Access parent documents field in Firestore rules

Question

I\'m implementing a recipe book in Firestore where every user is able to see all the recipes all users created but only the original author of the recipe is allowed to edit or d

Answer 1

Building upon Dan's answer, you should be able to reduce the number of reads on your database for update and delete on the subcollection by adding the creatorUID to the subcollection document.

You'll have to restrict create to just the creator and make sure the creatorUID is set. Here's my modification of Dan's rules:

service cloud.firestore {
  match /databases/{database}/documents {

    function isSignedIn() {
      return request.auth != null;
    }

    match /ListOfRecipes/{recipe} {
        allow read, create: if isSignedIn();
        allow update, delete: if resource.data.creatorUID == request.auth.uid;

        function recipeData() {
            return get(/databases/$(database)/documents/ListOfRecipes/$(recipe)).data
        }

        match /List/{list} {
            allow read: if isSignedIn();
            allow update, delete: if resource.data.creatorUID == request.auth.uid;
            allow create: if recipeData().creatorUID == request.auth.uid
                          && request.resource.data.creatorUID == request.auth.uid;
        }
    }
  }
}