自动售货机程序的更改值不正确

Question

main.cpp中：

#include <iostream>
#include <string>
#include "Money.h";
#include "Product.h";
using namespace std;

int main() {
    string pName; //productName
    double pAmount, pPrice; //productAmount
    cout << "Product's Available are ... " << endl;
    cout << "---Water--- " << endl;
    cout << "---Energy Drink--- " << endl;
    cout << "---Thirst Quencher---" << endl;
    cout << "---Protein Shake---" << endl;
    cout << endl;
    cout << "Please enter your selection" << endl;
    //To trigger an exception, type in a product that is not stated on the list
    cin >> pName;
    Product p(pName);
    cout << "Please enter the amount you are paying into the vending machine" << endl;
    cin >> pAmount;
    Money m(pAmount, p.productPrice);

}

Product.h：

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

#ifndef PRODUCT_H
#define PRODUCT_H

class Product {
public:
    Product();
    Product(string name); //default constructor 
    void givePrice(string Productname);
//protected:
    string productName;
    double productPrice;
};

#endif //PRODUCT_H

Product.cpp：

#include <iostream>
#include <string>
#include "Product.h";

Product::Product(string name) {
    givePrice(name);
}

Product::Product() {}

void Product::givePrice(string productName) {
    try {


        if (productName == "Protein Shake" || productName == "protein shake") {
            productPrice = 5;
            cout << "The price for " << productName << " will be $" << productPrice << endl;
            cout << endl;
        }

        else if (productName == "Water" || productName == "water") {
            productPrice = 2.0;
            cout << "The price for " << productName << " will be $" << productPrice << endl;
            cout << endl;
        }

        else if (productName == "Energy Drink" || productName == "energy drink") {
            productPrice = 4.25;
            cout << "The price for " << productName << " will be $" << productPrice << endl;
            cout << endl;
        }

        else if (productName == "Thirst Quencher" || productName == "thirst quencher") {
            productPrice = 3.75;
            cout << "The price for " << productName << " will be $" << productPrice << endl;
            cout << endl;
        } 

        else {
            throw productName;
        }
    } catch (string x) {
        cout << x << " does not exist! Please try again" << endl;
        cout << endl;
    }

 } 

Money.h：

#include <iostream>
#include <string>
#include "Product.h";
using namespace std;

#ifndef MONEY_H
#define MONEY_H

class Money : public Product {
public:
    Money(double amountP, double pPrice);
    void setChange(double& amount);
    void addMoney(double& amount);
protected:
    bool insertMoney;
    double amountPaid;
    bool sufficientAmount;
    double change;
};

#endif //MONEY_H

Money.cpp：

#include "Money.h"
#include <iostream>
using namespace std;


Money::Money(double amountP, double pPrice) {
    addMoney(amountP);
    setChange(amountP);
    cout << "Const: Value of PP = " << productPrice << endl;
}
void Money::addMoney(double& amount) {
     amountPaid = amount;
}

void Money::setChange(double& amount) {
    try {   
        sufficientAmount = false;
        cout << "You have paid " << amountPaid << endl; //it always comes here
        cout << "Current change value: " << change << endl;
        cout << "Product Price: " << productPrice << endl;
        while (sufficientAmount == false) {
            if (amount < productPrice) {
                cout << "You do not have enough money $" << change << " has been returned";
                sufficientAmount = false;
            }

            else if (amount > productPrice) {
                //ness. Come again." << endl; doesnt come in here. 
                change = amountPaid-productPrice; //calculate change
                cout << "Your change is $" << change << endl;
                sufficientAmount = true;
                cout << "Enjoy your product! Please come back again!" << endl;
            }

            else if (amount = productPrice) {
                cout << "Thank you for your business. Come again and enjoy your drink.";
                sufficientAmount = true; 
            }





            else if (amount < 0 || amount == 0) {
                throw 0;
            }

        }
    } catch(int x) {
        cout << "Please enter an amount that is higher than $" << x;
    }
}

输入 - ＆gt;水作为产品，数量为5.这是我得到的输出：

为什么我会得到这些随机数？由于某种原因，productPrice被更改为-9******个数字。

Answer 1

您不会在任何地方初始化双变量变量，本质上也是相同的产品价格。

您在此处未使用pPrice变量。

Money::Money(double amountP, double pPrice) {
...
}