Thread: Varying size classes

For a project I am involved in, I have a 2D array representing a map. I want to create a class representing a zone on the map. There will be numerous zones on my map that will be different sizes, i.e. varying numbers of map array elements in each zone. What I have in mind is as follows:

Code:

class zone
{
private:
int num_of_squares;
int square_coordinates[num_of_squares][2];
//array giving map x and y coordinate for each square
public:

void set_squares(int a);
void set_coordinates(int i, int pos_x, int pos_y);

}zone1;

void zone::set_squares(int a)
{
num_of_squares = a;
}

void zone::set_coordinates(int i, int pos_x, int pos_y)
{
square_coordinates[i][0] = pos_x;
square_coordinates[i][1] = pos_y;
}

//here I call zone1.set_squares and zone1.set_coordinates to initialise all class variables

Is what I have in mind possible? I am getting errors and I think it is to do with the non-constant nature of num_of_squares.

Any help would be much appreciated

Thanks

It should work if number of_squares is set in the constructor, but I'm not a big fan of doing things this way. Not every compiler will compile this code correctly. You should just do dynamic allocation. You can do something like this in your set_squares function:

Code:

void zone::set_squares(int a)
{
    //assumes square_coordinates is an **int
    num_of_squares = a;

    square_coordinates = new *int[a];
    for(;a--;)
        square_coordinates[a] = new int[2];
}

zone::~zone() {
    for(;num_of_squares--;) {
         delete[]
square_coordinates[num_of_squares];
    }
    delete[] square_coordinates;
}

[edit]
stupid smilies
[/edit]

Excellent!! Thank you. Thought I might need to dynamically allocate but wasn't sure how to implement it.