Question

我想在我的一个集合上设置一个自动递增ID（_id太长）。为此，我创建了一个＆＃39; counter＆＃39;收集按照Mongos官方网站（下文）等多个帖子的建议收集：

var mongoose = require('mongoose');

module.exports = mongoose.model('Counter', {
    _id: String,
    sequence_value: Number
});

然后我插入一个带有seq值的计数器。下面是在创建新项目时调用的函数。添加新项的逻辑工作和获取计数器值的查询在console.log(data.sequence_value);返回sequence_value的范围内工作。

但我不能通过执行以下操作将sequence_value应用于项目创建逻辑：

 module.exports.newitem = function(req, res){            
            var nextId = Counter.findByIdAndUpdate(
                {_id: 'productid'},
                { $inc: { incr: 1 } },
                function (err, data) {
                    if(err){
                        console.log(err.stack || err.message)
                    } else{
                        console.log("successful")
                    }
                    console.log(data.sequence_value);
                    return data.sequence_value
                });

        var item = new Item();
        item.itemId = nextId;

        // Save the item that has been sent.
        item.save();

        // If adding the user is successful. Send back the user.
        res.json(req.body);
    };

逻辑的当前脱节版本如下：

module.exports.newitem = function(req, res){

        Counter.findByIdAndUpdate(
            {_id: 'productid'},
            { $inc: { incr: 1 } },
            function (err, data) {
                if(err){
                    console.log(err.stack || err.message)
                } else{
                    console.log("successful")
                }
                console.log(data.sequence_value);
            });



    var item = new Item();
    item.itemId = "2000";

    // Save the item that has been sent.
    item.save();

    // If adding the user is successful. Send back the user.
    res.json(req.body);
};

希望以上是有道理的。非常感谢任何帮助。

Answer 1

findByIdAndUpdate是一个异步函数。你应该把你的逻辑放在回调本身的回调中，如下所示：

        var nextId = Counter.findByIdAndUpdate(
            {_id: 'productid'},
            { $inc: { incr: 1 } },
            function (err, data) {
                if(err){
                    console.log(err.stack || err.message)
                } else{
                    console.log("successful")
                }
                console.log(data.sequence_value);

                var item = new Item();
                item.itemId = data.sequence_value;

                 // Save the item that has been sent.
                item.save();  // arguably, your response would come in the .save() callback, if you care about whether that was successful or not. 

               // If adding the user is successful. Send back the user.
                res.json(req.body);
            });


};

Answer 2

以为我会用保罗的答案把我最终的结果放在一边。

module.exports.newitem = function(req, res){

        Counter.findByIdAndUpdate(
            {_id: 'productid'},
            { $inc: { sequence_value: 1 } },
            { "upsert": true },
            function (err, data) {
                if(err){
                    console.log(err.stack || err.message)
                } else{
                    var item = new Item();
                    item.itemId = data.sequence_value;
                    ...

                    // Save the item that has been sent.
                    item.save();

                    // If adding the user is successful. Send back the user.
                    res.json(req.body);
                    console.log("successful")
                }
            });
};

在node.js中使用计数器集合来增加ID字段

2 个答案: