1.operator =正常情况

#include <iostream>
using namespace std;

class Box
{
public:
    Box(double L) : length(L) {}
	Box(const Box& b){}
    Box& operator = (const Box&){return *this;}

public:
    double length;   // 长度
};

int main() {
    Box box1(1.0);
    Box box2(2.0);
    cout << box1.length << endl;
    cout << box2.length << endl;
    box1 = box2;
    cout << box1.length << endl;
    return 0;
}

• 输出

1
2
1

2.operator = 返回void

#include <iostream>
using namespace std;

class Box
{
public:
    Box(double L) : length(L) {}
	Box(const Box& b){}
    void operator = (const Box&){}

public:
    double length;   // 长度
};

int main() {
    Box box1(1.0);
    Box box2(2.0);
    cout << box1.length << endl;
    cout << box2.length << endl;

    box1 = box2;
    cout << box1.length << endl;
    return 0;
}

3.1和2结果是一样的，没有差别？

• operator = 返回void，连续赋值情形

4.总结：operator = 返回void，合理合法，但是不适用连续赋值的情形