重载下标运算符“[]”在l值和r值情况下 [英] Overloading the subscript operator "[ ]" in the l-value and r-value cases

问题描述

我在类间隔中重载了[]运算符以返回分钟或秒。

I have overloaded [] operator in my class Interval to return minutes or seconds.

但我不知道如何使用[]运算符将值分配给分钟或秒。

But I am not sure how to assign values to minutes or second using [] operator.

例如：我可以使用这个语句


cout<< a [1]< min和< a [0]< sec< endl;

For example : I can use this statement

cout << a[1] << "min and " << a[0] << "sec" << endl;

但我想重载[]运算符，所以我甚至可以使用

but I want to overload [] operator, so that I can even assign values to minutes or seconds using

a[1] = 5;
a[0] = 10;

我的代码：

#include <iostream>

using namespace std;

class Interval
{

public:

    long minutes;
    long seconds;

    Interval(long m, long s)
    {
        minutes = m + s / 60;
        seconds = s % 60;
    }

    void Print() const
    {
        cout << minutes << ':' << seconds << endl;
    }

    long operator[](int index) const
    {
        if(index == 0)
            return seconds;

        return minutes;
    }

};

int main(void)
{
    Interval a(5, 75);
    a.Print();
    cout << endl;

    cout << a[1] << "min and " << a[0] << "sec" << endl;
    cout << endl;

}

我知道我必须将成员变量声明为私有，

I know I have to declare member variables as private, but I have declared here as public just for my convenience.

推荐答案

返回对相关成员的引用，而不是其值：

Return a reference to the member in question, instead of its value:

long &operator[](int index)
{
    if (index == 0)
        return seconds;
    else
        return minutes;
}

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