Is there a way to count elements in a VBA enum?

Question

is there a proper way to count elements of an enum in VBA ? At the moment, I leave an enum value such as KeepThisOneHere in the following example

Enum TestEnum
   ValueA
   ValueB
   ValueC
   KeepThisOneHere
End Enum

I use the last value to know the size... I don't like this solution, because I am not sure I have a guarantee the values will always be indexed the same way, and the code might be changed by a third party who might add values after this last special one, silently breaking the rest of the code.

Answer 1

Not sure on the etiquette here, so I'll post it and if advised, I'll come back and delete it. Chip Pearson posted this code on the Code Cage Forums (http://www.thecodecage.com/forumz/microsoft-excel-forum/170961-loop-enumeration-constants.html). I don't have the TypeLinInfo DLL on my machine, so I can't test it (I'm sure google will turn up places to download TLBINF32.dll). Nonetheless, here is his entire post to save someone else from registering for a forum:

You can do this ONLY IF you have the TypeLibInfo DLL installed on your computer. In VBA, go to the Tools menu, choose References, and scroll down to "TypeLib Info". If this item exists, check it. If it does not exist, then quit reading because you can't do what you want to do. The file name of the DLL you need is TLBINF32.dll.

The following code shows how to get the names and values in the XLYesNoGuess enum:

Sub AAA()
    Dim TLIApp As TLI.TLIApplication
    Dim TLILibInfo As TLI.TypeLibInfo
    Dim MemInfo As TLI.MemberInfo
    Dim N As Long
    Dim S As String
    Dim ConstName As String

    Set TLIApp = New TLI.TLIApplication
    Set TLILibInfo = New TLI.TypeLibInfo
    Set TLILibInfo = TLIApp.TypeLibInfoFromFile( _
        ThisWorkbook.VBProject.References("EXCEL").FullPath)

    ConstName = "XLYesNoGuess"
    For Each MemInfo In _
        TLILibInfo.Constants.NamedItem(ConstName).Members
        S = MemInfo.Name
        N = MemInfo.Value
        Debug.Print S, CStr(N)
    Next MemInfo
End Sub

Using this knowledge, you can create two useful functions. EnumNames returns an array of strings containing the names of the values in an enum:

Function EnumNames(EnumGroupName As String) As String()
    Dim TLIApp As TLI.TLIApplication
    Dim TLILibInfo As TLI.TypeLibInfo
    Dim MemInfo As TLI.MemberInfo
    Dim Arr() As String
    Dim Ndx As Long
    Set TLIApp = New TLI.TLIApplication
    Set TLILibInfo = New TLI.TypeLibInfo
    Set TLILibInfo = TLIApp.TypeLibInfoFromFile( _
        ThisWorkbook.VBProject.References("EXCEL").FullPath)
    On Error Resume Next
    With TLILibInfo.Constants.NamedItem(EnumGroupName)
        ReDim Arr(1 To .Members.Count)
        For Each MemInfo In .Members
            Ndx = Ndx + 1
            Arr(Ndx) = MemInfo.Name
        Next MemInfo
    End With

    EnumNames = Arr
End Function

You would call this function with code such as:

Sub ZZZ()
    Dim Arr() As String
    Dim N As Long
    Arr = EnumNames("XLYesNoGuess")
    For N = LBound(Arr) To UBound(Arr)
        Debug.Print Arr(N)
    Next N
End Sub

You can also create a function to test if a value is defined for an enum:

Function IsValidValue(EnumGroupName As String, Value As Long) As
    Boolean
    Dim TLIApp As TLI.TLIApplication
    Dim TLILibInfo As TLI.TypeLibInfo
    Dim MemInfo As TLI.MemberInfo
    Dim Ndx As Long
    Set TLIApp = New TLI.TLIApplication
    Set TLILibInfo = New TLI.TypeLibInfo
    Set TLILibInfo = TLIApp.TypeLibInfoFromFile( _
        ThisWorkbook.VBProject.References("EXCEL").FullPath)
    On Error Resume Next
    With TLILibInfo.Constants.NamedItem(EnumGroupName)
        For Ndx = 1 To .Members.Count
            If .Members(Ndx).Value = Value Then
                IsValidValue = True
                Exit Function
            End If
        Next Ndx
    End With
    IsValidValue = False
End Function

This function returns True if Value is defined for EnumGroupName or False if it is not defined. You would call this function with code like the following:

Sub ABC()
    Dim B As Boolean
    B = IsValidValue("XLYesNoGuess", xlYes)
    Debug.Print B ' True for xlYes
    B = IsValidValue("XLYesNoGuess", 12345)
    Debug.Print B ' False for 12345
End Sub

Cordially, Chip Pearson Microsoft MVP 1998 - 2010 Pearson Software Consulting, LLC www.cpearson.com [email on web site]

Answer 2

Here's an example of my workaround, which is pretty straightforward:

Enum FileSpecFields
    FileSpecFields_Start                    '(zero-based)
        FileNameIdx = FileSpecFields_Start
        FolderNameIdx
        BasePathIdx
        FullPathIdx
        CopyStatus
    FileSpecFields_End = CopyStatus
End Enum

'...

ReDim FileSpecList(1 To MaxFiles, FileSpecFields_Start To FileSpecFields_End) As String

'...

But note that, if you are using a one-based Enum you may have to adjust the _End value definition, depending on how you're using it. Also, for zero-based Enums, the _End value is not the same as its count of items. And, if you add items at the end, you must update the _End value's definition accordingly. Finally, if your enum is a non-contiguous range of values, all bets are off with this approach!