关于C++父子类转换问题

原则：

• 父类指针和引用可以指向子类对象 ，而子类对象指针不能直接指向父类，但是可以通过强制转换来把父类指针转换为子类指针。 子类转父类后能访问的函数是父类非虚函数和子类虚函数，父类转子类后能访问到的是子类的非虚函数和继承的父类函数。子类的虚函数并没有隐藏父类的所以访问到的是父类虚函数。eg:
  CFather *pFather = new CFather; //父类指针
  CSon *pSON = static_cast<CSon *>(pFather); //父类转子类
  pSON->eat(); //调用的是父类的虚函数，因为new的是父类的
  pSON->play(); //调用的是子类的非虚函数
• 爷爷类和孙子类关系同上。
• 子类向上为隐式转换 父类向下需要用static_cast<> 强转

测试demo如下：
test.h

#pragma once
//爷爷类
class CGrandFather {
public:
	virtual void eat();
	virtual void learn() = 0;

};
//爸爸类
class CFather :public CGrandFather{
public:
	virtual void eat();
	virtual void learn();
	void money();
private:
	void work();
};
//妈妈类
class CMother :public CGrandFather {
public:
	virtual void eat();
	virtual void learn();
	void buetiful();
private:
	void work();
};
//孙子类
class CSon :public CFather ,public CMother{
public:
	virtual void eat();
	virtual void learn();
	void play();
};

test.cpp

#include "test.h"
#include <iostream>
using namespace std;


void CGrandFather::eat()
{
	cout << "GrandFather eat" << endl;
}

void CFather::eat()
{
	cout << "CFather eat" << endl;
}

void CFather::learn()
{
	cout << "CFather learn" << endl;
}

void CFather::money()
{
	cout << "CFather money" << endl;
}

void CFather::work()
{
	cout << "CFather work" << endl;
}

void CSon::eat()
{
	cout << "CSon eat" << endl;
}

void CSon::learn()
{
	cout << "CSon learn" << endl;
}


void CSon::play()
{
	cout << "CSon play" << endl;
}
void CMother::eat()
{
	cout << "CMother eat" << endl;
}

void CMother::learn()
{
	cout << "CMother learn" << endl;
}

void CMother::buetiful()
{
	cout << "CMother buetiful" << endl;
}

void CMother::work()
{
	cout << "CMother work" << endl;
}


int main()
{
//	CGrandFather *pGrandFather = new CSon;  //
//	pGrandFather->learn();
	//CSon * pSon = static_cast<CSon *>(pGrandFather);  //
	//pSon->play();
	CSon *pSon = new CSon;
	CFather *pFather = pSon;
	pFather->money();
	CMother *pMother =static_cast<CSon *> (pFather);	
	pMother->eat();	
//	CSon * pSon2 = static_cast<CSon *>(pFather);
//	pSon2->play();
}