如何处理具有循环依赖性的父子猫鼬模式？

Question

我的父级模型和子级模型require彼此对应，所以我有cyclic dependencies。

由于循环依赖性，const Parent = require("./Parent");并未将Parent导入Child.js中。因此，当我致电child.remove()时，我得到TypeError: Parent.findById is not a function。

他们互相引用的原因是，当删除一个孩子时，其引用ID也将从其父对象中删除。而且，当删除父对象时，我还需要从数据库中删除它的所有子对象。这些是在模式的pre hooks

中完成的

在没有这种周期性依赖关系而导致错误的情况下，我该如何照顾删除孩子在其父母中的引用以及父母的孩子？

Parent.js

const mongoose = require('mongoose');
const Child = require('./Child');

const parentSchema = new mongoose.Schema(
  {
    name: String,
    childrenIds: [
      {
        type: mongoose.Schema.Types.ObjectId,
        ref: 'child',
      },
    ],
  },
  { timestamps: { createdAt: 'created_at' } }
);

parentSchema.pre('remove', async function (next) {
  await Child.deleteMany({ _id: { $in: this.childrenIds } });
  next();
});

const Parent = mongoose.model('Parent', parentSchema);
module.exports = Parent;

Child.js：

const mongoose = require('mongoose');
const Child = require('./Child');

const parentSchema = new mongoose.Schema(
  {
    name: String,
    childrenIds: [
      {
        type: mongoose.Schema.Types.ObjectId,
        ref: 'child',
      },
    ],
  },
  { timestamps: { createdAt: 'created_at' } }
);

parentSchema.pre('remove', async function (next) {
  await Child.deleteMany({ _id: { $in: this.childrenIds } });
  next();
});

const Parent = mongoose.model('Parent', parentSchema);
module.exports = Parent;

app.js：

const Parent = require('./models/Parent');
const Child = require('./models/Child');
const mongoose = require('mongoose');

mongoose
  .connect('mongodb://localhost/circularDep_db', {
    useNewUrlParser: true,
    useUnifiedTopology: true,
    useFindAndModify: true,
  })
  .then(() => console.log('Successfully connect to MongoDB.'))
  .catch((err) => console.error('Connection error', err));

const addChild = async (parent, child) => {
  child.parentId = parent._id;
  await child.save();
  parent.childrenIds.push(child);
  await parent.save();
};

async function run() {
  const parent = await Parent.create({ name: 'Caryn' });
  const child = await Child.create({ name: 'Dashie' });
  const child2 = await Child.create({ name: 'Chappie' });
  await addChild(parent, child);
  await addChild(parent, child2);
  await child.remove(); // throws a type error
  await parent.remove();
}

run();