Variable not defined?!?

[Darren123]

Hey, I'm using Vb6 and I have a problem with my code but I don't know why.
Here it is:

Option Explicit
 
'Opacity -------------------------
Private Declare Function GetWindowLongA Lib "user32" (ByVal hwnd As Long, ByVal nIndex As Long) As Long
Private Declare Function SetWindowLongA Lib "user32" (ByVal hwnd As Long, ByVal nIndex As Long, ByVal dwNewLong As Long) As Long
Private Declare Function SetLayeredWindowAttributes Lib "user32" (ByVal hwnd As Long, ByVal crey As Byte, ByVal bAlpha As Byte, ByVal dwFlags As Long) As Long
 
Private Const GWL_EXSTYLE = (-20)
Private Const WS_EX_LAYERED = &H80000
Private Const LWA_ALPHA = &H2&
'--------------------------------------
 
Private Function Opacity(Value As Byte, Frm As Form)
On Error GoTo ErrorHandler
 
Dim MaxVal As Byte, MinVal As Byte
 
MinVal = 20: MaxVal = 255
 
If Value > MaxVal Then Value = MaxVal
If Value < MinVal Then Value = MinVal
 
SetWindowLongA Frm.hwnd, GWL_EXSTYLE, GetWindowLongA(Frm.hwnd, GWL_EXSTYLE) Or WS_EX_LAYERED
SetLayeredWindowAttributes Frm.hwnd, 0, Value, LWA_ALPHA
 
ErrorHandler:   Exit Function
End Function
 
Private Sub hsbOpacity_Change()
Opacity hsbOpacity.Value, Me
End Sub
 
Private Sub Text1_Change()
n = Text1
For i = 0 To n - 1
NewStr = NewStr + Text2.Text + ";"
Next i
Text3 = NewStr
End Sub
 

The problem is when I run the program it says "Variable not defined" and highlights "n =" under "Private Sub Text1_Change()" but when I test this part of the code on it's own, it works fine, the other part of the code is for the opacity of the form and this works ok too.
When I put the code together I get the problem, Anyone know a solution?

Thanks, Darren.

[Darren123]

I was looking at random code and it gave me an idea, so I tried:

Private Sub Text1_Change()
Dim n As Variant
Dim i As Variant
Dim NewStr As String
n = Text1
For i = 0 To n - 1
NewStr = NewStr + Text2.Text + ";"
Next i
Text3 = NewStr
End Sub

And it has worked.

[kadghar]

Hey, I'm using Vb6 and I have a problem with my code but I don't know why.
(...)

The problem is when I run the program it says "Variable not defined" and highlights "n =" under "Private Sub Text1_Change()" but when I test this part of the code on it's own, it works fine, the other part of the code is for the opacity of the form and this works ok too.
When I put the code together I get the problem, Anyone know a solution?

Thanks, Darren.

sure, when you write Option Explicit, it forces you to declare any variable used in the code. when you run only a part, the 'option explicit' isnt activated so you dont have to define 'n'. The way to solve it is:

Remove the line 'Option Explicit' (i dont recomend you doing this, since i think using option explicit is a good habit), or
Declare 'n':  Dim n As Long  - that will do (yeah!, that's better).

Please check in your VB help file the types of variables to see which one fits your code better.

HTH

[Killer42]

Yes, you should always use Option Explicit. It prevents a lot of weird problems that can be very difficult to track down. Because when you mistype a variable name, this causes VB to stop and tell you. without this option turned on, VB will just create a new variable with the new name, and continue on.

Think about this. Let's assume that for some reason, you create a variable called nnnnnnnn. Then later, somewhere else in your code, you see this line...

For Counter = 1 To nnnnnnn

Unless you've got very sharp eyes, you won't spot any difference (trust me, there is one). If you have set Option Explicit for this module, VB will refuse to compile, because the variable nnnnnnn doesn't exist. If you don't, it will create a new local variable at that point. The new variable will have value 0, so the loop will never execute. You can waste days, desperately trying to figure out why your FOR loop never accomplishes anything.


kadghar, I have to take exception to your statement "when you run only a part, the 'option explicit' isnt[sic] activated". Although I can't guarantee it 100%, I'm pretty sure this is not true. If the option is there, it takes effect for that module.

[kadghar]

...
kadghar, I have to take exception to your statement "when you run only a part, the 'option explicit' isnt[sic] activated". Although I can't guarantee it 100%, I'm pretty sure this is not true. If the option is there, it takes effect for that module.

Yes, sorry about that.

[Darren123]

That's for the info guys, I'll remember this for future use.