migration from TrueBasic

migration from TrueBasic

• gxo

  To answer the OP question: yes it can be done. You can encapsulate the functionality within classes.

  The reason the origional language used this nested subroutine method was to provide encapsulation - it's unneccessary, today, since we have object orientation and fine control of encapsulation (whic by no means eliminates the need for straight-forward functions...).

  For example (note this simply replicates the functionality defined in the OP - hopefully...):

  Module < xml:namespace prefix = st1 ns = "urn:schemas-microsoft-com:office:smarttags" />Main< xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

   

      Public Class SubFunction

   

          ' This var is only visible

          ' to This Class and any Sub classes

          Private Shared A As Integer

   

          Public Shared Sub XXX()

              ' Call the Embedded function

              Call Embedded.ZZZ()

          End Sub

   

          Private Class Embedded

   

              ' This Var is not exposed

              ' in any way

              Private Shared B As Integer

   

              Public Shared Sub ZZZ()

                  ' This can ONLY be called from

                  ' SubFunction

                  B = 55

                  A = 6

              End Sub

   

          End Class

   

      End Class

   

      Sub YYY()

   

          ' No variables are exposed

          SubFunction.XXX()

   

      End Sub

   

  End Module

   

  
  
  

• YorickPeterse

  Why not simply merge sub xxx and sub zzz into one Sub www That would put the a & b variables in the same sub and you can seperate the code of both subs via conditional statements or so. Sub yyy would not see a or b.
  
  
  

• ThePatrickP

  thank you very much

  it works

  Federico

  
  

• WolfgangEngel

  Spidermans_DarkSide wrote:

  I know the two GLOBAL a and b are independent, i don't need a timer to show me. I put a breakpoint in various parts of this to see what was going on, hence my comments in the code. How about an example from you then illustrating GLOBAL, PRIVATE and PUBLIC variables then please

  OK

  Well first of all the variables declared at the top are not Global, they are member variables or form level variables or module level variables and possibly several other names I've forgotten. They are declared with Dim which makes them Private so they can be accessed only from anywhere within that class.

  In Sub1 you have declared two local variables with the same names as the member variables but that does not mean they are the same variables - they are not. These variables can only be accessed from within Sub1

  In Sub2 you have declared two parameters with the same names as the member variables. Parameters, delcared ByVal, behave in the same way as local variables with the major difference that they are set when the procedure is called by supplying arguments in the procedure call.

  Your confusion has arisen because you used breakpoints to determine what was going on. If you pause the program in the middle of Sub1 or Sub2 and then point to the variables a and b you will be told the value of that variable in the current sub. This applies even if you point at the member variables at the top or even to the variables in the other sub, which at the time are not even in scope so have no value. This is a peculiarity of the debugger which you need to be aware of.

  I have modified my timer routine to show more clearly what is going on. I strongly suggest you try it out. Paste this lot into a wide form with a button and an enabled timer. It is based on your code but without the comments.

  Public Class Form1
  Dim a As Integer = 4
  Dim b As Integer = 5
  Dim MeText As String
  Public Sub Sub1()
  Dim a As Integer = 6
  Dim b As Integer = 7
  MeText = "Sub1 variables: a = " & a.ToString & ", b = " & b.ToString
  MsgBox("a= " & a.ToString)
  MsgBox("b= " & b.ToString)
  MeText = ""
  End Sub
  Public Sub Sub2(ByVal a As Integer, ByVal b As Integer)
  MeText = "Sub2 variables: a = " & a.ToString & ", b = " & b.ToString
  MsgBox("a= " & a.ToString)
  MsgBox("b= " & b.ToString)
  End Sub
  Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click
  Call Sub2(2, 3)
  Call Sub1()
  MsgBox("a= " & a.ToString)
  MsgBox("b= " & b.ToString)
  End Sub
  Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick
  Static count As Integer
  If count = 0 Then Me.Text = ""
  count += 1
  Me.Text = MeText & " Member variables - a = " & a.ToString & ", b = " & b.ToString
  End Sub
  End Class
  

  
  

• vkmurari

  Hi,

  'This may be a bad example but i hope it highlights some issues

  'GLOBAL VARIABLES a and b set to 4 and 5 respectively.

  Dim a As Integer = 4

  Dim b As Integer = 5

  Public Sub Sub1()

  Dim a As Integer = 6

  Dim b As Integer = 7

  MsgBox("a= " & a.ToString)

  MsgBox("b= " & b.ToString)

  End Sub

  'Notice when this Sub is called the values 2 & 3 are passed to a & b.

  Public Sub Sub2(ByVal a As Integer, ByVal b As Integer)

  MsgBox("a= " & a.ToString)

  MsgBox("b= " & b.ToString)

  End Sub

  Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Button1.Click

  Call Sub2(2, 3) ' GLOBAL variables a gets assigned 2 , b gets assigned 3

  'As soon as Sub2() exits they revert back to 4 and 5 respectively.

  Call Sub1() ' a gets 6 and b gets 7

  'As soon as Sub1() exits they revert back to 4 and 5 respectively.

  MsgBox("a= " & a.ToString)

  MsgBox("b= " & b.ToString)

  End Sub

   

  Check out the keywords;  PRIVATE , PUBLIC and SHARED on.>>

  http://msdn.microsoft.com/library/default.asp

   

   

  Regards,

  S_DS

   

   

  
  
  

• Sergei Dorogin

  Spidermans_DarkSide wrote:

  'This may be a bad example

  It certainly is.

  The member variables a and b, the local variables a and b in Sub1 and the parameters a and b in Sub2 are all independent.

  To see this try adding a timer to your form and the following code. You will then see that the member variables, which are the only ones the timer.tick event can access do not change as you call the other routines.

  Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick
  Static count As Integer
  count += 1
  Me.Text = count.ToString & " - a = " & a.ToString & ", b = " & b.ToString
  End Sub
  

  
  

• rene schrieken

  Dave299,

   Hi,

  Well at least i admit it.... ( LOL ).   :-)

   I know the two GLOBAL a and b are independent, i don't need a timer to show me.

   I put a breakpoint in various parts of this to see what was going on, hence my comments in the code.

   How about an example from you then illustrating GLOBAL, PRIVATE and PUBLIC variables then please

   I very rarely use any GLOBAL variables myself.

   I prefer to use a seperate STRUCTURE or a CLASS or a FUNCTION and pass variables ByVal or ByRef.

   I rarely use ByRef too. I occasionally use the OPTIONAL keyword.

   

   

  Regards,

  S_DS

   

  
  
  
• migration from TrueBasic