Node.js mysql 查询传递给 async.waterfall 中的下一个函数

Question

我在 node.js 中有一些使用 express 的代码。我将一个调用路由到从 mysql 数据库请求数据，我想要做的是将它传递给另一个函数，以将返回的 json 从表格形式（表查询）重组为层次结构类型 json。

我已经单独测试了脚本以重构我的 sql 查询的输出。但是，我无法将它从我的查询函数传递到我的新脚本（函数）

我只是没有看到我做错了什么。请提供任何帮助，谢谢。

exports.get_site_menu = function (req, res) {
    var dbc;
    console.log('In menu setup');
    async.waterfall([
        // get a connection

        function (callback) {
            db.db(callback);
        }

        ,
        querylookup, modifyjson
    ], completed);

    function querylookup(dbclient, res) {
        dbc = dbclient;
        dbc.query("SELECT categories, " +
            "subcategories, " +
            "pid, " +
            "title, " +
            "description " +
            "FROM MENU_SELECT_ACTIVE_VIEW " +
            "where company_id = ? and site_id = ?", [req.query.companyid, req.query.siteid], res);
    }

    function modifyjson(err, res) {

        categories = [];

        console.log('results ' + res);

        res.forEach(function (entry) {
            var cindex = categories.map(function (category) {
                return category.name;
            }).indexOf(entry.categories);

            console.log(cindex);
            if (cindex < 0) {
                // Not found in categories array
                cindex = categories.push({
                    name: entry.categories,
                    subcategories: []
                }) - 1; // -1 to fix the index
            }
            // Lets search the subcategory
            var category = categories[cindex];

            var sindex = category.subcategories.map(
                function (subcategory) {
                    return subcategory.name;
                }
            ).indexOf(entry.subcategories);

            if (sindex < 0) {
                // Not Found
                sindex = category.subcategories.push({
                    name: entry.subcategories,
                    items: []
                }) - 1;
            }
            // Subcategory exists. Just push
            category.subcategories[sindex].items.push({
                pid: entry.pid,
                description: entry.description,
                title: entry.title
            });
        });

        menu = {
            menu: {
                categories: categories
            }
        };
        console.log('menu ' + menu);
    }


    function completed(err, menu, fields) {
        if (dbc) dbc.end();
        if (err) {
            callback(err);
        } else {
            console.log(menu);
            res.contentType('json');
            res.send(JSON.stringify(menu));
        }
    }
};

Answer 1

您需要将每个结果传递给自己的回调以传递下一个函数。我已经像这样重构了你的代码；

exports.get_site_menu = function (req, res) {
    var dbc;
    console.log('In menu setup');
    async.waterfall([
        // get a connection

        function (callback) {
            db.db(callback, some_result);
        },
        function querylookup(dbclient, res, callback) {
            dbc = dbclient;
            dbc.query("SELECT categories, " +
                "subcategories, " +
                "pid, " +
                "title, " +
                "description " +
                "FROM MENU_SELECT_ACTIVE_VIEW " +
                "where company_id = ? and site_id = ?", [req.query.companyid, req.query.siteid], res);
                callback(null, result_from_queryLookup);
        },
        function modifyjson(err, res, callback) {

            categories = [];

            console.log('results ' + res);

            res.forEach(function (entry) {
                var cindex = categories.map(function (category) {
                    return category.name;
                }).indexOf(entry.categories);

                console.log(cindex);
                if (cindex < 0) {
                    // Not found in categories array
                    cindex = categories.push({
                        name: entry.categories,
                        subcategories: []
                    }) - 1; // -1 to fix the index
                }
                // Lets search the subcategory
                var category = categories[cindex];

                var sindex = category.subcategories.map(
                    function (subcategory) {
                        return subcategory.name;
                    }
                ).indexOf(entry.subcategories);

                if (sindex < 0) {
                    // Not Found
                    sindex = category.subcategories.push({
                        name: entry.subcategories,
                        items: []
                    }) - 1;
                }
                // Subcategory exists. Just push
                category.subcategories[sindex].items.push({
                    pid: entry.pid,
                    description: entry.description,
                    title: entry.title
                });
            });

            menu = {
                menu: {
                    categories: categories
                }
            };
            console.log('menu ' + menu);
            callback(null, menu, fields);
        }
    ], function completed(err, menu, fields) {
        if (dbc) dbc.end();
        if (err) {
            callback(err);
        } else {
            console.log(menu);
            res.contentType('json');
            res.send(JSON.stringify(menu));
        }
    });
};

尤其是回调部分要小心。