How do I test if optional arguments are supplied or not?

Question

How do I test if optional arguments are supplied or not? -- in VB6 / VBA

Function func (Optional ByRef arg As Variant = Nothing)

    If arg Is Nothing Then          


        

Answer 1

"IsMissing"...Figured there would have to be a way. Thanks all!

SQL has a function, In(), where you can pass multiple arguments to see if the target value is in the list. I've always liked that as a solution, so here's my take on that, hope it helps:

Public Function IsIn(ByVal TestVal, ByVal VersusVal1, _
            Optional ByVal VersusVal2, Optional ByVal VersusVal3, _
            Optional ByVal VersusVal4, Optional ByVal VersusVal5, _
            Optional ByVal VersusVal6, Optional ByVal VersusVal7, _
            Optional ByVal VersusVal8, Optional ByVal VersusVal9, _
            Optional ByVal VersusVal10, Optional ByVal VersusVal11, _
            Optional ByVal VersusVal12, Optional ByVal VersusVal13, _
            Optional ByVal VersusVal14, Optional ByVal VersusVal15, _
            Optional ByVal VersusVal16, Optional ByVal VersusVal17, _
            Optional ByVal VersusVal18, Optional ByVal VersusVal19, _
            Optional ByVal VersusVal20) As Boolean

Dim CheckVals(1 To 20) as Variant
VersusVals(1) = VersusVal1
VersusVals(2) = VersusVal2
VersusVals(3) = VersusVal3
VersusVals(4) = VersusVal4
VersusVals(5) = VersusVal5
VersusVals(6) = VersusVal6
VersusVals(7) = VersusVal7
VersusVals(8) = VersusVal8
VersusVals(9) = VersusVal9
VersusVals(10) = VersusVal10
VersusVals(11) = VersusVal11
VersusVals(12) = VersusVal12
VersusVals(13) = VersusVal13
VersusVals(14) = VersusVal14
VersusVals(15) = VersusVal15
VersusVals(16) = VersusVal16
VersusVals(17) = VersusVal17
VersusVals(18) = VersusVal18
VersusVals(19) = VersusVal19
VersusVals(20) = VersusVal20

On Error Goto 0

IsIn = False

For x = 1 To 20
   If Not IsMissing(VersusVals(x)) Then
      If TestVal = VersusVals(x) Then
         IsIn = True
         Exit For
      End If
   End If
Next x

End Function

So, that's obviously why I needed "IsMissing"; doesn't work without it.