自动售货机 C++ - while 循环中的错误

Question

我正在用 C++ 编写“自动售货机/杂货店购物”代码，其中我有一个包含 5 个项目的菜单，用户可以根据需要选择添加为我的项目。最后计算价格。

由于用户可以添加任意数量的商品，因此我使用了while 循环，以便他们可以“继续购物”。但是，我无法成功地做到这一点，因为他们的代码会继续运行。我试图将 switch 语句放在一个函数中，但没有正确调用“回复”。

有人可以帮我处理这段代码，特别是 while 循环和称为 int shoppingCart() 的 switch 语句函数。如果有人可以帮助我抽象出这段代码，那就太好了！）

下面的代码（这是原文，我在下面放了一个编辑过的）：

#include <iostream>
using namespace std;


void vendingMachine() {
  cout << "1. Popcorn: $2" << endl;
  cout << "2. Coconut Clusters: $3" << endl;
  cout << "3. Granola Bar: $2.50" << endl;
  cout << "4. Trail Mix: $1.50" << endl;
  cout << "5. Chocolate: $1" << endl;
  cout << "Press 0 to checkout" << endl;
}

int main() {
  cout << "Vending Machine" << endl;
  cout << "----Items------" << endl;

  vendingMachine();

  
  cout << "Enter you selection: " << flush;
  int input;
  cin >> input;
  float cost;

  switch (input) {
  case 1:
    cout << "You added Popcorn to your cart." << endl;
    cost = 2;
    break;
  case 2:
    cout << "You added Coconut Clusters to your cart." << endl;
    cost = 3;
    break;
  case 3:
    cout << "You added Granola Bar to your cart." << endl;
    cost = 2.50;
    break;
  case 4:
    cout << "You added Trail Mix to your cart." << endl;
    cost = 1.50;
    break;
  case 5:
    cout << "You added Chocolate to your cart." << endl;
    cost = 1;
    break;
  case 6:
    cout << "Checkout" << endl;
    break;
  default:
    cout << "Please select an item from the menu" << endl;
  }
  cout << "Continue shopping (y/n): " << flush;
  string reply;
  cin >> reply;


  while(reply == "y") {
    cout << "Enter your selection: " << flush;
    int input;
    cin >> input;
    float cost;

    switch (input) {
    case 1:
      cout << "You added Popcorn to your cart." << endl;
      cost = 2;
      break;
    case 2:
      cout << "You added Coconut Clusters to your cart." << endl;
      cost = 3;
      break;
    case 3:
      cout << "You added Granola Bar to your cart." << endl;
      cost = 2.50;
      break;
    case 4:
      cout << "You added Trail Mix to your cart." << endl;
      cost = 1.50;
      break;
    case 5:
      cout << "You added Chocolate to your cart." << endl;
      cost = 1;
      break;
    case 6:
      cout << "Checkout" << endl;
      break;
    default:
      cout << "Please select an item from the menu" << endl;
    }
    cout << "Continue shopping (y/n): " << flush;
    string reply;
    cin >> reply;
    break;
  }
  cout << "Proceding to checkout..." << endl;
  



  

  cout << "Pay amount: $" << flush;
  float money;
  cin >> money;

  if (money > cost) {
    float change = money-cost;
    cout << "Thank you! You have $" << change << " change." << endl;
  }

  if (money == cost) {
    cout << "Thank you! Have a nice day!." << endl;
  }

  if (money < cost) {
    float amountOwed = cost-money;
    cout << "Please insert another $" << amountOwed << endl;

    cout << "Enter amount: " << flush;
    float payment;
    cin >> payment;

    if (payment > amountOwed) {
    float change2 = payment-cost;
    cout << "Thank you! You have $" << change2 << " change." << endl;
    }

    if (payment == amountOwed) {
      cout << "Thank you! Have a nice day!." << endl;
    }

    if (payment < amountOwed) {
      cout << "Sorry, you did not enter enough money. Your cart has emptied." << endl;
    }

  }
  return 0;
}

修改后的代码：

#include <iostream>
using namespace std;


void vendingMachine() {
  cout << "1. Popcorn: $2" << endl;
  cout << "2. Coconut Clusters: $3" << endl;
  cout << "3. Granola Bar: $2.50" << endl;
  cout << "4. Trail Mix: $1.50" << endl;
  cout << "5. Chocolate: $1" << endl;
  cout << "Press 0 to checkout" << endl;
}

int processSelection() {
  cout << "Enter your selection: " << flush;
  int input;
  cin >> input;
  
  return input;
}

int shoppingCart() {
  int selection = processSelection();
  float cost;
  switch (selection) {
  case 1:
    cout << "You added Popcorn to your cart." << endl;
    cost = 2;
    break;
  case 2:
    cout << "You added Coconut Clusters to your cart." << endl;
    cost = 3;
    break;
  case 3:
    cout << "You added Granola Bar to your cart." << endl;
    cost = 2.50;
    break;
  case 4:
    cout << "You added Trail Mix to your cart." << endl;
    cost = 1.50;
    break;
  case 5:
    cout << "You added Chocolate to your cart." << endl;
    cost = 1;
    break;
  case 6:
    cout << "Checkout" << endl;
    break;
  default:
    cout << "Please select an item from the menu" << endl;
  }
  cout << "Continue shopping (y/n): " << flush;
  string reply;
  cin >> reply;

  return reply;
}

int main() {
  cout << "Vending Machine" << endl;
  cout << "----Items------" << endl;

  vendingMachine();

  int reply = shoppingCart();

  float cost;
  

  


  while(reply == "y") {
    processSelection();

    shoppingCart();
  }
  cout << "Proceding to checkout..." << endl;
  



  

  cout << "Pay amount: $" << flush;
  float money;
  cin >> money;

  if (money > cost) {
    float change = money-cost;
    cout << "Thank you! You have $" << change << " change." << endl;
  }

  if (money == cost) {
    cout << "Thank you! Have a nice day!." << endl;
  }

  if (money < cost) {
    float amountOwed = cost-money;
    cout << "Please insert another $" << amountOwed << endl;

    cout << "Enter amount: " << flush;
    float payment;
    cin >> payment;

    if (payment > amountOwed) {
    float change2 = payment-cost;
    cout << "Thank you! You have $" << change2 << " change." << endl;
    }

    if (payment == amountOwed) {
      cout << "Thank you! Have a nice day!." << endl;
    }

    if (payment < amountOwed) {
      cout << "Sorry, you did not enter enough money. Your cart has emptied." << endl;
    }

  }
  return 0;
}

Answer 1

看起来您在学习编码方面取得了很大进步。一些想法：

1. 抽象重复代码。您的 switch 语句在两个地方是相同的。这使得错误很容易出现！例如，如果一件商品的价格发生变化，您可能会忘记在一个地方更新它而不是另一个地方，这可能会导致棘手的错误。
2. 您在 while 循环的末尾有一个 break 语句。你想在每次迭代中中断吗？可能不是。当做你想跳出循环？在什么情况下不想继续？想想控制流，以及 while 循环是如何工作的。当某些条件为真时，继续循环。一旦它是假的，停止循环。那是什么条件？只是reply == y？这适用于第一次迭代，那么其他迭代呢？
3. 你们中的一些人如果陈述说“祝你有美好的一天”之类的话。对我来说，这听起来像是跳出循环的好时机。你怎么看？