Mongoose Model.UpdateMany is not a function error on pre hook, this is working for similar schema and on the resolver

Question

This throws error Station.UpdateMany is not a function but works when on resolver.

const mongoose = require('mongoose')
const Station = require('./Station')

const customerSchema = mongoose.Schema({
  stations: [{
    type: mongoose.Schema.Types.ObjectId,
    ref: 'Station'
  }]
 })

customerSchema.pre('save', async function() {
  await Station.updateMany( { _id:{ $in: this.stations } } ,{ $addToSet:{ customers: this._id } })
})    

module.exports = mongoose.model('Customer', customerSchema)

Similar works on Station Schema

const mongoose = require('mongoose')
const uniqueValidator = require('mongoose-unique-validator')
const Customer = require('./Customer')

const stationSchema = new mongoose.Schema({
  customers: [{
    type: mongoose.Schema.Types.ObjectId,
    ref: 'Customer'
  }]
})

stationSchema.plugin(uniqueValidator)

stationSchema.pre('save',async function() {
  await Customer.updateMany({ _id:{ $in: this.customers } }, { $addToSet:{ stations: this._id } })
})

module.exports =  mongoose.model('Station',stationSchema)

No Idea why one works and not other?

Answer 1

Finally figured it out, the issue was because of cyclic dependency Station => Customer => Station. I solved it by importing the Model inside the pre hook instead of beginning on both Station and Customer. Hope this will help somebody.

   customerSchema.pre('save', async function() {
      const Station = require('./Station')
      await Station.updateMany( { _id:{ $in: this.stations } } ,{ $addToSet:{ customers: this._id } })
    })