检查多个Mongoose集合中特定字段的总和

Question

我正在尝试为餐厅预订mongoose架构，但我不希望人们能够预订，如果有人＆＃39;所有收藏中的价值都超过50。

var reservationSchema = new mongoose.Schema ({
    people: Number,
    date: String,
    name: String,
    email: String
});

var Reservation = mongoose.model("Reservation", reservationSchema);

app.post('/reservation', (req, res) => {
    var people = parseFloat(req.body.people);
    var date = req.body.date;
    var name = req.body.name;
    var email = req.body.email;   

    var newReservation = {people: people, date: date, name: name, email: email};
    Reservation.create(newReservation, (err, newlyCreated) => {
        if(err) {
            console.log(err);
        } 
        else {
            res.redirect('/');
        }
    })
});

如何过滤所有集合以查找从人们添加所有值时的数字是什么？

Answer 1

您需要使用聚合管道来总计人数。如果计数小于50，请创建新预订，否则显示一些消息。

为此，您可以使用statics方法。

var reservationSchema = new mongoose.Schema ({
    people: Number,
    date: String,
    name: String,
    email: String
});


reservationSchema.statics = {
    createIfSpaceAvailable : function(newReservation, done){
        var Reservation = this;
        Reservation.aggregate([
        {
         $group:{
             _id: null,
             noOfPeople: { $sum: "$people"}
         }
        }], 
        function(err, result){
        if(err){
            return done(err);
        }
        else if(result[0].noOfPeople > 50){
            // do something
        }
        else{
            Reservation.create(newReservation, (err, newlyCreated) => {
                if(err) {
                     return done(err);
                } 
                else {
                     return done();
                }
            })
        }
    })
   }
};
var Reservation = mongoose.model("Reservation", reservationSchema);

app.post('/reservation', (req, res) => {
    var people = parseFloat(req.body.people);
    var date = req.body.date;
    var name = req.body.name;
    var email = req.body.email;   

    var newReservation = {people: people, date: date, name: name, email: email};
    Reservation.createIfSpaceAvailable(newReservation, (err, newlyCreated) => {
        if(err) {
            console.log(err);
        } 
        else {
            res.redirect('/');
        }
    })
});

Answer 2

您可以使用聚合管道 - 请参阅：

• https://docs.mongodb.com/manual/core/aggregation-pipeline/

，特别是$sum运算符：

• https://docs.mongodb.com/manual/reference/operator/aggregation/sum/

顺便说一句，因为Node v4.x而不是写：

var newReservation = {people: people, date: date, name: name, email: email};

您可以使用更短的语法：

var newReservation = {people, date, name, email};

请参阅：

• https://developer.mozilla.org/en/docs/Web/JavaScript/Reference/Operators/Object_initializer