Folding maps

main.dart

void main() {
  final map = {
   Product(price: 1): 2,
   Product(price: 2): 3,
  };
  
  final total = map.entries.fold(
    0,
    (total, entry) => total + (entry.key.price * entry.value)
  );
  
  print('total $total');
}

class Product {
  final price;
  Product({this.price});
}