c++ - 重载时出现堆栈溢出 >> 为类调用运算符函数。我需要做哪些改变？

Question

下面是>>运算符重载的类文件。

class Timepoint {
public:
    Timepoint();
    Timepoint(unsigned short yearValue = 9999, unsigned short month = 12, unsigned short date = 31, unsigned short hour = 23, unsigned short minute = 59);
    ~Timepoint();
    unsigned short get_dayOfYear();
    void operator++();
    friend std::ostream& operator<<(std::ostream& out, const Timepoint& timepoint);
    friend std::istream& operator>>(std::istream&, const Timepoint&);

private:
    unsigned short dayOfYear;
    unsigned short year;
    unsigned short time;
    const static short days[];
};

下面是触发堆栈溢出错误的重载函数。我必须将时间作为用户的时间戳并存储在对象数据中。当控制权到达此函数时，将触发堆栈溢出。

std::istream& operator>>(std::istream& in, const Timepoint& timepoint)
{
    int day, month, hour, minute;
    std::string timestamp;
    in >> timestamp;
    std::stringstream ss(timestamp);
    ss >> timepoint.year;
    ss.ignore();
    ss >> month;
    ss.ignore();
    ss >> day;
    ss.ignore();
    ss >> hour;
    ss.ignore();
    ss >> minute;

    const_cast<Timepoint&>(timepoint).dayOfYear = timepoint.days[month] + day;
    const_cast<Timepoint&>(timepoint).time = hour * 60 + minute;
    return in;
}

Answer 1

ss >> timepoint.year 解释为

ss >> Timepoint(timepoint.year);

这是读入 const unsigned short 的唯一可行方法。这当然会导致无限递归。

这里的根本原因是，您莫名其妙地将一个 const 对象传递给一个明确目标是修改该对象的函数。只需删除 const。

您可能还想使构造函数显式，以避免此类意外转换。