Comparing strings to ObjectIds in Rules

MongoDB Atlas App Services & Realm
1

I’m having trouble creating a document rule for matching the %%user.id (which I believe is a string) to an ObjectId field (_id).

The scenario is documents that have _ids which are ObjectId conversions of the authenticated user_id.

Here is the rule that does not work:

{
  "_id": "%%user.id"
}

However, if I make an id field that is a string of the same value and adjust the rule from _id to id, it works.

Should I just make my document _id’s strings, or is there a way to compare an ObjectId to a string in a rule?

2

My solution is to make a string id field that equals the _id so I can compare it to %%user.

{
  "id": "%%user.id"
}

It would be nice if I could do something like

{
  "_id": "ObjectId(%%user.id)"
}

but this will work for now.

3

@Matt_Jennings Yes you can either use a string as an Id or use a function to perform the conversion and compare for you -

https://docs.mongodb.com/realm/functions/call-a-function/index.html#call-from-a-json-expression

4

Hello all,
Thanks for opening this subject.
I’m trying to click on the link shared by Ian, but it seems no more available.
Do you have an other link for this docs ?
Thank in advance,
Kévin