Structs vs Classes

[jkhippie]

I wrote a game using an array of structs to represent a 9x9 grid. Now I'm re-writing it as a class to '++ it up' a bit and to better understand classes. Part of the game used a seperate struct to keep track of selected board squares (to see if they match). Would it be proper ettiquete to include a struct as a class member, or is there a more 'proper' way?

[vmanes]

In C++ today, the only significant difference between a struct and a class is the default access - struct, all members are public, class, they're private.

So you could rename your struct as a class, and then include it as a data member of a larger class. Or leave it as a struct if all it has are data members, no functions.

[jkhippie]

Thanks, vmanes. Sounds like I'll be making the board a class ( for the init and draw funcs ) and leave the struct for matching, just declare a struct object as a class member. Next up, re-writing again as a FSM. One thing at a time, though.

[Ancient Dragon]

In c++ stucts can even have methods just like class. The only method I use in a struct is a constructor to initialize all the data. If you add other methods then you'd be better off just renaming the struct as class.

[jkhippie]

Well, it looks like I'm not quite getting it. Have a look, please...

class GridCell      // One cell of a 9x9 grid
{
public:
    GridCell();
    GridCell( int x, int y, int spriteNum ) // x, y = actual screen location
        :                                   // spriteNum (1-27) Match3 3x27=81 cells
    posX( x ),
    posY( y ),
    spriteNum( spriteNum ),
    Matched( false ),       
    Covered( true ),
    Selected( false ),
    Flipping( false )
    {}
    ~GridCell();
    const void SetMatched( bool mchd ) { Matched = mchd; }
    const void SetCovered( bool cvrd ) { Covered = cvrd; }
    const void SetSelected( bool slctd ) { Selected = slctd; }
    const void SetFlipping( bool flpng ) { Flipping = flpng; }
    const bool IsMatched() { return Matched; }
    const bool IsCovered() { return Covered; }
    const bool IsSelected() { return Selected; }
    const bool IsFlipping() { return Flipping; }

private:
    int posX;
    int posY;
    int spriteNum;
    bool Matched;
    bool Covered;
    bool Selected;
    bool Flipping;

};

class TileGrid : public GridCell    // This should be 81 gridcells
{
public:
    TileGrid();
    ~TileGrid()
    {
        for( int i = 0; i < BOARDSIZE; i++ )
        {
            delete Board[ i ];
        }
        delete [] Board;
    }
    GridCell GetCell( int num ) { return *Board[ num ]; }   // trying to get access
    const void Initialize();
    const void Reset();
    const void ResetMatches();
    const void SetMatch( int num );
    const void CheckMatches();
    const void Draw( D3DGraphics& gfx );
private:
    GridCell** Board;
    int posX;
    int posY;
    struct Match
    {
        int grdnm;
        int sprnm;
    } match[2];

SurfaceSequence Flips;
SurfaceSequence Tiles;
KeyedSurface CoverTile;
};

I'm jumping through hoops trying to access GridCell vars and still keep them private. Am I looking at this all wrong?

[Ancient Dragon]

lines 16-19 and 50-54. Remove the const keyword before void.

[jkhippie]

Thanks, AD. So I don't need 'const' on funcs that set a value because something changes, right? As I've been learning, I've been encouraged to make things const if possible. Like 'const void Draw()' - I've used that before without a hitch.

[Ancient Dragon]

you have the word const in the wrong place

void Draw() const

See this tutorial

[jkhippie]

Got it! Seems I was constipated in the brain. Now, as for all those funcs in the base class for dealing with the private data, am nI on the right track there? If so, I guess I'm on my way with it.