VBScript conditional short-circuiting workaround

Question

I have a large classic ASP app that I have to maintain, and I repeatedly find myself thwarted by the lack of short-circuit evaluation capability. E.g., VBScript won\'t let you

Answer 1

If you write it as two inline IF statements, you can achieve short-circuiting:

if not isNull(Rs("myField")) then if Rs("myField") <> 0 then ...

But your then action must appear on the same line as well. If you need multiple statements after then, you can separate them with : or move your code to a subroutine that you can call. For example:

if not isNull(Rs("myField")) then if Rs("myField") <> 0 then x = 1 : y = 2

Or

if not isNull(Rs("myField")) then if Rs("myField") <> 0 then DoSomething(Rs("myField"))

Answer 2

Nested IFs (only slightly less verbose):

if not isNull(Rs("myField")) Then
   if Rs("myField") <> 0 then

Answer 3

Would that there were, my friend -- TernaryOp is your only hope.

Answer 4

Yeah it's not the best solution but what we use is something like this

function ReplaceNull(s)
    if IsNull(s) or s = "" then
        ReplaceNull = " "
    else
        ReplaceNull = s
    end if
end function

Answer 5

Two options come to mind:

1) use len() or lenb() to discover if there is any data in the variable:

if not lenb(rs("myField"))=0 then...

2) use a function that returns a boolean:

if not isNothing(rs("myField")) then...

where isNothing() is a function like so:

function isNothing(vInput)
    isNothing = false : vInput = trim(vInput)
    if vartype(vInput)=0 or isEmpty(vInput) or isNull(vInput) or lenb(vInput)=0 then isNothing = true : end if 
end function

Answer 6

I always used Select Case statements to short circuit logic in VB. Something like..

Select Case True

Case isNull(Rs("myField"))

    myField = 0

Case (Rs("myField") <> 0)

    myField = Rs("myField")

Case Else

    myField = -1        

End Select

My syntax may be off, been a while. If the first case pops, everything else is ignored.