uniqueListen method
Listens and iterates through obj.addListener
by calling fn
.
The listener is disposed in the dispose function.
Whenever you call uniqueListen
we will make sure that clear any listener with the same id
.
Implementation
void uniqueListen(Symbol id, ChangeNotifier obj, void Function() fn) {
_sanity();
obj.addListener(fn);
final cur = _uniqueListeners[id];
if (cur != null) {
cur.item1.removeListener(cur.item2);
}
_uniqueListeners[id] = Tuple2(obj, fn);
}