C/code/派生对象和基类对象指针的使用（类型兼容性规则）.cpp

#include <iostream>
using namespace std;

class BaseClass {
public:
    void fn1() {
        cout << "the fn1 founction of the baseclass" << endl;
    }

    void fn2() {
        cout << "the fn2 founction of the baseclass" << endl;
    }
};

class DerivedClass : public BaseClass {
public:
    void fn1() {
        cout << "the fn1 founction of the DerivedClass" << endl;
    }
    
    void fn2() {
        cout << "the fn2 founction of the DerivedClass" << endl;
    }
};

int main() {
    DerivedClass derivedObj;

    derivedObj.fn1();
    derivedObj.fn2();

    BaseClass* basePtr = &derivedObj;
    basePtr->fn1();
    basePtr->fn2();

    DerivedClass* derivedPtr = &derivedObj;
    derivedPtr->fn1();
    derivedPtr->fn2();

    return 0;
}