智能指针

shared_ptr

//
// Created by Administrator on 2022/2/21.
//
/*
 * 智能指针 shared_ptr
 */
#include<bits/stdc++.h>
using namespace std;
int main() {
    shared_ptr<int> p1(new int(10));
    shared_ptr<int> p2(p1);
    cout<<*p2<<endl;
    p1.reset(); // 引用计数 -1
    if(p1) {
        cout<<"p1 不为空"<<endl;
    }
    else{
        cout<<"p1 为空"<<endl;
    }
    cout<<*p2<<endl;
    cout<<p2.use_count()<<endl;
    return 0;
}

unique_ptr

//
// Created by Administrator on 2022/2/21.
//
/*
 * unique_ptr 不共享内存，没有拷贝构造函数，只有移动构造函数
 */
#include<bits/stdc++.h>
using namespace std;
int main() {
    unique_ptr<int> p5(new int);
    *p5 = 10;
    int *p = p5.release(); // 释放所有权，但是堆内存不会销毁
    cout<<*p<<endl;
    if(p5) {
        cout<<"p5 is not nullptr"<<endl;
    }
    else {
        cout<<"p5 is nullptr"<<endl;
    }
    unique_ptr<int> p6;
    p6.reset(p); // 释放当前指向的内存并且获取 p 指向的堆内存所有权
    cout<<*p6<<endl;
    return 0;
}

weak_ptr

//
// Created by Administrator on 2022/2/21.
//
/*
 * weak_ptr
 */
#include<bits/stdc++.h>
using namespace std;
int main() {
    shared_ptr<int> sp1(new int(10));
    shared_ptr<int> sp2(sp1);
    weak_ptr<int> wp(sp2);
    cout<<wp.use_count()<<endl;
    sp2.reset();
    cout<<wp.use_count()<<endl;
    cout<<*(wp.lock())<<endl;
    return 0;
}