构造函数、拷贝构造函数、赋值操作符

　　对于这样一种类与类之间的关系，我们希望为其编写“深拷贝”。两个类的定义如下：

class Point {
    int x;
    int y;
};

class Polygon : public Shape {
    Point *points;
};

　　1. 构造函数

//构造函数
Polygon(const Point &p) : _point(new Point)
{
　　this->_point->x = p.x;
　　this->_point->y = p.y;
}

　　2. 拷贝构造函数

//拷贝构造
Polygon(const Polygon &p) : _point(new Point)
{
    this->_point->x = p._point->x;
    this->_point->y = p._point->y;
}

　　3. 赋值构造函数

//赋值操作符
void operator= (const Polygon &rhs)
{
    this->_point->x = rhs._point->x;
    this->_point->y = rhs._point->y;
}

　　全部代码 & 测试用例

#include <iostream>

using namespace std;

struct Shape {
    int no; //形状编号
};

struct Point {
    int x;
    int y;

    Point(int x, int y) : x(x), y(y) {}
    Point() = default;
};

struct Polygon :public Shape {
    Point *_point;

    //构造函数
    Polygon(const Point &p) : _point(new Point)
    {
        this->_point->x = p.x;
        this->_point->y = p.y;
    }

    //拷贝构造
    Polygon(const Polygon &p) : _point(new Point)
    {
        this->_point->x = p._point->x;
        this->_point->y = p._point->y;
    }

    //赋值操作符
    void operator= (const Polygon &rhs)
    {
        this->_point->x = rhs._point->x;
        this->_point->y = rhs._point->y;
    }

    ~Polygon()
    {
        delete this->_point;
    }
};

int main()
{
    Point x1(1, 2);

    Polygon p1(x1);
    Polygon p2 = p1;
    Polygon p3(p2);

    p1 = p2;

    return 0;
}

　　内存中变量地址

　　p1 . _ponit 内存地址 0x002c0cb8

　　p2 . _point 内存地址 0x002c0cf0

　　p3 . _point 内存地址 0x002c0d28

　　（都是不相同的内存地址）

成功