tic-tac-toe source code

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talekin

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Hey, I'm pretty new at VB.NET and had gained interest in creating a tic-tac-toe game from scratch.. although i had no idea where to begin so i downloaded some source code... though i need some help decifering it as a lot of it doesn't make sense... mainly what each private sub does and some of the confusing bits in it.. like bytes and chars and whatnot...

I know it's a lot of code to just go and summerize, but any help is appreciated, especially with the math and checking stuff. The form is composed of 9 picturebox controls.. XO 1-5 and thats for the playing board.

Again, any help is appreciated :)

Code: 
Dim chrXOChar As Char = "X"

Private Sub XO1PictureBox_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles XO9PictureBox.Click, XO6PictureBox.Click, XO8PictureBox.Click, XO5PictureBox.Click, XO7PictureBox.Click, XO4PictureBox.Click, XO3PictureBox.Click, XO2PictureBox.Click, XO1PictureBox.Click
        Dim lblClicked As Label
        lblClicked = sender

        If GetLblText(lblClicked.Tag()) <> Nothing Then Exit Sub

        Call SetLblText(lblClicked.Tag(), chrXOChar)
        If CheckWin(lblClicked.Tag) = True Then
            MessageBox.Show(chrXOChar & " Wins!")
            Exit Sub
        End If

        If chrXOChar = "X" Then
            chrXOChar = "O"
        Else
            chrXOChar = "X"
        End If
    End Sub
    Private Function CheckWin(ByVal bindex As Byte) As Boolean
        CheckWin = True
        If CheckGrid(1, 3, 1) = True Then Exit Function
        If CheckGrid(4, 6, 1) = True Then Exit Function
        If CheckGrid(7, 9, 1) = True Then Exit Function

        If CheckGrid(1, 7, 3) = True Then Exit Function
        If CheckGrid(2, 8, 3) = True Then Exit Function
        If CheckGrid(3, 9, 3) = True Then Exit Function

        If CheckGrid(1, 9, 4) = True Then Exit Function
        If CheckGrid(3, 7, 2) = True Then Exit Function
        CheckWin = False

        Dim i As Byte
        For i = 1 To 9
            If GetLblText(i) = Nothing Then
                Exit Function
            End If
        Next
        MessageBox.Show("Draw!")
    End Function
    Private Function CheckGrid(ByVal bfrom As Byte, ByVal bto As Byte, ByVal bstep As Byte) As Boolean
        Dim bctr As Byte
        Dim i As Byte = 0
        Dim c(2) As Char

        For bctr = bfrom To bto Step bstep
            c(i) = GetLblText(bctr)
            i = i + 1
        Next
        If c(0) = c(1) And c(1) = c(2) Then
            If c(0) <> Nothing Then
                CheckGrid = True
            End If
        End If
    End Function

    Private Sub SetLblText(ByVal bIndex As Byte, ByVal sText As Char)
        Select Case bIndex
            Case 1 : XO1PictureBox.Text = sText
            Case 2 : XO2PictureBox.Text = sText
            Case 3 : XO3PictureBox.Text = sText
            Case 4 : XO4PictureBox.Text = sText
            Case 5 : XO5PictureBox.Text = sText
            Case 6 : XO6PictureBox.Text = sText
            Case 7 : XO7PictureBox.Text = sText
            Case 8 : XO8PictureBox.Text = sText
            Case 9 : XO9PictureBox.Text = sText
            Case Else
                MessageBox.Show("Please contact game designers and quote error #69")
        End Select
    End Sub

    Private Function GetLblText(ByVal bIndex As Byte) As Char
        Select Case bIndex
            Case 1 : GetLblText = XO1PictureBox.Text
            Case 2 : GetLblText = XO2PictureBox.Text
            Case 3 : GetLblText = XO3PictureBox.Text
            Case 4 : GetLblText = XO4PictureBox.Text
            Case 5 : GetLblText = XO5PictureBox.Text
            Case 6 : GetLblText = XO6PictureBox.Text
            Case 7 : GetLblText = XO7PictureBox.Text
            Case 8 : GetLblText = XO8PictureBox.Text
            Case 9 : GetLblText = XO9PictureBox.Text
            Case Else
                MessageBox.Show("Please contact game designers and quote error #96")
        End Select
    End Function

