C++运算符'<<'错误

Question

我有一个关于家庭作业的问题.

我有两节课.一个叫做ticket.cpp,另一个叫做TicketOrder.cpp

主要在ticket.cpp内.

我在Linux上使用g ++编译器.

我正在做的是尝试打印出一个TicketOrder名为orders 的对象的向量,但它给了我以下错误:

ticket.cpp:57:错误:'std :: cout <<命令中的'operator <<'不匹配.std :: vector <_Tp,_Alloc> :: operator [],_Tp = TicketOrder,_Alloc = std :: allocator'

这是我的代码:

ticket.cpp

#include <iostream>
#include <vector>
#include <limits>
#include <cctype>
#include "TicketOrder.cpp"
using namespace std;

int main ()
{
    int numberoftickets=0;
    string input2;
    char input3;
    int profit=0;
    vector <TicketOrder> orders;
    int atotalmoney=0;
    int btotalmoney=0;
    int ctotalmoney=0;
    int dtotalmoney=0;
    int etotalmoney=0;

    do
    {
        cout << "\nPick a ticket that you would like to buy: \n\n";
        cout << "(A) Students without an activity card: $2.00 \n";
        cout << "(B) Faculty and staff: $3.00 \n";
        cout << "(C) USC alumni: $5.00 \n";
        cout << "(D) UCLA students and alumni: $20.00 \n";
        cout << "(E) Everyone else: $10.00 \n";

        cin >> input3;

        if (input3=='A')
        {
            cout << "How many tickets do you wish to buy? " <<endl;

            if (numberoftickets >0)
            {
                TicketOrder order;
                order.setQuantity(numberoftickets);
                order.setType(input3);
                orders.push_back(order);
                for (int i=0; i< orders.size(); i++)
                {
                    cout << orders[i];
                }
            }
        }
        else
        {
            cout << "Sorry did not recognize input, try again. " << endl;
        }
    } while (input3 != 'S');

TicketOrder.cpp:

#include <iostream>
using namespace std;

class TicketOrder
{
public :
    //Getters

    int getQuantity() const
    {
        return quantity;
    }

    char  getType() const
    {
        return type;
    }

    //Setters

    void setQuantity (int x)
    {
        quantity=x;
    }

    void setType(char y)
    {
        type =y;
    }

private:
    char type;
    char quantity;

};

Answer 1

由于编译器笨拙地试图解释,代码缺少operator<<的TicketOrder类.

class TicketOrder {
public:
    friend std::ostream& operator<<(std::ostream& os, TicketOrder const& order) {
        os << "Type: " << type << ", quantity: " << quantity;
        return os;
    }

    char type;
    int quantity;
};

(注意:您可能想要更改quantity为int.)

Answer 2

您必须将运算符 << 函数添加为友元，才能使用 cout 从 TicketOrder 对象中打印值。进一步阅读