c++ 弱引用指针 管理目标交换 简单实验

1.概要

交换管理的两个目标对象，交换后两个指针管理的最终目标会发生变化。
weak_ptr<T>.swap(weak_ptr<T> wp);

2.代码

#include <iostream>
using namespace std;

int main()
{
    shared_ptr<int> sh_ptr = std::make_shared<int>();
    shared_ptr<int> sh_ptr1 = sh_ptr;
    weak_ptr<int> wp1(sh_ptr);
    

    shared_ptr<int> sh_ptr3 = std::make_shared<int>();
    std::weak_ptr<int> wp2(sh_ptr3);
    //交换前
    cout << "-- pre-switch ------------------------------------------\n";
    cout << "wp1 use_count:" << wp1.use_count() << endl;//2
    cout << "wp2 use_count:" << wp2.use_count() << endl;//1

    //交换
    wp1.swap(wp2);
    
    //交换后
    cout << "-- After exchange ------------------------------------------\n";
    cout << "wp1 use_count:" << wp1.use_count() << endl;//1
    cout << "wp2 use_count:" << wp2.use_count() << endl;//2

    cout << "Hello World!\n";
}

3.运行结果

-- pre-switch ------------------------------------------
wp1 use_count:2
wp2 use_count:1
-- After exchange ------------------------------------------
wp1 use_count:1
wp2 use_count:2
Hello World!