    Private Sub NewGameMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles NewGameMenuItem.Click
        Dim i As Byte
        For i = 1 To 9 Step 1
            Call SetLblText(i, Nothing)
        Next
    End Sub
    'Exits the program
    Private Sub ExitMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ExitMenuItem.Click
        Me.Close()
    End Sub
 
talekin said:
Hey, I'm pretty new at VB.NET and had gained interest in creating a tic-tac-toe game from scratch.. although i had no idea where to begin so i downloaded some source code... though i need some help decifering it as a lot of it doesn't make sense... mainly what each private sub does and some of the confusing bits in it.. like bytes and chars and whatnot...

I know it's a lot of code to just go and summerize, but any help is appreciated, especially with the math and checking stuff. The form is composed of 9 picturebox controls.. XO 1-5 and thats for the playing board.

Again, any help is appreciated :)
Click to expand...

Code: 
'They are declaring a global variable here an initially setting it to 'X' - confusing and not good practice.
Dim chrXOChar As Char = "X"
'The handles portion is saying that any of the 9 pictures boxes that are clicked will execute this procedure
Private Sub XO1PictureBox_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles XO9PictureBox.Click, XO6PictureBox.Click, XO8PictureBox.Click, XO5PictureBox.Click, XO7PictureBox.Click, XO4PictureBox.Click, XO3PictureBox.Click, XO2PictureBox.Click, XO1PictureBox.Click
        'Here they are assigning the object that was clicked into a label - which
        'in itself is odd because this being called by Picture Box events...not
        'great coding practice.
        Dim lblClicked As Label
        lblClicked = sender

        'This is saying that if the object that was clicked doesn't have a tag
        'then to exit the sub.   Also it should be lblClicked.Tag not Tag() - it's
        'a property not a method.
        If GetLblText(lblClicked.Tag()) <> Nothing Then Exit Sub

        'This is calling a method called SetLblText - there is no reason to use
        ' the Call statement - this is old VB6 coding style, it should be removed.
        Call SetLblText(lblClicked.Tag(), chrXOChar)
        'This is calling a function called CheckWin where the label tag is being
        'passed in as an argument.  The ' = True' part is not necessary if the
        'function is returning Boolean.
        If CheckWin(lblClicked.Tag) = True Then
            'The shows a message box.
            MessageBox.Show(chrXOChar & " Wins!")
            'This exits the sub...ideally this hole block would be a part of the
            'CheckWin method.
            Exit Sub
        End If

        'This litle end if part is switching the current 'turn' - again with the
        'the way the global variable is used and this logic it might be confusing
        'to a novice.
        If chrXOChar = "X" Then
            chrXOChar = "O"
        Else
            chrXOChar = "X"
        End If
    End Sub

    'This function checks for the winner but doesn't end the game.
    Private Function CheckWin(ByVal bindex As Byte) As Boolean
        'This is setting the value of the return (incorrectly) - this is VB6
        'style, and not good style at that.  Ideally you would have something
        'like:  Dim hasWon as Boolean and a whole different flow to check for
        'the winner, this isn't a very well written function.
        CheckWin = True
        'All these if's are just look across a Grid (through the CheckGrid
        'function) to see if there is a TIC-TAC-TOE win (all across, diag, etc.)
        If CheckGrid(1, 3, 1) = True Then Exit Function
        If CheckGrid(4, 6, 1) = True Then Exit Function
        If CheckGrid(7, 9, 1) = True Then Exit Function

