Curiously recurring template pattern: Difference between revisions

Revision as of 08:38, 6 September 2019

Revision as of 08:47, 6 September 2019

Line 210:

<source lang="cpp">

// Base class has a pure virtual function for cloning

class ShapeAbstractShape {

public:

virtual ~ShapeAbstractShape () = default;

virtual ShapeAbstractShape *clone() const = 0;

};

// This CRTP class implements clone() for Derived

template <typename Derived>

class Shape_CRTPShape : public ShapeAbstractShape {

public:

Shapestd::unique_ptr<AbstractShape> *clone() const override{

return new Derived(static_cast<Derived const&>(*this));

}

protected:

// We make clear Shape Class need to be inherited

Shape() = default;

Shape(const Shape&) = default;

};

// Every derived class inherits from Shape_CRTPCRTP class instead of Shapeabstract class

// Nice macro which ensures correct CRTP usage

#define Derive_Shape_CRTP(Type) class Type: public Shape_CRTP<Type>

class Square : public Shape<Square>{};

class Circle: public Shape<Square>{};

// Every derived class inherits from Shape_CRTP instead of Shape

Derive_Shape_CRTP(Square) {};

Derive_Shape_CRTP(Circle) {};

</source>