Question

Vectors if are data of a class should be assigned as private member of that class.
The class should provide the methods to access the vector methods needed.

Now I have my class Snake which encapsulate a snake for the classic game.

typedef std::vector<Polygon4>::const_iterator const_iterator;
enum directions{UP, DOWN, RIGHT, LEFT, IN, OUT, FW, RW };

class Snake
{
private:
    enum directions head_dir;
    int cubes_taken;
    float score;
    struct_color snake_color;
    V4 head_pos;
    std::vector<Polygon4> p_list; //the vector
public:   

    Snake();
    V4 get_head_pos();
    Polygon4 create_cube(V4 point);
    void initialize_snake();
    void move(directions);

    void set_head_dir(directions dir);
    directions get_head_dir();
    void sum_cubes_taken(int x);
    int get_cube_taken();

    void sum_score(float x);
    float get_score();

    void set_snake_color();

 //vector manipulation functions
 const_iterator p_list_begin() const {return p_list.begin();}
 const_iterator p_list_end() const {return p_list.end();}
 void add_IntToP_list(Polygon4 cube){p_list.push_back(cube);}
 void clear_list(){p_list.clear();}
 unsigned int get_list_size(){return p_list.size();}

};

I have an other class in my program, the graphic management:

class MyGLBox{
private:
std::vector<Polygon4> p_list;
public:
     //do stuff...
     //management vectors:
     const_iterator p_list_begin() const {return p_list.begin();}
     const_iterator p_list_end() const {return p_list.end();}
     void add_IntToP_list(Polygon4 cube){p_list.push_back(cube););
     void clear_list(){p_list.clear();}
     unsigned int get_list_size(){return p_list.size();}
}

Now every frame in the game I need to copy the snake p_list into the MyGLbox p_list. If the vectors were public it would have been pretty easy:

myGLBox.p_list = snake.p_list;

now if they are private:

transfer_function(*MyGLBox box, *Snake snake){
    const_iterator cube;
    for(cube = snake->p_list_begin(); cube != snake->p_list_end(); cube++){
         box->add_InTop_list(*cube);
    }
}

is it right what I’m trying to do? Is there a better way to do it? To me the for cycle seems pretty inefficent

Answer 1

If you already have a function

void add_IntToP_list(Polygon4 cube){p_list.push_back(cube););

for adding a single element, you can add another overload for adding a range of elements

void add_IntToP_list(vector<Polygon4>::const_iterator first, 
                      vector<Polygon4>::const_iterator last)
{ p_list.insert(p_list.end(), first, last); }

and then call that with the range you want to add, maybe

box->add_IntToP_list(snake->p_list_begin(), snake->p_list_end());