c++ - 重载 << 运算符错误 C2804 : binary 'operator <<' has too many parameters

Question

这是我的类(class):

#ifndef CLOCK_H
#define CLOCK_H
using namespace std;

class Clock
{
    //Member Variables

    private: int hours, minutes;

    void fixTime( );

    public:
        //Getter & settor methods.
        void setHours(int hrs); 
        int getHours() const;
        void setMinutes(int mins); 
        int getMinutes() const; 

        //Constructors
        Clock(); 
        Clock(int);
        Clock(int, int);
        //Copy Constructor
        Clock(const Clock &obj);
        //Overloaded operator functions
        void operator+(const Clock &hours);
        void operator+(int mins);
        void operator-(const Clock &hours);
        void operator-(int minutes1);
        ostream &operator<<(ostream &out, Clock &clockObj); //This however is my problem where i get the error C2804. Saying that it has to many parameters 
};
#endif

所有这个函数应该做的是输出时钟在不同时间的值。

Answer 1

ostream &operator<<(ostream &out, Clock &clockObj); 

应该是

friend ostream &operator<<(ostream& out, Clock &clockObj);    

在类之外定义。

参见此处:Should operator<< be implemented as a friend or as a member function?