Firestore rules for document field

Question

I\'m struggling within Firestore to set security rules for a document. With the RTDB is was possible to set rules for a specific object property and I\'m trying to do the sa

Answer 1

Looks like this is now supported:

service cloud.firestore {
  match /databases/{database}/documents {
    // Allow the user to read data if the document has the 'visibility'
    // field set to 'public'
    match /cities/{city} {
      allow read: if resource.data.visibility == 'public';
    }
  }
}

The resource variable refers to the requested document, and resource.data is a map of all of the fields and values stored in the document.

---

To give a concrete example, in my case I needed to provide read access to a group only if the requesting user is in the members field (which is an array) of the groups collection. So I did this:

rules_version = '2';
service cloud.firestore {
  match /databases/{database}/documents {
    function isMember(userId) {
      return (userId in resource.data.members);
    }
    match /groups/{group} {
      allow read: if request.auth != null && isMember(request.auth.uid);
    }
    //...
  }
}