        If CheckGrid(1, 7, 3) = True Then Exit Function
        If CheckGrid(2, 8, 3) = True Then Exit Function
        If CheckGrid(3, 9, 3) = True Then Exit Function

        If CheckGrid(1, 9, 4) = True Then Exit Function
        If CheckGrid(3, 7, 2) = True Then Exit Function
        'If a win wasn't found this is setting the return (incorrectly) to
        'false.
        CheckWin = False
        
        'This For loop and message box are checking for a draw - horrible
        'logic.
        Dim i As Byte
        For i = 1 To 9
            If GetLblText(i) = Nothing Then
                Exit Function
            End If
        Next
        MessageBox.Show("Draw!")
    End Function
    
    'I myself am having a hard time figuring out what the heck they are
    'trying to accomplish here...Basically it appears they're checking for
    ' a winning pattern.
    Private Function CheckGrid(ByVal bfrom As Byte, ByVal bto As Byte, ByVal bstep As Byte) As Boolean
        Dim bctr As Byte
        Dim i As Byte = 0
        Dim c(2) As Char

        For bctr = bfrom To bto Step bstep
            c(i) = GetLblText(bctr)
            i = i + 1
        Next
        If c(0) = c(1) And c(1) = c(2) Then
            If c(0) <> Nothing Then
                CheckGrid = True
            End If
        End If
    End Function

    'This is setting the X or the O value of the labels
    Private Sub SetLblText(ByVal bIndex As Byte, ByVal sText As Char)
        Select Case bIndex
            Case 1 : XO1PictureBox.Text = sText
            Case 2 : XO2PictureBox.Text = sText
            Case 3 : XO3PictureBox.Text = sText
            Case 4 : XO4PictureBox.Text = sText
            Case 5 : XO5PictureBox.Text = sText
            Case 6 : XO6PictureBox.Text = sText
            Case 7 : XO7PictureBox.Text = sText
            Case 8 : XO8PictureBox.Text = sText
            Case 9 : XO9PictureBox.Text = sText
            Case Else
                MessageBox.Show("Please contact game designers and quote error #69")
        End Select
    End Sub

    'This is getting the X or O value of the labels.
    Private Function GetLblText(ByVal bIndex As Byte) As Char
        Select Case bIndex
            Case 1 : GetLblText = XO1PictureBox.Text
            Case 2 : GetLblText = XO2PictureBox.Text
            Case 3 : GetLblText = XO3PictureBox.Text
            Case 4 : GetLblText = XO4PictureBox.Text
            Case 5 : GetLblText = XO5PictureBox.Text
            Case 6 : GetLblText = XO6PictureBox.Text
            Case 7 : GetLblText = XO7PictureBox.Text
            Case 8 : GetLblText = XO8PictureBox.Text
            Case 9 : GetLblText = XO9PictureBox.Text
            Case Else
                MessageBox.Show("Please contact game designers and quote error #96")
        End Select
    End Function

     'This sets up a new game.
    Private Sub NewGameMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles NewGameMenuItem.Click
        Dim i As Byte
        For i = 1 To 9 Step 1
            'Again Call isn't necessary - it's VB6 legacy style - this is setting
            'the default text of the TIC-TAC-TOE boxes.
            Call SetLblText(i, Nothing)
        Next
    End Sub
    'Exits the program

     'This exits the function
    Private Sub ExitMenuItem_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles ExitMenuItem.Click
        Me.Close()
    End Sub

Listen, this is a poorly written program. It has a lot of legacy VB6 coding styles and poor logic. I wouldn't consider this as a good program to jump into and learn VB (or .NET) correctly. It's no wonder you're confused.
 
Listen, also, I wasn't trying to bash the person who wrote it, it works, it does the job, and that's what counts - it just had some coding preferences that I don't like and I just would like to see you or anyone else learn 'better' practice (mine certaintly aren't perfect), I spent the last half hour writing a TIC-TAC-TOE program for you...hopefully it will be easier to follow.
 

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