How can I delete this object I created?

Question

Take this program as an example:

class Piece
{
public:
    Piece(bool color);

protected:
    bool color;
};

Piece::Piece(bool color)
{
    this->color = color;
}

//-----------------------------

class King : public Piece
{
public:
    King(bool color);
};

King::King(bool color) : Piece(color)
{
    // empty
}

//-----------------------------

class Tile
{
public:
    // constructors/destructors
    Tile(Piece * ppiece, int rrow, int ccol);
    ~Tile();

private:
    Piece * piece;
    int row, col;

};

Tile::Tile(Piece * ppiece, int rrow, int ccol)
{
    this->ppiece = piece;
    this->row = rrow;
    this->col = ccol;
}

//---------------------------

int main() 
{
    Tile * tile = new Tile(new King(0), 1, 1);
}

In the function main() I declare a new King and pass it to the Tile constructor. How can I delete the King object I created?

Answer 1

As written, the Tile Constructor receives the new King as parameter ppiece .

The Tile Constructor then doesn't do anything with ppiece, and the memory is cannot be freed. It is "leaked".

Given that Tile has a member piece , I'd suggest assigning it there:

Tile::Tile(Piece * ppiece, int rrow, int ccol)
{
    this->row = rrow;
    this->col = ccol;
    this->piece = ppiece;
}

Then you can later free it in the Tile destructor:

Tile::~Tile()
{
    delete piece;
}

Answer 2

There are several good answers already, but I thought I'd at least mention this... The topic may be too advanced for you at the moment, but at some point it's definitely worth learning about "smart" pointers. Boost::shared_ptr is a good place to start. Also std::unique_ptr.

Answer 3

I would recommend keeping all of the pieces in their own array outside of the Tile set, creating and deleting them at the same level.

However, if that is impossible. I would say delete it if the piece is removed from the tiles.

Also, have a function that clears your tile set, that iterates through and deletes the pieces on that tile.

You could also make it part of ~Tile(), but I personally dislike creating/deleting at different levels.

If you go with the destructor, be careful about keeping pointers to the piece outside of the Tile.

Answer 4

There really is no need to use new and delete in the first place (C++ isn't Java). You can treat the class objects as values, much like you do with an int .

class Tile
{
public:
    // constructors/destructors
    Tile(Piece ppiece, int rrow, int ccol);
    ~Tile();

private:
    Piece piece;
    int row, col;

};

Tile::Tile(Piece ppiece, int rrow, int ccol)
{
    this->ppiece = piece;
    this->row = rrow;
    this->col = ccol;
}

//---------------------------

int main() 
{
    Tile tile(King(0), 1, 1);
}

No new , no delete , no problem.