c++ - 在 C++ 中循环不正确

Question

所以我写了这段代码:

#include <iostream>
#include <string>
using namespace std;

double balance = 0, withdraw = 0, deposit = 0;
string choice, quitOrNo;

class Bank
{
    public:
        void withdrawMoney()
        {
            if(balance - withdraw >= 0)
            {
                balance = balance - withdraw;
            }
            else
            {
                cout << "$5 penalty for attempting to withdraw more than you have.";
                balance -= 5;
            }
        }
    public:
        void depositMoney()
        {
            balance = balance + deposit;
        }
};
int main()
{
    Bank bankObject;
    cout << "Welcome to the Bank Program!" << endl;
    while(true)
    {
        while(true)
        {
            cout << "Would you like to make a withdrawal, a deposit, or quit the program: ";
            cin >> choice;
            if(choice.compare("withdrawal") == 0 || choice.compare("w") == 0)
            {
                cout << "Please enter the amount to withdraw: ";
                cin >> withdraw;
                bankObject.withdrawMoney();
                cout << "New balance is: $" << balance << endl;
                break;
            }
            else if(choice.compare("deposit") == 0 || choice.compare("d") == 0)
            {
                cout << "Please enter the amount to deposit: ";
                cin >> deposit;
                bankObject.depositMoney();
                cout << "New balance is: $" << balance << endl;
                break;
            }
            else if(choice.compare("quit") == 0 || choice.compare("q") == 0)
            {
                break;
            }
            else
            {
                cout << "Invalid input." << endl;
                break;
            }
        }
        if(choice.compare("quit") == 0)
        {
            break;
        }
        cout << "Would you like to try again or quit: ";
        cin >> quitOrNo;
        if(quitOrNo.compare("quit") == 0)
        {
            break;
        }
    }
    cout << "Thank you for using the Bank Program." << endl;
    return 0;
}

当我尝试运行代码时，我得到了这个输出:--> 欢迎使用银行计划!您要取款、存款还是退出程序:存款 请输入要存款的金额:100 新余额为:$100 您想再试一次吗或退出:再试一次 您要取款、存款还是退出程序:输入无效。您要再试一次还是退出:<--它将继续这样做，直到我退出程序。有人知道为什么吗？ 粗体 文本是我的输入，斜体 文本是计算机给自己的输入。箭头中的所有内容都是控制台文本。

Answer 1

try again 是两个词，但应用于 std::string 的 >> 仅提取一个词。 again 由下一个循环迭代提取。使用 getline 精确提取一行输入。

我不确定它是否或如何进入无限循环，但如果 cin 无法处理已提供的某些输入，它将停止接受更多输入，直到您调用 cin.clear()。同时，语句 if (cin) 将看到 cin 评估为 false。缺少这种检查的程序通常会默认读取无限的无效输入。