Mongoose:无法填充ids的嵌套数组

const mongoose = require('mongoose');

const ParentSchema = new mongoose.Schema({
  children: [{
    type: mongoose.Schema.Types.ObjectId,
    ref: 'Child'
  }]
});

ParentSchema.virtual('populatedChildren', {
  ref: 'Child',
  localField: 'children',
  foreignField: '_id',
  justOne: false
});

const Parent = mongoose.model('Parent', ParentSchema);

Parent.findById(parentId)
  .populate('populatedChildren')
  .exec((err, parent) => {
    if (err) {
      // 错误处理
    } else {
      // parent对象中的populatedChildren属性将包含填充后的嵌套数组
    }
  });