dynamic_cast

1. 测试代码：

#include <iostream>
using namespace std;

class Base
{
public:
    Base() {};
    virtual void Show() { cout << "This is Base calss"; }
};
class Derived :public Base
{
public:
    Derived() {};
    void Show() { cout << "This is Derived class"; }
};
int main()
{
    Base* base;
    Derived* der = new Derived;
    base = dynamic_cast<Base*>(der); 
    base->Show(); // This is Derived class

输出结果：

 

2. 测试结果：

#include<iostream>                                                        
#include<typeinfo>
using namespace std;

class A {
    virtual void process() {}
};

class B : public A {
    virtual void size() {}
};

int main() 
{
    A* a1 = new B;
    B* b1 = dynamic_cast<B*>(a1);
    if (b1 == nullptr) 
    {
        cout << "b1 nullptr!!" << endl;
    }
    A* a2 = new A;
    B* b2 = dynamic_cast<B*>(a2);
    if (b2 == nullptr) 
    {
        cout << "b2 nullptr!!" << endl;
    }

    B bb;
    A& a3 = bb;
    B& b3 = dynamic_cast<B&>(a3);
    try 
    {
        A aa;
        A& a4 = aa;
        B& b4 = dynamic_cast<B&>(a4);
    }
    catch (bad_cast & c) 
    {
        cout << "bad cast!" << endl;
    }
    return 0;
}

输出结果：

 

3. 测试结果：
 

参考资料：

dynamic_cast的几种情况

https://www.cnblogs.com/QG-whz/p/4517336.html