How to check for empty array in vba macro

By : Vicky
Source: Stackoverflow.com
Question!

I want to check for empty arrays. Google gave me varied solutions but nothing worked. Maybe I am not applying them correctly.

Function GetBoiler(ByVal sFile As String) As String
'Email Signature
    Dim fso As Object
    Dim ts As Object
    Set fso = CreateObject("Scripting.FileSystemObject")
    Set ts = fso.GetFile(sFile).OpenAsTextStream(1, -2)
    GetBoiler = ts.ReadAll
    ts.Close
End Function

Dim FileNamesList As Variant, i As Integer
' activate the desired startfolder for the filesearch
FileNamesList = CreateFileList("*.*", False) ' Returns File names
' performs the filesearch, includes any subfolders
' present the result
' If there are Signatures then populate SigString
Range("A:A").ClearContents
For i = 1 To UBound(FileNamesList)
    Cells(i + 1, 1).Formula = FileNamesList(i)
Next i

SigString = FileNamesList(3)

If Dir(SigString) <> "" Then
    Signature = GetBoiler(SigString)
Else
    Signature = ""
End If

Here if FileNamesList array is empty, GetBoiler(SigString) should not get called at all. When FileNamesList array is empty, SigString is also empty and this calls GetBoiler() function with empty string. I get an error at line

Set ts = fso.GetFile(sFile).OpenAsTextStream(1, -2)

since sFile is empty. Any way to avoid that?

By : Vicky


Answers
Function IsVarArrayEmpty(anArray As Variant) as boolean
    On Error Resume Next
    IsVarArrayEmpty = true
    IsVarArrayEmpty = UBound(anArray) < LBound(anArray)
End Function

==> maybe ubound crashes and it remains at true, and if ubound

By : Pierre


You can check if the array is empty by retrieving total elements count using JScript's VBArray() object (works with arrays of variant type, single or multidimensional):

Sub Test()

    Dim a() As Variant
    Dim b As Variant
    Dim c As Long

    ' Uninitialized array of variant
    ' MsgBox UBound(a) ' gives 'Subscript out of range' error
    MsgBox GetElementsCount(a) ' 0

    ' Variant containing an empty array
    b = Array()
    MsgBox GetElementsCount(b) ' 0

    ' Any other types, eg Long or not Variant type arrays
    MsgBox GetElementsCount(c) ' -1

End Sub

Function GetElementsCount(aSample) As Long

    Static oHtmlfile As Object ' instantiate once

    If oHtmlfile Is Nothing Then
        Set oHtmlfile = CreateObject("htmlfile")
        oHtmlfile.parentWindow.execScript ("function arrlength(arr) {try {return (new VBArray(arr)).toArray().length} catch(e) {return -1}}"), "jscript"
    End If
    GetElementsCount = oHtmlfile.parentWindow.arrlength(aSample)

End Function

For me it takes about 0.3 mksec for each element + 15 msec initialization, so the array of 10M elements takes about 3 sec. The same functionality could be implemented via ScriptControl ActiveX (it is not available in 64-bit MS Office versions, so you can use workaround like this).



Go with a triple negative:

If (Not Not FileNamesList) <> 0 Then
    ' Array has been initialized, so you're good to go.
Else
    ' Array has NOT been initialized
End If

Or just:

If (Not FileNamesList) = -1 Then
    ' Array has NOT been initialized
Else
    ' Array has been initialized, so you're good to go.
End If

In VB, for whatever reason, Not myArray returns the SafeArray pointer. For uninitialized arrays, this returns -1. You can Not this to XOR it with -1, thus returning zero, if you prefer.

               (Not myArray)   (Not Not myArray)
Uninitialized       -1                 0
Initialized    -someBigNumber   someOtherBigNumber

Source

By : ahuth


This video can help you solving your question :)
By: admin