在將欄位保存到資料庫之前，我應該如何更改它的值？

我是 Node.js 的新手，我現在正在嘗試執行 CRUD 操作。我有這個功能可以將資料保存到 mongoDB 資料庫，但問題是我試圖在將一個特定欄位保存到資料庫之前更改它的值。問題是我的資料首先被保存，然后正在執行計算。這是我的帖子功能：

router.post('/', async(req, res) => {
    const reservation = new Reservation({
        guestID: mongoose.Types.ObjectId(req.body.guestID),
        roomID: mongoose.Types.ObjectId(req.body.roomID),
        checkIn: req.body.checkIn,
        checkOut: req.body.checkOut,
        numberOfAdults: req.body.numberOfAdults,
        totalCost: req.body.totalCost,
        numberOfChildren: req.body.numberOfChildren
    })
    try
    {
        
        const reservationRecord = await reservation.save()
        res.json(reservationRecord)
    }
    catch(err)
    {
        console.log(err)
        res.send("Error")
    }
})

這是架構

const mongoose = require('mongoose')
const axios = require('axios')

const reservationSchema = new mongoose.Schema({
    guestID: {
        type: mongoose.SchemaTypes.ObjectId,
        required: true
    },
    roomID: {
        type: mongoose.SchemaTypes.ObjectId,
        required: true
    },
    checkIn: {
        type: Date,
        required: true
    },
    checkOut: {
        type: Date,
        required: true
    },
    numberOfAdults: {
        type: Number,
        required: true
    },
    numberOfChildren: {
        type: Number,
        required: true
    },
    totalCost: {
        type: Number,
        required: false,
        default: 0
    }
})
reservationSchema.pre('save', function(next){
        var date1 = new Date(this.checkIn);
        var date2 = new Date(this.checkOut);
        var diff = Math.abs(date1.getTime() - date2.getTime());
        var diffDays = Math.ceil(diff / (1000 * 3600 * 24));
        console.log(diffDays)
        var roomCost
        var totalRoomCost 
        axios.get("http://localhost:5555/rooms/"   this.roomID).then((response) => {
                console.log(response)
                roomCost = response.data.cost;
                console.log("room cost is "   roomCost)
                totalRoomCost = (this.numberOfAdults   this.numberOfChildren) * response.data.cost * diffDays
                this.totalCost = totalRoomCost
            })
            //this.totalCost = (this.numberOfAdults   this.numberOfChildren) * roomCost * diffDays
            console.log(this.totalCost)
            next()
})
const Reservation = mongoose.model('reservation', reservationSchema)

module.exports = Reservation

我想在將 totalCost 保存到資料庫之前更改它的值。有人可以讓我知道代碼有什么問題嗎？謝謝！

uj5u.com熱心網友回復：

在創建新Reservation實體之前，您應該只處理 POST 方法中的計算：

router.post('/', async (req, res) => {
  try {
    const {
      numberOfChildren,
      numberOfAdults,
      roomID,
      checkIn,
      checkOut,
    } = req.body;

    var date1 = new Date(checkIn);
    var date2 = new Date(checkOut);
    var diff = Math.abs(date1.getTime() - date2.getTime());
    var diffDays = Math.ceil(diff / (1000 * 3600 * 24));

    const room = await Room.findById(roomID)

    const newTotalCost = (numberOfAdults   numberOfChildren) * room.cost * diffDays;
    const reservation = new Reservation({
      ...req.body,
      totalCost: newTotalCost,
    });
    const reservationRecord = await reservation.save();
    res.json(reservationRecord);
  } catch (err) {
    console.log(err);
    res.send('Error');
  }
});

當然，reservationSchema.pre('save')在這種情況下，該函式是不必要的。

標籤：节点.js mongodb 猫鼬

上一篇：“node.js的mongodb物件建模”是什么意思？

下一篇：“DockerforWindows”環境中節點紅色的連接錯誤