How can I speed up this For Each loop in VBA? - excel

Question

I have an Worksheet_Change macro that hides/unhides rows depending on the choice a user makes in a cell with a data validation list.
The code takes a minute to run. It's looping over c.2000 rows. I'd like it to take closer to a few seconds so it becomes a useful user tool.
Option Explicit
Private Sub Worksheet_Change(ByVal Target As Range)
'Exit the routine early if there is an error
On Error GoTo EExit
'Manage Events
Application.ScreenUpdating = False
Application.DisplayAlerts = False
Application.EnableEvents = False
'Declare Variables
Dim rng_DropDown As Range
Dim rng_HideFormula As Range
Dim rng_Item As Range
'The reference the row hide macro will look for to know to hide the row
Const str_HideRef As String = "Hide"
'Define Variables
'The range that contains the week selector drop down
Set rng_DropDown = Range("rng_WeekSelector")
'The column that contains the formula which indicates if a row should
'be hidden c.2000 rows
Set rng_HideFormula = Range("rng_HideFormula")
'Working Code
'Exit sub early if the Month Selector was not changed
If Not Target.Address = rng_DropDown.Address Then GoTo EExit
'Otherwise unprotect the worksheet
wks_DailyPlanning.Unprotect (str_Password)
'For each cell in the hide formula column
For Each rng_Item In rng_HideFormula
With rng_Item
'If the cell says "hide"
If .Value2 = str_HideRef Then
'Hide the row
.EntireRow.Hidden = True
Else
'Otherwise show the row
.EntireRow.Hidden = False
End If
End With
'Cycle through each cell
Next rng_Item
EExit:
'Reprotect the sheet if the sheet is unprotected
If wks_DailyPlanning.ProtectContents = False Then wks_DailyPlanning.Protect (str_Password)
'Clear Events
Application.ScreenUpdating = True
Application.DisplayAlerts = True
Application.EnableEvents = True
End Sub
I have looked at some links provided by other users on this website and I think the trouble lies in the fact I'm having to iterate through each row individually.
Is it possible to create something like an array of .visible settings I can apply to the entire range at once?

Answer 1

I'd suggest copying your data range to a memory-based array and checking that, then using that data to adjust the visibility of each row. It minimizes the number of interactions you have with the worksheet Range object, which takes up lots of time and is a big performance hit for large ranges.
Sub HideHiddenRows()
Dim dataRange As Range
Dim data As Variant
Set dataRange = Sheet1.Range("A13:A2019")
data = dataRange.Value
Dim rowOffset As Long
rowOffset = IIf(LBound(data, 1) = 0, 1, 0)
ApplicationPerformance Flag:=False
Dim i As Long
For i = LBound(data, 1) To UBound(data, 1)
If data(i, 1) = "Hide" Then
dataRange.Rows(i + rowOffset).EntireRow.Hidden = True
Else
dataRange.Rows(i + rowOffset).EntireRow.Hidden = False
End If
Next i
ApplicationPerformance Flag:=True
End Sub
Public Sub ApplicationPerformance(ByVal Flag As Boolean)
Application.ScreenUpdating = Flag
Application.DisplayAlerts = Flag
Application.EnableEvents = Flag
End Sub

Answer 2

Another possibility:
Dim mergedRng As Range
'.......
rng_HideFormula.EntireRow.Hidden = False
For Each rng_Item In rng_HideFormula
If rng_Item.Value2 = str_HideRef Then
If Not mergedRng Is Nothing Then
Set mergedRng = Application.Union(mergedRng, rng_Item)
Else
Set mergedRng = rng_Item
End If
End If
Next rng_Item
If Not mergedRng Is Nothing Then mergedRng.EntireRow.Hidden = True
Set mergedRng = Nothing
'........

Answer 3

to increase perfomance you can populate dictionary with range addresses, and hide or unhide at once, instead of hide/unhide each particular row (but this is just in theory, you should test it by yourself), just an example:
Sub HideHiddenRows()
Dim cl As Range, x As Long
Dim dic As Object: Set dic = CreateObject("Scripting.Dictionary")
x = Cells(Rows.Count, "A").End(xlUp).Row
For Each cl In Range("A1", Cells(x, "A"))
If cl.Value = 0 Then dic.Add cl.Address(0, 0), Nothing
Next cl
Range(Join(dic.keys, ",")).EntireRow.Hidden = False
End Sub
demo: