C++ 重载提取运算符 - 错误无法访问类中声明的私有(private)成员

Question

我正在做一些家庭作业并收到最奇怪的错误。希望你能帮忙。我收到此错误:

Cannot access private member in class

注意:显然我还没有写完这篇文章，但我会尝试边写边测试错误。非常感谢您的任何意见!

// Amanda 
// SoccerPlayer.cpp : main project file.
// October 6, 2012
/* a. Design a SoccerPlayer class that includes three integer fields: a player's jersey     number,
number of goals, and number of assists. Overload extraction and insertion operators for     the class.
b. Include an operation>() function for the class. One SoccerPlayer is considered greater
than another if the sum of goals plus assists is greater.
c. Create an array of 11 SoccerPlayers, then use the > operator to find the player who   has the
greatest goals plus assists.*/

#include "stdafx.h"
#include<conio.h>
#include<iostream>
#include<string>



class SoccerPlayer
{
    friend std::ostream operator<<(std::ostream, SoccerPlayer&);
//  friend std::istream operator>>(std::istream, SoccerPlayer&);
private:
    int jerseyNum;
    int numGoals;
    int numAssists;
public:
    SoccerPlayer(int, int, int);

};

SoccerPlayer::SoccerPlayer(int jersey, int goal, int assist)
{
    jerseyNum = jersey;
    numGoals = goal;
    numAssists = assist;
} 

std::ostream operator<<(std::ostream player,  SoccerPlayer& aPlayer)
{
    player << "Jersey #" << aPlayer.jerseyNum <<
        " Number of Goals " << aPlayer.numGoals << 
        " Number of Assists " << aPlayer.numAssists;
    return player ;
};

int main()
{
return 0;
} 

Answer 1

您想通过引用传递和返回流:您不能复制 IOStream 对象。此外，在写入的情况下，您可能想要传递一个 SoccerPlayer const&。通过这些更改，您的代码应该编译器(尽管在输出运算符的定义之后也有一个多余的分号)。

也就是说，你的输出运算符应该声明为

std::ostream& operator<< (std::ostream&, SockerPlayer const&)

(在其定义和 friend 声明中)。