I m working with some code where I have the following setup.

struct data
{
      void change_safe_member(){}
      void read_data(){}
      void change_unsafe_member(){}
};

struct data_processor
{
     std::shared_ptr<data> get_data(){}
     void return_data(std::shared_ptr<data> my_data)
     {
           my_data->change_unsafe_member(); // ONLY data_processor should call this function.
     }
};

struct client
{
     void foo(std::shared_ptr<data_processor>& my_processor)
     {
           auto my_data = my_processor->get_data();
           my_data->change_safe_member();
           //my_data->change_unsafe_member(); SHOULD NOT BE POSSIBLE TO CALL
           my_processor->return_data(my_data);
     }
};

改变“unsafe”成员只能由处理人内部使用,因此,我要隐瞒这种变化,或者让客户失望。 但是,我不知道在不诉诸于丑恶之s的情况下这样做的极端方法。

struct internal_data
{
      void change_unsafe_member(){}
};

struct data : public internal_data
{
      void change_safe_member(){}
      void read_data(){}
};

struct data_processor
{
     std::shared_ptr<data> get_data(){}
     void return_data(std::shared_ptr<data> my_data)
     {
           auto internal_data = std::static_pointer_cast<internal_data>(my_data);
           internal_data->change_unsafe_member(); 
     }
};

Anyone know of a good pattern to use in situations like this? Maybe visitor pattern or something similar?

EDIT:

正如在评论中指出的,人们可以宣布朋友班级,但有一个问题,即:以下工作不会奏效。

struct data
{
      void change_safe_member(){}
      void read_data(){}
private:
      friend class data_processor;
      virtual void change_unsafe_member(){}
};

struct data_decorator : public data
{
      data_decorator(const std::shared_ptr<data>& decoratee) : decoratee_(decoratee){}
      void change_safe_member(){decoratee_->change_safe_member();}
      void read_data(){decoratee_->read_data();}
private:
      virtual void change_unsafe_member()
      {
             std::cout << "Hello!"; // Add functionality
             decoratee_->change_unsafe_member(); // Won t work... compiler error
      }
      std::shared_ptr<data> decoratee_;
};

// Another example
struct data_group_decorator : public data
{
      data_group_decorator (const std::vector<std::shared_ptr<data>>& decoratees) : decoratees_(decoratees){}
      void change_safe_member(){decoratee_->change_safe_member();}
      void read_data(){decoratee_->read_data();}
private:
      virtual void change_unsafe_member()
      {
             for(size_t n = 0; n < decoratees_.size(); ++n)
                   decoratees_[n]->change_unsafe_member(); // Won t work... compiler error
      }
      std::vector<std::shared_ptr<data>> decoratees_;;
};