究竟什么是c ++中的动态转换

Question

任何人都可以告诉c ++中动态强制转换的确切含义.我们在哪里可以使用这种动态铸造？这是在采访中向我询问的,我对这个问题一无所知:).

Answer 1

dynamic_cast是在运行时查找对象类的cast方法.

class Base
{
    public:
    virtual bool func1();
};


class Derived1 : Base
{
    public:
    virtual bool func1();

    virtual bool funcDer1();
};



class Derived2 : Base
{
    public:
    virtual bool func1();
    virtual bool funcDer2();
};

Base* pDer1 = new Derived1;
Base* pDer2 = new Derived2;


Derived2* pDerCasted = dynamic_cast<Derived2*>(pDer2);
if(pDerCasted)
{
    pDerCasted->funcDer2();
}


-> We cannot call funcDer2 with pDer2 as it points to Base class
-> dynamic_cast converts the object to Derived2 footprint 
-> in case it fails to do so, it returns NULL .( throws bad_cast in case of reference)

注意:通常,应该通过仔细的OO设计来避免Dynamic_cast.