How to check for empty array in vba macro

Asked 2008-10-15T20:31:20.837

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?

vba excel

Edit Report

2 Answers

When writing VBA there is this sentence in my head: "Could be so easy, but..."

Here is what I adopted it to:

Private Function IsArrayEmpty(arr As Variant)
  ' This function returns true if array is empty
  Dim l As Long

  On Error Resume Next
  l = Len(Join(arr))
  If l = 0 Then
    IsArrayEmpty = True
  Else
    IsArrayEmpty = False
  End If

  If Err.Number > 0 Then
      IsArrayEmpty = True
  End If

  On Error GoTo 0
End Function

Private Sub IsArrayEmptyTest()
  Dim a As Variant
  a = Array()
  Debug.Print "Array is Empty is " & IsArrayEmpty(a)
  If IsArrayEmpty(a) = False Then
    Debug.Print "  " & Join(a)
  End If
End Sub

answered 2011-04-01T09:55:22.073

This code doesn't do what you expect:

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

If you pass an empty string ("") or vbNullString to Dir, it will return the name of the first file in the current directory path (the path returned by CurDir$). So, if SigString is empty, your If condition will evaluate to True because Dir will return a non-empty string (the name of the first file in the current directory), and GetBoiler will be called. And if SigString is empty, the call to fso.GetFile will fail.

You should either change your condition to check that SigString isn't empty, or use the FileSystemObject.FileExists method instead of Dir for checking if the file exists. Dir is tricky to use precisely because it does things you might not expect it to do. Personally, I would use Scripting.FileSystemObject over Dir because there's no funny business (FileExists returns True if the file exists, and, well, False if it doesn't). What's more, FileExists expresses the intent of your code much clearly than Dir.

Method 1: Check that SigString is non-empty first

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

Method 2: Use the FileSystemObject.FileExists method

Dim fso As Object
Set fso = CreateObject("Scripting.FileSystemObject")

If fso.FileExists(SigString) Then
    Signature = GetBoiler(SigString) 
Else
    Signature = "" 
End If

answered 2008-10-15T21:14:01.450

How to check for empty array in vba macro

2 Answers

Your Answer