C++：阻止衍生類別(derived class)重新定義虛函數(final&sealed)

阻止衍生類別重新定義虛函數, 在java和C#中可以很簡單的實現(finale&sealed),

但在C++中則需要使用public繼承+複合(composition)的方法;

注意: 使用私人繼承(private), 無法實現此要求.

如:

/************************************************* File: test.cpp Copyright: C.L.Wang Author: C.L.Wang Date: 2014-04-11 Description: test Email: morndragon@126.com **************************************************/      /*eclipse cdt, gcc 4.8.1*/      #include <iostream>        using namespace std;        class Timer {  public:      virtual void onTick() const {          std::cout << "Tick! Tick! Tick! " << std::endl;      }  };        class Widget : private Timer {  public:      void say() {          onTick();      }  private:      virtual void onTick() const override{          std::cout << "Widget Tick!" << std::endl;      }  };        class AnotherWidget : private Widget {  public:      void say() {          onTick();      }  private:      virtual void onTick() const override{          std::cout << "Another Widget Tick!" << std::endl;      }  };        int main () {      Widget w;      w.say();      AnotherWidget aw;      aw.say();      return 0;  }

輸出:

Widget Tick!  Another Widget Tick!

注意: 私人繼承, 仍然可以繼續重新定義虛函數;

更多精彩內容：http://www.bianceng.cnhttp://www.bianceng.cn/Programming/cplus/

具體實現:public繼承+複合的方式, 代碼實現, 如下:

/************************************************* File: test.cpp Copyright: C.L.Wang Author: C.L.Wang Date: 2014-04-11 Description: test Email: morndragon@126.com **************************************************/      /*eclipse cdt, gcc 4.8.1*/      #include <iostream>        using namespace std;        class Timer {  public:      virtual void onTick() const {          std::cout << "Tick! Tick! Tick! " << std::endl;      }  };        class Widget : private Timer {  public:      void say() {          timer.onTick();      }  private:      class WidgetTimer : public Timer {      public:          virtual void onTick() const {              std::cout << "Widget Tick! " << std::endl;          }      };      WidgetTimer timer;  };        int main () {      Widget w;      w.say();      return 0;  }

輸出:

Widget Tick!

作者：csdn部落格 Spike_King