問(wèn)題描述

我在用node查詢(xún)數(shù)據(jù)庫(kù)中使用如下代碼：var _password =mysql.query(table,' where name = ' + '’' + name + '’','password');其中mysql.query為query(table,others,column){

var connection = this.connection; var sql; if(column) sql = 'select ' + column + ' from ' + table; else{sql = 'select * from ' + table;} if(others) sql += ' ' + others; console.log(sql); var result; connection.query(sql,function(err,rows,fields){if(err){ throw err;}if(rows.length > 1){ rows.forEach(function(row){console.log(row); });}else if(rows.length == 1){ console.log(rows[0]); rows = rows[0];} else{ console.log('沒(méi)有數(shù)據(jù)');}return rows; }); console.log(’result:’); console.log(result); return result;}

最終的結(jié)果是：

很顯然query之后的語(yǔ)句先執(zhí)行了，此處無(wú)法使用yield，請(qǐng)大神指教

問(wèn)題解答

rows.forEach(function(row){ console.log(row);});

這里面的循環(huán)是異步的，所以出問(wèn)題了，你要控制住異步。

給你一個(gè)例子，我剛學(xué)著寫(xiě)，應(yīng)該寫(xiě)的不咋地，但是可以給你演示如何控制異步。

這里是引用的cc這個(gè)model里的，不寫(xiě)全了，大概看一下 getGrades: async () => { return new Promise((resolve, reject) => { db.pool.query(’SELECT * FROM set_grades’, function (err, rows) {if(rows){ resolve(rows);}else{ console.log(err); reject(err);} }); }); }, getTerms: async (grade_id) => { return new Promise((resolve, reject) => { db.pool.query(’SELECT * FROM set_terms WHERE grade_id = ?’, grade_id,function (err, rows) {if(rows){ resolve(rows);}else{ console.log(err); reject(err);} }); }); },// ------------創(chuàng)建合同-------------exports.createContract = async (ctx, next)=> { // 1 獲取types let types = new Array(); await cc.getTypes().then(result => { types = result; }); // 2 獲取cats let cats = new Array(); await cc.getCats().then(result => { cats = result; }); // 3 獲取grades let grades = new Array(); await cc.getGrades().then(result => { grades = result; }); // 4 獲取terms // 遍歷每一個(gè)grades，然后獲取下面的terms，合并到grades let forGrades = async function(grades) { for(let grade of grades){ await cc.getTerms(grade.grade_id).then(result => {grade.terms = result; }); } } await forGrades(grades); await ctx.render(’cc/createContract’,{ title: ’Create Contract’, student_id: ctx.params.id, types: types, cats: cats, grades: grades })}