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書名： XNA 4.0 Game Development by Example Beginner's Guide（Visual Basic Edition）
作者名： Kurt Jaegers
本章字數： 272字
更新時間： 2021-08-20 15:50:38

Time for action – GamePiece class methods – part 2 – rotation

Add the RotatePiece() method to the GamePiece class:

Public Sub RotatePiece(clockwise As Boolean)
  Select Case _pieceType
    Case "Left,Right"
      _pieceType = "Top,Bottom"
    Case "Top,Bottom"
      _pieceType = "Left,Right"
    Case "Left,Top"
      If (clockwise) Then
        _pieceType = "Top,Right"
      Else
        _pieceType = "Bottom,Left"
      End If
    Case "Top,Right"
      If (clockwise) Then
        _pieceType = "Right,Bottom"
      Else
        _pieceType = "Left,Top"
      End If
    Case "Right,Bottom"
      If (clockwise) Then
        _pieceType = "Bottom,Left"
      Else
        _pieceType = "Top,Right"
      End If
    Case "Bottom,Left"
      If clockwise Then
        _pieceType = "Left,Top"
      Else
        _pieceType = "Right,Bottom"
      End If
  End Select
End Sub

What just happened?

The only information the RotatePiece() method needs is a rotation direction. For straight pieces, rotation direction does not matter (a left/right piece will always become a top/bottom piece and vice-versa).

For angled pieces, the piece type is updated based on the rotation direction and the previous screenshot.

Tip

Why all the strings?

It would certainly be reasonable to create constants that represent the various piece positions, instead of fully spelling out things, such as Bottom,Left as strings. However, because the Flood Control game is not taxing on the system, the additional processing time required for string manipulation will not impact the game negatively and helps clarify how the logic works, especially when we get to determine which pipes are filled with water.

Pipe connectors

Our GamePiece class will need to be able to provide information about the connectors it contains (top, bottom, left, and right) to the rest of the game. Since we have represented the piece types as simple strings, a string comparison will determine what connectors the piece contains.

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

Time for action – GamePiece class methods – part 2 – rotation

What just happened?

Tip

Pipe connectors