Question

I am trying to define a class. This is what I have:

enum Tile {
GRASS, DIRT, TREE 
};

class Board {
public:
    int toShow;
    int toStore;
    Tile* shown;
    Board (int tsh, int tst);
    ~Board();
};

Board::Board (int tsh, int tst) {
    toShow = tsh;
    toStore = tst;
    shown = new Tile[toStore][toStore]; //ERROR!
}

Board::~Board () {
    delete [] shown;
}

However, I get the following error on the indicated line — Only the first dimension of an allocated array can have dynamic size.

What I want to be able to do is rather then hard code it, pass the parameter toShow to the constructor and create a two-dimensional array which only contains the elements that I want to be shown.

However, my understanding is that when the constructor is called, and shown is initialized, its size will be initialized to the current value of toStore. Then even if toStore changes, the memory has already been allocated to the array shown and therefore the size should not change. However, the compiler doesn’t like this.

Is there a genuine misconception in how I’m understanding this? Does anyone have a fix which will do what I want it to without having to hard code in the size of the array?

Answer 1

Use C++’s containers, that’s what they’re there for.

class Board {
public:
    int toShow;
    int toStore;
    std::vector<std::vector<Tile> > shown;
    Board (int tsh, int tst) : 
      toShow(tsh), toStore(tst), 
      shown(tst, std::vector<Tile>(tst))
    {
    };
};

...

    Board board(4, 5);
    board.shown[1][3] = DIRT;