强制转换为一个类并从同级类中调用函数？ [英] Casting to one class and calling function from sibling class?

问题描述

我正在获得一个指向基类的指针（实际上是指向某些派生类的指针）。然后我想在该派生类上调用一个函数，但是我不知道它是哪个。

I'm getting a pointer to a base class (which is actually a pointer to some derived class). Then I want to call a function on that derived class, but I don't know which one it is.

class Base
{

};

class DerivedOne : public Base
{
    public:
        void functionA()
        {   int x = 0;  }
};

class DerivedTwo : public Base
{
    public:
        void functionA()
        {   int x = 0;  }
};

int main()
{   
    Base* derivedTwoPtr = new DerivedTwo();

    reinterpret_cast<DerivedOne*>(derivedTwoPtr)->functionA(); 

    return 0;
}

这是我想要的功能，但我不得不说它看起来很狡猾。它是定义的行为吗？如果不是，是否有合法的方法可以动态地解决此问题？

This works as I want, but I have to say it looks rather dodgy. Is it defined behavior? If not, is there a legal way to dynamically resolve this?

推荐答案

嘿，不要那样做。这就是虚拟方法的目的。

Hey, don't do that. That's what virtual methods are for.

class Base
{
public:
    virtual void functionA()=0;

};

class DerivedOne : public Base
{
    public:
        virtual void functionA()
        {       int x = 0;      }
};

class DerivedTwo : public Base
{
    public:
        virtual void functionA()
        {       int x = 0;      }
};

int main()
{   
    Base* derivedTwoPtr = new DerivedTwo();

    derivedTwoPtr->functionA(); 

    return 0;
}

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