Mongoose不会填充数组或对象

const mongoose = require('mongoose');

// 定义模式
const userSchema = new mongoose.Schema({
  name: String,
  posts: [{ type: mongoose.Schema.Types.ObjectId, ref: 'Post' }]
});

const postSchema = new mongoose.Schema({
  title: String,
  content: String
});

// 定义模型
const User = mongoose.model('User', userSchema);
const Post = mongoose.model('Post', postSchema);

// 查询用户并填充其关联的帖子
User.findOne({ name: 'John' })
  .populate('posts')
  .exec((err, user) => {
    if (err) {
      console.error(err);
    } else {
      console.log(user);
    }
  });