Question 188445 in Mongodb Question posted in
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Mongodb – Understanding Mongoose ObjectID and Validation Error when Saving a Scenario with User Reference

I have a scenario object that I want to save using Mongoose. The scenario object has a "user" field, which should be an ObjectId referencing a "User" document. Here’s the schema definition:

const Scenario = new Schema({
    user: { type: Schema.Types.ObjectId, ref: 'User', required: true },
    name: { type: String, required: true },
    categories: [{ type: Schema.Types.ObjectId, ref: 'Category' }],
    questions: [{ type: Schema.Types.ObjectId, ref: 'Question' }],
    createdAt: { type: Number, default: Date.now, required: true },
    updatedAt: { type: Number, default: Date.now, required: true }
});

I’m passing the scenario data to Mongoose as follows:

const scenario = new Scenario({
    user: "user_id_here",
    name: "scenario1",
    categories: ["648da0a443d3568c50c873e7"]
});
await scenario.save();

However, when I check the saved scenario in the database, the user field is not set to the provided user_id_here value. Instead, it has a different value like 757365725f69645f68657265. Why does this happen? (Noted that, neither user_id_here nor 757365725f69645f68657265 is an id in User table)

Also, if I change the user value to user_id_here1, I get a validation error: Cast to ObjectId failed for value 'user_id_here1' (type string) at path 'user' because of 'BSONTypeError'. What could be causing this error?

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2

Answers


  1. 0

    You don’t get an error by chance when the user value is user_id_here because it is 12 character length.

    But when you use value user_id_here1, since it is 13 characters length you get validation error.

    You can validate the user value using isObjectIdOrHexString function before trying to save.

        const userId = "some value from request body or req params"

    if (!mongoose.isObjectIdOrHexString(userId))
        return res.status(404).send('Invalid ID.');

    const scenario = new Scenario({
        user: userId,
        name: 'scenario1',
        ....
    });

    await scenario.save();
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  2. 0 
    user:"user_id_here",
categories: ["648da0a443d3568c50c873e7"]

    You are getting the error because you are passing the string.

    Solution :
    You have to parse the string into ObjectId using below code

    user:new mongoose.Types.ObjectId("user_id_here"),
categories: [new mongoose.Types.ObjectId("648da0a443d3568c50c873e7")]
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