c++ - 强制沿长链调用基类虚函数

Question

我的问题扩展了 this problem具有更长的继承链

这是我的代码:

////////// View ///////////////
class View{
public:
    void Render(){
        std::cout << "View::Render" << std::endl;
        render();
    }
protected:
    virtual void render() = 0;
};
////////// ImageView ///////////////
class ImageView : public View{
public:
protected:
    void render(){
        std::cout << "ImageView:render" << std::endl;
    }
};
////////// Sprite ///////////////
class Sprite : public ImageView{
public:
protected:
    void render(){
        std::cout << "Sprite:render" << std::endl;
    }
};
////////// Utility ///////////////
void Draw(View *vw){
    vw->Render();
}
////////// main ///////////////
int main(){
    std::cout << "... Draw ImageView ..." << std::endl;
    ImageView *imgvw = new ImageView;
    Draw(imgvw);
    delete imgvw;

    std::cout << "... Draw Sprite ..." << std::endl;
    Sprite *sp = new Sprite;
    Draw(sp);
    delete sp;
    
    return 0;
}

实际输出:

.. Draw ImageView ...
View::Render
ImageView:render
... Draw Sprite ...
View::Render
Sprite:render

要求的输出:

.. Draw ImageView ...
View::Render
ImageView:render
... Draw Sprite ...
View::Render
ImageView:render
Sprite:render

我试图只保留一个应该调用所有虚拟方法链的基类公共(public)方法。在 C++ 中可以实现这样的功能吗？

Answer 1

根据 this question (Can I call a base class's virtual function if I'm overriding it?) ，像这样改变你的定义:

class Sprite : public ImageView{
public:
protected:
    void render(){
        ImageView::render(); // this calls the superclass' virtual method
        std::cout << "Sprite:render" << std::endl;
    }
};