當對象聲明爲指針時，我們使用多態嗎？

Question

我讀了關於多態性的時間分配，但當我們使用它時仍然感到困惑。我試着理解這個例子，但每個例子看起來都是一樣的，我只是想問一下，當BASE & Derived具有相同的功能和對象正在使用指針？

Answer 1

想象一下這樣的類層次結構：

class Polygon { 
    public: 
     virtual double area(); 
     // Some other member functions 
    private: 
     // Some members 
}; 

class Triangle : public Polygon { 
    public: 
     virtual double area() { /* code */ } 
     // Some other member functions 
    private: 
     // Some members 
}; 

class Square : public Polygon { 
    public: 
     virtual double area() { /* code */ } 
     // Some other member functions 
    private: 
     // Some members 
}; 

您不必使用指針，您可以使用引用過。

int main(int argc, char *argv[]) { 
    Triangle t; 
    Square s; 
    Polygon *pt = &t, *ps = &s; 
    Polygon &rt = t, &rs = s; 

    pt->area();   // Calls member function area from class Triangle 
    ps->area();   // Calls member function area from class Square 

    rt.area();   // Calls member function area from class Triangle 
    rs.area();   // Calls member function area from class Square 

    return 0; 
}