如何在另一个模型中使用mongoose模型？

const mongoose = require('mongoose');

const userSchema = new mongoose.Schema({
  name: String,
  age: Number,
  email: String
});

const User = mongoose.model('User', userSchema);

const User = require('./userModel'); // 假设userModel.js是包含User模型的文件

const orderSchema = new mongoose.Schema({
  user: {
    type: mongoose.Schema.Types.ObjectId,
    ref: 'User'
  },
  product: String,
  quantity: Number
});

const Order = mongoose.model('Order', orderSchema);

Order.findOne({ product: 'Apple' })
  .populate('user')
  .exec((err, order) => {
    if (err) {
      console.error(err);
    } else {
      console.log(order.user.name); // 输出关联的用户姓名
    }
  });