ReDim Preserve to a Multi-Dimensional Array in Visual Basic 6

Question

I m using VB6 and I need to do a ReDim Preserve to a Multi-Dimensional Array     Dim n  m As Integer     n   1     m   0     Dim arrCity   As String     ReDim arrCity n  m       n   n   1     m   m   1     ReDim Preserve arrCity n  m    Whenever I do it as I have written it  I get the following error      runtime error 9  subscript out of range   Because I can only change the last array dimension  well in my task I have to change the whole array  2 dimensions in my example     Is there any workaround or another solution for this

User · Answer

You can use a user defined type containing an array of strings which will be the inner array. Then you can use an array of this user defined type as your outer array.

Have a look at the following test project:

'1 form with:
'  command button: name=Command1
'  command button: name=Command2
Option Explicit

Private Type MyArray
  strInner() As String
End Type

Private mudtOuter() As MyArray

Private Sub Command1_Click()
  'change the dimensens of the outer array, and fill the extra elements with "1"
  Dim intOuter As Integer
  Dim intInner As Integer
  Dim intOldOuter As Integer
  intOldOuter = UBound(mudtOuter)
  ReDim Preserve mudtOuter(intOldOuter + 2) As MyArray
  For intOuter = intOldOuter + 1 To UBound(mudtOuter)
    ReDim mudtOuter(intOuter).strInner(intOuter) As String
    For intInner = 0 To UBound(mudtOuter(intOuter).strInner)
      mudtOuter(intOuter).strInner(intInner) = "1"
    Next intInner
  Next intOuter
End Sub

Private Sub Command2_Click()
  'change the dimensions of the middle inner array, and fill the extra elements with "2"
  Dim intOuter As Integer
  Dim intInner As Integer
  Dim intOldInner As Integer
  intOuter = UBound(mudtOuter) / 2
  intOldInner = UBound(mudtOuter(intOuter).strInner)
  ReDim Preserve mudtOuter(intOuter).strInner(intOldInner + 5) As String
  For intInner = intOldInner + 1 To UBound(mudtOuter(intOuter).strInner)
    mudtOuter(intOuter).strInner(intInner) = "2"
  Next intInner
End Sub

Private Sub Form_Click()
  'clear the form and print the outer,inner arrays
  Dim intOuter As Integer
  Dim intInner As Integer
  Cls
  For intOuter = 0 To UBound(mudtOuter)
    For intInner = 0 To UBound(mudtOuter(intOuter).strInner)
      Print CStr(intOuter) & "," & CStr(intInner) & " = " & mudtOuter(intOuter).strInner(intInner)
    Next intInner
    Print "" 'add an empty line between the outer array elements
  Next intOuter
End Sub

Private Sub Form_Load()
  'init the arrays
  Dim intOuter As Integer
  Dim intInner As Integer
  ReDim mudtOuter(5) As MyArray
  For intOuter = 0 To UBound(mudtOuter)
    ReDim mudtOuter(intOuter).strInner(intOuter) As String
    For intInner = 0 To UBound(mudtOuter(intOuter).strInner)
      mudtOuter(intOuter).strInner(intInner) = CStr((intOuter + 1) * (intInner + 1))
    Next intInner
  Next intOuter
  WindowState = vbMaximized
End Sub

Run the project, and click on the form to display the contents of the arrays.

Click on Command1 to enlarge the outer array, and click on the form again to show the results.

Click on Command2 to enlarge an inner array, and click on the form again to show the results.

Be careful though: when you redim the outer array, you also have to redim the inner arrays for all the new elements of the outer array

