訪問類C++的私有變量

Question

試圖重載==操作符，想要比較小時，分鐘，秒變量，但它們被聲明爲私有變量，並且我們被告知我們不允許調整標題文件。如何在我的代碼中訪問它們以重載==運算符？我也無法將它們作爲h，m，s來訪問，因爲它們是在setTime方法中調用的。

// using _TIMEX_H_ since _TIME_H_ seems to be used by some C++ systems 

#ifndef _TIMEX_H_ 
#define _TIMEX_H_ 

using namespace std; 

#include <iostream> 

class Time 
{ public: 
    Time(); 
    Time(int h, int m = 0, int s = 0); 
    void setTime(int, int, int); 
    Time operator+(unsigned int) const; 
    Time& operator+=(unsigned int); 
    Time& operator++(); // postfix version 
    Time operator++(int); // prefix version 

    // new member functions that you have to implement 

    Time operator-(unsigned int) const; 
    Time& operator-=(unsigned int); 
    Time& operator--();  // postfix version 
    Time operator--(int); // prefix version 

    bool operator==(const Time&) const; 
    bool operator<(const Time&) const; 
    bool operator>(const Time&) const; 

    private: 
    int hour, min, sec; 

    friend ostream& operator<<(ostream&, const Time&); 

    // new friend functions that you have to implement 

    friend bool operator<=(const Time&, const Time&); 
    friend bool operator>=(const Time&, const Time&); 
    friend bool operator!=(const Time&, const Time&); 

    friend unsigned int operator-(const Time&, const Time&); 
}; 

#endif 

.cpp文件

using namespace std; 

#include <iostream> 
#include <iomanip> 
#include "Time.h" 

Time::Time() 
{ hour = min = sec = 0; 
} 

Time::Time(int h, int m, int s) 
{ setTime(h, m, s); 
} 

void Time::setTime(int h, int m, int s) 
{ hour = (h>=0 && h<24) ? h : 0; 
    min = (m>=0 && m<60) ? m : 0; 
    sec = (s>=0 && s<60) ? s : 0; 
} 

Time operator==(Time &t1, Time &t2) 
{ 
    return (t1.hour==t2.hour); 
} 

Answer 1

你應該實現==運營商是一個成員函數，所以你應該定義

bool Time::operator==(const Time& t) const 
{ 
    return hour == t.hour && min == t.min && sec == t.sec; 
} 

Answer 2

這裏有一個竅門：

bool operator==(Time &t1, Time &t2) 
{ 
    return !(t1 != t2); 
} 
bool operator!=(const Time& t1, const Time& t2) 
{ 
    return t1.hour != t2.hour || t1.min != t2.min || t1.sec != t2.sec; 
} 

你不能acc在您的運營商==功能中使用您的私人字段。但是因爲你的操作符！=被定義爲朋友，所以你可以在那裏做。