Unable to set up Sync Permissions properly

[Arkar_Kyaw_Aung]

Hi, I am unable to set up Rules for Atlas app services properly.

Now, I have 2 collections: Users and Groups

• A User contains _id and an array of ObjectId referencing groups they are part of
• A Group contains _id, creator_id and an array of ObjectId, trip_members referencing members in the group

When it is readAllWriteAll on Groups, I can run functions which run as user which created the group without a problem.

Now, when I change to

{
  "creator_id": "%%user.custom_data._id”
},
{
  “trip_members”: { “$all" : [" %%user.custom_data.id" ] }
}

or

{
  "creator_id": "%%user.id"
},
{
  “trip_members”: { “$all" : [ "%%user.id" ] }
}

for both read and write, the query which previously works now returns null.

Unsure where I am missing since this is also an example in the guides but does not seem to work

[Tyler_Kaye]

Hi, can you try updatijng it to {“trip_members”: "%%user.custom_data.id"}. I believe you have two issues.

1. You have a space in this string " %%user.custom_data.id"
2. There is no need to use $all for an array with a single element, just use the basic ANY approach which is much much easier to express as {“trip_members”: "%%user.custom_data.id"}

Best,
Tyler

[Arkar_Kyaw_Aung]

Hi, thanks for the quick reply.

About the syntax issue, I did fix it but the issue actually came from the following:

• creator_id was stored as ObjectId in my schema.

• Looking at add-collaborators sample application in your docs, I realised that examples of owner_id actually uses string. So I am assuming that %%user.id is expanding into a string? When I switched to checking with string fields, it works.

“email” : “%%user.custom_data.email"

Then, what would be the best practice?

1. Introducing redundant field: creator_id is user._id.toString()
2. Using another queryable field, such as email, and using Array<String> instead of Array<ObjectId>

For 2. Thanks for the tip! Will do.

Cheers

[Tyler_Kaye]

Oh, glad to know you figured it out. For that, we have these expressions you can use to translate the value in the expression: https://www.mongodb.com/docs/atlas/app-services/rules/expressions/#convert-ejson-values

So you could do something like {“trip_members”: {"%stringToOid": "%%user.custom_data.id"}}

[Arkar_Kyaw_Aung]

Got it! Thank you so much!