C++之virtual 方法

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1、例子1

#include <iostream>class A{public:    const char* fetchClassName() { return "A"; }};class B: public A{public:    const char* fetchClassName() { return "B"; }};int main(void){   B obj_b;   A &obj_a = obj_b;   std::cout << obj_a.fetchClassName() << "\n";}

运行结果
A

2、例子2

#include <iostream>class A{public:    virtual const char* fetchClassName() { return "A"; }};class B: public A{public:    virtual const char* fetchClassName() { return "B"; }};int main(void){   B obj_b;   A &obj_a = obj_b;   std::cout << obj_a.fetchClassName() << "\n";}

运行结果
B

3、例子3

#include <iostream>class A{public:    virtual const char* fetchClassName() { return "A"; }};class B: public A{public:     const char* fetchClassName() { return "B"; }};int main(void){   B obj_b;   A &obj_a = obj_b;   std::cout << obj_a.fetchClassName() << "\n";}

运行结果
B

4、例子4

#include <iostream>class A{public:    virtual const char* fetchClassName() { return "A"; }};class B: public A{public:     const char* fetchClassName() { return "B"; }};class C: public B{public:     const char* fetchClassName() { return "C"; }};int main(void){   C obj_c;   A &obj_a = obj_c;      std::cout << obj_a.fetchClassName() << "\n";}

运行结果
C

5、例子5

#include <iostream>class A{public:    virtual const char* fetchClassName() { return "A"; }};class B: public A{public:     const char* fetchClassName() { return "B"; }};class C: public B{public:      const char* fetchClassName(int a) { return "C"; }};int main(void){   C obj_c;   A &obj_a = obj_c;   std::cout << obj_a.fetchClassName() << "\n";}

运行结果
B

reason:You can see that the prototype of the function in Class ‘C’ is different in the above sample code.

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