基类指针保存派生类对象，基类指针只能访问基类里成员（7）

#ifndef
#define
class A {
public:
  int a;
  int b;
  A();

};

#endif

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

A::A():a(1),b(2) {
  cout << "a = " << a << "b= " << b << endl;
}

#ifndef
#define
#include "A.h"
class B:public A {
public:
  B();
  int c;
  int d;

};

#endif

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


B::B() :c(3), d(4) {
  cout << "c= " << c << "d= " << d << endl;
}

#include "A.h"
#include "B.h"

int main() {


  B b1;
  A *a1 = &b1;//基类指针或引用保存派生类对象，指针能访问的只有基类里的内容
  a1->a;
  a1->b;
  //a1->c;  错

  b1.a;
  b1.a;
  b1.c;
  b1.d;

  
  return 0;
}