C++虚函数、赋值兼容原则

 1 #include <iostream.h>
 2 
 3 class A
 4 {
 5 public:
 6     void f1()
 7     { cout << "a" << endl; }
 8     virtual void f2()
 9     { cout << "b" << endl; }
10 };
11 
12 class B : public A
13 {
14 public:
15     void f1()
16     { cout << "c" << endl; }
17     virtual void f2()
18     { cout << "d" << endl; }
19 };
20 
21 void main()
22 {
23     A a;
24     B b;
25     a.f1();
26     a.f2();
27     b.f1();
28     cout << "--------------------" << endl;
29 
30     A *pa = &b;
31     pa->f1();//a
32     pa->f2();//d
33     cout << "-------------------" << endl;
34 
35     A *fa = (A *)&b;
36     fa->f1();//a
37     fa->f2();//d
38     cout << "-------------------" << endl;
39 }

当你坚持做一件完全正确的事情，有可能在很长一段时间内，你的价值都是零。