参考网址：https://www.xqiao123.site/2018/10/03/%E6%95%99%E7%A8%8B%EF%BC%9A%E7%AC%AC37%E8%AF%BE-%E6%99%BA%E8%83%BD%E6%8C%87%E9%92%88/

test.cpp

#include <iostream>
#include <string> 

using namespace std;

class Test {
	int i;
public:
	Test(int i) {
		cout << "Test(int i)" << endl;
		this->i = i;
	}
	int value() {
		return i;
	}
	Test() {
		cout << "~Test()" << endl;
	}
};

class Pointer {
	Test* mp;
public:
	Pointer(Test* p = NULL) {
		mp = p;
	}
	Pointer(const Pointer& obj) {
		mp = obj.mp;
		const_cast<Pointer&>(obj).mp = NULL;
	}
	Pointer& operator = (const Pointer& obj) {
		if (this != &obj) {
			delete mp;
			mp = obj.mp;
			const_cast<Pointer&>(obj).mp = NULL;
		}
		return *this;
	}
	Test* operator -> () {
		return mp;
	}
	Test& operator * () {
		return *mp;
	}
	bool isNULL() {
		return (mp == NULL);
	}
	~Pointer() {
		delete mp;
	}
};

int main() {
	Pointer p1 = new Test(0);
	cout << p1->value() << endl;
	Pointer p2 = p1;
	cout << p1.isNULL() << endl;
	cout << p2.isNULL() << endl;
	getchar();
	return 0;
}