应用折扣

本课属于 Coddy Dart 学习旅程的“逻辑与流程控制”单元。第 36 课，共 65 课。

挑战

简单

创建一个程序，继续完成购物车计算器项目，实现一个折扣系统，为符合条件的订单提供按百分比计算的折扣。在上一课计算总费用的基础上，你的程序应当：

使用之前设置中的现有商品目录 Map 和购物车功能
读取多个字符串输入，表示顾客想要添加到购物车的商品（当你收到 "cart_done" 时，输入结束）
对于每件商品，使用 containsKey() 检查它是否存在于商品目录中，并将有效商品添加到购物车
将购物车中所有商品的价格相加，计算小计
读取一个表示折扣门槛金额的字符串输入
读取一个表示要应用的折扣百分比的字符串输入
仅当小计达到或超过门槛金额时才应用折扣
计算折扣金额以及应用折扣后的最终总额
按照下方所示的准确格式显示折扣计算报告

例如，如果商店有价格为 "Apple" 对应 1.50、"Banana" 对应 0.80、"Orange" 对应 2.00、"Milk" 对应 3.25 的商品，顾客想要添加 "Apple"、"Orange"、"Milk"、"Apple"，折扣门槛为 5.00，折扣百分比为 10，你的程序应输出：

Shopping Cart Operations:
Adding 'Apple': Item added to cart successfully
Adding 'Orange': Item added to cart successfully
Adding 'Milk': Item added to cart successfully
Adding 'Apple': Item added to cart successfully
Cart Contents: [Apple, Orange, Milk, Apple]
Cost Calculation:
Apple: $1.50
Orange: $2.00
Milk: $3.25
Apple: $1.50
Subtotal: $8.25
Discount Analysis:
Threshold: $5.00
Discount Rate: 10%
Subtotal ($8.25) meets threshold requirement
Discount Applied: $0.83
Final Total: $7.42
Cart Summary:
Total items in cart: 4
Unique products in cart: 3
Items successfully added: 4
Items not found: 0
Discount Status: 10% discount applied
Cart Status: Ready for checkout

如果商店有价格为 "Laptop" 对应 999.99、"Mouse" 对应 25.50、"Keyboard" 对应 75.00 的商品，顾客想要添加 "Mouse"、"Keyboard"，折扣门槛为 150.00，折扣百分比为 15，你的程序应输出：

Shopping Cart Operations:
Adding 'Mouse': Item added to cart successfully
Adding 'Keyboard': Item added to cart successfully
Cart Contents: [Mouse, Keyboard]
Cost Calculation:
Mouse: $25.50
Keyboard: $75.00
Subtotal: $100.50
Discount Analysis:
Threshold: $150.00
Discount Rate: 15%
Subtotal ($100.50) does not meet threshold requirement
Discount Applied: $0.00
Final Total: $100.50
Cart Summary:
Total items in cart: 2
Unique products in cart: 2
Items successfully added: 2
Items not found: 0
Discount Status: No discount applied
Cart Status: Ready for checkout

如果商店有价格为 "Novel" 对应 12.99、"Magazine" 对应 4.50、"Textbook" 对应 89.00 的商品，顾客想要添加 "Novel"、"Textbook"、"Magazine"、"Novel"，折扣门槛为 75.00，折扣百分比为 20，你的程序应输出：

Shopping Cart Operations:
Adding 'Novel': Item added to cart successfully
Adding 'Textbook': Item added to cart successfully
Adding 'Magazine': Item added to cart successfully
Adding 'Novel': Item added to cart successfully
Cart Contents: [Novel, Textbook, Magazine, Novel]
Cost Calculation:
Novel: $12.99
Textbook: $89.00
Magazine: $4.50
Novel: $12.99
Subtotal: $119.48
Discount Analysis:
Threshold: $75.00
Discount Rate: 20%
Subtotal ($119.48) meets threshold requirement
Discount Applied: $23.90
Final Total: $95.58
Cart Summary:
Total items in cart: 4
Unique products in cart: 3
Items successfully added: 4
Items not found: 0
Discount Status: 20% discount applied
Cart Status: Ready for checkout

你的程序必须先计算小计，然后使用条件 if 语句检查小计是否达到或超过折扣门槛。如果达到门槛，则用小计乘以折扣百分比再除以 100，计算折扣金额。从小计中减去折扣金额，得到最终总额。所有金额都必须格式化为恰好 2 位小数。输入格式为：要添加到购物车的商品名称，以 "cart_done" 结束，随后输入折扣门槛金额和折扣百分比（两者都是需要转换为适当数值类型的字符串）。

亲手试试

import 'dart:io';

void main() {
  // Product catalog with prices
  Map<String, double> products = {
    'Apple': 1.50,
    'Banana': 0.80,
    'Orange': 2.00,
    'Milk': 3.25,
    'Laptop': 999.99,
    'Mouse': 25.50,
    'Keyboard': 75.00,
    'Novel': 12.99,
    'Magazine': 4.50,
    'Textbook': 89.00
  };
  
  // Shopping cart list
  List<String> cart = [];
  
  // Counters for summary
  int itemsAdded = 0;
  int itemsNotFound = 0;
  
  print('Shopping Cart Operations:');
  
  // Read items until "cart_done"
  String? item;
  while ((item = stdin.readLineSync()) != 'cart_done') {
    if (item != null) {
      if (products.containsKey(item)) {
        cart.add(item);
        print("Adding '$item': Item added to cart successfully");
        itemsAdded++;
      } else {
        print("Adding '$item': Item not available in store");
        itemsNotFound++;
      }
    }
  }
  
  // Display cart contents
  print('Cart Contents: $cart');
  
  // Calculate total cost
  print('Cost Calculation:');
  double totalCost = 0.0;
  
  for (String cartItem in cart) {
    double price = products[cartItem]!;
    totalCost += price;
    print('$cartItem: \$${price.toStringAsFixed(2)}');
  }
  
  print('Total Cost: \$${totalCost.toStringAsFixed(2)}');
  
  // Cart summary
  Set<String> uniqueProducts = cart.toSet();
  print('Cart Summary:');
  print('Total items in cart: ${cart.length}');
  print('Unique products in cart: ${uniqueProducts.length}');
  print('Items successfully added: $itemsAdded');
  print('Items not found: $itemsNotFound');
  print('Cart Status: Ready for checkout');
}

逻辑与流程控制中的所有课

2函数式列表操作

使用 'map' 进行转换使用 'where' 进行筛选使用 '.toList()'使用 'any' 检查条件使用 'every' 检查条件使用 'firstWhere' 查找复习：数据筛选

5项目：购物车计算

应用折扣

8项目：简单文本分析器

自己练习： Dart 在线编译器