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  1. #include <iostream>
  2. using namespace std;
  3. class RigidBody{
  4.     float position=1;
  5.     public: float getPosition()const{ return position;}
  6.     public: void setPosition(float ppos){ position=ppos;}
  7. };
  8. class Adaptor{
  9.     RigidBody const& body;
  10.     int offset;
  11.  
  12.     Adaptor(RigidBody body, int offset=2)
  13.         : body(body),
  14.           offset(offset)
  15.     {}
  16.     protected:
  17.     RigidBody& get_body() { return const_cast<RigidBody&>(body); }
  18.     RigidBody const& get_body() const { return body; }
  19.     public:
  20.     static Adaptor *adapt(RigidBody& body, int offset = 2) { return new Adaptor{ body, offset }; }
  21.     static Adaptor const *adapt(RigidBody const& body, int offset = 2) { return new Adaptor{ body, offset }; }
  22.      float getPosition() const
  23.     {
  24.         // this uses the const get_body()
  25.         return get_body().getPosition() + offset;
  26.     }
  27.  
  28.     void setPosition(float ppos)
  29.     {
  30.         // this uses the mutable get_body()
  31.         get_body().setPosition(ppos-offset);
  32.     }
  33. };
  34.  
  35. int main()
  36. {
  37.     {
  38.         RigidBody b;
  39.         auto *a = Adaptor::adapt(b);
  40.         a->setPosition(15.);
  41.         a->getPosition();
  42.     }
  43.  
  44.     /*{
  45.         RigidBody const b;
  46.         auto *a = Adaptor::adapt(b);
  47.         a->setPosition(15.);     // error: passing ‘const Adaptor’ as ‘this’ argument discards qualifiers
  48.         a->getPosition();
  49.     }*/
  50. }
  51.  
Success #stdin #stdout 0s 15240KB
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https://ideone.com/eedaK6
language:
C++14 (gcc 8.3)
created:
6 years ago
visibility:
public

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