initializing an array multiple times in vba - arrays

Question

I'm working on a VBA code in which I'm inserting Integer values:
Dim IgnoreCol() As Integer
For j = 1 To LastCol
If Cells(1, j).Value = "IGNORE" Then
ReDim Preserve IgnoreCol(Temp)
IgnoreCol(Temp) = j
Temp = Temp + 1
End If
Next
After this part of the code, I have in my program an Int array of column numbers - now, in the next loop I would like to approach the array:
For j = 1 To LastCol
If Not IsInArray(j, IgnoreCol) Then
DataLine = DataLine + Trim(Cells(Row, j).Value)
End If
Next j
So now I have 2 questions:
Say that neither of the columns in the sheet had "IGNORE" in their first cell and that my array "IgnoreCol" is empty, and none of the cells were initialized - what condition returns "True" if the array is really empty?
I'm using this code inside another loop - which means, I want to initialize my "IgnoreCol" array at the end of this code before entering it again (by initializing I mean delete all, not just put 0 in all of the cells for instance)
Thank you very much!

Answer 1

This would test for an empty array:
Function ArrayIsEmpty(a) As Boolean
Dim temp
On Error Resume Next
temp = LBound(a)
If Err.Number <> 0 Then ArrayIsEmpty = True
End Function
Use the Erase function to clear the array:
Dim a() As Integer
If ArrayIsEmpty(a) Then Debug.Print "Array starts empty" Else Debug.Print "Array NOT empty???"
Redim a(1 To 100)
If ArrayIsEmpty(a) Then Debug.Print "Array empty" Else Debug.Print "Array NOT empty"
Erase a
If ArrayIsEmpty(a) Then Debug.Print "Array NOW empty" Else Debug.Print "Array still not empty"
But I'd prefer to use a Dictionary object (from the "Microsoft Scripting Runtime", which you can add using "Tools...References" in the VBA editor).
Dim IgnoreCols As New Dictionary
For j = 1 To LastCol
If Cells(1, j).Value = "IGNORE" Then
IgnoreCols.Add j, 1
End If
Next
For j = 1 To LastCol
If Not IgnoreCols.Exists(j) Then
DataLine = DataLine + Trim(Cells(Row, j).Value)
End If
Next j
... or even better, something like this:
Dim IncludeCols As New Dictionary
For j = 1 To LastCol
If Cells(1, j).Value <> "IGNORE" Then
IncludeCols.Add j, 1 ' store the cols we *want*
End If
Next
' now just loop through the list of wanted cols
For j = 0 To IncludeCols.Count
DataLine = DataLine + Trim(Cells(Row, IncludeCols.Keys(j)).Value)
Next j