Allow update on single field in firestore

Question

I want to give a user the right to update a document. But ONLY if the user updates one specific field of this document. All other fields shouldn\'t be changed by this user.<

Answer 1

Since request.resource.data will show the future object after the write - the only way is to check every field using the following:

   function notUpdating(field) {
     return !(field in request.resource.data)
      || resource.data[field] == request.resource.data[field]
   }

   allow update: if notUpdating('title') && notUpdating('description')

Make sure you validate that the user doesn't update all of the fields except the field you want him to have access to