I am new to node.js, so I have a feeling that this will be something silly that I have overlooked, but I haven't been able to find an answer that fixes my problem. What I'm trying to do is create a path that will create a new child object, add it to the parent's array of children, then return the child object to the requester. The problem that I am running into is that if I pass the string id into findById, node crashes with

TypeError: Object {} has no method 'cast'

If I try to pass in an ObjectId instead, I get

CastError: Cast to ObjectId failed for value "[object Object]" at path "_id"

Here is a rough outline of my code:

var mongoose = require('mongoose');
var Schema = mongoose.Schema;
var ObjectId = Schema.ObjectId; //Have also tried Schema.Types.ObjectId, mongoose.ObjectId

mongoose.connect('mongodb://user:[email protected]:port/database');

app.get('/myClass/:Id/childClass/create', function(request, result) {
  var id = new ObjectId(request.params.Id);
  MyClass.findById(id).exec( function(err, myClass) {
    if (err || !myClass) { result.send("error: " + err + "<br>" + JSON.stringify(id) || ("object '" + request.params.Id + "' not found: " + id)); return; }
    var child = ChildClass();

If I execute this code with the path "/myClass/51c35e5ced18cb901d000001/childClass/create", this is the output of the code:

error: CastError: Cast to ObjectId failed for value "[object Object]" at path "_id" {"path":"51c35e5ced18cb901d000001","instance":"ObjectID","validators":[],"setters":[],"getters":[],"_index":null}

I've tried using findOne and passing in {_id:id} instead, but this appears to be exactly what findById does. I've tried the different classes for ObjectId that I've seen listed on other sites. I've tried calling ObjectId() like a function instead of a constructor and that returns undefined. At this point, I'm running out of ideas and it doesn't seem that googling for an answer is helping. Any ideas on what I'm doing wrong?

Also, like I said, I'm new to node/Mongo/Mongoose/Express, so if there is a better way to accomplish my goal, please let me know. I appreciate all feedback.


After the workaround from Peter Lyons, I googled another error that I was running into and found findByIdAndUpdate, which works as expected and does exactly what I was hoping to do. I'm still not sure why findById and findOne were giving me such issues and I'm curious to know (maybe a bug report needs to be filed), so I'll leave this open in case someone else has an answer.

Solution 1

Short answer: use mongoose.Types.ObjectId.

Mongoose (but not mongo) can accept object Ids as strings and "cast" them properly for you, so just use:


However, the caveat is if req.params.id is not a valid format for a mongo ID string, that will throw an exception which you must catch.

So the main confusing thing to understand is that mongoose.SchemaTypes has stuff you only use when defining mongoose schemas, and mongoose.Types has the stuff you use when creating data objects you want to store in the database or query objects. So mongoose.Types.ObjectId("51bb793aca2ab77a3200000d") works, will give you an object you can store in the database or use in queries, and will throw an exception if given an invalid ID string.

findOne takes a query object and passes a single model instance to the callback. And findById is literally a wrapper of findOne({_id: id}) (see source code here). Just find takes a query object and passes an array of matching model instances to the callback.

Just go slow. It's confusing but I can guarantee you you are getting confused and not hitting bugs in mongoose at this point. It's a pretty mature library, but it takes some time to get the hang of it.

The other suspect thing I see in your snippet is not using new when instantiating ChildClass. Beyond that, you'll need to post your schema code in order for us to help you tract down any CastErrors that remain.

Solution 2

I've faced this error, That was because the value you want to filter in the _id field is not in an ID format, one "if" should solve your error.

const mongoose = require('mongoose');

// true
// false

To solve it, always validate if the criteria value for search is a valid ObjectId

const criteria = {};
criteria.$or = [];

if(params.q) {
  if(mongoose.Types.ObjectId.isValid(params.id)) {
    criteria.$or.push({ _id: params.q })
  criteria.$or.push({ name: { $regex: params.q, $options: 'i' }})
  criteria.$or.push({ email: { $regex: params.q, $options: 'i' }})
  criteria.$or.push({ password: { $regex: params.q, $options: 'i' }})

return UserModule.find(criteria).exec(() => {
  // do stuff

Solution 3

For all those people stuck with this problem, but still couldn't solve it: I stumbled upon the same error and found the _id field being empty.

I described it here in more detail. Still have not found a solution except changing the fields in _id to not-ID fields which is a dirty hack to me. I'm probably going to file a bug report for mongoose. Any help would be appreciated!

Edit: I updated my thread. I filed a ticket and they confirmed the missing _id problem. It is going to be fixed in the 4.x.x version which has a release candidate available right now. The rc is not recommended for productive use!

Solution 4

If you are having this issue and you are performing a populate somewhere along the lines, see this Mongoose issue.

Update to Mongoose 4.0 and the issue has been fixed.

