issues with firebase rules

Question

I am trying to write some simple firebase rules that will only allow the authenticated user to be able to write over their data.

{
  "rules": {
    "users": {
      "uid": {
        ".read": true,
        ".write": "auth != null && auth.uid == uid"
// unknown variable uid.
      }
    }
  }
}

for some reason, I keep getting error above. The uid is inside so I don't get why there is a error?

Answer 1

To declare a wildcard capture variable the name of the node needs to start with a $. So:

{
  "rules": {
    "users": {
      "$uid": { // 👈 add $ here
        ".read": true,
        ".write": "auth != null && auth.uid == $uid" // 👈 now you can use the variable here
      }
    }
  }
}