How to check for empty array in vba macro [duplicate] - vba

Question

This question already has answers here:
How do I determine if an array is initialized in VB6?
(24 answers)
Closed 3 years ago.
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?

Answer 1

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

Answer 2

As you are dealing with a string array, have you considered Join?
If Len(Join(FileNamesList)) > 0 Then

Answer 3

If you test on an array function it'll work for all bounds:
Function IsVarArrayEmpty(anArray As Variant)
Dim i As Integer
On Error Resume Next
i = UBound(anArray,1)
If Err.number = 0 Then
IsVarArrayEmpty = False
Else
IsVarArrayEmpty = True
End If
End Function

Answer 4

I see similar answers on here... but not mine...
This is how I am unfortunatley going to deal with it... I like the len(join(arr)) > 0 approach, but it wouldn't work if the array was an array of emptystrings...
Public Function arrayLength(arr As Variant) As Long
On Error GoTo handler
Dim lngLower As Long
Dim lngUpper As Long
lngLower = LBound(arr)
lngUpper = UBound(arr)
arrayLength = (lngUpper - lngLower) + 1
Exit Function
handler:
arrayLength = 0 'error occured. must be zero length
End Function

Answer 5

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

Answer 6

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

Answer 7

I am simply pasting below the code by the great Chip Pearson. It works a charm.
Here's his page on array functions.
I hope this helps.
Public Function IsArrayEmpty(Arr As Variant) As Boolean
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
' IsArrayEmpty
' This function tests whether the array is empty (unallocated). Returns TRUE or FALSE.
'
' The VBA IsArray function indicates whether a variable is an array, but it does not
' distinguish between allocated and unallocated arrays. It will return TRUE for both
' allocated and unallocated arrays. This function tests whether the array has actually
' been allocated.
'
' This function is really the reverse of IsArrayAllocated.
'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
Dim LB As Long
Dim UB As Long
err.Clear
On Error Resume Next
If IsArray(Arr) = False Then
' we weren't passed an array, return True
IsArrayEmpty = True
End If
' Attempt to get the UBound of the array. If the array is
' unallocated, an error will occur.
UB = UBound(Arr, 1)
If (err.Number <> 0) Then
IsArrayEmpty = True
Else
''''''''''''''''''''''''''''''''''''''''''
' On rare occasion, under circumstances I
' cannot reliably replicate, Err.Number
' will be 0 for an unallocated, empty array.
' On these occasions, LBound is 0 and
' UBound is -1.
' To accommodate the weird behavior, test to
' see if LB > UB. If so, the array is not
' allocated.
''''''''''''''''''''''''''''''''''''''''''
err.Clear
LB = LBound(Arr)
If LB > UB Then
IsArrayEmpty = True
Else
IsArrayEmpty = False
End If
End If
End Function

Answer 8

Simplified check for Empty Array:
Dim exampleArray() As Variant 'Any Type
If ((Not Not exampleArray) = 0) Then
'Array is Empty
Else
'Array is Not Empty
End If

Answer 9

Here is another way to do it. I have used it in some cases and it's working.
Function IsArrayEmpty(arr As Variant) As Boolean
Dim index As Integer
index = -1
On Error Resume Next
index = UBound(arr)
On Error GoTo 0
If (index = -1) Then IsArrayEmpty = True Else IsArrayEmpty = False
End Function

Answer 10

Based on ahuth's answer;
Function AryLen(ary() As Variant, Optional idx_dim As Long = 1) As Long
If (Not ary) = -1 Then
AryLen = 0
Else
AryLen = UBound(ary, idx_dim) - LBound(ary, idx_dim) + 1
End If
End Function
Check for an empty array; is_empty = AryLen(some_array)=0

Answer 11

Public Function IsEmptyArray(InputArray As Variant) As Boolean
On Error GoTo ErrHandler:
IsEmptyArray = Not (UBound(InputArray) >= 0)
Exit Function
ErrHandler:
IsEmptyArray = True
End Function

Answer 12

You can use the below function to check if variant or string array is empty in vba
Function IsArrayAllocated(Arr As Variant) As Boolean
On Error Resume Next
IsArrayAllocated = IsArray(Arr) And _
Not IsError(LBound(Arr, 1)) And _
LBound(Arr, 1) <= UBound(Arr, 1)
End Function
Sample usage
Public Function test()
Dim Arr(1) As String
Arr(0) = "d"
Dim x As Boolean
x = IsArrayAllocated(Arr)
End Function

Answer 13

Another method would be to do it sooner. You can create a Boolean variable and set it to true once you load data to the array. so all you really need is a simple if statement of when you load data into the array.

Answer 14

To check whether a Byte array is empty, the simplest way is to use the VBA function StrPtr().
If the Byte array is empty, StrPtr() returns 0; otherwise, it returns a non-zero value (however, it's not the address to the first element).
Dim ar() As Byte
Debug.Assert StrPtr(ar) = 0
ReDim ar(0 to 3) As Byte
Debug.Assert StrPtr(ar) <> 0
However, it only works with Byte array.

Answer 15

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 < lbound, it's empty

Answer 16

I'll generalize the problem and the Question as intended.
Test assingment on the array, and catch the eventual error
Function IsVarArrayEmpty(anArray as Variant)
Dim aVar as Variant
IsVarArrayEmpty=False
On error resume next
aVar=anArray(1)
If Err.number then '...still, it might not start at this index
aVar=anArray(0)
If Err.number then IsVarArrayEmpty=True ' neither 0 or 1 yields good assignment
EndIF
End Function
Sure it misses arrays with all negative indexes or all > 1... is that likely? in weirdland, yes.

Answer 17

Personally, I think one of the answers above can be modified to check if the array has contents:
if UBound(ar) > LBound(ar) Then
This handles negative number references and takes less time than some of the other options.

Answer 18

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).

Answer 19

if Ubound(yourArray)>-1 then
debug.print "The array is not empty"
else
debug.print "EMPTY"
end if

Answer 20

You can check its count.
Here cid is an array.
if (jsonObject("result")("cid").Count) = 0 them
MsgBox "Empty Array"
I hope this helps.
Have a nice day!

Answer 21

Another solution to test for empty array
if UBound(ar) < LBound(ar) then msgbox "Your array is empty!"
Or, if you already know that LBound is 0
if -1 = UBound(ar) then msgbox "Your array is empty!"
This may be faster than join(). (And I didn't check with negative indexes)
Here is my sample to filter 2 string arrays so they do not share same strings.
' Filtering ar2 out of strings that exists in ar1
For i = 0 To UBound(ar1)
' filter out any ar2.string that exists in ar1
ar2 = Filter(ar2 , ar1(i), False)
If UBound(ar2) < LBound(ar2) Then
MsgBox "All strings are the same.", vbExclamation, "Operation ignored":
Exit Sub
End If
Next
' At this point, we know that ar2 is not empty and it is filtered
'

Answer 22

Public Function arrayIsEmpty(arrayToCheck() As Variant) As Boolean
On Error GoTo Err:
Dim forCheck
forCheck = arrayToCheck(0)
arrayIsEmpty = False
Exit Function
Err:
arrayIsEmpty = True
End Function