports = {
    getMerchants,
    createMerchant,
    deleteMerchant,
}

Answer 1

根据我的评论:

Second parameter for query is the query parameters, and not a callback function. Pass in [], if you do not have parameters. Other than that, your code looks largely redundant. You should follow proper async pattern that library offers, and not re-create all those useless promises...

const getMerchants = () => pool.query('SELECT * FROM userIds ORDER BY id ASC');

然后像这样使用它:

const {rows} = await getMerchants();