Cannot overwrite model once compiled Mongoose

Another reason you might get this error is if you use the same model in different files but your require path has a different case.

For example, in my situation I had require('./models/User') in one file, and then in another file where I needed access to the User model, I had require('./models/user').

I guess the lookup for modules & mongoose is treating it as a different file. Once I made sure the case matched in both it was no longer an issue.

The error is occurring because you already have a schema defined, and then you are defining the schema again. Generally what you should do is instantiate the schema once, and then have a global object call it when it needs it.

For example:

user_model.js

var mongoose = require('mongoose');var Schema = mongoose.Schema;var userSchema = new Schema({   name:String,   email:String,   password:String,   phone:Number,   _enabled:Boolean});module.exports = mongoose.model('users', userSchema);          

check.js

var mongoose = require('mongoose');var User = require('./user_model.js');var db = mongoose.createConnection('localhost', 'event-db');db.on('error', console.error.bind(console, 'connection error:'));var a1= db.once('open',function(){  User.find({},{},function (err, users) {    mongoose.connection.close();    console.log("Username supplied"+username);    //doSomethingHere   })});

insert.js

var mongoose = require('mongoose');var User = require('./user_model.js');mongoose.connect('mongodb://localhost/event-db');var new_user = new User({    name:req.body.name  , email: req.body.email  , password: req.body.password  , phone: req.body.phone  , _enabled:false });new_user.save(function(err){  if(err) console.log(err); });

I had this issue while 'watching' tests.When the tests were edited, the watch re-ran the tests, but they failed due to this very reason.

I fixed it by checking if the model exists then use it, else create it.

import mongoose from 'mongoose';import user from './schemas/user';export const User = mongoose.models.User || mongoose.model('User', user);