重载运算符std :: ostream＆operator <<打印实例内存地址

Question

I'm trying to overload std::ostream& operator<< doing this:

#include <iostream>

class MyTime
{
private:
    unsigned char _hour;
    unsigned char _minute;
    float _second;
    signed char _timeZone;
    unsigned char _daylightSavings;
    double _decimalHour;

    friend std::ostream& operator<<(std::ostream&, const MyTime&);
public:
    MyTime();
    ~MyTime();
};

And operator's implementation:

std::ostream& operator<<(std::ostream &strm, const MyTime &time)
{
    return strm << (int)time._hour << ":" << (int)time._minute << ":" << time._second << " +" << (int)time._daylightSavings << " zone: " << (int)time._timeZone << " decimal hour: " << time._decimalHour;
}

But when I do this:

MyTime* anotherTime = new MyTime(6, 31, 27, 0, 0);
std::cout << "Time: " << anotherTime << std::endl;

It only prints anotherTime memory address.

What am I doing wrong?

Answer 1

You meant:

std::cout << "Time: " << *anotherTime << std::endl;

Or, even better:

MyTime anotherTime (6, 31, 27, 0, 0);
std::cout << "Time: " << anotherTime << std::endl;

Answer 2

Your operator expects an instance object by const reference but you're giving it a pointer. Either do std::cout << "Time: " << *anotherTime << std::endl; (note the * ) or add another operator:

friend std::ostream& operator<<(std::ostream&, const MyTime*);

Answer 3

std::cout << "Time: " << anotherTime << std::endl;

in that code above anotherTime instance is a myTime*, but it must be myTime.

You have two solutions to fix this:

Making myTime on stack, and it will work fine because anotherTime now not a pointer.

MyTime anotherTime(6, 31, 27, 0, 0);
    std::cout << "Time: " << anotherTime << std::endl;

dereference the pointer in your code, like this:

MyTime* anotherTime = new MyTime(6, 31, 27, 0, 0);
std::cout << "Time: " << *anotherTime << std::endl;