onSnapshot method
Find first record (null if none) and listen for changes.
Returns a single subscriber stream that must be cancelled.
Implementation
Stream<RecordSnapshot<K, V>?> onSnapshot(Database database) {
if (sembastQueryRef.finder?.limit != 1) {
return SembastQueryRef(sembastQueryRef.store,
cloneFinderFindFirst(sembastQueryRef.finder))
.onSnapshot(database);
}
return onSnapshots(database)
.map((list) => list.isNotEmpty ? list.first : null);
}