基类与派生类对象的关系

#include <iostream>using namespace std;class A{int a;public:void setA(int x) {a=x;}int getA() {return a;}};class B:public A{int b;public:void setB(int x) {b=x;}int getB() {return b;}};void f1(A a,int x) {a.setA(x);}void f2(A *pA,int x) {pA->setA(x);}void f3(A &rA,int x) {rA.setA(x);}void main(){A a1,*pA;B b1,*pB;a1.setA(1);b1.setA(2);a1=b1;cout<<a1.getA()<<endl;cout<<b1.getA()<<endl;a1.setA(10);cout<<a1.getA()<<endl;cout<<b1.getA()<<endl;pA=&b1;pA->setA(20);cout<<pA->getA()<<endl;cout<<b1.getA()<<endl;A &ra=b1;ra.setA(30);cout<<pA->getA()<<endl;cout<<b1.getA()<<endl;b1.setA(7);cout<<b1.getA()<<endl;f1(b1,100);cout<<b1.getA()<<endl;f2(&b1,200);cout<<b1.getA()<<endl;f3(b1,300);cout<<b1.getA()<<endl;}