User · Answer

As you correctly point out  one can ReDim Preserve only the last dimension of an array  ReDim Statement on MSDN       If you use the Preserve keyword  you can resize only the last array   dimension and you can t change the number of dimensions at all  For   example  if your array has only one dimension  you can resize that   dimension because it is the last and only dimension  However  if your   array has two or more dimensions  you can change the size of only the   last dimension and still preserve the contents of the array   Hence  the first issue to decide is whether 2-dimensional array is the best data structure for the job  Maybe  1-dimensional array is a better fit as you need to do ReDim Preserve   Another way is to use jagged array as per Pieter Geerkens s suggestion  There is no direct support for jagged arrays in VB6  One way to code  array of arrays  in VB6 is to declare an array of Variant and make each element an array of desired type  String in your case   Demo code is below   Yet another option is to implement Preserve part on your own  For that you ll need to create a copy of data to be preserved and then fill redimensioned array with it   Option Explicit  Public Sub TestMatrixResize       Const MAX D1 As Long   2     Const MAX D2 As Long   3      Dim arr   As Variant     InitMatrix arr  MAX D1  MAX D2     PrintMatrix  Original array    arr      ResizeMatrix arr  MAX D1   1  MAX D2   1     PrintMatrix  Resized array    arr End Sub  Private Sub InitMatrix a   As Variant  n As Long  m As Long      Dim i As Long  j As Long     Dim StringArray   As String      ReDim a n      For i   0 To n         ReDim StringArray m          For j   0 To m             StringArray j    i    m   1    j         Next j         a i    StringArray     Next i End Sub  Private Sub PrintMatrix heading As String  a   As Variant      Dim i As Long  j As Long     Dim s As String      Debug Print heading     For i   0 To UBound a          s              For j   0 To UBound a i               s   s  amp  a i  j   amp               Next j         Debug Print s     Next i End Sub  Private Sub ResizeMatrix a   As Variant  n As Long  m As Long      Dim i As Long     Dim StringArray   As String      ReDim Preserve a n      For i   0 To n - 1         StringArray   a i          ReDim Preserve StringArray m          a i    StringArray     Next i     ReDim StringArray m      a n    StringArray End Sub

User · Answer

I know this is a bit old but I think there might be a much simpler solution that requires no additional coding   Instead of transposing  redimming and transposing again  and if we talk about a two dimensional array  why not just store the values transposed to begin with  In that case redim preserve actually increases the right  second  dimension from the start  Or in other words  to visualise it  why not store in two rows instead of two columns if only the nr of columns can be increased with redim preserve   the indexes would than be 00-01  01-11  02-12  03-13  04-14  05-15     0 25-1 25 etcetera instead of 00-01  10-11  20-21  30-31  40-41 etcetera   As long as there is only one dimension that needs to be redimmed-preserved the approach would still work  just put that dimension last   As only the second  or last  dimension can be preserved while redimming  one could maybe argue that this is how arrays are supposed to be used to begin with  I have not seen this solution anywhere so maybe I m overlooking something    Posted earlier on similar question regarding two dimensions  extended answer here for more dimensions

User · Answer

In regards to this       in my task I have to change the whole array  2 dimensions    Just use a  jagged  array  ie an array of arrays of values   Then you can change the dimensions as you wish  You can have a 1-D array of variants  and the variants can contain arrays    A bit more work perhaps  but a solution

User · Answer

Since VB6 is very similar to VBA  I think I might have a solution which does not require this much code to ReDim a 2-dimensional array - using Transpose  if you are working in Excel   The solution  Excel VBA    Dim n  m As Integer n   2 m   1 Dim arrCity   As Variant ReDim arrCity 1 To n  1 To m   m   m   1 ReDim Preserve arrCity 1 To n  1 To m  arrCity   Application Transpose arrCity  n   n   1 ReDim Preserve arrCity 1 To m  1 To n  arrCity   Application Transpose arrCity    What is different from OP s question  the lower bound of arrCity array is not 0  but 1  This is in order to let Application Transpose do it s job   Note that Transpose is a method of the Excel Application object  which in actuality is a shortcut to Application WorksheetFunction Transpose   And in VBA  one must take care when using Transpose as it has two significant limitations  If the array has more than 65536 elements  it will fail  If ANY element s length exceed 256 characters  it will fail  If neither of these is an issue  then Transpose will nicely convert the rank of an array form 1D to 2D or vice-versa   Unfortunately there is nothing like  Transpose  build into VB6

User · Answer

If you not want include other function like  ReDimPreserve  could use temporal matrix for resizing  On based to your code   Dim n As Integer  m As Integer  i as Long  j as Long  Dim arrTemporal   as Variant      n   1     m   0     Dim arrCity   As String     ReDim arrCity n  m       n   n   1     m   m   1       VBA automatically adapts the size of the receiving matrix      arrTemporal   arrCity     ReDim arrCity n  m        Loop for assign values to arrCity     For i   1 To UBound arrTemporal   1          For j   1 To UBound arrTemporal   2              arrCity i  j    arrTemporal  i  j          Next     Next  If you not declare of type VBA assume that is Variant  Dim n as Integer  m As Integer

User · Answer

Function Redim2d ByRef Mtx As Variant  ByVal QtyColumnToAdd As Integer      ReDim Preserve Mtx LBound Mtx  1  To UBound Mtx  1   LBound Mtx  2  To UBound Mtx  2    QtyColumnToAdd  End Function   Main Code sub Main        Call Redim2d MtxR8Strat  1    Add one column end sub   OR sub main2       QtyColumnToAdd   1  Add one column     ReDim Preserve Mtx LBound Mtx  1  To UBound Mtx  1   LBound Mtx  2  To UBound Mtx  2    QtyColumnToAdd  end sub

