Firebase Cloud Firestore : Invalid collection reference. Collection references must have an odd number of segments

Question

I have the following code and getting an error :

Invalid collection reference. Collection references must have an odd number of segments

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Answer 1

Then you need change this:

db.collection("app/users/" + uid + "/notifications")...

for this:

db.collection("app").document("users").collection(uid).document("notifications")

You welcome ;)