c++ - 我如何重载 << 以输出枚举的字符串值

Question

实现代表一周中某一天的 Day 类。重载 operator+=、operator-=、operator++(前缀)、operator--(前缀)和 operator<<，如下所述。

我会在重载的 << 定义中使用 switch 语句来计算枚举的字符串值吗？ main 中的代码是测试我们的代码是否正常运行(仍然需要完成操作符的定义)我应该回复枚举和整数之间的隐式转换吗？我不知道如何将枚举放入参数中(如果合适的话)

这是我的代码:

/*
Class Implementation for Day of the week
includes overloaded operators 
*/

#include <iostream>
#include <string>

using std::cout;
using std::cin;
using std::endl;



class Day
{
public:
    enum Dia { SUNDAY, MONDAY, TUESDAY, WEDNESDAY, THURSDAY, FRIDAY, SATURDAY };
    Day(int); // Default Constructor
    Day(const Day&); // Copy Contructor
    Day& operator+=(const Day&); // Overloaded +=
    int getDummy() const;
private:
    int dummyDay;
};

std::ostream& operator<<(std::ostream&, const Day&);


int main()

{
    Day today = Day::WEDNESDAY;
    cout << today;
    std::cout << today << std::endl; // "Wednesday"

    Day generic_day; // default constructor-- default day is Sunday
    std::cout << generic_day << std::endl; // "Sunday"

    ++generic_day;
    std::cout << generic_day << std::endl; // "Monday"

    today += 5;
    std::cout << today << std::endl; // "Monday"

    today -= 1;
    std::cout << today << std::endl; // "Sunday
    return 0;
}
Day::Day(int DayDay = 0)
{
    dummyDay = DayDay;
};

Day& Day::operator+=(const Day& z)
{
    dummyDay += z.dummyDay;
    return *this;
}
std::ostream& operator<<(std::ostream& out, const Day& z)
{

    return out;
}

Day::Day(const Day& z)
{
    dummyDay = z.dummyDay;
}

int Day::getDummy() const
{
    return dummyDay;
}

Answer 1

您可以重载枚举。您不需要创建一个全新的类，您只需为 enum 创建重载并在任何时候调用它们；查看 main 函数中的用法。将 C++ 11 与 enum class 一起使用并实现以下内容，我对其进行了测试并且它正在运行:

#include <iostream>

using namespace std;

enum class Day
{
    Sunday,
    Monday,
    Tuesday,
    Wednesday,
    Thursday,
    Friday,
    Saturday
};

Day& operator++(Day& day)
{
    int i = static_cast<int>(day) + 1;

    // Handle wrap around.
    if(i > 6)   // Saturday = 6
        i = 0;  // Sunday = 0

    day = static_cast<Day>(i);

    return day;
}

ostream& operator<<(ostream& os, const Day day)
{
    switch(day)
    {
        case Day::Sunday:    return os << "Sunday";
        case Day::Monday:    return os << "Monday";
        case Day::Tuesday:   return os << "Tuesday";
        case Day::Wednesday: return os << "Wednesday";
        case Day::Thursday:  return os << "Thursday";
        case Day::Friday:    return os << "Friday";
        case Day::Saturday:  return os << "Saturday";
    }

    return os;
}

int main()
{
    Day day = Day::Monday;
    cout << day << endl;

    ++day;
    cout << day << endl;

    return 0;
}