c++逐渐退化的虚函数

#include <map>
#include <iostream>
/*
    类虚函数遇到构造和析构就退化了
 */

class Event; //类的前置声明
class Event {};
class Base {
    public:
        virtual ~Base() {} //why? virtual
        Base(int _id) : m_id(_id) {}
        virtual void act(Event const&) = 0;
        virtual void print() const = 0;
        int id() const { return m_id; } 
    private:
        int m_id;
};
class Drived : public Base { //why public?
    public:
        void act (Event const&);
        void print() const;
        Drived(int id);
        ~Drived();
    private:

};
class Grouped : public Base {
    public:
        void act(Event const&);
        void print() const;
        void addBase(Base* b);
        void removeBase(int id);
        Grouped(int id);
        ~Grouped();
    private:
        std::map<int, Base *> m_info;
};
void test() {
    //int a = 1;
    /*
    Drived *info = new Drived(1);   
    Grouped *group = new Grouped();

    group->print();
    group->act(ev);
    group->addBase(info);
    group->removeBase(info->id());
    group->id();

    Base *baseGroup = group;
    baseGroup->act(ev);
    baseGroup->print();
    baseGroup->id();
    //removeBase()
    //addBase()
    //而基类的指针baseGroup中强制把派生类转换,而基类在虚函数中干的事,与派生类的一样
    //相当于派生类来实现函数,而不是基类.这就实现了指针对接口进行编程.
    delete group; //delete baseGroup;没有内存泄露,　与delete group等价
    delete info;
    */
}


int main(void) {
    test();
    return 0 ;
}

c++逐渐退化的虚函数

原文：https://www.cnblogs.com/lyxf/p/12358254.html