如何在Mongoose中为现有模式定义嵌套对象？

npm install mongoose

const mongoose = require('mongoose');
mongoose.connect('mongodb://localhost/my_database', { useNewUrlParser: true, useUnifiedTopology: true });

const Schema = mongoose.Schema;

const addressSchema = new Schema({
  street: String,
  city: String,
  state: String,
  zip: String
});

const userSchema = new Schema({
  firstName: String,
  lastName: String,
  age: Number,
  address: addressSchema
});

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

// 创建用户
const user = new User({
  firstName: 'John',
  lastName: 'Doe',
  age: 30,
  address: {
    street: '123 Main St',
    city: 'Anytown',
    state: 'CA',
    zip: '12345'
  }
});

user.save(function (err) {
  if (err) return console.error(err);
  console.log('User saved successfully');
});

// 查询用户
User.findOne({ firstName: 'John', lastName: 'Doe' }, function (err, user) {
  if (err) return console.error(err);
  console.log('Found user:', user);
});

// 更新用户地址
User.findOne({ firstName: 'John', lastName: 'Doe' }, function (err, user) {
  if (err) return console.error(err);
  user.address.street = '456 New St';
  user.save(function (err) {
    if (err) return console.error(err);
    console.log('User address updated successfully');
  });
});