Question

I am creating a CAD software in which I have a class point & a class line.

#include <vector>
using namespace std;
class point
{
private:
    vector<int>* child;
    int id;//this is unique id of a point
    double x;//absolute x, y, z co-ord
    double y;//
    double z;//
};

class line
{
private:
    point *a;
    point *b;
    int id;//this is unique for each line object
}

any line object is the child of 2 point objects.
so if i delete a point of a line then the line object shud also be deleted.
For this i want to store the id of all children (line, circle, triangle,….) of a point object in a vector child (instance variable of class point as shown in code).

my question is is my approach correct?
i mean that, there will be around 100’s of point objects in an execution.
since each vector allocates some extra memory, there will be a lot of allocated memory which will not be used in an execution.
can anybody suggest an alternative way of storing unknown no of int as a sequence in each point object?

Answer 1

my question is how do i create this vector & where (so that it doesnt go out of scope)?

You have already done this correctly. I’d suggest that you dont’t use a pointer to your vector but simply a vector itself:

private:
    vector<int> child;

This makes handling it much easier, and you don’t have to allocate/deallocete it by yourself.

---

how do i make my child point to the created vector without memory leak?

If you really need to have a dynamically allocated pointer, you have to call new and delete. For this to behave correctly, you have to define both a constructor and a destructor in your point class:

class point
{
private:
    point() : child(new vector<int>) {}
    ~point() { delete child; }

    vector<int>* child;
    int id;//this is unique id of a point
    double x;//absolute x, y, z co-ord
    double y;//
    double z;//
};

But I still recommend that you don’t use a pointer to a vector as I have explained above.