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; }