getUniqueShoppingCategories function

List<ShoppingCategory> getUniqueShoppingCategories (
  1. List<CreditCard> cards
)

Implementation

List<ShoppingCategory> getUniqueShoppingCategories(List<CreditCard> cards) {
  Map<String, bool> promoIdDict = {};
  List<ShoppingCategory> uniqueCategories = [];
  for (CreditCard card in cards) {
    for (Promotion promo in card.promotions) {
      if (!promoIdDict.containsKey(promo.id)) {
        promoIdDict[promo.id] = true;
        uniqueCategories.add(promo.category);
      }
    }
  }
  return uniqueCategories;
}