SetSignalMixin is a mixin for a Signal that adds reactive methods for Set.
class MySignal extends Signal<Set<int>> with SetSignalMixin<int> { MySignal(Set<int> value) : super(value);} void main() { final signal = MySignal({1, 2, 3}); effect(() { print(signal.length); }); signal.add(4); signal.remove(1); print(signal.contains(2)); // true}