类定义（3） 类声明，类定义，类对象

using namespace std;class Screen;  //<span style="color:#ff0000;">类声明</span>class Y;  //类的前置声明class X   //名称出现及声明{//各种成员private:Y *ptr; //Y声明即可Y *pt; //<span style="color:#ff0000;">指针型成员，指向自己</span>};class Y       //类定义{private:X *ptr;X obj;};class Record  //一个完整的类：类定义，类声明{public:Record():byte_count(0){}Record(size_t s):byte_count(s){}Record(string nm):name(nm),byte_count(0){}size_t get_count() const{return byte_count;}string get_name() const{return name;}private:size_t byte_count;string name;};struct person  //struct 默认是public{public:person(const string &nm,const string &ad):name(nm),address(ad){}//struct 可以有构造函数 C++功能增强string GetName(){return name;} //C++ struct 可以写函数string GetAdress(){return address;}private:string name;string address;};int main(){class Record r2;//class 省略Record r; //堆栈上创建对象Record *p=new Record; //在堆上创建对象delete p;//Screen S;//error 未定义类 失败person a("perter","shanghai");getchar();return 0;}