Can i fix the “casterror: cast to objectid failed for value” or not?

Question

Here is the program I run:

var mongoose = require('mongoose');
 var Schema = mongoose.Schema;
 var ObjectId = Schema.ObjectId; //Have also tried Schema.Types.ObjectId, mongoose.ObjectId
 
 mongoose.connect('mongodb://user:password@server: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();
  myClass.Children.addToSet(child);
  myClass.save();
  result.send(child);
  });
 });

After I run, it returns an error:

TypeError: Object {} has no method 'cast'

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

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

Does anyone have any suggestions for the problem below: casterror: cast to objectid failed for value in the javascript- How to correct it?

hdtutoria · Accepted Answer

The cause: I think the cause of this error is that the value in the _id field that you want to filter is not in an ID format.

const mongoose = require('mongoose');

console.log(mongoose.Types.ObjectId.isValid('53cb6b9b4f4ddef1ad47f943'));
// true
console.log(mongoose.Types.ObjectId.isValid('whatever'));
// false

Solution: Always verify that the search criterion value is a valid ObjectId to fix this error

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
})

Jules Bodin · Answer

Short answer: use mongoose.Types.ObjectId.

Mongoose, but not mongo, can accept object IDs as strings and "cast” them for you.

MyClass.findById(req.params.id)

The caveat is that req.params.id may not be a valid format to use with a mongo ID string. This will throw an exception, which you need to catch.

The main thing to remember is that mongoose.SchemaTypes contains stuff you use for defining mongoose schemes, while mongoose.Types contains stuff you use to create data objects you want stored in the database. mongoose.Types.ObjectId("51bb793aca2ab77a3200000d") will create an object that you can store in the database, or use in queries. If you give an invalid ID string, it will throw an exception.

findOne takes a query object, and passes one model instance to the callback. findById is a wrapper for findOne({_id: id}) ( ). find simply takes a query object, and passes an array with matching model instances to its callback.

Take it slow. Although it's confusing, I guarantee that you won't get lost and you will not be able to hit bugs in mongoose. Although it's a mature library, it can be difficult to master.

Another thing that I suspect is your new not being used when instantiating ChildClass. To help us find any CastErrors, we will need your schema code.

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Can i fix the “casterror: cast to objectid failed for value” or not?