universal variables

universal variables

• jnquinn

  Well.....yes I can see that but then you get modifiers like Protected and Friend. They aren't very intuitive are they - not to me anyway.

  Any views on the second bit - is it a mistake or is there something there I really don't understand.

  
  

• RalfCJ

   

  Sj, I apologize for my lack of clarity and didn't direct my comment to you. I was referring to dave who said local variables default to public.

  It just occurred to me that I never use DIM statements for member variables. I will either will invariabley explicitly declare each variable and specifically declare its scope.  So actually what dave and I both said could be true at the same time. I've never seen a local variable default to public because I never use DIM for memeber variables.

  
  
  

• gkostel

  Sorry, I edited that after you replied...I was adding a bit more to it to try and relate it to the origional problem :)
  
  

• GroZZleR

  I don't understand that in terms of what I experience in coding. I've never seen that occur.

  
  
  

• TOM_MUE

  Another point is the use of Dim: are these variables public or private Unless the variable is used within a subroutine (where the variables are private by definition, or static), you should always declare the scope of the variables, e.g.:

  Public a ,b ,c ,d ,e as Decimal

  
  
  

• redhot2006

  Probably, I dunno...but of course you would have to know that. Which is the problem. That's why it's better to declare them explicitly, so you 'know' just by looking at it.

  Even so, the origional problem is actually that the 'global' variables aren't being touched at all: the locl variables are being used (specifically, the passed parameters):

  Private a As Decimal< xml:namespace prefix = o ns = "urn:schemas-microsoft-com:office:office" />

  Private b As Decimal

   

  Private Sub DoStuff()

      a = 1

      b = 2

      Call ChangeThings(a, b)

      Debug.WriteLine(String.Format("A={0} B={1}", a, b))

  End Sub

   

  Private Sub ChangeThings(ByVal a As Single, ByVal b As Single)

      a = 5.76543

      b = 12.2232115

  End Sub

  What is the result i.e. what will get printed by the debug line

  is it:

  A=1 B=2

  or:

  A=5.76543 B=12.22321

  The moral of the story is to use meaningful names, and identify the global variables (often the global variables are prefixed with something like m_ for module level variables, or g_ for application global variables): whatever scheme floats your boat. Personally, I've got away from the m_ and simply have global variables pascal cased, and local variables camel cased - it saves a LOT of headaches.

   

  
  
  

• kimo

  First of all get of the "calls". They aren't needed.

  Dim a, b, c, d, e As Decimal

  Private Sub determine_variables(ByRef a As Decimal, ByRef b As Decimal, ByRef c As Decimal, ByRef d As Decimal, ByRef e As Decimal)

  a = 1

  b = 2

  c = 3

  End Sub

  Private Sub cbGo_Click(ByVal sender As Object, ByVal eeeeeee As System.EventArgs) Handles cbGo.Click

  determine_variables(a, b, c, d, e)

  show_variables(a, b, c, d, e)

  End Sub

  Sub show_variables(ByVal a As Decimal, ByVal b As Decimal, ByVal c As Decimal, ByVal d As Decimal, ByVal e As Decimal)

  d = a / b

  e = a / c

  End Sub

  a,b,c, etc are Value Types. In order to chnage their value in a subroutine you need to address them by reference.

  
  
  

• pst_grant

  Dave299 wrote:

  Well.....yes I can see that but then you get modifiers like Protected and Friend. They aren't very intuitive are they - not to me anyway. Any views on the second bit - is it a mistake or is there something there I really don't understand.

  You're right, the additional modifiers can get confusing (I'm always saying to myself "what does Protected mean, again I'm sure Mr. Eff One will tell me..."). Just wait 'til you get into overloads, overrides, notinheritable, shadows, etc.... :)

  Even so, by positively declaring the scope of the variable will mean the computer is doing what you told it to do, rather than what you think it should do...(I think...).

  
  
  

• Cout60039

  Woah

  I didn't say locals default to Public - that's what the Help and MSDN say.

  I don't understand what it means. Can anyone clarify

  
  

• molnarcs

  Ummm... okay. Let me get this straight:

  In order to change the values of the variables in the sub routines, I need to put "ByRef" instead of "ByVal"
  I also need to put "Public" instead of "dim" when I declare my variables, to make sure they are public and accessable by the entire program

  Thanks... I understood a lot of what you said, but some of it just went over my head. :p
  Thankyou for helping a poor, backwards, VB6 user. ;)

  
  

• Lechal

  Do you really need to pass the variables to your procedures.

  For your simple example the following works just as well.

  Dim a, b, c, d, e As Decimal
  Private Sub Button_Click(ByVal eventSender As System.Object, ByVal eventArgs As System.EventArgs) Handles Button.Click
  determine_variables()
  show_variables()
  End Sub
  Sub determine_variables()
  a = 1
  b = 2
  c = 3
  End Sub
  Sub show_variables()
  d = a / b
  e = a / c
  Label1.Text = d
  Label2.Text = e
  End Sub
  

  
  

• Alexander Marinov

  Dave, I agree it works as well.

  There's a problem not at all with what you did but with this conceptually, I use member variables all the time. When I dod I ealize that it's very close to a Fortran Common which has been made fun of for several decades and I am an ex-Fortran programmer. I have to admit that I love to use member variables and they do have lots of uses. I always feel guilt at my enjoyment of them because they do function and are used exactly in the same way a fortran common is used.

  
  
  

• bsun

  Aren't

  Dim A As Decimal

  Private A As Decimal

  the same thing at module level

  According to the Help file local variables default to Public access - which is something I've never understood.

  
  

• Thymen

   

  Drake there are two ways to go as Dave and I pointed out. As dave point out there is no reason to use member variables in a call because the member variable are already "inscope" or visible to the called methods. Actually it slows the code down to use them in calls because the machine has to either copy the value variable or propagate references to them on the machine's stack to make a call frame.

  ANY TIME you want to change a passed Value Type such as an Integer or string, pass it by reference (byref) because essentially that's a point to the address in memory containing the data. If you pass a Value type to a method byvalue, a copy is made and if you modify the copy that has the results that you saw last night.

  The "correct" way to do this would be to do as Dave recommended and he addressed that. I addressed why your code failed.

   

   

  
  
  
• universal variables