Firebase Cloud Firestore Security Rules for updateData FieldValue.delete() [swift] - swift

Question

I'm removing the map element in the Test field.
Removing the "myID" key from the "Test"
self.db.collection("events").document("bkxREqn24JpdKYBLnBio").updateData([
"Test.myID": FieldValue.delete(),
]) { err in
if let err = err {
print("Error updating document: \(err)")
} else {
print("Document successfully updated")
}
}
How do I get the key of an item that I remove in the "security rules"?
That's not how it works:
service cloud.firestore {
match /databases/{database}/documents {
match /events/{eventID} {
allow write, update : if request.resource.data.Test.keys()[0] == "myID"
}
}
}
although this rule works for the record
self.db.collection("events").document("bkxREqn24JpdKYBLnBio").updateData([
"Test.myID": "MyText",
]) { err in
if let err = err {
print("Error updating document: \(err)")
} else {
print("Document successfully updated")
}
}

Answer 1

If I understand correctly, you want to only allow the write if the new document still contains myID value in the Test field, which is an array.
That'd be this in security rules:
allow write, update : if "myID" in request.resource.data.Test;
If you want to check if myID is being added, you'll compare request.resource.data with resource.data. So something like:
allow write, update : if "myID" in request.resource.data.Test
&& !("myID" in resource.data.Test);