Cannot overwrite model once compiled Mongoose

Question

Not Sure what I m doing wrong  here is my check js  var db   mongoose createConnection  localhost    event-db    db on  error   console error bind console   connection error       var a1  db once  open  function    var user   mongoose model  users            name String         email String         password String         phone Number         enabled Boolean           user find       function  err  users        mongoose connection close        console log  Username supplied  username         doSomethingHere              and here is my insert js  var mongoose   require  mongoose    mongoose connect  mongodb   localhost event-db    var user   mongoose model  users         name String       email String       password  String       phone Number        enabled Boolean         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             Whenever I m trying to run check js  I m getting this error  Cannot overwrite  users  model once compiled   I understand that this error comes due to mismatching of Schema  but I cannot see where this is happening   I m pretty new to mongoose and nodeJS   Here is what I m getting from the client interface of my MongoDB    MongoDB shell version  2 4 6 connecting to  test   gt  use event-db    switched to db event-db   gt  db users find          id    ObjectId  52457d8718f83293205aaa95          name     MyName         email     myemail me com         password     myPassword         phone    900001123         enable    true        gt

User · Answer

This problem might occur if you define 2 different schema s with same Collection name

User · Answer

You can easily solve this by doing   delete mongoose connection models  users    const usersSchema   mongoose Schema         export default mongoose model  users   usersSchema

User · Answer

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

User · Answer

I solved this issue by doing this    Created Schema - Users    models Users js const mongoose   require  quot mongoose quot     const Schema   mongoose Schema   export const userSchema   new Schema                 Then in other files    Another file    index js import   userSchema   from  quot    models Users quot   const conn   mongoose createConnection process env CONNECTION STRING        useNewUrlParser  true      useUnifiedTopology  true      conn models       const Users   conn model  quot Users quot   userSchema   const results   await Users find       Better Solution let User  try     User   mongoose model  quot User quot      catch     User   mongoose model  quot User quot   userSchema      I hope this helps

User · Answer

To Solve this check if the model exists before to do the creation   if   mongoose models entityDBName       return mongoose model entityDBName  entitySchema     else     return mongoose models entityDBName

User · Answer

Here is one more reason why this can happen  Perhaps this can help someone else  Notice the difference  Members vs Member  They must be the same    export default mongoose models Members    mongoose model  Member   FamilySchema   Change to  export default mongoose models Member    mongoose model  Member   FamilySchema

User · Answer

I know there is an accepted solution but I feel that the current solution results in a lot of boilerplate just so that you can test Models   My solution is essentially to take you model and place it inside of a function resulting in returning the new Model if the Model has not been registered but returning the existing Model if it has   function getDemo           Create your Schema   const DemoSchema   new mongoose Schema       name  String      email  String            collection   demo            Check to see if the model has been registered with mongoose      if it exists return that model   if  mongoose models  amp  amp  mongoose models Demo  return mongoose models Demo      if no current model exists register and return new model   return mongoose model  Demo   DemoSchema     export const Demo   getDemo     Opening and closing connections all over the place is frustrating and does not compress well   This way if I were to require the model two different places or more specifically in my tests I would not get errors and all the correct information is being returned

User · Answer

I had the same problem  reason was I defined schema an model in a JS function   they should be defined globally in a node module  not in a function

User · Answer

You are using mongoose model with the same variable name  user  in check js and insert js

User · Answer

If you are working with expressjs  you may need to move your model definition outside app get   so it s only called once when the script is instantiated

User · Answer

So Another Reason why 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 look up for modules  amp  mongoose is treating it as a different file  Once I made sure the case matched in both it was no longer an issue

User · Answer

I just have a mistake copy pasting  In one line I had same name that in other model  Ad model    const Admin   mongoose model  Ad   adminSchema     Correct is   const Admin   mongoose model  Admin   adminSchema     By the way  if someone have  auto-save   and use index for queries like     adSchema   index  title  text   description  text   phone  text   reference  text      It has to delete index  and rewrite for correct model     adminSchema   index  title  text   description  text   phone  text   reference  text

User · Answer

The reason of this issue is    you given the model name  users  in the line   lt  lt  lt var user   mongoose model  users    gt  gt  gt  in check js file  and again the same model name you are giving in the insert file  lt  lt  lt  var user   mongoose model  users     gt  gt  gt  in insert js  This  users  name shouldn t be same when you declare a model that should be different  in a same project

