Trying to modify a specific property of an object from a list of that object

Question

This is Food

class Food {
  String imgUrl;
  String desc;
  String name;
  String waitTime;
  num score;
  int price;
  int quantity;
  List<Map<String, String>> ingredients;
  String about;
  bool highlight;
  Food(this.imgUrl, this.desc, this.name, this.waitTime, this.score, this.price,
      this.quantity, this.ingredients, this.about,
      {this.highlight = false});
}

I have a list of Food named userOrders and I'm trying to create a provider function that will increment and decrement the quantity paramter when I call it but of the specific instance of Food I'm dealing with. For example:

class FoodCounter with ChangeNotifier {
  int _count = userOrders[0].quantity;

  int get count => _count;

  void increment() {
    _count++;
    notifyListeners();
  }

  void decrement() {
    _count--;
    notifyListeners();
  }

  void reset() {
    _count = 0;
    notifyListeners();
  }

  void update() {
    notifyListeners();
  }
}

I'm trying to do something like this but the problem is I can only modify the first element in the list of food. I'm wondering if I can do something like int _count = userOrders[element].quantity; or int _count = userOrders[context].quantity;

Answer 1

Try using the following code to manage quantity and total count.

class FoodCounter with ChangeNotifier {
  FoodCounter(){
    for(final order in userOrders) {
       _count += order.quantity;
    }
  }
  int _count = 0;

  int get count => _count;

  void increment(UserOrder order) {
    order.quantity += 1;
    _count++;
    notifyListeners();
  }

  void decrement(UserOrder order) {
    if (order.quantity > 0) {
      order.quantity -= 1;
      _count--;
      notifyListeners();
    }
  }

  void reset() {
    _count = 0;
    for(final order in userOrders) {
       order.quantity = 0;
    }
    notifyListeners();
  }

  void update() {
    notifyListeners();
  }
}