观察基类与派生类中成员函数的调用

一、问题描述。

用对象和指针来观察基类与派生类中成员函数的调用。

二、设计思路。

1、定义一个拥有fn1，fn2两个成员函数的基类BaseClass

2、由基类BaseClass派生出一个同样拥有fn1，fn2两个成员函数的派生类DerivedClass

3、在主函数中声明一个派生类的对象，及基类与派生类的指针

4、观察运行结果

三、程序流程图

 

 四、代码实现。

#pragma once
#include<iostream>
using namespace std;
class BaseClass
{
public:
BaseClass();
~BaseClass();
void fn1();
void fn2();
};

#include "BaseClass.h"

BaseClass::BaseClass()
{
}

BaseClass::~BaseClass()
{
}
void BaseClass::fn1()
{
cout << "base.fn1()" << endl;
}
void BaseClass::fn2()
{
cout << "base.fn2()" << endl;
}

#pragma once
#include"BaseClass.h"
class DerivedClass:public BaseClass
{
public:
DerivedClass();
~DerivedClass();
void fn1();
void fn2();
};

#include "DerivedClass.h"

DerivedClass::DerivedClass()
{
}

DerivedClass::~DerivedClass()
{
}

void DerivedClass::fn1()
{
cout << "Derived.fn1()" << endl;
}
void DerivedClass::fn2()
{
cout << "Derived.fn2()" << endl;
}

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

int main()
{
DerivedClass a;
BaseClass b;
DerivedClass c;
BaseClass *pb=&b;
DerivedClass *pd=&c;
cout << "用对象调用" << endl;
a.fn1(); a.fn2();
cout << "用BaseClass指针调用" << endl;
pb->fn1(); pb->fn2();
cout << "用DerivedClass指针调用" << endl;
pd->fn1(); pd->fn2();
}