侯捷 (7、8 pointer-likeclasses&function-likeclasses)

shared_ptr

• 实现一个简单的shared_ptr

1. 两个成员：引用计数与指针
2. 成员函数：构造函数、拷贝构造函数、拷贝赋值操作符、析构函数、解引用操作符重载、指向对象操作符重载

#pragma once
#include 
using namespace std;

template <typename T>
class Shared_ptr{
public:
    Shared_ptr(T *p):ptr(p),pn(new long(1)){}
    Shared_ptr(const Shared_ptr& rhs) : pn(&(++*rhs.pn)),ptr(rhs.ptr){}
    Shared_ptr& operator=(const Shared_ptr& rhs){
        Shared_ptr temp = rhs;
        if( this->ptr == nullptr && --*this->pn == 0 )
        {
            delete ptr;
            delete pn;
        }
        ptr = temp.ptr;
        pn = temp.pn;
        return *this;
    }

    ~Shared_ptr()
    {
        if(--*pn == 0)
        {
            delete ptr;
            delete pn;
        }
    }

    int getref()
    {
        return *pn;
    }

    T& operator*()
    {
        return *ptr;
    }

    T* operator->()
    {
        return ptr;
    }

private:
    T* ptr;
    long* pn;
};

```cpp
#include 
#include "My_shared_ptr.hpp"
using namespace std;

struct a
{
    void print()
    {
        cout << "out" << endl;
    }
};

int main()
{
    My_shared_ptr<a>A = new a;
    A->print();
    return 0;
}

function-like classes（仿函数）

class a
{
	bool operator()(bool a)const
	{
		return a;
	}
};