set.contains with custom equals

main.dart

// SO 29567322 
class Action {
  final Function function;
  final String description;

  Action(this.function, this.description);

  call() => function();

  int get hashCode => description.hashCode;
  
  @override
  bool operator== (other) {
    if(other is! Action) {
      return false;
    }
    return description == (other as Action).description;
  }

  @override
  String toString() => description;
}

void main() {
  Set<Action> actions = new Set()
    ..add(new Action(() => print("a"), "print a"))  
    ..add(new Action(() => print("a"), "print a"))
    ..add(new Action(() => print("b"), "print b"));
  print(actions);
}