XNA 4.0 Game Development by Example Beginner's Guide（Visual Basic Edition）

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Time for action – manipulating the GameBoard

Add public methods to the GameBoard class to interact with GamePieces:

Public Sub RotatePiece(x As Integer, y As Integer,
  clockwise As Boolean)
  boardSquares(x, y).RotatePiece(clockwise)
End Sub

Public Function GetSourceRect(
  x As Integer, y As Integer) As Rectangle
  Return boardSquares(x, y).GetSourceRectangle()
End Function

Public Function GetSquare(x As Integer, y As Integer) As String
  Return boardSquares(x, y).PieceType
End Function

Public Sub SetSquare(x As Integer, y As Integer, pieceType As String)
  boardSquares(x, y).SetPiece(pieceType)
End Sub

Public Function HasConnector(x As Integer, y As Integer, direction As String) As Boolean
  Return boardSquares(x, y).HasConnector(direction)
End Function

Public Sub RandomPiece(x As Integer, y As Integer)
  boardSquares(x, y).SetPiece(GamePiece.PieceTypes(
    rand.Next(0, GamePiece.MaxPlayablePieceIndex + 1)))
End Sub

What just happened?

RotatePiece(), GetSourceRect(), GetSquare(), SetSquare(), and HasConnector() methods simply locate the appropriate GamePiece within the boardSquares array and pass on the function request to the piece.

The RandomPiece() method uses the rand object to get a random value from the PieceTypes array and assigns it to a GamePiece. It is important to remember that with the Random.Next() method overload used here, the second parameter is non-inclusive. In order to generate a random number from 0 through 5, the second parameter needs to be 6.

Tip

Subs, functions, and methods

Method is the generic term for a callable code block inside a class. Both Subs and Functions are methods. The difference between the two is that a Function returns a value, while a Sub does not.

Filling in the gaps

Whenever the player completes a scoring chain, the pieces in that chain are removed from the board. Any pieces above them fall down into the vacated spots and new pieces are generated.