c++ - 添加到私有(private)变量不起作用

Question

我目前正在学习 C++ 并尝试制作一台自动售货机!我知道我的代码真的很糟糕，对此我感到很抱歉。我正在尝试实现一家银行并让用户从中贷款，唯一的问题是银行无法向用户添加资金。这是我的代码。

void Bank::askLoan() {
//ColaMachine object
ColaMachine cola;

bool loanGranted = false;

cout << string(100, '\n');
cout << "You do not have enough money!\n\n";
cout << "Would you like to take a loan?\n\n(1)-Yes\n(2)-No\n\n\n";
int choice;
cin >> choice;

switch (choice) {
case 1:
    //Print the bank menu!

    printBank();
    while (loanGranted != true) {
        cout << "Enter the amount to lend: $";
        cin >> _loanValue;
        //Test if _loanValue is less than or = to bankmoney, so they would scam the bank.
        if (_loanValue <= _bankMoney) {
            //Supposed to add money to the user.
            cola.addMoney(_loanValue);
            break;
        }
        else {
            cout << "You entered too much! Try again..." << endl;
        }
    }
    break;
case 2:
    //User does not want to take a loan! Quit the game!
    //Not implemented, yet.
    break;
default:
    cout << "Bad input! Please retry..." << endl;
}

如果输入的金额在正确的范围内，它会调用 ColaMachine 类的 addMoney() 函数。

void ColaMachine::addMoney(int money) {

//This part doesnt seem to modify the actual value
//Whenever It goes back to the main game loop it doesnt change.
_money += money;

据我了解 += 与 _money = _money + money 相同；

我在这里做错了什么？GitHub 上的完整源代码- https://github.com/Rohukas/-LearningCPP

Answer 1

问题是您正在 askLoan() 方法中创建新的可乐对象，该对象在函数结束时被销毁，因此调用 addMoney() 方法会修改该临时可乐对象的状态。一种选择是通过指向 askLoan() 方法的指针提供可乐对象。例如，在 ColaMachine::chooseDrink() 中，您将调用 bo.askLoan(this)。 this 是指向您调用 bo.askLoan() 的对象的指针。您需要修改您的 askLoan() 签名:void askLoan(ColaMachine * cola) 并从 askLoan() 本身中删除 ColaMachine cola;。