18

所以..我最难学习如何承诺。

我正在使用bluebird（https://github.com/petkaantonov/bluebird），正如我所建议的那样——为了驯服我的回调地狱。例子：

function login(req,res,con,mysql,P) {
var ref = undefined;
    con.getConnection(function(err,connection) {
        if (err) console.log("Get Connection Error.. "+err);
        con.query('SELECT password,id FROM player WHERE name='+mysql.escape(req.body.user),function(err,rows,fields) {
            if (err) throw err;
            if (!rows[0]) {
                res.send({
                    "msg":"Your username and or password was incorrect.",
                    "flag":true,
                    "title":": Login Failed"
                });
            }
            if (rows[0].password !== "undefined") {
                if (hash.verify(req.body.pass,rows[0].password)) {
                    req.session.loggedIn = true;
                    req.session.user = rows[0].id;
                    ref = new P(rows[0].id,con,req);
                    res.send({
                        "msg":"You have logged in!",
                        "flag":false,
                        "title":": Logged In"
                    });
                } else {
                    res.send({
                        "msg":"Your username and or password was incorrect.",
                        "flag":true,
                        "title":": Login Failed"
                    });
                }
            }
        });
        connection.release();
    });
    console.log(ref);
    return ref;
}

很恶心，到处都是回调，而且函数ref在查询回调执行完之前就返回了。

解决方案：承诺！

我尝试使用快速入门转换我的功能.. 所以我在创建连接之前promisefyAll我的mysql模块：

var mysql = require("mysql");
var Promise = require("bluebird");
Promise.promisifyAll(mysql);

我写了我的函数如下：

function login(req,res,con,mysql,P) {
    var ref = undefined;
    Promise.promisify(con.getConnection)().then(function(connection) { //updated line returns error no method promisify. Bluebird v. 1.1.1
        con.query('SELECT password,id FROM player WHERE name='+mysql.escape(req.body.user)).then(function(rows,fields) {
            if (hash.verify(req.body.pass,rows[0].password)) {
                req.session.loggedIn = true;
                req.session.user = rows[0].id;
                ref = new P(rows[0].id,con,req);
                res.send({
                    "msg":"You have logged in!",
                    "flag":false,
                    "title":": Logged In"
                });
            } else {
                res.send({
                    "msg":"Your username and or password was incorrect.",
                    "flag":true,
                    "title":": Login Failed"
                });
            }
        });
        return ref;
    });
}

但我不断得到TypeError: Cannot call method 'then' of undefined at Object.login (/var/www/post/posts.js:36:22)

和

TypeError: undefined is not a function at Pool.<anonymous> (/var/www/node_modules/mysql/lib/Pool.js:53:14)

错误。有人可以帮助我了解如何实现查询我的数据库的承诺（正确）吗？

编辑（接受回答后：）：这是我调用登录功能的方式：

app.post("/login",function(req,res) {
    Player = post.login(req,res,con,mysql,p);
    console.log(Player); // logs [Object object]
}); //inside the login function, it logs the object like it should
4

1 回答 1

11

当您对原型进行承诺时，承诺返回的方法将具有 *Async 后缀

承诺的想法是假装图书馆的设计初衷就是返回承诺。您不应在运行时在应用程序代码中调用 promisify，而应在应用程序引导初始化代码或类似代码中调用。

var mysql = require("mysql");
var Promise = require("bluebird");
//Only need to be called once per application so probably not here
Promise.promisifyAll(require("mysql/lib/Connection").prototype);
Promise.promisifyAll(require("mysql/lib/Pool").prototype);

function login(req,res,con,mysql,P) {
    return con.getConnectionAsync().then(function(connection) {
        return connection.queryAsync('SELECT password,id FROM player WHERE name='+
               mysql.escape(req.body.user)).spread(function(rows, fields) {
            if (hash.verify(req.body.pass,rows[0].password)) {
                req.session.loggedIn = true;
                req.session.user = rows[0].id;
                var ref = new P(rows[0].id,con,req);
                res.send({
                    "msg":"You have logged in!",
                    "flag":false,
                    "title":": Logged In"
                });
                return ref;
            } else {
                res.send({
                    "msg":"Your username and or password was incorrect.",
                    "flag":true,
                    "title":": Login Failed"
                });
            }
        }).finally(function() {
            connection.release();
        });
    });
}

未来版本将有更好的资源管理，您将能够：

function login(req,res,con,mysql,P) {
    return Promise.using(con.getConnectionAsync(), function(connection) {
        return connection.queryAsync('SELECT password,id FROM player WHERE name='+
               mysql.escape(req.body.user));
    }).spread(function(rows, fields) {
        if (hash.verify(req.body.pass,rows[0].password)) {
            req.session.loggedIn = true;
            req.session.user = rows[0].id;
            var ref = new P(rows[0].id,con,req);
            res.send({
                "msg":"You have logged in!",
                "flag":false,
                "title":": Logged In"
            });
            return ref;
        } else {
            res.send({
                "msg":"Your username and or password was incorrect.",
                "flag":true,
                "title":": Login Failed"
            });
        }
    });
}

如何使用结果：

app.post("/login",function(req,res) {
    post.login(req,res,con,mysql,p).then(function(Player) {

    }); 
})
于 2014-03-25T19:09:19.987 回答