C++智能指针模板应用详细介绍

void remodel(std::string & str)
{
    std::string *ps =new std::string(str);
    ....
    if(oh_no)
        throw exception();
    ...
    delete ps;
    return;
}

template<class X>
class auto_ptr
{
public:
    explicit auto_ptr(X* p) noexcept;
    ....
}

//智能指针1.cpp
#include<iostream>
#include<string>
#include<memory>
class Report
{
private:
    std::string str;
public:
    Report(const std::string &s):str(s){std::cout<<"Object created!\n";}
    ~Report(){std::cout<<"Object deleted";}
    void comment() const{std::cout<<str<<"\n";}
};
int main()
{
    {
        std::auto_ptr<Report> ps(new Report("using auto_ptr"));
        ps->comment();
    }
    {
        std::unique_ptr<Report> ps(new Report("using unique_ptr"));
        ps->comment();
    }
    {
        std::shared_ptr<Report> ps(new Report("using shared_ptr"));
        ps->comment();
    }
}

shared_ptr<double> pd;
double *p_reg=new double;
pd=p_reg;//不允许因为构造函数是`explicit`修饰的,所以不能隐式类型转换
pd=shared_ptr<double>(p_reg);//允许,使用赋值运算符
shared_ptr<double> pshared=p_reg;//不允许,因为不能隐式类型转换
shared_ptr<double> pshared(p_reg);//允许调用构造函数。

int a=5;
int *p=&a;
shared_ptr<int> ps(p);

#include<memory>
#include<iostream>
int main()
{
    using namespace std;
    /*{
        auto_ptr<int[]> ps(new int[2]{1,2});
        cout<<ps[0]<<endl;
        cout<<ps[1]<<endl;
    }*/
    {
        unique_ptr<int[]> ps(new int[2]{1,2});
        cout<<ps[0]<<endl;
        cout<<ps[1]<<endl;
    }
    {
        shared_ptr<int []> ps(new int[2]{1,2});
        cout<<ps[0]<<endl;
        cout<<ps[1]<<endl;
    }
}

auto_ptr<string> ps(new string("I reigned lonely as a cloud."));
auto_ptr<string> pd;
pd=ps;

//智能指针3.cpp
#include<iostream>
#include<string>
#include<memory>
int main()
{
    using namespace std;
    auto_ptr<string> films[5]=
    {
        auto_ptr<string>(new string("1")),
        auto_ptr<string>(new string("2")),
        auto_ptr<string>(new string("3")),
        auto_ptr<string>(new string("4")),
        auto_ptr<string>(new string("5"))
    };
    auto_ptr<string> p;
    p=films[2];
    for(int i=0;i<5;i++)
    {
        cout<<*films[i]<<endl;
    }
    cout<<*p<<endl;
}

unique_ptr<string> ps(new string("I reigned lonely as a cloud."));
unique_ptr<string> pd;
pd=ps;

unique_ptr<string> demo(const char*s)
{
    unique_ptr<string> temp(new string(s));
    return temp;
}
...
unique_ptr<string>ps;
ps= demo("something");
...

unique_ptr<string> pu1;
pu1=unique_ptr<string>(new string("yo!"));

unique_ptr<string> ps(new string("I reigned lonely as a cloud."));
unique_ptr<string> pd;
pd=std::move(ps);

#include<memory>
#include<iostream>
#include<vector>
#include<cstdlib>
#include<algorithm>
std::unique_ptr<int> make_int(int n)
{
    return std::unique_ptr<int>(new int(n));
}
void show(const std::unique_ptr<int> &pi)
{
    std::cout<<*pi<<' ';
}
int main()
{
    using std::vector;
    using std::unique_ptr;
    using std::rand;
    int size=10;
    vector<unique_ptr<int>> vp(size);
    for(int i=0;i<size;i++)
        vp[i]=make_int(rand()%1000);//#1
    vp.push_back(make_int(rand()%1000));//#2
    std::for_each(vp.begin(),vp.end(),show);//#3
}

unique_ptr<int> pup(make_int(rand()%1000));//ok
shared_ptr<int> spp(pup);//不允许,构造函数不能接受`unique_ptr`的左值
shared_ptr<int> spr(make_int(rand()%1000));//ok

#include<memory>
#include<iostream>
int main()
{
    using std::shared_ptr;
    using std::weak_ptr;
    using std::cout;
    using std::endl;
    shared_ptr<int> p1(new int(255));
    weak_ptr<int>wp(p1);
    cout<<"引用计数: "<<wp.use_count()<<endl;
    cout<<"存储信息: "<<*(wp.lock())<<endl;
    shared_ptr<int> p2=p1;
    cout<<"引用计数: "<<wp.use_count()<<endl;
    cout<<"存储信息: "<<*(wp.lock())<<endl;
}