dynamic_cast

#include <iostream>
#include <string>

class BaseClass
{
public:
    BaseClass(){}
    ~BaseClass(){}

    virtual void display()
    {
        std::cout << "base class" << std::endl;
    }


};

class DerivedClass: public BaseClass
{
public:
    DerivedClass(){}
    ~DerivedClass(){}

    void display()
    {
        std::cout << "derived class" << std::endl;
    }

    void display1()
    {
        std::cout << "derived calss display1" << std::endl;
    }

private:

};

int main()
{
    BaseClass *base = new BaseClass();
    base->display();

    DerivedClass *derived = new DerivedClass();
    derived->display();

    std::cout << "*******************************" << std::endl;

    BaseClass *bs1 = dynamic_cast<BaseClass*>(derived);

    bs1->display();


    DerivedClass *dr1 = dynamic_cast<DerivedClass*>(base);

    if(dr1 == NULL)
    {
        std::cout << "dr1 is null" << std::endl;
    }


    system("pause");

    return 0;
}

运行结果

base class
derived class
*******************************
derived class
dr1 is null

 

父类指针转子类指针，结果为空

子类指针转父类指针，结果正常