User · Answer

For  all people ending here because of a codebase with a mix of Typegoose and Mongoose     Create a db connection for each one     Mongoose     module exports   db mongoose model  Car   CarSchema     Typegoose    db typegoose model  Car   CarModel schema   cars

User · Answer

is because your schema is already  validate before create new schema   var mongoose   require  mongoose    module exports   function      var db   require     libs db-connection        schema de mongoose var Schema   require  mongoose   Schema   var Task   Schema       field1  String      field2  String      field3  Number      field4  Boolean      field5  Date     if mongoose models  amp  amp  mongoose models tasks  return mongoose models tasks   return mongoose model  tasks   Task

User · Answer

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

User · Answer

This happened to me when I write like this   import User from     myuser User js     However  the true path is     myUser User js

User · Answer

The schema definition should be unique for a collection  it should not be more then one schema for a collection

User · Answer

If you made it here it is possible that you had the same problem i did  My issue was that i was defining another model with the same name   I called my gallery and my file model  File   Darn you copy and paste

User · Answer

There is another way to throw this error   Keep in mind that the path to the model is case sensitive   In this similar example involving the  Category  model  the error was thrown under these conditions   1  The require statement was mentioned in two files    category js and   index js  2  I the first  the case was correct  in the second file it was not as follows   category js    index js

User · Answer

If you want to overwrite the existing class for different collection using typescript then you have to inherit the existing class from different class   export class User extends Typegoose     prop   username  string   password  string     export class newUser extends User      constructor             super             export const UserModel   new User    getModelForClass User     schemaOptions    collection   collection1         export const newUserModel   new newUser    getModelForClass newUser     schemaOptions    collection   collection2

User · Answer

ther are so many good answer but for checking we can do easier job  i mean in most popular answer there is check js  our guy made it so much complicated  i suggest  function connectToDB       if  mongoose connection readyState     1        console log  quot already connected quot        return        mongoose connect      process env MONGODB URL              useCreateIndex  true        useFindAndModify  false        useNewUrlParser  true        useUnifiedTopology  true              err    gt          if  err  throw err        console log  quot DB connected quot                    readyState   1 means connected so does not try to connect again  so you won t  get the error i think it because of connecting while it is connected it is another way of connecting to db

User · Answer

I solved this by adding  mongoose models        before the line     mongoose model  lt MODEL NAME gt    lt MODEL SCHEMA gt     Hope it solves your problem

User · Answer

Since this issue happened because calling model another time  Work around to this issue by wrapping your model code in try catch block   typescript code is like this -            Import  Schema  model  from  mongoose            export function user                  try                     return model  user   new Schema                                FirstName  String                              Last name  String                                                        catch                     return model  user                                 Similarly you can write code in js too

User · Answer

I have been experiencing this issue  amp  it was not because of the schema definitions but rather of serverless offline mode - I just managed to resolve it with this   serverless offline --skipCacheInvalidation   Which is mentioned here https   github com dherault serverless-offline issues 258  Hopefully that helps someone else who is building their project on serverless and running offline mode

User · Answer

just export like this exports User   mongoose models User    mongoose model  User   userSchema

User · Answer

What you can also do is at your export  make sure to export an existing instance if one exists  Typescript solution  import   Schema  Document  model  models   from  mongoose    const UserSchema  Schema   new Schema       name            type  String            export interface IUser extends Document       name  string    export default models Users    model lt IUser gt   Users   UserSchema

User · Answer

I have a situation where I have to create the model dynamically with each request and because of that I received this error  however  what I used to fix it is using deleteModel method like the following   var contentType    Product   var contentSchema   new mongoose Schema schema  virtuals    var model   mongoose model contentType  contentSchema    mongoose deleteModel contentType     I hope this could help anybody

User · Answer

If you are using Serverless offline and don t want to use --skipCacheInvalidation  you can very well use   module exports   mongoose models Users    mongoose model  Users   UsersSchema

User · Answer

I had this issue while unit testing   The first time you call the model creation function  mongoose stores the model under the key you provide  e g   users    If you call the model creation function with the same key more than once  mongoose won t let you overwrite the existing model   You can check if the model already exists in mongoose with   let users   mongoose model  users     This will throw an error if the model does not exist  so you can wrap it in a try catch in order to either get the model  or create it   let users try     users   mongoose model  users     catch  error      users   mongoose model  users    lt UsersSchema    gt

User · Answer

This may give a hit for some  but I got the error as well and realized that I just misspelled the user model on importing  wrong  const User   require    UserModel    correct  const User   require    userModel    Unbelievable but consider it

[node.js] Cannot overwrite model once compiled Mongoose

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