dependOn method
Sends a notification to itself when the target listenable
is updated.
Implementation
void dependOn(
Listenable listenable, [
Map<K, V> Function(Map<K, V> origin)? filter,
]) {
listenable.addListener(() {
if (filter != null) {
value = filter.call(value);
} else {
notifyListeners();
}
});
}