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C++句柄类

ops 2025/6/30 17:52:47

假设有一个父类base，然后从base继承了多个子类base1，base2等等，C++句柄类主要是用来管理多个子类，统一个的接口，不同的操作．

句柄类需要智能指针的基础知识和多态的知识，句柄类其实就是智能指针＋多态知识．如果，对智能指针不是很了解，可以查看我上篇博客．

直接看代码如下:

#include <iostream>
#include <string>
class animal
{
public:virtual animal* clone() const=0;virtual void eat() const = 0;virtual void haul() const = 0;
};class cat:public animal
{
public:cat(std::string n):name(n){std::cout<<"create cat:"<<name<<std::endl;}~cat(){}virtual animal* clone() const{return new cat(*this);}virtual void eat() const{std::cout<<name<<" \teat"<<std::endl;}virtual void haul() const{std::cout<<name <<" \thaul"<<std::endl;}
private:std::string name;
};class dog:public animal
{
public:dog(std::string n):name(n){std::cout<<"create dog:"<<name<<std::endl;}~dog(){}virtual animal* clone() const{return new dog(*this);}virtual void eat() const{std::cout<<name<<" \teat"<<std::endl;}virtual void haul() const{std::cout<<name <<" \thaul"<<std::endl;}
private:std::string name;
};class handle
{
public:handle():an(NULL),use(new std::size_t(1)){}handle(const animal&);handle(const handle& h):an(h.an),use(h.use){++*use;}handle& operator=(const handle&);~handle(){decr_use();}const animal* operator->()const {if(an) return an;elsereturn (animal*)-1;}const animal* operator*() const {if(an) return an;elsereturn (animal*)-1;}
private:animal *an;std::size_t *use;void decr_use(){if (--*use==0) {//std::cout<<"use is = "<<*use<<std::endl;delete an;delete use;}}
};handle::handle(const animal &an):an(an.clone()),use(new std::size_t(1)){    }handle& handle::operator=(const handle& h)
{++*h.use;decr_use();an=h.an;use=h.use;return *this;
}

以下是测试函数，

<span style="font-size:18px;">#include "smart_ptr.h"
#include <iostream>int main(void)
{cat c("tom");dog d("jim");handle h(c);h->eat();//通过重载->操作符实现(*h)->haul();//通过重载*操作符实现handle h1(d);h1->eat();(*h1)->haul();// handle *h2=new handle(h);// delete h2;return 0;
}</span>

输出结果为：