派生类对象在对象向量中重写基类的功能 [英] Derived class object override a function of base class in a vector of objects

问题描述

所以当存储在派生类的基类数组中时，我有一个调用派生类的重写函数的问题.

so I'm having an issue of calling the override function of a derived class when it's stored in an array of it's base class.

该基类称为Obstacle，而派生类为Cliff. Obstacle具有一个名为drawToBackground的虚拟函数，而从Obstacle继承来的Cliff也具有一个名为drawToBackground的函数，两者均无效.

The base class is called Obstacle, and the derived class is Cliff. Obstacle has a virtual function called drawToBackground, and Cliff, which inherits from Obstacle also has a function called drawToBackground, both of which are void.

然后我有了一个称为ObstsVec的障碍向量.在此向量中，我存储了一堆障碍物和一个悬崖.现在说悬崖是向量的第五个元素.当我调用obstsVec [5] .drawToBackground();时它从Obstacle类而不是悬崖类中调用drawToBackground函数.

I then have a vector of Obstacles, called obstsVec. In this vector, I store a bunch of Obstacles and a Cliff. Now say that the cliff is the fifth element of the vector. When I call obstsVec[5].drawToBackground(); it calls the drawToBackground function from the Obstacle class, not the cliff class.

这是c ++中的功能吗?或者我可能声明的内容有误?

Is this a feature in c++ or might I just have something declared wrong?

谢谢

推荐答案

您的类可能类似于:

#include <iostream>
#include <vector>

class Obstacles {
public:
    Obstacles() {};
    virtual void drawToBackground() {
    std::cout << "Obstacle ";
    }
};

class Cliff : public Obstacles {
public:
    Cliff() : Obstacles() {};
    virtual void drawToBackground() {
    std::cout << "Cliff ";
    }
};



int main(int argc, char* argv[]) {
    std::vector<Obstacles*> vec;
    vec.push_back(new Obstacles());
    vec.push_back(new Cliff());
    vec[1]->drawToBackground();
    delete vec[1];
    delete vec[0];
    vec.clear();
}

您在上面提到了数组...请确保不要以多态使用数组，因为这将导致不确定的行为.

You mentioned arrays above...make sure never to use arrays polymorphically, as this will lead to undefined behaviour.

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