VBA check if array is one dimensional

Question

I have an array (that comes from SQL) and can potentially have one or more rows.

I want to be able to figure out if the array has just one row.

UBound doesn't seem to be helpful. For 2-dimensional arrays UBound(A,1) and UBound(A,2) returns the number of rows and columns respectively, but when the array has only one row, UBound(A,1) returns the number of columns and UBound(A,2) returns a <Subscript out of range>.

I have also seen this Microsoft help page for determining the number of dimensions in an array. It is a very horrifying solution that involves using the error handler.

How can I determine whether the array has just one row (hopefully without using the error handler)?

Answer 1

I realized that my original answer can be simplified - rather than having the VARIANT and SAFEARRAY structures defined as VBA Types, all that is needed is a few CopyMemorys to get the pointers and finally the Integer result.

UPDATE: This version should work on both 32 bit and 64 bit systems (original preserved below the break for posterity):

Option Explicit

Private Declare PtrSafe Sub CopyMemory Lib "kernel32.dll" Alias "RtlMoveMemory" (ByVal Destination As LongPtr, ByVal Source As LongPtr, ByVal Length As Integer)

Public Function GetDims(VarSafeArray As Variant) As Integer
    Dim variantType As Integer
    Dim pointer As LongPtr
    Dim arrayDims As Integer

    CopyMemory VarPtr(variantType), VarPtr(VarSafeArray), 2& 'the first 2 bytes of the VARIANT structure contain the type

    If (variantType And &H2000) > 0 Then 'Array (&H2000)
        'If the Variant contains an array or ByRef array, a pointer for the SAFEARRAY or array ByRef variant is located at VarPtr(VarSafeArray) + 8
        CopyMemory VarPtr(pointer), VarPtr(VarSafeArray) + 8, LenB(pointer)

        'If the array is ByRef, there is an additional layer of indirection through another Variant (this is what allows ByRef calls to modify the calling scope).
        'Thus it must be dereferenced to get the SAFEARRAY structure
        If (variantType And &H4000) > 0 Then 'ByRef (&H4000)
            'dereference the pointer to pointer to get the actual pointer to the SAFEARRAY
            CopyMemory VarPtr(pointer), pointer, LenB(pointer)
        End If
        'The pointer will be 0 if the array hasn't been initialized
        If Not pointer = 0 Then
            'If it HAS been initialized, we can pull the number of dimensions directly from the pointer, since it's the first member in the SAFEARRAY struct
            CopyMemory VarPtr(arrayDims), pointer, 2&
            GetDims = arrayDims
        Else
            GetDims = 0 'Array not initialized
        End If
    Else
        GetDims = 0 'It's not an array... Type mismatch maybe?
    End If
End Function

---

Here is the simplest complete GetDims that checks the dimensions directly through the variables in memory:

Option Explicit

Private Declare Sub CopyMemory Lib "kernel32.dll" Alias "RtlMoveMemory" (ByVal Destination As Long, ByVal Source As Long, ByVal Length As Integer)

Public Function GetDims(VarSafeArray As Variant) As Integer
    Dim variantType As Integer
    Dim pointer As Long
    Dim arrayDims As Integer
    
    CopyMemory VarPtr(variantType), VarPtr(VarSafeArray), 2& 'the first 2 bytes of the VARIANT structure contain the type
    
    If (variantType And &H2000) > 0 Then 'Array (&H2000)
        'If the Variant contains an array or ByRef array, a pointer for the SAFEARRAY or array ByRef variant is located at VarPtr(VarSafeArray) + 8
        CopyMemory VarPtr(pointer), VarPtr(VarSafeArray) + 8, 4&
        
        'If the array is ByRef, there is an additional layer of indirection through another Variant (this is what allows ByRef calls to modify the calling scope).
        'Thus it must be dereferenced to get the SAFEARRAY structure
        If (variantType And &H4000) > 0 Then 'ByRef (&H4000)
            'dereference the pointer to pointer to get the actual pointer to the SAFEARRAY
            CopyMemory VarPtr(pointer), pointer, 4&
        End If
        'The pointer will be 0 if the array hasn't been initialized
        If Not pointer = 0 Then
            'If it HAS been initialized, we can pull the number of dimensions directly from the pointer, since it's the first member in the SAFEARRAY struct
            CopyMemory VarPtr(arrayDims), pointer, 2&
            GetDims = arrayDims
        Else
            GetDims = 0 'Array not initialized
        End If
    Else
        GetDims = 0 'It's not an array... Type mismatch maybe?
    End If
End Function

Answer 2

Identify 1-row arrays without Error handling or API functions

"I want to be able to figure out if the array has just one row."

