在 firestore 安全规则中使用集合的父文档

Question

This is my firestore collection path /chat/{doc}/messages

I written rules like below,

match /chat/{documents=**}{
  allow create: if request.auth.uid != null;
  allow read, update, delete: if request.auth.uid in resource.data.users;
}
 
match /chat/{doc}/messages/{documents=**}{
  allow read, create:if request.auth.uid != null;
  allow update, delete: if false;
}

The problem is messages collection under the doc . I want to write rule like below for messages

match /chat/{doc}/messages/{documents=**}{
  allow read, create:if request.auth.uid in doc.data.users;
  allow update, delete: if false;
}

I am not well experienced in firestore rules. Can someone help me to resolve the issues? Thanks in advance!

Answer 1

You can write firestore security rules that reference parent documents by querying for the parent document in the security rule with get :

match /chat/{chatId}/messages/{messageId}{
  allow read, create: if request.auth.uid in get(/databases/$(database)/documents/chat/$(chatId)).data.users
  allow update, delete: if false;
}

This answer is based on Access other documents in the Firebase documentation.