Firebase安全规则request.writeFileds

Question

一旦我设置了安全规则，就会出现以下错误，

POST https://firestore.googleapis.com/v1beta1/projects/revents-229904/databases/(default)/documents:commit 403

match / events / {eventId} {

allow read;

  allow create: if request.auth.uid != null;

  allow write: if request.auth.uid != null

  && (('attendees.' + request.auth.uid) in request.writeFields)

    || (('attendees.' + request.auth.uid + '.photoURL') in 
   request.writeFields)

  allow update: if resource.data.hostUid == request.auth.uid;

}