dynamic_cast.cpp

#include <iostream>
using namespace std;

class A{
public:
    A(int a = 0, int b = 0): m_a(a), m_b(b){}
private:
    int m_a;
    int m_b;
};

int main(){
    //将 char* 转换为 float*
    char str[]="http://c.biancheng.net";
    float *p1 = reinterpret_cast<float*>(str);
    cout<<*p1<<endl;
    //将 int 转换为 int*
    int *p = reinterpret_cast<int*>(100);
    //将 A* 转换为 int*
    p = reinterpret_cast<int*>(new A(25, 96));
    cout<<*p<<endl;
   
    return 0;
}

/*#include <iostream>
using namespace std;

class A{
public:
    virtual void func() const { cout<<"Class A"<<endl; }
private:
    int m_a;
};

class B: public A{
public:
    virtual void func() const { cout<<"Class B"<<endl; }
private:
    int m_b;
};

class C: public B{
public:
    virtual void func() const { cout<<"Class C"<<endl; }
private:
    int m_c;
};

class D: public C{
public:
    virtual void func() const { cout<<"Class D"<<endl; }
private:
    int m_d;
};

int main(){
    A *pa = new A();
    B *pb;
    C *pc;
   
    //情况①
    pb = dynamic_cast<B*>(pa);  //向下转型失败
    if(pb == NULL){
        cout<<"Downcasting failed: A* to B*"<<endl;
    }else{
        cout<<"Downcasting successfully: A* to B*"<<endl;
        pb -> func();
    }
    pc = dynamic_cast<C*>(pa);  //向下转型失败
    if(pc == NULL){
        cout<<"Downcasting failed: A* to C*"<<endl;
    }else{
        cout<<"Downcasting successfully: A* to C*"<<endl;
        pc -> func();
    }
   
    cout<<"-------------------------"<<endl;
   
    //情况②
    pa = new D();  //向上转型都是允许的
    pb = dynamic_cast<B*>(pa);  //向下转型成功
    if(pb == NULL){
        cout<<"Downcasting failed: A* to B*"<<endl;
    }else{
        cout<<"Downcasting successfully: A* to B*"<<endl;
        pb -> func();
    }
    pc = dynamic_cast<C*>(pa);  //向下转型成功
    if(pc == NULL){
        cout<<"Downcasting failed: A* to C*"<<endl;
    }else{
        cout<<"Downcasting successfully: A* to C*"<<endl;
        pc -> func();
    }
   
    return 0;
}*/