Mongoose: Cast to array of object failed for value [{"someKey": "someValue"}]

Question

I'm getting error whenever I'm trying to save into my database a document with this schema:

var schemaForBooks = new Schema({
    book: String,
    author: String,
    who_has_this: Object,
    points: Number,
    upvoted_by_users: [Schema.Types.ObjectId],
    downvoted_by_users: [Schema.Types.ObjectId]
});

Rest all is good, but putting anything into upvoted_by_users or downvoted_by_users, I get this error:

[ERROR] Trace- CastError: Cast to [ObjectId] failed for value "[{"userName":"Vibhu","userId":"3833d1g870feaf4a38723"}]" at path "upvoted_
by_users"

I'm pretty sure I'm doing something wrong with the schema itself, but I don't know what.

Any help would be appreciated.

{"userName":"Vibhu","userId":"3833d1g870feaf4a38723"}, is this what you're placing in the array? — Talha Awan
– Talha Awan, Commented Jun 11, 2017 at 16:46
Yes, I wanted to do that, but now I know, I'll have to create a nested Schema for that. I was too dumb here. — Vibhum Bhardwaj
– Vibhum Bhardwaj, Commented Jun 15, 2017 at 4:42

boehm_s · Accepted Answer · 2017-06-11 16:55:37Z

1

The error says that you're trying to cast the following array of object {"userName":"Vibhu", "userId":"3833d1g870feaf4a38723"} to an array of ObjectId.

So, you need to get rid of the userName field, so you can turn your array of String + ObjectId to an array of ObjectId.

You can do it with the Array#map method on your js Array, for example :

var arr = [{"userName":"Vibhu","userId":"3833d1g870feaf4a38723"}];
var myCorrectArr = arr.map(field => field.userId);

Hope it helps,
Best regards,

answered Jun 11, 2017 at 16:55

boehm_s

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1 Comment

Vibhum Bhardwaj Over a year ago

Thanks @boehm_s, your reply didn't directly answered my query but got me to that. I was confusing ObjectId with some generic Object object

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