c++ 智能指针的使用

https://www.cnblogs.com/TenosDoIt/p/3456704.html

#include <QCoreApplication>
#include <string>
#include <iostream>
#include <memory>

using namespace  std;

class Test
{
public:
    Test(string s)
    {
        str = s;
       cout<<"Test creat : " << str << endl;
    }
    ~Test()
    {
        cout<<"Test delete:"<<str<<endl;
    }
    string& getStr()
    {
        return str;
    }
    void setStr(string s)
    {
        str = s;
    }
    void print()
    {
        cout<<str<<endl;
    }
private:
    string str;
};

unique_ptr<Test> fun()
{
    return unique_ptr<Test>(new Test("789"));
}

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);

    auto_ptr<Test> ptest0(new Test("123"));
    ptest0->setStr("hello ");
    ptest0->print();
    ptest0.get()->print();
    ptest0->getStr() += "world !";
    (*ptest0).print();
    ptest0.reset(new Test("123"));
    ptest0->print();
    cout << "
";

    unique_ptr<Test> ptest1(new Test("123"));
    unique_ptr<Test> ptest2(new Test("456"));
    ptest1->print();
    ptest2 = std::move(ptest1);//不能直接ptest2 = ptest1
    if(ptest1 == NULL)cout<<"ptest = NULL
";
    Test* p = ptest2.release();
    p->print();
    ptest1.reset(p);
    ptest1->print();
    ptest2 = fun(); //这里可以用=，因为使用了移动构造函数
    ptest2->print();
    cout << "
";


    shared_ptr<Test> ptest(new Test("123"));
    shared_ptr<Test> ptest23(new Test("456"));
    cout<<ptest23->getStr()<<endl;
    cout<<ptest23.use_count()<<endl;
    ptest = ptest23;//"456"引用次数加1，“123”销毁
    ptest->print();
    cout<<ptest23.use_count()<<endl;//2
    cout<<ptest.use_count()<<endl;//2
    ptest.reset();
    ptest23.reset();//此时“456”销毁
    cout<<"done !
";

    return a.exec();
}