Is Variable Declared?

MikeSchinkel
24th December 2005 06:21 UTC

Is Variable Declared?
Is there any way to determine in a script if a variable has been declared or not? I want to be able to declare a variable using a macro, but only if it hasn't already been declared.

Animaether
24th December 2005 07:13 UTC

Variables aren't so much declared as that they either contain data, or they don't. So you could just use :
StrCmp $Var "" +2 0
MessageBox MB_OK "Var is 'declared'"

Afrow UK
24th December 2005 09:27 UTC

Yes but if a variable hasn't been declared from within a macro, then that will throw a compiler warning.
You should define a constant of the same name of that variable and check if that constant exists with !ifdef.

E.g.

!macro Var VarName
 Var "${Var}"
 !define "${Var}"
!macroend

!insertmacro Var MyVar

Function MyFunc
!ifdef MyVar
 StrCpy $MyVar "blah"
!endif
FunctionEnd

-Stu

Animaether
24th December 2005 10:28 UTC

ah, good point!

dandaman32
25th December 2005 22:17 UTC

!ifndef VAR_DECLARED
  !define VAR_DECLARED
  Var VAR_NAME
!endif

-dandaman32

MikeSchinkel
26th December 2005 09:02 UTC

Thanks for the suggestions. That's certainly a clever and viable workaround!

But not exactly what I was looking for as it pollutes the macro namespace and is more apt to cause collisions when using headers from multiple sources. :(

OTOH, I rearchitected what I was doing so I didn't end up needing it anyway. At least not this time. :)