To solve OP's requirement focussing on arrays already dimensioned as 1- and 2-dim arrays, it isn't necessary to determine the array's actual dimension, it suffices to get the number of its "rows". So I came across the following surprisingly simple solution considering the following:

• It's possible to slice 1-dim or 2-dim arrays to isolate their first "column" via Application.Index(arr, 0, 1).
• An eventual UBound now will show the correct number of rows, especially for the asked one-row case.

Function UBndOne(arr) As Long
'Purp: get rows count of (array) input
'Note: returns 1 as the function result for 
'    a) one-dimensional arrays 
'    b) 2-dim arrays with only one row
'      UBound(arr,1) isn't helpful for 1-dim array as it would return the number of elements
    UBndOne = UBound(Application.Index(arr, 0, 1))
End Function

Side note: The combined code UBound(Application.Index(arr, 0, 1)) could be applied even upon other data types than arrays, returning as well 1 as function result.

Answer 3

I found Blackhawks's accepted and revised answer very instructive, so I played around with it and learned some useful things from it. Here's a slightly modified version of that code that includes a test sub at the bottom.

Option Explicit

Private Declare Sub CopyMemory Lib "kernel32.dll" Alias "RtlMoveMemory" ( _
    ByVal Destination As Long, ByVal Source As Long, ByVal Length As Integer)

Public Function GetDims(VarSafeArray As Variant) As Integer
    Dim variantType As Integer
    Dim pointer As Long
    Dim arrayDims As Integer

    'The first 2 bytes of the VARIANT structure contain the type:
    CopyMemory VarPtr(variantType), VarPtr(VarSafeArray), 2&

    If Not (variantType And &H2000) > 0 Then
    'It's not an array. Raise type mismatch.
        Err.Raise (13)
    End If

    'If the Variant contains an array or ByRef array, a pointer for the _
        SAFEARRAY or array ByRef variant is located at VarPtr(VarSafeArray) + 8:
    CopyMemory VarPtr(pointer), VarPtr(VarSafeArray) + 8, 4&

    'If the array is ByRef, there is an additional layer of indirection through_
    'another Variant (this is what allows ByRef calls to modify the calling scope).
    'Thus it must be dereferenced to get the SAFEARRAY structure:
    If (variantType And &H4000) > 0 Then 'ByRef (&H4000)
        'dereference the pointer to pointer to get actual pointer to the SAFEARRAY
        CopyMemory VarPtr(pointer), pointer, 4&
    End If
    'The pointer will be 0 if the array hasn't been initialized
    If Not pointer = 0 Then
        'If it HAS been initialized, we can pull the number of dimensions directly _
            from the pointer, since it's the first member in the SAFEARRAY struct:
        CopyMemory VarPtr(arrayDims), pointer, 2&
        GetDims = arrayDims
    Else
        GetDims = 0 'Array not initialized
    End If
End Function

Sub TestGetDims()
' Tests GetDims(). Should produce the following output to Immediate Window:
'
' 1             One
' 2             Two
' Number of array dimensions: 2

    Dim myArray(2, 2) As Variant
    Dim iResult As Integer
    myArray(0, 0) = 1
    myArray(1, 0) = "One"
    myArray(0, 1) = 2
    myArray(1, 1) = "Two"

    Debug.Print myArray(0, 0), myArray(1, 0)
    Debug.Print myArray(0, 1), myArray(1, 1)

    iResult = GetDims(myArray)

    Debug.Print "Number of array dimensions: " & iResult
End Sub

Answer 4

I know you want to avoid using the error handler, but if it's good enough for Chip Pearson, it's good enough for me. This code (as well as a number of other very helpful array functions) can be found on his site:

http://www.cpearson.com/excel/vbaarrays.htm

Create a custom function:

Function IsArrayOneDimensional(arr as Variant) As Boolean
    IsArrayOneDimensional = (NumberOfArrayDimensions(arr) = 1)
End Function

