#ifdef #if #else and classes.

[Thomas Halsvik]

I have a module that is used in several projects. If a certain class is present I want to declare this class inside the module. Is there a way to use the #ifdef to do this?

#If clsMyClass-Exist
  Dim clsMyClass As New clsMyClass
#End If

I will be using that further down in the code as well to use the class if it is available.

[kedaman]

something like this?

If not clsMyClass is nothing then
   Dim clsMyClass As New clsMyClass
End If

[Thomas Halsvik]

I was thinking to have it globally inside the class so i dont have to pass it to every function.

Private MyClass As New clsMyClass

Dont know if one can use normal if else outside a function or sub.

[kedaman]

No If statements outside functions! Just declarations.
Well now i understand your point, you want to check if a class module is in the project, well no that won't get compiled, sorry

[Kali]

By definition, what you want to do is conditional compilation. Therefore, you cannot check against a global variable other than what is stored in the conditional compilation arguments.

What you need to do is put something like blnGoodProject = 1 as a conditional compilation argument. You could then have:

#If blnGoodProject = 1 Then
Set objItme = New clsItem
#End If

Unfortunately, since conditional compilation only allows boolean values (whatever evaluates to true and false), you can't really have a Select Case statement either in your code. Not that there is a #Select Case... statement anyway.

BTW, please do not do this:

#If Not blnGoodProject = 1

Not is a bitwise operator, this will not evaluate properly. Do a blnGoodProject <> 1 instead.

[Shark]

What is the difference when you place a # sign infront of "IF"?

[Kali]

Shark,

That means it's conditional compilation. If the #If statement does not evaluate to true, whatever code is in there will not be compiled either in debug mode or to the compiled component.

Therefore, you can make a reference to a class that does not exist in the project, as long as the IF...Then statement does not evaluate.

[Shark]

Can you give me an example of both "If" and "#If"? I like to know when to use which?

Thanks

[Edited by Shark on 10-10-2000 at 02:06 PM]

[Thomas Halsvik]

Here is an example

Private Const SWpresent = 1 '1=true 0=false
#If SWpresent = 0 Then
  Private Const MyNumb = 1000
#Else
  Private Const MyNumb = 99
#End If

Sub Test()
  MsgBox MyNumb
End Sub

I actually get the inverse of what the If-line says.
Output here is 1000. If i change "SWpresent = 0" to "SWpresent = 1" i get 99. Weird.

[Shark]

Thanks Thomas, that make sense. So when you place a "#" sign infront of an If, you can use it outside of a procedure?

[Thomas Halsvik]

Yes you can in a way do this. But it tells the compiler what to compile and what not to compile. Normally I would get an error if I declared a class that did not exist. With the #if #else I can tell it only to declare it if it exist. In my case I just declare a Constant saying if I have the class or not. Without the #if #else, you would get an error when pressing F5 to run, before the execution actually begin. The compiler would say "That class does not exist" and wont run the program.