c++ - "No viable overloaded ' = ' "为什么？

Question

我正在为我的一门类(class)做一个项目，我很确定我几乎完成了这个项目。基本上我必须输入 2 人的票，我必须找到最高价和最低价。我需要重载 * 和/运算符来解决该项目的问题。此外，根据老师的指示，friend 声明对于该项目来说是必需的。

现在，对于这个问题。我正在尝试将正确的票证变量(t1 或 t2)存储到 t3 中，以便我可以将其返回给主变量。当我使用“=”将 t1 设置为 t3 时，它说“没有可行的重载 '='”。以下是我的代码:

#include <iostream>

using namespace std;

class ticket
{
public:
    ticket();
    double input();
    double output();
    friend ticket operator *(const ticket &t1, const ticket &t2);
    friend ticket operator /(const ticket &t1, const ticket &t2);
private:
    void cost();
    string name;
    double miles, price;
    int transfers;
};


int main()
{
    ticket customer1, customer2, customer3;

    //------------------------------------------------
    cout << "*** Customer 1 ***" << endl;
    customer1.input();
    cout << "--- Entered, thank you ---" << endl;


    cout << "*** Customer 2 ***" << endl;
    customer2.input();
    cout << "--- Enter, thank you ---" << endl;
    //------------------------------------------------



    //------------------------------------------------
    cout << "Testing of the * operator: " << endl;
    customer3 = customer1 * customer2;
    cout << "*** Database printout: ***" << endl;
    customer3.output();
    cout << endl;
    cout << "--- End of Database ---" << endl;
    //------------------------------------------------


    //------------------------------------------------
    cout << "Testing of the / operator:" << endl;
    customer3 = customer1 / customer2;
    cout << "*** Database printout: ***" << endl;
    customer3.output();
    cout << endl;
    cout << "--- End of Database ---" << endl;
    //------------------------------------------------


        return 0;
}

ticket operator *(const ticket &t1, const ticket &t2)
{
    ticket t3;

    if (t1.price > t2.price)
        t3 = t1.price;
    else
        t3 = t2.price;
    return t3;
}
ticket operator /(const ticket &t1, const ticket &t2)
{
    ticket t3;

    if (t1.price < t2.price)
        t3 = t1.price;
    else
        t3 = t2.price;
        return t3;
}
ticket::ticket()
{
}

double ticket::input()
{
    cout << "Miles? ";
    cin >> miles;

    cout << endl << "Transers? ";
    cin >> transfers;

    cout << endl << "Name? ";
    cin >> name;

    cost();

    cout << endl << "Price is: " << price << endl;

    return miles;
}

double ticket::output()
{
    cout << name << '\t' << miles << "mi \t " << transfers << " transfers \t" << price;
    return miles;
}

void ticket::cost()
{
    price = (.5 * miles) - (50 * transfers);
}

Answer 1

您没有为 ticket 定义一个 operator=，它接受一个 double 作为它的参数。因此，您不能将 double 分配给 ticket 对象。