Mongoose：.findById 不是函数

Question

我有 2 个不同的模型 User 和 Leave，我想对其进行设置，以便每当删除休假时，该休假也将从用户文档中的叶子数组中提取。

用户模型：

const mongoose = require('mongoose');
const Schema = mongoose.Schema;
const muv = require('mongoose-unique-validator');
const Leave = require('./leave');
const { ObjectID } = require('mongodb');

var schema = new Schema({
  fullName: {
    type: String,
    required: true,
    unique: true
  },
  leaveCredits: {
    type: Number
  },
  filedLeaves: [{
    type: Schema.Types.ObjectId,
    ref: 'Leave'
  }]
}, {
  usePushEach: true
});

schema.plugin(muv);

schema.pre('remove', function (next) {
  let user = this;
  let toDelete = [];
  user.filedLeaves.forEach(function(item) {
    Leave.findByIdAndRemove(new ObjectID(item), (err, succ) => {
      if (succ) {
        console.log(`${item} Deleted`);
      }
    });
  });
  next();
});

module.exports = mongoose.model('User', schema);

留下型号：

const mongoose = require('mongoose');
const Schema = mongoose.Schema;
const User = require('../models/user');
const { ObjectID } = require('mongodb');

var schema = new Schema({
  userId: {
    type: Schema.Types.ObjectId,
    ref: 'User'
  },
  status: {
    type: String,
    required: true
  },
  start: {
    type: String,
    required: true
  },
  end: {
    type: String,
    required: true
  },
  type: {
    type: String,
    required: true
  }
});

// makes sure that the removed date is also removed from the User's leave array
schema.pre('remove', function (next) {
  let leave = this;
  User.findById(new ObjectID(leave.userId), function (err, user) {
    user.filedLeaves.pull(leave._id);
    user.save();
  });
  next();
});

module.exports = mongoose.model('Leave', schema);

它一直给我一个错误，User.findById is not a function但我很确定我已经将两者正确导出为模型，因为除了我现在遇到的这个小问题之外，我的整个应用程序都可以正常工作。

尝试用谷歌搜索，但我看到的任何东西都没有帮助我解决这个问题。

编辑： 尝试仅使用 find() 但仍然抛出相同的错误，它不是一个函数。

Answer 1

您遇到的问题是您的两种模式都需要另一种模式才能工作。这是一个循环需求问题。

为了使其工作，您可以使用如下修复：

// makes sure that the removed date is also removed from the User's leave array
schema.pre('remove', function (next) {
  const User = require('../models/user');  

  let leave = this;

  User.findById(new ObjectID(leave.userId), function (err, user) {
    user.filedLeaves.pull(leave._id);
    user.save();
  });
  next();
});

schema.pre('remove', function (next) {
  const Leave = require('./leave');

  let user = this;
  let toDelete = [];

  user.filedLeaves.forEach(function(item) {
    Leave.findByIdAndRemove(new ObjectID(item), (err, succ) => {
      if (succ) {
        console.log(`${item} Deleted`);
      }
    });
  });
  next();
});

我们仅在被调用时才提出要求pre。这避免了循环问题。