User · Answer

I haven t tested every single one of these answers but you don t need to use complicated functions to accomplish this  It s so much easier than that  My code below will work in any office VBA application  Word  Access  Excel  Outlook  etc   and is very simple  Hope this helps     Dimension 2 Arrays Dim InnerArray 1 To 3  As Variant   The inner is for storing each column value of the current row Dim OuterArray   As Variant   The outer is for storing each row in Dim i As Byte      i   1     Do While i  lt   5            Enlarging our outer array to store a another row         ReDim Preserve OuterArray 1 To i             Loading the current row column data in         InnerArray 1     My First Column in Row    amp  i         InnerArray 2     My Second Column in Row    amp  i         InnerArray 3     My Third Column in Row    amp  i            Loading the entire row into our array         OuterArray i    InnerArray          i   i   1     Loop        Example print out of the array to the Intermediate Window     Debug Print OuterArray 1  1      Debug Print OuterArray 1  2      Debug Print OuterArray 2  1      Debug Print OuterArray 2  2

User · Answer

I stumbled across this question while hitting this road block myself  I ended up writing a piece of code real quick to handle this ReDim Preserve on a new sized array  first or last dimension   Maybe it will help others who face the same issue   So for the usage  lets say you have your array originally set as  MyArray 3 5   and you want to make the dimensions  first too   larger  lets just say to MyArray 10 20   You would be used to doing something like this right    ReDim Preserve MyArray 10 20    lt -- Returns Error   But unfortunately that returns an error because you tried to change the size of the first dimension   So with my function  you would just do something like this instead    MyArray   ReDimPreserve MyArray 10 20    Now the array is larger  and the data is preserved  Your ReDim Preserve for a Multi-Dimension array is complete      And last but not least  the miraculous function  ReDimPreserve     redim preserve both dimensions for a multidimension array  ONLY Public Function ReDimPreserve aArrayToPreserve nNewFirstUBound nNewLastUBound      ReDimPreserve   False      check if its in array first     If IsArray aArrayToPreserve  Then                 create new array         ReDim aPreservedArray nNewFirstUBound nNewLastUBound           get old lBound uBound         nOldFirstUBound   uBound aArrayToPreserve 1          nOldLastUBound   uBound aArrayToPreserve 2                    loop through first         For nFirst   lBound aArrayToPreserve 1  to nNewFirstUBound             For nLast   lBound aArrayToPreserve 2  to nNewLastUBound                  if its in range  then append to new array the same way                 If nOldFirstUBound  gt   nFirst And nOldLastUBound  gt   nLast Then                     aPreservedArray nFirst nLast    aArrayToPreserve nFirst nLast                  End If             Next         Next                      return the array redimmed         If IsArray aPreservedArray  Then ReDimPreserve   aPreservedArray     End If End Function   I wrote this in like 20 minutes  so there s no guarantees  But if you would like to use or extend it  feel free   I would ve thought that someone would ve had some code like this up here already  well apparently not  So here ya go fellow gearheads

User · Answer

This is more compact and respect the intial first position in array and just use the inital bound to add old value   Public Sub ReDimPreserve ByRef arr  ByVal size1 As Long  ByVal size2 As Long  Dim arr2 As Variant Dim x As Long  y As Long   Check if it s an array first If Not IsArray arr  Then Exit Sub   create new array with initial start ReDim arr2 LBound arr  1  To size1  LBound arr  2  To size2    loop through first For x   LBound arr  1  To UBound arr  1      For y   LBound arr  2  To UBound arr  2           if its in range  then append to new array the same way         arr2 x  y    arr x  y      Next Next  return byref arr   arr2 End Sub   I call this sub with this line to resize the first dimension  ReDimPreserve arr2  UBound arr2  1    1  UBound arr2  2    You can add an other test to verify if the initial size is not upper than new array  In my case it s not necessary

User · Answer

Easiest way to do this in VBA is to create a function that takes in an array  your new amount of rows  and new amount of columns   Run the below function to copy in all of the old data back to the array after it has been resized    function dynamic preserve array1  num rows  num cols           dim array2 as variant          array2   array1          reDim array1 1 to num rows  1 to num cols           for i   lbound array2  1  to ubound array2  2                  for j   lbound array2 2  to ubound array2 2                         array1 i j    array2 i j                  next j          next i          dynamic preserve   array1  end function

[arrays] ReDim Preserve to a Multi-Dimensional Array in Visual Basic 6

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