C++多态实现

#include <iostream>
#include <functional>
using namespace std;



using EatPtr = function<void()>;
using PlayPtr = function<void()>;
struct VirtualTable {
	EatPtr m_eat;
	PlayPtr m_play;
};

struct Base {
	VirtualTable m_table;
};

struct DeriveA {
	Base m_base;
};

struct DeriveB {
	Base m_base;
};

void BaseEat() {
	cout << "base eat" << endl;
}

void BasePlay() {
	cout << "base play" << endl;
}

void DeriveAEat() {
	cout << "derive a eat" << endl;
}
void DeriveAPlay() {
	cout << "derive a play" << endl;
}

void DeriveBEat() {
	cout << "derive b eat" << endl;
}
void DeriveBPlay() {
	cout << "derive b play" << endl;
}



int main() {
	DeriveA a;
	DeriveB b;
	a.m_base.m_table.m_eat = DeriveAEat;
	a.m_base.m_table.m_play = DeriveAPlay;
	
	b.m_base.m_table.m_eat = DeriveBEat;
	b.m_base.m_table.m_play = DeriveBPlay;
	
	Base* basea = (Base*)&a;
	basea->m_table.m_eat();
	basea->m_table.m_play();
	
	Base* baseb = (Base*)&b;
	baseb->m_table.m_eat();
	baseb->m_table.m_play();
	return 0;
}