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  1. #include <iostream>
  2. #include <memory>
  3. using namespace std;
  4.  
  5. //Extras
  6. class ShapeExtra
  7. {
  8.     public:
  9.     ShapeExtra() {}
  10.     void ShapeFunc() { std::cout << "Shape"; }
  11.     virtual ~ShapeExtra() = default; //Important!
  12. };
  13.  
  14. class Shape
  15. {
  16.     public:
  17.     std::unique_ptr<ShapeExtra> m_var;
  18.  
  19. 	//require a pointer on construction
  20. 	//make sure to document, that Shape class takes ownership and handles deletion
  21. 	Shape(ShapeExtra* p):m_var(p){}
  22.  
  23.     //The common functions
  24.     ShapeExtra& GetVar(){ return *m_var; }
  25.     void ShapeFunc() {m_var->ShapeFunc();}
  26. };
  27.  
  28.  
  29. class CircleExtra : public ShapeExtra
  30. {
  31. 	public:
  32.     void CircleExtraFunc() {std::cout << "Circle";}
  33. };
  34.  
  35. class Circle : public Shape
  36. {
  37. 	CircleExtra* m_var;
  38.  
  39.     public:
  40.     Circle() : Shape(new CircleExtra()) {
  41.     	m_var = static_cast<CircleExtra*>(Shape::m_var.get()); 
  42.     }
  43.  
  44.     void CircleFunc()
  45.     {
  46.         m_var->CircleExtraFunc();
  47.     }
  48. };
  49.  
  50.  
  51. int main() {
  52. 	Circle c;
  53. 	//use the ShapeExtra Object
  54. 	c.GetVar().ShapeFunc();
  55. 	//call via forwarded function
  56. 	c.ShapeFunc();
  57. 	//call the circleExtra Function
  58. 	c.CircleFunc();
  59. 	return 0;
  60. }
Success #stdin #stdout 0s 3468KB
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ShapeShapeCircle
https://ideone.com/BW6era
language:
C++14 (gcc 8.3)
created:
7 years ago
visibility:
public

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