C++接口与实现分离

#include <memory>
class X

{

public:

    virtual void f() = 0;

    virtual void g() = 0;
    virtual ~X() { printf("~X\n");}

};

class X_impl: public X

{

private:

    X_impl(){};   

public:

    ~X_impl()
 {
  printf("~X_impl\n");
 };

    virtual void f()

    {

      printf("X_impl.f()\n");

    }

    virtual void g()

    {

      printf("X_impl.g()\n");

    }

private:

 friend std::auto_ptr<X> createX();

};

std::auto_ptr<X> createX()

{

    std::auto_ptr<X> px(new X_impl);

    return px;

}