在下面的代码中,我试图将第一个和第二个查询的结果放在一个名为result
的全局变量中。问题是Promise.all()
没有等待查询完成并且在向then()
进行处理之前。
我该如何解决?
代码:
var result = {};
Promise.all([
connection.query('SELECT * FROM analysis',
function(err, rows, fields) {
if (err) throw err;
result.analysis = rows;
console.log("query 1");
}),
connection.query('SELECT * FROM analysis_description',
function(err, rows, fields) {
if (err) throw err;
result.analysis_description = rows;
console.log("query 2");
})
])
.then(function(result){
console.log(result);
console.log("result");
});
输出:
result
query 1
query 2
答案 0 :(得分:2)
就像在评论中所说的那样,你需要手动宣传异步调用:
queryAsync = query => new Promise((resolve, reject) => {
connection.query(query, (err, rows) => {
if(err) return reject(err)
resolve(rows)
})
})
或首选方式是使用bluebird
等库:
connection = require('bluebird').promisifyAll(connection)
您的代码可以修改为:
var result = {};
Promise.all([
connection.queryAsync('SELECT * FROM analysis').then(rows => result.analysis = rows),
connection.queryAsync('SELECT * FROM analysis_description').then(rows => result.analysis_description = rows)
]).then(function(result){
console.log(result);
console.log("result");
}).catch(e => console.error(e));
答案 1 :(得分:0)
谢谢大家!就像每个人都说的那样,问题出现在Promise.all()
的错误参数中。这是更改后的代码。
代码:
Promise.promisifyAll(require("mysql/lib/Connection").prototype)
var result = {};
Promise.all([
connection.queryAsync('SELECT * FROM analysis')
.then(function(rows){
console.log(rows);
result.analysis = rows;
}),
connection.queryAsync('SELECT * FROM analysis_description')
.then(function(rows){
result.analysis_description = rows;
})
])
.then(function(){
console.log(result);
console.log("result");
});