A derived class of a base class that functions as an abstract class

Question

I defined a superclass element. There is some derived class elementsay triangle, quadand cube. Some of the objects elementare boundary elements. If it elementis a boundary element, then I have to define additional data members and functions. I could easily get a class boundary_elementif the class is elementnot a base class. (I meant that if triangle, quadand cubeare separate classes, I can define separate derived classes, such as boundary_triangle, boundary_quadand boundary_cube).

So my problem is that I have to define a subclass boundary_elementthat should be the base (or even abstract) class to define the derived classes boundary_quad, boundary_triangleand boundary_cube.

How is this possible in C ++? can anyone suggest any architecture that serves the purpose?

Another way to solve my problem according to my logic is to define a class as shown below:

class boundary_element
{    
    element* m_boundary_elem;  
    //data members needed for quad,triangle and cube
    public:
    boundary (element*);
    //functions for modifying data of triangle,cube,quad.

}

A pointer is elementdefined as a member variable of another class. How can I restructure this class efficiently using inheritance. (i.e. use it as an abstract class to get classes boundary_triangle, boundary_quadand boundary_cube)

, , , , , . , .

Answer 1

++ , Element Boundary .

- :

class Element {
};

class Boundary {
};

class Triangle : public Element {
};

class BoundaryTriangle : public Triangle, public Boundary {
};

. . .

Answer 2

++?

, .

- , ?

- :

• class AbstractShape {
       boundary getBoundary() const = 0;
       void draw(OutputScreen& screen) const = 0;
  };
  

• ,

  Triangle : public AbstractShape {
      // Implement the triangle specifics   
  };
  
  Rectangle : public AbstractShape {
      // Implement the rectangle specifics   
  };
  
  Circle : public AbstractShape {
      // Implement the circle specifics   
  };