Solution 5

Had the same problem, I just coerced the id into a string.

My schema:

const product = new mongooseClient.Schema({
    retailerID: { type: mongoose.SchemaTypes.ObjectId, required: true, index: true }

And then, when inserting:

retailerID: `${retailer._id}`

Solution 6

My solution is that i want data from all docs and i dont want _id, so

User.find({}, {_id:0, keyToShow:1, keyToNotShow:0})

Solution 7

I had the same problem, turned out after I have updated my schema, I have forgotten I was calling the model using the old id, which was created by me; I have updated my schema from something like:

patientid: {
           type: String,
            required: true,
            unique: true


patientid: { type: mongoose.SchemaTypes.ObjectId, ref: "Patient" },

It turned out, since my code is big, I was calling the findOne with the old id, therefore, the problem.

I am posting here just to help somebody else: please, check your code for unknown wrong calls! it may be the problem, and it can save your huge headacles!

Solution 8

I was receiving this error CastError: Cast to ObjectId failed for value [object Object] at path _id after creating a schema, then modifying it and couldn't track it down. I deleted all the documents in the collection and I could add 1 object but not a second. I ended up deleting the collection in Mongo and that worked as Mongoose recreated the collection.

Solution 9

For the record: I had this error trying to fill a subdocument in a wrong way:

[CastError: Cast to ObjectId failed for value "[object Object]" at path "_id"]
message: 'Cast to ObjectId failed for value "[object Object]" at path "_id"',
name: 'CastError',
type: 'ObjectId',
path: '_id'
  [ { timestamp: '2014-07-03T00:23:45-04:00',
  date_start: '2014-07-03T00:23:45-04:00',
  date_end: '2014-07-03T00:23:45-04:00',
  operation: 'Deactivation' } ],

look ^ value is an array containing an object: wrong!

Explanation: I was sending data from php to a node.js API in this way:

$history = json_encode(
  'timestamp'  => date('c', time()),
  'date_start' => date('c', time()),
  'date_end'   => date('c', time()),
  'operation'  => 'Deactivation'

As you can see $history is an array containing an array. That's why mongoose try to fill _id (or any other field) with an array instead than a Scheme.ObjectId (or any other data type). The following works:

$history = json_encode(
  'timestamp'  => date('c', time()),
  'date_start' => date('c', time()),
  'date_end'   => date('c', time()),
  'operation'  => 'Deactivation'

Solution 10

I am not sure this will help but I resolved the issue by importing mongoose like below and implementing it as below

const mongoose = require('mongoose')

_id: new mongoose.Types.ObjectId(),

Solution 11

I also encountered this mongoose error

CastError: Cast to ObjectId failed for value \"583fe2c488cf652d4c6b45d1\" at path \"_id\" for model User

So I run npm list command to verify the mongodb and mongoose version in my local. Heres the report:

 [email protected]2.2.19  
 [email protected]4.7.2  

It seems there's an issue on this mongodb version so what I did is I uninstall and try to use different version such as 2.2.16

$ npm uninstall mongodb, it will delete the mongodb from your node_modules directory. After that install the lower version of mongodb.
$ npm install [email protected]
Finally, I restart the app and the CastError is gone!!

Solution 12

I was having the same problem.Turns out my Node.js was outdated. After upgrading it's working.

Solution 13

just change the path it will work for example

app.get('/myClass/:Id/childClass/create', function(request, result) .....

change to

app.get('/myClass**es**/:Id/childClass/create', function(request, result) .....

I just added --es-- to the path (myClass) to become (myClasses)

now should work and will not see that error

Solution 14

For me, the ID was undefined (req.params.id returns undefined)

Solution 15

If you're finding a document by its "_id" for a model, say Drivers, the command below works quite well:

const driver = await Drivers.findById(<your id>);

Ensure you use the async-await and try-catch ES6 syntax

Solution 16

For me, I was using a put request without sending any data. I changed it to a post request and it worked.

This thread covers more about put requests.

Solution 17

just change the path it will work for example

app.get('/myClass/:Id/childClass/create', function(request, result) 

change to

app.get('/myClass**es**/:Id/childClass/create', function(request, result)

I just added --es-- to the path (myClass) to become (myClasses)

now should work and will not see that error

Solution 18

so i was getting this error -> CastError: Cast to ObjectId failed for value ...

  1. I log the id out and checked if it corresponded to my id in my Database
  2. since i confirmed it was there and still getting the same error, I then used .trim() method to remove any blank space from the _id and the error was solved

check my code below and see if it helps

const checkItemId = req.body.checkbox;

// find the item by id and remove it make sure youuse .trim to remove any blank space
Item.findByIdAndRemove(checkItemId.trim(), (err) => {
        console.log("Removed Succesfull");