How do I define static array in .cpp file of my class

Question

I know there is many question talks about static function and variable but I can't find the one that explain me how do things like this:

board.h

 class board:public QGraphicsPixmapItem 
{
public:
    board();
    static basedice *gamepos[8][8];
};

and I want to defined my array like this:

board.cpp

board::board()
{
    for (int i=0;i<8;i++)
    {
        for (int j=0;j<8;j++)
        {
        gamepos[i][j]=NULL;
        }
    }

}

And I have one more question,Is that a right way to use an array in many classes something like global array... for example in chess game for holding postion of my pieces? Sorry for my bad english.

Answer 1

If you really want the gamepos array to be static you can declare a static method in class Board that will initialize the array.

Then you call this method from outside the class.

int main() {

    Board * myboard = new Board();
    Board::initGamepos();

}

However looking at your code and what you want to do (which is reinitialize the gamepos array everytime you create a new Board instance, it is clear that you do NOT want gamepos to be static. 1 board <=> 1 gamepos array : that is not the mark of a static member, that is the mark of a standard member.

Answer 2

Static variables are automatically initialized to zero/false/null, so you don't need to initialize the array.

Anyway, you should not be reinitializing a static variable from your instance constructor as that will produce funny results.