Reverse order of For Each loop - vba

Question

One of the most powerful things about VB is ability to loop through objects in a collection WITHOUT referring to the index - for each loop.
I find it very useful only want to remove objects from a collection.
When doing removing objects from a predefined such as rows on a spread sheet the code is simpler if I use indexing and start at the largest and work back to the first. (Step -1 with an iterator) (otherwise requires an offset as the For each moves the enumerator pointer back to the previous object once the active one is deleted)
eg.
For intA = 10 to 1 step -1
' ...
Next
What about when using a For Each | Next
eg.
For each rngCell in Selection.Cells
' ...
Next
How could I loop backwards using the for each loop syntax?

Answer 1

It's not possible to loop backwards using the for each loop syntax.
As an alternative you can use a For i = a To 1 Step -1 loop:
Sub reverseForEach()
Dim i As Long, rng As Range
Set rng = ActiveSheet.Range("A1:B2")
For i = rng.Cells.Count To 1 Step -1
Debug.Print rng.item(i).Address
' Or shorthand rng(i) as the Item property
' is the default property for the Range object.
' Prints: $B$2, $A$2, $B$1, $A$1
Next i
End Sub
This works with all collections that have the Item property. For instance Worksheets, Areas or Shapes.
Note: The order of the loop when using on the Range object is from right to left, then up.

Answer 2

For built in collections (eg a Range) the short answer is: you can't. For user defined collections the answer linked by #VBlades might be useful, although the cost might outweigh the benifit.
One work around is to seperate the identification of items to be removed from the actual removal. Eg, for a range, build up a new range variable using Union, then process that variable, eg delete all the rows in one go. For the Range example, you can also take advantage of the Variant Array method to further speed things up.
Whether or not any of this is useful will depend on your actual use case.

Answer 3

There are other good answers but here's another alternative method of "stepping backwards" through a Range.
Function to Invert Range into Array
This function returns a "backwards Range Array" that can be used with For..Each:
Function ReverseRange(rg As Range) As Range()
Dim arr() As Range, r As Long, c As Long, n As Long
With rg
ReDim arr(1 To .Cells.Count) 'resize Range Array
For r = .Cells(.Rows.Count, 1).Row To .Cells(1, 1).Row Step -1
For c = .Cells(1, .Columns.Count).Column To .Cells(1, 1).Column Step -1
n = n + 1
Set arr(n) = .Worksheet.Cells(r, c) 'set cell in Array
Next c
Next r
End With
ReverseRange = arr 'return Range Array as function result
End Function
Example Usage:
Sub test()
Dim oCell
For Each oCell In ReverseRange(ActiveSheet.Range("E5:A1"))
Debug.Print oCell.Address 'do something here with each cell
Next oCell
End Sub

Answer 4

use a second variable that is set as your wanted counter and use this one in your code
'ex: Loop from n = 19 to 16
For i = 0 To 3
n = 19 - i
'your code here using n as the counter
Next

Answer 5

Only for Range collections. They are more complicated if they have more than 1 Area.
Basically there are two loops, the first one keeps the index of all the cells in an array and the second one creates a union of ranges from back to front
Option Explicit
Private Sub Main()
Dim InvertedRange As Range
Set InvertedRange = InvertRange(Application.Union(ActiveSheet.Range("A1:A2"), _
ActiveSheet.Range("F6:F7"), ActiveSheet.Range("E4:F5"), ActiveSheet.Range("E1")))
Dim ActualRange As Range
For Each ActualRange In InvertedRange
Debug.Print (ActualRange.Address(False, False) & " : " & ActualRange.Value)
Next ActualRange
End Sub
Public Function InvertRange(ByVal rngRange_I As Range) As Range
Dim RangesArray() As Long
ReDim RangesArray(1 To rngRange_I.Count, 1 To rngRange_I.Count)
Dim ActualArea As Range
Dim ActualRange As Range
Dim ArrayIndex As Long
For Each ActualArea In rngRange_I.Areas
For Each ActualRange In ActualArea
ArrayIndex = ArrayIndex + 1
RangesArray(ArrayIndex, 1) = ActualRange.Row
RangesArray(ArrayIndex, 2) = ActualRange.Column
Next ActualRange
Next ActualArea
Dim ActualRow As Long
Dim ActualColumn As Long
ActualRow = RangesArray(UBound(RangesArray, 1), 1)
ActualColumn = RangesArray(UBound(RangesArray, 2), 2)
With rngRange_I.Worksheet
Dim InvertedRange As Range
Set InvertedRange = .Cells(ActualRow, ActualColumn)
For ArrayIndex = UBound(RangesArray, 1) To LBound(RangesArray, 1) Step -1
ActualRow = RangesArray(ArrayIndex, 1)
ActualColumn = RangesArray(ArrayIndex, 2)
Set InvertedRange = Application.Union(InvertedRange, _
.Cells(ActualRow, ActualColumn))
Next ArrayIndex
End With
Set InvertRange = InvertedRange
End Function

Answer 6

You can use a stack (LIFO data structure) for inventing your list and the code would be something like this:
Dim aStack as Object
Set aStack = CreateObject("System.Collections.Stack")
For Each arngCell in Selection.Cells
aStack.Push(arngCell)
Next
While aStack.Count > 0
rngCell = aStack.Pop
' ...
End While
Set stack = Nothing