Which calls Chip's function:

Public Function NumberOfArrayDimensions(arr As Variant) As Integer
''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
' NumberOfArrayDimensions
' This function returns the number of dimensions of an array. An unallocated dynamic array
' has 0 dimensions. This condition can also be tested with IsArrayEmpty.
'''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
Dim Ndx As Integer
Dim Res As Integer
On Error Resume Next
' Loop, increasing the dimension index Ndx, until an error occurs.
' An error will occur when Ndx exceeds the number of dimension
' in the array. Return Ndx - 1.
Do
    Ndx = Ndx + 1
    Res = UBound(arr, Ndx)
Loop Until Err.Number <> 0

Err.Clear

NumberOfArrayDimensions = Ndx - 1

End Function

Answer 5

If you REALLY want to avoid using On Error, you can use knowledge of the SAFEARRAY and VARIANT structures used to store arrays under the covers to extract the dimension information from where it's actually stored in memory. Place the following in a module called mdlSAFEARRAY

Private Declare Sub CopyMemory Lib "kernel32.dll" Alias "RtlMoveMemory" (ByVal Destination As Long, ByVal Source As Long, ByVal Length As Integer)

Private Type SAFEARRAY
    cDims As Integer
    fFeatures As Integer
    cbElements As Long
    cLocks As Long
    pvData As Long
End Type

Private Type ARRAY_VARIANT
    vt As Integer
    wReserved1 As Integer
    wReserved2 As Integer
    wReserved3 As Integer
    lpSAFEARRAY As Long
    data(4) As Byte
End Type

Private Enum tagVARENUM
    VT_EMPTY = &H0
    VT_NULL
    VT_I2
    VT_I4
    VT_R4
    VT_R8
    VT_CY
    VT_DATE
    VT_BSTR
    VT_DISPATCH
    VT_ERROR
    VT_BOOL
    VT_VARIANT
    VT_UNKNOWN
    VT_DECIMAL
    VT_I1 = &H10
    VT_UI1
    VT_UI2
    VT_I8
    VT_UI8
    VT_INT
    VT_VOID
    VT_HRESULT
    VT_PTR
    VT_SAFEARRAY
    VT_CARRAY
    VT_USERDEFINED
    VT_LPSTR
    VT_LPWSTR
    VT_RECORD = &H24
    VT_INT_PTR
    VT_UINT_PTR
    VT_ARRAY = &H2000
    VT_BYREF = &H4000
End Enum

Public Function GetDims(VarSafeArray As Variant) As Integer
    Dim varArray As ARRAY_VARIANT
    Dim lpSAFEARRAY As Long
    Dim sArr As SAFEARRAY
    CopyMemory VarPtr(varArray.vt), VarPtr(VarSafeArray), 16&
    If varArray.vt And (tagVARENUM.VT_ARRAY Or tagVARENUM.VT_BYREF) Then
        CopyMemory VarPtr(lpSAFEARRAY), varArray.lpSAFEARRAY, 4&
        If Not lpSAFEARRAY = 0 Then
            CopyMemory VarPtr(sArr), lpSAFEARRAY, LenB(sArr)
            GetDims = sArr.cDims
        Else
            GetDims = 0  'The array is uninitialized
        End If
    Else
        GetDims = 0  'Not an array - might want an error instead
    End If
End Function

Here is a quick test function to show usage:

Public Sub testdims()
    Dim anotherarr(1, 2, 3) As Byte
    Dim myarr() As Long
    Dim strArr() As String
    ReDim myarr(9)
    ReDim strArr(12)
    Debug.Print GetDims(myarr)
    Debug.Print GetDims(anotherarr)
    Debug.Print GetDims(strArr)
End Sub

Answer 6

For a 2D array (or more dimensions), use this function:

Function is2d(a As Variant) As Boolean
    Dim l As Long
    On Error Resume Next
    l = LBound(a, 2)
    is2d = Err = 0
End Function

which gives :

Sub test()
    Dim d1(2) As Integer, d2(2, 2) As Integer,d3(2, 2, 2) As Integer
    Dim b1, b2, b3 As Boolean

    b1 = is2d(d1) ' False
    b2 = is2d(d2) ' True
    b3 = is2d(d3) ' True

    Stop
End Sub